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Synthesis of nucleoside amino acids and glycosyl amino acids Dodd, Robert Hugh 1979

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SYNTHESIS OF NUCLEOSIDE AMINO ACIDS AND GLYCOSYL AMINO ACIDS BY ROBERT HUGH DODD B. Sc. (Honours), McGill University, 1974 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS. FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Chemistry) We accept this thesis as conforming to the required standard. THE UNIVERSITY OF BRITISH COLUMBIA August, 1979 (c) Robert Hugh Dodd, 1979 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of CJi*»ii-f4ry The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date W> i ABSTRACT The syntheses of g l y c o s - 3 - y l and C - g l y c o s y l a - and 3 -amino a c i d d e r i v a t i v e s ara d e s c r i b e d . The i n t r o d u c t i o n o f carbon-carbon l i n k e d s u b s t i t u e n t s i n c l u d i n g 3 - a l a n i n e , a t C-6 of u r i d i n e d e r i v a t i v e s i s a l s o r e p o r t e d . Knoevenagel condensation of e t h y l cyanoacetate (263) with 1,2: 5 , 6 - d i - O - i s o p r o p y l i d e n e - a - p - r i b o - h e x o f uranos-3-ulose (14) i n N,N-dimethylformamide using ammonium a c e t a t e as the c a t a l y s t gave 3-C-[ (R,S)-cyano(ethoxycarbonyl) methylene]-1,2:5,6-di-O-i s o p r o p y l i d e n e - a -E)-a l l o f uranose (264) i n 26% y i e l d as well as a ch r o m a t o g r a p h i c a l l y i n s e p a r a b l e mixture o f 3-C-[(R,S)-cyano (ethoxycarbonyl) methylene ]-3-ieoxy- 1,2: 5,6-di-O-i s o p r o p y l i d e n e - a - g - a l l o f uranose (265) and 3,3-C-bis[ (RS, SS, RR)-cyano (ethoxycarbonyl) methyl ]-3-deoxy- 1,2: 5,6-di-O-i s o p r o p y l i d e n e - a - D - a l l o f uranose (266) i n equal y i e l d s of 5%. Compound 2 64 was hydrogenated over platinum oxide i n a c e t i c anhydride t o give i n 96% y i e l d 3-C-[(R,S)-a cet a midomethyl (ethoxycarbonyl) methylene ]-1,2:5,6- di-O-i s o p r o p y l i d e n e - <* - D - a l l o f uranose (270) . , Dehydration-.of 264 with t h i o n y l c h l o r i d e i n p y r i d i n e a f f o r d e d 3-C-[ (R,S-cyano (ethoxycarbonyl) methylene ]-3-deoxy- 1,2: 5 , 6 - d i - 0 - i s o -p r o p y l i d e n e - a -^-erythro-hex-3-enofuranose (273). Compound 266 was i s o l a t e d by r e d u c t i o n of 265 with sodium cyanoborohydride i n methanol to give 3-deoxy-3-C-[ (R,S-cyano (ethoxycarbonyl) methylene ] - 1 , 2 z 5 , 6 - d i - O - i s o p r o p y l i d e n e - a -D - a l l o f u r a n o s e (268) followed by column chromatography on s i l i c a g e l -Reaction of 3-C - f o r m y l - 1 , 2 : 5 , 6 - d i - 0 - i s o p r o p y l i d e n e - a - D -i i allofuranose (2 78) with sodium cyanide, ammonium carbonate and carbon dioxide gave i n 53% y i e l d 3-C-(2,4-diketo-tetrahydcoimidazol-5- (R, SJ-yl) -1,2: 5,6-di-0-isopropylidene- a -D-allofuranose (280). Treatment of 2 80 with barium hydroxide gave a 2: 1 mixture of D-2 and L_-2-(1,2:5,6-di-0-isopropylidene-a -D-allofuranos-3-yl) glycine (28J.) , respectively, in a combined yield of 74%. When ethyl cyanoacetate (263) was reacted with 2,5-anhydro-3,4,6-tri-O-benzoyl-D-allose (203) i n N-N-dimethylformamide using ammonium acetate as ca t a l y s t , ethyl (E or Z)-4,7-anhydro-2-cyano-2,3 ,5-trideoxy-6, 8-di-0-benzoyl-D4erYthro-octon-2,4-dieneate (2.83) was produced in 31% y i e l d . . Hydrogenation of 283 over platinum oxide in acetic anhydride gave ethyl 4,7-anhydro-2-(B,S)-acetamidomethyl-6,8-di-O-benzoyl-2,3,5-trideoxy-4- (B,S)-p_-'erythro~i-D-octonate (2 84) . :Reaction of 2,3-0-isopropylidene-5-0-trityl-8 -D-rib o f uranosyl chloride (2J.0) with d i e t h y l sodium phthalimidomalonate i n K,N-dimethylformamide at 90° provided i n 46% overall y i e l d a 1:1 mixture of the a and 8 anomars of diet h y l 2,3-0-isopropylidane-5-0-trityl-D-ribofuranosyl phthalimidomalonate {287 and 288, respectively). An attempt to unblock 287 and 288 with hydrochloric acid was unsuccessful-Reaction of 2,4-di-t-butoxy-5-magnesiumbromopyrimidine (294) and acetone followed by treatment of the product with hydrochloric acid gave 5-{1-propen-2-yl) ur a c i l (296) i n 43% y i e l d . The di r e c t coupling of 294 with the glycosyl chloride 2_0 i n the presence of c a t a l y t i c iodo(phenyl)bis(triphanylphosphine) palladium (II) (298) was unsuccessful. I i i A d d i t i o n of 2, 2' -anhydro-1- { 3 - 0 _ - a c e t y l - 5 - 0 - t r i t y l - B -p_-a r a b i n o f u r a n o s y l ) u r a c i l (308) to excess 2 - l i t h i o ~ 1 , 3 - d i t h i a n e (126) i n t e t r a h y d r o f u r a n at -78<> gave 2 - { 1 , 3 - d i t h i a n-2-yl) - 1-^  (5-Q - t r i t y l - 8 -D-arabinof uranosyl)-4 {1 H)-pyriiaidinone (309) and 2,2 ,-anhydro-5,6-dihydro-6- (_}- ( 1 , 3 - d i t h i a a - 2 - y l ) - 1 - ( 5 - O - t r i t y l -3 - D - a r a b i n o f u r a n o s y l ) u r a c i l (310) i n y i e l d s of 15 and 30^, r e s p e c t i v e l y . Treatment of 309 with Raney n i c k e l gave 2-methyl-1 - ( 5 - G - t r i t y l - 3 - D - a r a b i n o f u r a n o s y l ) - 4 (1H)-pyrimidinone (3J3) while h y d r o l y s i s of 309 i n a c i d a f f o r d e d 2 - { 1 , 3 - d i t h i a n - 2 - y l ) - 4 -pyrimidinone (314) and arabinose. D e t r i t y l a t i o n of 309 without g l y c o s i d i c cleavage c o u l d only be e f f e c t e d by p r i o r a c e t y l a t i o n to 2 - ( 1 , 3 - d i t h i a n - 2 - y l ) - 1 - ( 2 , 3 - d i - O - a c e t y l - 5 - D - t r i t y l - 6 -D-ar a b i n o f u r a n o s y l ) - 4 ( 1 H ) - p y r i m i d i n o n e (3J5) which, a f t e r treatment with a c e t i c a c i d at room temperature f o l l o w e d by unblocking with sodium methoxide gave 2 - ( 1 , 3 - d i t h i a n-2-yl) - 1-3 -D - a r a b i a o f u r a n o s y l ) - 4 ( 1 H ) - p y r i m i d i n o n e (317) i n 45% y i e l d . H y d r o l y s i s of the d i t h i o a c e t a l moiety of 3_5 always l e d t o g l y c o s i d i c cleavage. Treatment of compound 310 with Ranay n i c k e l gave 41% o f 2 , 2 * - a n h y d r o - 5 , 6 - d i h y d r o - 6 - f i - r a e t h y 1 - 5 ' - 0 - t r i t y l u r i d i n e (318). D e t r i t y l a t i o n of 310 i n r e f l u x i n g a c e t i c a c i d provided 10 and 90% y i e l d s of 5,6-dihydro-6-(SJ - (1 , 3 - d i t h i a n - 2 - y l ) - 1 - 8 -D-ar a b i n o f u r a n o s y l u r a c i 1 (3.19) and 3-[ ( S ) - 1 - { 1 , 3 - d i t h i a n - 2 -yl) Ipropionamido- 3 -J)-ar abinof urano-[ 1' ,2* :4,5 ]-2-oxazolidone (320), r e s p e c t i v e l y . A c i d h y d r o l y s i s of 3_9 a f f o r d e d arabinose and 5,6-dihydro-6-(S)- ( 1 , 3 - d i t h i a n - 2 - y l ) u r a c i l (321). Haney n i c k e l treatment of 321 y i e l d e d the known 5,6-dihyd ro-6-m e t h y l u r a c i l (322). Whea 319 was allowed to stand i n water or i v methanol f o r 4 days, q u a n t i t a t i v e c o n v e r s i o n t o 320 occurred. Dehydration of 320 with t r i f l u o r o a c e t i c anhydride and p y r i d i n e a f f o r d e d 3-[ (S)-1- (1 , 3 - d i t h i a n - 2 - y 1) Jcyanoethyl- 3 - D -arabinofurano-[ 1',2':4,5]-2-oxazolidone (328) i n 77% y i e l d . S i m i l a r l y , 3-(_)-1-methylpropionamido-3 -D-arabinofurano-[ 1 * ,2%.z 4,5 ]-2-oxazolidone (329), obtained by Haney n i c k e l treatment of 320, gave 3-(R) - 1-methy.lcya noe t h y l - 3 - D -arabinofurano-[ 1•2 *;4,5]-2-oxazolidone (330). Treatment of 320 with excess p - n i t r o b e n z o y l c h l o r i d e i n p y r i d i n e y i e l d e d 3 - [ ( S ) -1 - ( 1 , 3 - d i t h i a n - 2 - y l ) ] c y a n o e t h y l - 3 ' , 5 ' - d i - 0 - p - n i t r o b e n z o y l - 3 -g-arabinofurano-[ 1 1,2*:4>5]-2-oxazolidone (333) which was converted by treatment with methyl i o d i d e i n dimethyl s u l f o x i d e to 3-<S)-1-formylcyanoethyl-3•,5'-di-O-p-nitrobenzoyl-3 -D-a r a b i n o f urano-[ 1' ,2*: 4, 5 ]-2-oxazolidone (335), c h a r a c t e r i z e d as i t s semicarbazone 336. an attempt to c y c l i z e 328 with ammonia f a i l e d . A d d i t i o n of 5-bromo-2',3'-0-isopropylidene-5»-0-trityl-u r i d i n e (340) i n p y r i d i n e to excess anion 1_26 i n t e t r a h y d r o f u r a n at -78° gave 5,6-dihydro-6-(fi)-(1,3-dithian-2-yl)-2»,3'-0-i s o p r o p y l i d e n e - 5 ' - 0 - t r i t y l u r i d i n e (3__), 5-(S)-bromo-5, 6-dihydro-6-(S) - (1,3-dithian-2-yl)-2»,3»-0-isopropylidene-5»-0-t r i t y l u r i d i n e (342) and i t s 5- (R) isomer 343 i n y i e l d s of 37, 35 and 10%, r e s p e c t i v e l y . D e s u l f u r i z a t i o n of 34__ with Raney n i c k e l a f f o r d e d 5,6-dihydro-2•,3*-0-isopropylidene-6-(S)-methyl-5*-0-t r i t y l u r i d i n e £346). Compound 341 was h y d r o l y z e d i n a c i d to g i v e r i b o s e and 5,6-dihydro-6-(B) - (1, 3 - d i t h i a n - 2 - y l ) u r a c i l (348) . Treatment of 342 with methyl i o d i d e i n aqueous acetone gave a 30% y i e l d of 5,6-dihydro-6-(R,S) - formy 1-2',3 * - O - i s o p r o p y l i dene— V 5'-0-tr.it y l u r i d i a e (349) , c h a r a c t e r i z e d as i t s semicarbazone 350. Both 342 and 343 gave 3__ upon b r i e f treatment with Raney n i c k e l . Both 342 and 343 gave 6-for my1-2*,3 1-O-isopropylidene-S ' - Q - t r i t y l u r i d i n e (351) i n approximately 4 1 % . y i e l d when t r e a t e d with methyl i o d i d e i n aqueous acetone c o n t a i n i n g 10% dimethyl s u l f o x i d e . A by-product, i d e n t i f i e d as 6-f ormyl-^2* ,3*-0-i s o p r o p y l i d e n e - 3 - m e t h y l - 5 , - 0 - t r i t y l u r i d i n e (353) was a l s o formed. Reduction of 351 with sodium borohydride i n e t h a n o l a f f o r d e d , a f t e r unblocking, 6-hydroxymethyluridine (356), c h a r a c t e r i z e d by i t s h y d r o l y s i s i n a c i d to the known 6-hyd r o x y m e t h y l u r a c i l (357). Knoevenagel condensation of a mixture of 351 and 353 with e t h y l cyanoacetate (263) y i e l d e d 38% of E-or Z-6-[(2-carboethoxy-2-cyano)ethylidene3~2»,3*-Q~ i s o p r o p y l i d e n e - 5 * - 0 - t r i t y l u r i d i n e (359)and 10% of i t s M-methyl d e r i v a t i v e 360. Hydrogeaation o f 359 over platinum oxide i n a c e t i c anhydride f o l l o w e d by unblocking gave 6-£ 3-amino-2-(R or SJ-carboxypropyl J u r i d i n e (363). ACKNOWLEDGEMENTS My s i n c e r e t h a n k s a r e e x t e n d e d t o Dr- A l e x R o s e n t h a l f o r h i s g u i d a n c e , s u g g e s t i o n s and e n c o u r a g e m e n t d u r i n g t h e c o u r s e o f t h i s r e s e a r c h . I a l s o w i s h t o t h a n k Dr. G-G.S- D u t t o n f o r h a v i n g r e a d p a r t s o f t h i s t h e s i s . The c o o p e r a t i o n and i n v a l u a b l e a s s i s t a n c e p r o v i d e d by D r - ' s B.L. C l i f f and K.C. D o o l e y and Mr. . J . K. Chow d u r i n g my p e r i o d a t 0 . B.C. a r e g r a t e f u l l y a c k n o w l e d g e d - , I t h a n k D r . A l e x a n d e r B l o c h o f R o s w e l l P a r k . M e m o r i a l I n s t i t u t e and t h e N a t i o n a l I n s t i t u t e o f H e a l t h f o r b i o l o g i c a l t e s t i n g o f s e v e r a l new compounds. As w e l l , I am i n d e b t e d t o P r o f . S i r Derek B a r t o n f o r work done on one o f my compounds. The f i n a n c i a l s u p p o r t o f C o n s o l i d a t e d - B a t h u r s t P a p e r C o r p . (1974-1976) and O g i l v i e F l o u r M i l l s L t d . (1977-1979) i s a c k n o w l e d g e d . v i i TABLE OF CONTENTS £ML_ I- „ j OBJECTIVE | - - - - . - - - . 1 -I I . '• INTRODUCTION ; . . . . . . . . . . . . . . . . . . . . . . . . . . ,..........,.,.3 1., Branched-Chain Sugars .................................3 1.1. S y n t h e s i s of Type A Sugars ...................... 4 1.2. Sy n t h e s i s o f Type B Sugars ...................... 6 1.3... S y n t h e s i s of G l y c o s y l Amino A c i d s ...............7 2. S y n t h e s i s of Amino A c i d s ..............................14 2.1- The Sorensen S y n t h e s i s of Amino Acids ........... 15 2.2- The Hydantoin S y n t h e s i s of Amino Acids ........... 17 2-3. The Knoevenagel Condensation: Access to & -Amino Acids .....................................20 3. 1, 3-Dithianes ................... . . .28 3.1. N u c l e o p h i l i c Reactions of the 1,3-.Dithiane Anion ...................................29 3.2. Conversion of 1,3-Dithianes to Carbonyls .......32 3.3. Reactions of 2 ~ L i t h i o - 1 , 3 - d i t h i a n e with Carbohydrates ...............................-..36 4. C-Nucleosides ........................................ 42 4.1 S y n t h e s i s o f C-Nucleosides and T h e i r Analogues ..44 5 . P a l l a d i u m - C a t a l y z e d S y n t h e s i s of Mo d i f i e d Nucleosides ..........................................49 5. 1. S y n t h e s i s of C-Nucleosides v i a Organopalladium I n t e r m e d i a t e s ...................................51 5.2. Synthesis of P y r i m i d i n e Nucleosides M o d i f i e d at C-5 Using Organopalladium I n t e r m e d i a t e s .....52 6. Modif i e d P y r i m i d i n e Bases and T h e i r Nucleosides ......52 6.1. I n t r o d u c t i o n of C-C Linked S u b s t i t u e n t s a t C-5 of U r a c i l D e r i v a t i v e s ........-......--.--.--.54 v i i i _ac_e 6.2. S y n t h e s i s of Base-Modified Pyrimidine Nucleosides .................................... 55 I I I . RESULTS AND DISCUSSION --.61 1. G l y c o s - 3 - y l Amino A c i d s : . S t r u c t u r a l Analogues of the Sugar Moiety of the P o l y o x i n s ....................62 1.1. S y n t h e s i s of D e r i v a t i v e s of G l y c o s - 3 - y l g-A l a n i n e : A p p l i c a t i o n of the Knoevenagel Condensation of E t h y l Cyanoacetate with a 3-Ulose ...-6 2 1.2. S y n t h e s i s of D e r i v a t i v e s of G l y c o s - 3 - y l G l y c i n e ; A p p l i c a t i o n o f t h e Bucherer Procedure via Condensation of 1,3-Dithiane Anion with a 3-Ulose -...75 2. S y n t h e t i c Approaches t o C-Nucleosides ................81 2.1. S y n t h e s i s o f F u n c t i o n a l i z e d P r e c u r s o r s t o C-Nu c l e o s i d e s ............................81 2.1.1. Knoevenagel Condensation of E t h y l Cyanoacetate with a 2,5-Anhydro-D-allose ...81 2.1.2., Condensation of D i e t h y l Sodium Phthalimidomalonate with a G l y c o s y l . Halide .....87 2.2. S y n t h e s i s of 5 - A l k y l U r a c i l . Attempted One-Step S y n t h e s i s of a Pseudouridine D e r i v a t i v e .........91 3., M o d i f i c a t i o n s of the 2- and 6- P o s i t i o n s of U r i d i n e Using 1,3-Dithiane Anion ............................. 96 3.1. Reaction o f 1,3-Dithiane Anion with a 2,2-Anhydronucleoside: F u n c t i o n a l i z a t i o n of the 2- and 6- P o s i t i o n s of P y r i m i d i n e Nucleosides ...............98 3.2. Reaction of 1,3-Dithiane Anion with Blocked 5-Bromouridine: S y n t h e s i s of a 6-g-Alanine D e r i v a t i v e of U r i d i n e ............................... 128 IV. BIOLOGICAL ASSAY 152_ V. EXPERIMENTAL 153 1. General Methods -....153 2. Chromatography 153 2.1. Column Chromatography ......................... 153 I! i x p_a_e 2.2. T h i n Layer Chromatography , 154 3. A b b r e v i a t i o n s .......................................154 4 . S y n t h e s i s of Glycos-3-yl Amino Acids ................ 154 1 ,2 : 5,6-Di-O-isopropy l i d e n e - a - D - r i b o - hexof uranos- 3-uiose r , . . . . . . . . . . . . . . . . - , , r . . r . , . . . . . . . . . . . . . . . 1 5 4 3-C-[ (R,S)-Cyano (ethoxycarb onyl) methylene,]-1, 2: 5, 6-d i - O - i s o p r o p y l i d e n e - a - D - a l l o f u r a n o s e (264) .......... 155 3,3-C-Bis[ (RS ,SS,RS) -cyano (ethoxycarbonyl) methyl J-3-deoxy-1,2:5,6-di-O-isopropylidene-a-D-a l l o f u r a n o s e (266) 156 3-C-[ (R, S) -Cyano (ethoxycarbonyl) methylene ]-3-deoxy-1,2: 5,6-di-O-isopropylidene-a-D-allofuranose (268) ., 156 3-C-[(R,S)-Acetamidomethyl (ethoxycarbonyl) methylene ]-1 ,2:5,6-d i - O - i s o p r o p y l i d e n e - a - D - a l l o f u r a n o s e (270) .......... 157 3-C-[ (R, S)-Cyano(ethoxycarbonyl) methylene]- 3-deoxy-1 ,2: 5,6-di-0-isopropylidene-a-D-lervthrO|-hex- 3-enof uranose {27 3) ............. ..............158 2- L i t h i o - 1 , 3 - D i t h i a n e (126) ...... .....159 3- C- (1,3-Dithian-2-yl) -1,2: 5, 6-di-0-isopropylidene-ct-D-a l l o f uranose (V76) ...,-..,.»,.......... - .-..---.15 9 3-C-Formyl-1,2:5,6-di-O-isopropylidene-a-D-a l l o f u r a n o s e (278) and i t s Semicarbazone 279 ........159 3-C- (2,4-Diketotetrahydroimidazol-5- (_,S)-yl) -1,2:5,6-di-g-isopropylidene-a-D-allofuranose (280) -.160 D- and L-2-(1, 2: 5, 6-Di-g-isopropylidene-a-D-a l l o f u r a n o s - 3 - y l ) g l y c i n e (281) ..-,-..-.-......-,,....161 5. , S y n t h e s i s of P r e c u r s o r s to C-Nucleosides ............ 162 2,5-Anhydro-3,4,6-tri-g-benzoyl-D-allose (203) ... 162 X E t h y l (E or Z)-4,7-anhydro-2-cyano-2,3,5-trideoxy-6,8 - di-O- be n zo y 1-D-fer^thro-octon-2,4-dieneate (283) -..-.163 E t h y l 4, 7-anhydro-2-(R, S) -acetamidomethyif 6,8-di-Q-benzoyl- 2, 3, 5-trideoxy-4- <R, S) -D-'.erythrg ,-D-octonate <284) .. .r..-.. . ^ r . ^ r i - . - i .......... 164 2 , 3 - O - I s o p r o p y l i d e n e - 5 - 0 - t r i t y l - B - f i - r i b o f u r a n o s y l c h l o r i d e (2J.0) ................... ................ 164 D i e t h y l sodium phthalimidomalonate {__) ......----...165 D i e t h y l 2 , 3 - _ - i s o p r o p y l i d e n e - 5 - g - t r i t y l - a - ( a n d 6 )-D - r i b o f u r a n o s y l phthalimidomalonate < 287 and 288) ...165 Attempted Unblocking of 287 and 288 ....166 6. Attempted S y n t h e s i s of C-Nucleosides Using a Palladium C a t a l y s t .................................. 167 5-Bromo-2,4-dichloropyrimidine (291) 167 5-Bromo-2,4-di-t-butoxypyrimidine (292) ............. 167 2,4-Di-t-butoxy-5-magnesiumbromopyrimidine (294) .-..168 5- (1-Propen-2-yl) u r a c i l (296) .. 168 lodo (phenyl) b i s (triphenylphosphine) palladium (II) (298) ........ ............ ..,.169 Attempted Palladium (II) - C a t a l y z e d Coupling of 2.10 and 294 ................................. -. 169 7. / S y n t h e s i s of 6-S u b s t i t u t e d N u c l e o s i d e s ..............170 2, 2'-Anhydro- 1- ( 5 - 0 - t r i t y l - B-fi-arabino-f u r a n o s y l ) u r a c i l (3 07) 170 2,2»-Anhydro-1-{3-g-acetyl-5-0-trity1-g-fi-a r a b i n o f u r a n o s y l ) u r a c i l (308) 170 2 - ( 1 , 3 - D i t h i a n - 2 - y l ) - 1 - ( 5 - 0 - t r i t y l - e-Jj-a r a b i n o f uranosyl)-4 (1 H)-pyrimidinone (309) ...,....,. 171 2,2' -ftnhydro-5,6-dihydro-6- (S) - (1, 3 - d i t h i a a - 2 - y l ) -1- { 5 - 0 - t r i t y l - 3 - D - a r a b i n o f urano;syll) u r a c i l (310) ...... 171 2 - M e t h y l - 1 - ( 5 - 0 - t r i t y l - e - D - a r a b i n o f u r a n o s y l ) - 4 ( 1 H ) -pyrimidinone (3 13) ..,...,.,.,,.,..,.......,..,...,,.172 Ac i d H y d r o l y s i s of 309 to Give Arabinose, 2-(1,3-D i t h i a n - 2 - y l ) - 4 - p y r i m i d i n o n e (111) and T r i p h e n y l c a r b i n o l ..................,......,..,.,.,,.173 2- (1,3-Dithian-2-yl)-1-(2,3-di-O-ace t y l - 5 ~ 0 - t r i t y l -g-D-arabinof uranosyl) -4 (1 H) -pyrimidinone (3_5) 17.4 2-{ 1 , 3 - D i t h i a n - 2 - y l ) - 1 - ( 2 , 3 - d i - _ - a c e t y l - 3 - D -a r a b i n o f uranosyl)-4 (1fl)-pyrimidinone (316) -. ..174 2-( 1, 3 - D i t h i a n - 2 - y l ) - 1 - 3 - D - a r a b i n o f u r a n o s y l - 4 {IH) -pyrimidinone (317) .,,...,.,.,,....,.,..........,....175 Attempted H y d r o l y s i s of the D i t h i o a c e t a l of Compound 3_5 ........................................176 2 ,2 •-Anhydro-5, 6-dihydro-6- (fi)— methyl- 5 *-0-t r i t y l u r i d i n e (3J8) .. -176 5,6-Dihydro-6-(S) -(1, 3 - d i t h i a n - 2 - y l ) -1-3-D-a r a b i n o f u r a n o s y l u r a c i l (3J9) ...............-.--..--.177 3~[- (S)- 1- (1, 3-Dithian-2-yl) jpropionamido- 3-D-a r a b i n o f urano-[ 1 *,2': 4, 5]-2-oxazolidone (_20) ------ .- 177 A c i d H y d r o l y s i s of 319 to Give Arabinose and 5,6-Dihydro-6-(S)-(1, 3 - d i t h i a n - 2 - y l ) u r a c i l {321) ........179 5,6-Dihydro-6-methyluracil |322) . -179 3-[ (S)-1-(1,3-Dithian-2-yl) ]propionamido-3»,5«-di-0 - t - b u t y l d i m e t h y l s i l y l - 3 ~ D -a r a b i n o f urano-[ 1' , 2': 4, 5]- 2-oxazolido:ne (323) ..... ..180 Conversion of 319 to the Oxazolidone 320 181 3-[ CS)-1-{1, 3-Dithian-2-yl) jcyanoethy 1-e-D-ara b i n o f urano-[ 1 • ,2* :4,5 ]-2-oxazolidone (328) - - 18 1 3-{R) -1-Methylpropionamido-B-D-a r a b i n o f urano-[ 1 • ,2* z 4 ,5]-2-oxazolidone (329) -..-,.. 182 3~{R) -1-Methylcyanoethy 1-8-D-arabinofurano-[ 1' ,2 •: 4,5 3~2-oxazolidone (330) ....... 18 3'-: 3-<R) -1-Methy lacetamidopropy1-B-D-arabinofurano-[ 1' ,2':4,5]-2-oxazolidone (331) ....... 18 3 Attempted D e t r i t y l a t i o n o f 3_1_ t o Give 2,2'-An h y d r o - 5 , 6 - d i h y d r o - 6 - ( S ) - { 1 , 3 - d i t h i a n - 2 - y l ) u r i d i n e (332) ,...185 D e t r i t y l a t i o n of Compound 31.8 to Give 329 ... ,..,. 186 3-[ (S) -1-{1,3-Dithian-2-yl) ]cyanoethy1-3«,5'-di-O-p-nitrobenzoyl-8-D-ar abinof urano-r.1 *,2':4,5 J-2-oxazolidone (333) ...,,,.,,,.,.,...,.,...,.,....-.,-.187 Conversion of| Compound) 333. t o Compound 328 ........... 187 3-(R) -1-Methylcyanoethyl-3',5 * - d i - O - p - n i t r o b e n z o y l -B-D-arabinofurano-C 1' ,2 J: 4 ,5 ]-2-oxazol.idone (334) 188 Conversion of Compound 323 t o Compound 320 .......... 189 Un s u c c e s s f u l Attempts a t H y d r o l y s i s of the D i t h i o a c e t a l o f 333 -,-190 3- { S )-1-Formylcyanoethyl-3 *,5 »-di-0-p-nitrobenzoyl-B-D-arabinof urano-[ 1 * , 2*: 4, 5 ]-2-oxazolidone (335) ...191 Attempted S y n t h e s i s of 5, 6-Dihydro-6-( 1, 3 - d i t h i a n -2-yl) c y t i d i n e <3_12) .......................'192 5 - B r o m o - 2 , # 3 , - g - i s o p r o p y l i d e n e u r i d i n e (339) ...,.,... 192 5 - B r o m o - 2 ' , 3 * - g - i s o p r o p y l i d e n e - 5 * - O - t r i t y l u r i d i n e (340) ., ,. 193 x i i i 5,6-Dihydro-6- (R) - {1, 3-dith i a n - 2 - y l ) -2', 3»-0-i s o p r o p y l I d e n e - 5 ' - g - t r i t y l u r i d i n e (34_) .,..,-..-.-...193 5- <S)-Bromo-5,6-dihydro-6- (S) - ( 1 , 3 - d i t h i a n - 2 - y l ) -2 S 3 , - 0 - i s o p r o p y l i d e n e - 5 , - D - t r i t y l u r . i d i . n e (342) .....193 5-(R) -Bromo-5,6-dihydro~6- (S) - {1, 3-dithian-2-yl)-2* , 3 ' - 0 - i s o p r o p y l i d e n e - 5 , - g - t r i t y l u r i d i a e {343) .....19& 5,6-Dihydro-2 *, 3*-0-isopropylidene-6- (S) -methyl-5'-g - t r i t y l u r i d i n e (346) -196 5,6~Dihydro-6-(R)-(1, 3-dithian-2-yl) u r i d i n e (347) ... 197 5,6-Dihydro-6-(R)-(1,3-dithian-2-yl) u r a c i l (348) .. ..19;8 5,6-Dihydro-6-(R,S)-forinyl-2*,3»-0-isopropylidene-5 ' - O - t r i t y l u r i d i n e (349) and i t s Semicarbazone 350 ..198 Debromination of Compound 342 to Give Compound 341_ ..199 Debromination of Compound 343 to Give Compound 34_ -.200 6-Formyl-2',3 » - o - i s o p r o p y l i d e n e - 5 ' - 0 - t r i t y l u r i d i n e (35_) and i t s Semicarbazone 352 .....................200 6-Formyl-2*,3'-O-isopropylidene-3-methyl-5'-Q-t r i t y l u r i d i n e (353) and i t s Semicarbazone 354 .......200 Compounds 351 and 353 from Compound 343 .............202 6-Hydroxymethyl-23'-O-isopropylidene-5'-0-t r i t y l u r i d i n e (355) .................... . ..202 6-Hydroxymethyluridine 3^56) .203 6-Hydroxymethyluracil (357) .........................204 Attempted S y n t h e s i s of 6-(2,4-Dik.etotetrahydroimidazol-5-yl)-2 • ,3'—0-iso p r o p y l i d e n e - 5 • - g - t r i t y l u r i d i n e (358) ............. 205 xiv page E- or z-6-[ (2-Carboathoxy-2-cyano) e t h y l i d e n e ]-2 ' , 3 » - g - i s o p r o p y l i d e n e - 5 ' - 0 - t r i t y l u r i d i n e (359) --.-.205 E- or Z-6-[ (2-Carboethoxy-2-cyano) e t h y l i d e n e ]-2', 3«-O-isopropylidene-3-methyl-5'-O-trityluridine (360) 205 6-[(2-{R or S)-Carboethoxy-2-acetamidomethy 1) e t h y l -2 , , 3 , - 0 - i s o p r o p y l i d e n e - 5 , - 3 - t r i t y l u r i d i n e (361) -....207 6-[ (2- (R or S) -Carboethoxy-2-acetamidomethyl) e t h y l ] u r i d i n e (362) ....... ...........208 6-[3-Amino-2-(R or S ) - c a r b o x y p r o p y l j u r i d i n e (363) ...208 V. BIBLIOGRAPHY .....,........,,.......,-..........--..-.-210 X V LIST OF FIGURES Figu r e Pa_e I. N a t u r a l l y - O c c u r r i n g C-Nucleosides ....... 43 I I . P a r t i a l 100 MHz PMR Spectrum of 3-C-[{B,S)-Cyano(ethoxycarbonyl) methylene]-1 ,225 ,6-di-O-i s o p r o p y l i d e n e - a - D - a l l o f u r a n o s e (264) i n CDCl^ .....64 I I I - P a r t i a l 100 KHz PMR Spectrum of 3-C-[(R,SJ-Cyano (ethoxycarbonyl) methylene]-3-deoxy-1 , 2 : 5 , 6 - d i - 0 - i s o p r o p y l i d e n e - a - D - a l l o f u r a n o s e (268) i n CDCl 3 . . . . . . . . . . . . . . . 7 . . . ---65 IV. , P a r t i a l 100 MHz PMR Spectrum of 3-C-[ (R,S)~ Cyano (ethoxycarbonyl) me thylene ]-3-deoxy-1,2:5,6-di-0-isopropyl!dene-a-D-ert hr y o-hex-3-enofuranose (273) i n Benzene-dg .....,...,.,.....,..73 V. P a r t i a l 100 MHz PMR Spectrum of 3-C- (2,4-D i k e t o t e t r a h y d r o i m i d a z o l - 5 - (_,S)- yl)-1,2:5,6-d i - O - i s o p r o p y l i d e n e - a - D - a l l o f u r a n o s e (280) i n DMSO-d& ......78 VI. P a r t i a l 100 MHz PMR Spectrum of E t h y l (E or Z) - 4, 7- a nhydro-2-cyano- 2,3, 5-1rIdeoxy- 6,8-d i -O-benzoyl -D-je r y th r o-octon-2,4-dieneate | (283) i n C DC 1 ^  mm >• * • • m m m'm • m m m • «* m • m- m m mm'm m m • m m mm m m m m m m. •» -m w 83 VI I . 60 MHz PMR Spectrum of D i e t h y l 2,3-0-i s o p r o p y l i d e n e - 5 - 0 - t r i t y l - a - (and 8 )-D-r i b o f u r a n o s y l phthalimidomalonate (287 and 288) i n CDCI3 ..,.,..,,...,,.,.....,--,--,..,-,-.,,-86 V I I I . P a r t i a l 100 MHz PMR Spectrum of 5-(1-Propen-2-y l ) u r a c i l (296) i n DMSO-d^ -. -93 IX. P a r t i a l 100 MHz PMR Spectrum, of 2-(1,3-D i t h i a n - 2 - y l ) - 1 - B - D - a r a b i n o f uranosyl-4 (1H)-pyrimidinone (317) i n DMSO-d^ .....................104 X. P a r t i a l 100 MHz PMR Spectrum of 2,2'-Anhydro-5 , 6 - d i h y d r o - 6 - _ - m e t h y l - 5 * - 0 - t r i t y l u r i d i n e (31.8) i n DMSO-d6 .............. .................108 XI. P a r t i a l 100 MHz PMR Spectrum of 5,6-Dihydro-6-(S) - { 1 , 3 - d i t h i a n - 2 - y l ) - 1 - B-D-ar a b i n o f urano-[ 1 ' ,2* ; 4 ,5 ]-2-oxazolidone (320) i n DMSO-d6 .... .... -.110 XII. P a r t i a l 100 MHz PMR Spectrum of 3-[ (S) - 1- (1 ,3-D i t h i a n - 2 - y l ) ]propionamido- B-D-ar a b i n o f urano-[ 1' , 2* : 4, 5 ]-2-oxazolidone (320) x v i F i g u r e Pacje X I I I . P a r t i a l 100 MHz PME Spectrum of 5-(S)-Bromo-5,6-dihydro-6- (S) - (1, 3 - d i t t i i a n - 2 - y l ) - 2 ' , 3'-0-isopropylidene-5»-o-trityluridiae (342) i n CDC1 3 ................. - 130 XIV. P a r t i a l 100 MHz PMR Spectrum of 5-(_)-Bromo-5,6-dihydro-6- (S) - (1, 3-dithian-2-y 1)-2' ,3'-0-i s o p r o p y l i d e n e - 5 * - O - t r i t y l u r i d i n e (3U3) i n CDC1 3 . . 131 XV. H a l f - C h a i r Conformation o f Dihydropyrimidine Rings ............................................. 135 XVI. The 5 , 6 - D i a x i a l R e l a t i o n s h i p of the D i t h a i n y l and Bromo S u b s t i t u e n t s of Compound 342 ............ 135 XVII. P a r t i a l 100 MHz PMR Spectrum of E-(or Z)-6-[ (2-Carboethoxy-2-cyano) e t h y l i d e n e j-2*,3>-0-i s o p r o p y l i d e n e - 5 * - 0 - t r i t y l u r i d i n e (359) i n 1 I. .OBJECTIVE I t has been r e p e a t e d l y shown i n the past two decades t h a t v a r i o u s analogues of the common n a t u r a l l y - o c c u r r i n g n u c l e o s i d e s e x h i b i t a wide range of b i o l o g i c a l p r o p e r t i e s - These m o d i f i e d n u c l e o s i d e s , o b t a i n e d e i t h e r from n a t u r a l sources or by s y n t h e t i c means, have o f t e n been found t o be a n t i f u n g a l , a n t i b i o t i c , a n t i v i r a l or antitumour i n t h e i r a c t i o n -Three c l a s s e s of modified n u c l e o s i d e s can be d i s t i n g u i s h e d ; ( 1 ) n u c l e o s i d e s i n which the r i b o s y l p o r t i o n i s a l t e r e d by the i n c o r p o r a t i o n of v a r i o u s groups, (2) C - n u c l e o s i d e s , i n which a py r i m i d i n e or purine base i s l i n k e d to the sugar moiety by a carbon-carbon r a t h e r than a carbon-nitrogen bond, and (3) base-modified n u c l e o s i d e s , i n which the common purine or pyrim i d i n e moiety has been a l t e r e d . Moreover, a f e a t u r e common to many of the n a t u r a l l y - o c c u r r i n g b i o l o g i c a l l y - a c t i v e n u c l e o s i d e analogues i s the presence of an amino a c i d , u s u a l l y ^ l i n k e d by a p e p t i d y l bond to the sugar moiety- Thus, puromycin (an a n t i b i o t i c ) and the p o l y o x i n s ( f u n g i c i d e s ) i n c o r p o r a t e an a -amino a c i d while b l a s t i c i d i n S possesses a 3 -amino a c i d component. The o b j e c t i v e of the work d e s c r i b e d i n t h i s t h e s i s i s t o develop g e n e r a l methods of a t t a c h i n g a - or 3.-amino a c i d s t o nu c l e o s i d e s or n u c l e o s i d e p r e c u r s o r s by carbon-carbon bonds. I n the f i r s t p a r t of t h i s work, the s y n t h e s i s of a 3-C-3 - a l a n y l d e r i v a t i v e of D-glucose by way of a Knoevenagel condensation of e t h y l cyanoacetate with a 3-ketose was s t u d i e d . , fin a l t e r n a t e method of making 3 - C - g l y c y l a l l o f u r a n o s e u s i n g the Bucherer hydantoin procedure was a l s o achieved. The second p a r t o f t h i s t h e s i s i s concerned with the 2 e s y n t h e s i s of f u n c t i o n a l i z e d p r e c u r s o r s t o C - n u c l e o s i d e s . Th p r e c u r s o r s e n v i s i o n e d were the C - g l y c o s y l amino a c i d d e r i v a t i v e s , the amino and c a r b o x y l i c groups of the amino a c i d being p o t e n t i a l l y amenable to f u r t h e r d e r i v a t i z a t i o a . ,The two routes employed f o r t h e s y n t h e s i s o f such p r e c u r s o r s were the condensation of e t h y l cyanoacetate with.a 2,5-anhydro-D-allose d e r i v a t i v e and r e a c t i o n of the anion of d i e t h y l phthalimidomalonate with a r i b o s y l c h l o r i d e d e r i v a t i v e . A one-step s y n t h e s i s of a C - n u c l e o s i d e using a palladium c a t a l y s t was a l s o attempted. In the t h i r d part of t h i s t h e s i s , the r e a c t i o n of 1,3-d i t h i a n e anion with u r i d i n e d e r i v a t i v e s was i n v e s t i g a t e d with a view t o modifying the p y r i m i d i n e moiety of n u c l e o s i d e s . A general method of i n t r o d u c i n g s u b s t i t u e n t s , i n c l u d i n g 3 -a l a n i n e , at C-6 of u r i d i n e was thus developed and some o f the r e s u l t i n g analogues were evaluated f o r b i o l o g i c a l a c t i v i t y . , 3 I I . INTRODUCTION 1. Branched-Chain Sugars A branched — ch a i n sugar i s a carbohydrate i n which a hydrogen or h y d r o x y l group i s r e p l a c e d by an o r g a n i c group through a carbon-carbon bond thereby g i v i n g r i s e to branching of the carbohydrate s k e l e t o n . The f i r s t such branched-chain sugar, apiose Q ) was i s o l a t e d from p a r s l e y by V o n g e r i c h t e n 1 i n 190 1 but i t s s t r u c t u r e was only e l u c i d a t e d t h i r t y y e a rs l a t e r by 0. Th. Schmidt. 2 A second branched-chain sugar, hamamelose 3, was dis c o v e r e d i n the h y d r o l y s a t e of the tannin of Hamamelis v i r g i n i a n a by F i s c h e r and Freudenberg i n ' 1912 : and i t s s t r u c t u r e was l a t e r shown to be 2-C-hydroxymethyl-D-ribose 4(2). I n t e r e s t i n these anomalous sugars l a y dormant u n t i l branched-chain sugars were d i s c o v e r e d to be v i t a l g l y c o s i d i c components 5 i n the s t r u c t u r e of a n t i b i o t i c s . * - 1 1 For i n s t a n c e , s t r e p t o s e 1 2 ( 3 ) was found as a c o n s t i t u e n t of streptomycin. Branched-chain sugars have now been i s o l a t e d from higher p l a n t s 1 3 - 1 4 from c e l l wall p o l y s a c c h a r i d e s 1 * - 1 5 and even from man. 1 6 However, the d i s c o v e r y that n u c l e o s i d e s of branched-chain sugars can have c y t o s t a t i c and v i r o s t a t i c a c t i v i t y has s t i m u l a t e d i n t e r e s t i n the s y n t h e s i s of such c o m p o u n d s . 1 7 - 1 9 H0-•0H VCH20H OH OH 1 HOH^ OH OH 2 H3C -0 VCHO OH OH OH 3 Branched-chain sugars have been d i v i d e d i n t o two c l a s s e s . 2 0 Those i n which branching occurs by s u b s t i t u t i o n of a carbon-4 l i n k e d hydrogen by a group fi belong t o the Type A c l a s s i f i c a t i o n while s u b s t i t u t i o n of a hydroxyl group by E gives r i s e to Type B. The l a t t e r are o f t e n r e f e r r e d to as "deoxy" sugars. Both D-a p i o s e 2 1 (1) and D-haniamelose 2o (2) are examples of Type A sugars. Type B sugars are e x e m p l i f i e d by L - e v e r n i t r o s e 2 2 - 2 3 (4) . The s y n t h e s i s of branched-chain sugars has been the s u b j e c t of s e v e r a l r e v i e w s 7 - 8 2 4 and so the f o l l o w i n g d i s c u s s i o n w i l l summarize the more important methods of s y n t h e s i z i n g Type A, Type B, and the more s p e c i a l i z e d g l y c o s y l amino a c i d sugars. The use of 1 , 3 - d i t h i a n e s to c o n s t r u c t branched-chains w i l l be d i s c u s s e d i n a separate s e c t i o n (see S e c t i o n 3.3). i 1. 1 Synthesis of Type A Sugars iE-C-gH_. Keto s u g a r s 8 2 5 have been w i d e l y used as s t a r t i n g m a t e r i a l f o r the s y n t h e s i s of Type A carbohydrates. For i n s t a n c e , a d d i t i o n of diazomethane t o a keto sugar r e s u l t s i n the formation of an epoxide 5 which can be reduced to the C-raethyl compound 6, hydrolyzed to the C-hydroxymethyl compound (7) or converted by ammonolysis to the C-aminomethy1 compound (8). 2 6 - 2 7 A d d i t i o n of o r g a n o l i t h i u m and organomagnesium reagents to keto sugars can occur i n a s t e r i c a l l y complementary manner, as was shown f o r the 2-ketose 9. Reaction of 9 with o r g a n o l i t h i u m compounds gave the L - r i b o branched — c h a i n sugar (10) whereas organomagnesium reagents a f f o r d e d mainly the L-arabino sugars 5 C=0 ' 0 OH' J^IH, HOCCH. •> HOCCH,OH 7 I 2 HOCCH 2NH 2 8 I { I D - 2 8 However, changing the b l o c k i n g groups of the r e a c t i n g keto sugar has been shown to i n f l u e n c e the s t e r e o s e l e c t i v i t y of these r e a c t i o n s - 2 9 4Q \9 HO/ OCH, O C H . , OH 10 11 The b a s e - c a t a l y z e d condensation of nitromethane with keto sugars y i e l d s branched-chain n i t r o m e t h y l d e r i v a t i v e s , 3 0 - 3 2 the n i t r o group of which can be reduced to give aminomethyl sugars of Type A. The n i t r o m e t h y l group of _ 2 has a l s o been o x i d i z e d with potassium permanganate to the 3 - a l d e h y d e 3 3 (13) , an analogue of s t r e p t o s e (3)- Again, the type of b l o c k i n g groups X Xo°I] C H2 N 02 / Q OH 6-J— 12 \CH0_ OH O-j— 13 used on the keto sugar a f f e c t s the s t e r e o c h e m i c a l course of nitromethane a d d i t i o n - 3 2 Other methods which have been employed to s y n t h e s i z e Type A sugars from ketoses have i n c l u d e d the n u c l e o p h i l i c a d d i t i o n of C-methyl groups using dimethylsulfoxonium m e t h y l i d e 3 * and condensation with sodium c y a n i d e 3 5 and a c e t o n i t r i l e 3 6 to g i v e cyano and cyanomethyl compounds r e s p e c t i v e l y - A l s o , 6 photoamidation of a d i s u b s t i t u t e d 3-enofuranose a f f o r d s the 3-C-carbamoyl d e r i v a t i v e . 3 7 i 1-2 Synt h e s i s of „ D _ B Sugars _(R-C-H)_. A p p l i c a t i o n of the W i t t i g , r e a c t i o n t o keto sugars has allowed ready access to f u n c t i o a a l i z e d branched-chain sugars o f Type B. 3 8 - 4 4 I t was f i r s t employed by Rose n t h a l and Nguyen 3 8 who r e a c t e d the 3~ketose _ 4 with methyl dimethoxypho'sphonoacetate and potassium t e r t - b u t o x i d e to g i v e the c i s and t r a n s branched-c h a i n sugars 1 5 and _ 6 . C a t a l y t i c r e d u c t i o n o f t h i s mixture gave e x c l u s i v e l y the a l i o raethoxycarbonylmethyl branched-chain sugar 1 7 . 1 R 1 CH 2C0 2Me 1_ 15. R=C0,Me; R = H 17 16. R=H: R=C02Me The W i t t i g r e a c t i o n has al s o been used t o s y n t h e s i z e Type A sugars not a v a i l a b l e by the methods p r e v i o u s l y d i s c u s s e d . Thus, whereas r e a c t i o n of ketose _8 with .methylmagnesium i o d i d e gave the L - r i b o branched-chain sugar 1_9,4 5 treatment with triphenylmethylenephosphorane and then with mercuric a c e t a t e and sodium borohydride gave the L-arabino analogue of _ 9 (20).** Type B sugars can a l s o be obtained by the a d d i t i o n of n u c l e o p h i l e s t o anhydro s u g a r s . 4 7 - 4 9 T r a n s - d i a x i a l opening o f the epoxide i s g e n e r a l l y observed. * a ~ 5 0 As an example, r e a c t i o n of the 2 , 3-anhydro sugar 2_ with s o d i o d i e t h y l malonate gave the 2-C-branched-chain sugar 22 which.could be reduced with l i t h i u m 0 20 aluminum hydride t o provide the hydroxyathyl d e r i v a t i v e ( 2 3 ) S 1 . Unsaturated sugars have found use as p r e c u r s o r s t o "deoxy 1 1 branched-chain carbohydrates by way of the oxo r e a c t i o n ; the a p p l i c a t i o n of which t o carbohydrates has been reviewed by R o s e n t h a l . 5 2 The r e a c t i o n allows i n t r o d u c t i o n of a formyl group at one end of the unsaturated bond. 5 3 A l s o , unsaturated sugars undergo photoamidation r e a c t i o n s by which a carbamoyl branched-c h a i n can be added. Thus, i r r a d i a t i o n of a s o l u t i o n of the g l y c a l 24 i n formamide gave the C-2 a d d i t i o n product 25 together with products a r i s i n g from photoamidation at C - 1 . s * 21 22 R = C ( C 0 2 M e ) 2 23 R = C H 2 C H 2 O H A c O C 0 N H 2 Ik 25 1.3 Syn t h e s i s of G l y c o s y l * Amino A c i d s . •Used i n the extended sense. 8 1-3. 1 "-_____ ______ The importance of n u c l e o s i d e s as components of many a n t i b i o t i c s has been a c k n o w l e d g e d . 1 7 - 1 9 In p a r t i c u l a r , n u c l e o s i d e s having peptide l i n k a g e s and amino a c i d groups attached to t h e i r carbohydrate m o i e t i e s have evinced a n t i b i o t i c p r o p e r t i e s . Among the n a t u r a l l y o c c u r r i n g compounds of t h i s type are b l a s t i c i d i n S {2.6), gougerotin (27), puromycin (28) and the pol y o x i n s (29); a l l except the l a t t e r i n h i b i t p r o t e i n s y n t h e s i s 1 9 . The p o l y o x i n s , of which t h e r e a r e twelve v a r i a t i o n s and whose s t r u c t u r e s were e l u c i d a t e d by I s o n o 5 5 , are mainly a n t i f u n g a l i n t h e i r a c t i o n and have been used t o c o n t r o l sheath b l i g h t i n r i c e p l a n t s . The p o l y o x i n s have a l s o shown e f f e c t i v e n e s s i n i n h i b i t i n g tobacco mosaic v i r u s . 5 6 They have no a c t i v i t y towards animals, f i s h or p l a n t s . , The mode of a c t i o n of the p o l y o x i n s probably i n v o l v e s i n h i b i t i o n of glucosamine u p t a k e 5 7 t h e r e b y 5 8 i n t e r f e r i n g with c e l l - w a l l c h i t i n b i o s y n t h e s i s . 1 a a Whereas the chemical s y n t h e s i s of analogues of b l a s t i c i d i n s (__)t gougerotin (27) and puromycin (28) i n v o l v e s attachment of an amino a c i d f u n c t i o n a l i t y t o a carbohydrate through a n i t r o g e n a t o m 5 9 - 6 4 , the sugar components of the p o l y o x i n s are l i n k e d d i r e c t l y t o the a - c a r b o n o f the amino a c i d . Such u n i t s are r e f e r r e d to s p e c i f i c a l l y as g l y c o s y l amino a c i d s . . Most syntheses of g l y c o s y l amino a c i d s r e p o r t e d t o date have u t i l i z e d the displacement of a m e t h a n e s u l f o n y l o x y 6 5 - 6 7 or a t o l u e n e s u l f o n y l o x y 6 * - 7 0 group with sodium a z i d e f o l l o w e d by red u c t i o n of the r e s u l t i n g a z i d e t o the amine. Thus, i n the f i r s t r e p o r t e d s y n t h e s i s of an analogue of a po l y o x i n sugar 9 HOO 0=C-NH CHNH 2 CH 2-N-C-NH 2 CH, Blasticidin S (26.) o=c CH 2NHCH 3 Gougerotin (22) OCH, HOCH OH OH £H2OCONH2 R^CH^H.CO^.CHJ.H R2=OH. S=<^N RjOH.H C 0 2H \ Polyoxin Complex • i . (29) ' moiety, Naka and c o - w o r k e r s 6 S used the az i d e displacement of the Puromycin (28) 1 5 - s u l f o n y l o x y group of the hexofuranose 30 which a f t e r c a t a l y t i c r e d u c t i o n of the azide f o l l o w e d by permanganate o x i d a t i o n of the unblocked 6-hydroxyl a l l o f u r a n u r o n i c a c i d 31. group gave the 5-amino-5-deoxy T r 0 - i hOMs. C02Me B z HN — I I OBz 0-f-30 OBz 0-f-31 & s i m i l a r route beginning with the u r i d i n e analogue of 3 0 was used by Emoto 6 7 to c o n s t r u c t the b a s i c p o l y o x i n s k e l e t o n . The l a t t e r was a l s o obtained by Mo f f a t t and c o - w o r k e r s 6 6 who .st a r t e d wit hi the 5'-aldehyde j (32) the r e a c t i o n of which with 10 sodium cyanide i n aqueous methanolic potassium carbonate and hydrogen peroxide y i e l d e d the e p i m e r i c C-5 hydroxy amides 33 and 3_. Mesylation of the f r e e h y d r o x y l group of 33 f o l l o w e d by a z i d e displacement of the s u l f o n a t e , h y d r o l y s i s of the amide and r e d u c t i o n of the a z i d e gave the p o l y o x i n analogue 35. 32 33 R=H;R=OH 35 3_ R=0HiR=H The s y n t h e s i s of g l y c o s y l amino a c i d s with branching a t C-3 has been pursued mainly by Rosenthal and c o w o r k e r s . 6 8 - 7 * Beginning with the a , 3 - d i h y d r o x y e s t e r 36, obtained by permanganate or osmium t e t r a o x i d e o x i d a t i o n of the double-bond of _6, , monotosylation of the e x o c y c l i c hydroxyl group was achieved whence c o n v e r s i o n to the amine by the sequence j u s t d i s c u s s e d y i e l d e d , a f t e r unblocking, the D-amino a c i d sugar d e r i v a t i v e (37) , 7 1 S i m i l a r treatment of the c i s - i s o m e r _5 gave the L-amino a c i d {38) 7 1 - The 3-deoxy analogue of 38 {39) was obtained by s e l e c t i v e a c e t y l a t i o n of the a-hydroxy group o f the dihydroxy e s t e r 36 f o l l o w e d by s t e r e o s e l e c t i v e dehydration with t h i o n y l c h l o r i d e and p y r i d i n e and subsequent c o n v e r s i o n of the f r e e a-hydroxy group to the a m i n e 6 8 as b e f o r e . S i m i l a r l y , compound _5 a f f o r d e d the expected 3-deoxy-D-amino a c i d sugar (_0). 7 o The D - g l u c o j isomers of 37 (4_ and _2 r e s p e c t i v e l y ) 11 •O-i ,0H H - f - O H C02Me - R ' 0 -1 -26 C02Me 37 R=NH 2 ; R--H 38 R = H ; R = N H , R R' ° " T -C02Me 39 R = H ; R = N H , 40. R = N H 2 ; R=H have been s y n t h e s i z e d by condensation of methyl n i t r o a c e t a t e with the 3-ketose _4 to give 43, f o l l o w e d by r e d u c t i o n of the n i t r o group of the a c e t y l a t e d p r o d u c t s - 7 2 x: 0-, C02Me 0-| CHN02 43 41 R=H i R= N H 2 42. R = N H 2 : R = H A blocked D-amino a c i d sugar (44) was generated when Jordaan and B r i n k 7 3 7 * reduced the product {43) obtained from the r e a c t i o n of e t h y l i s o c y a n o a c e t a t e with the ketose _4_ The sequence has a l s o been a p p l i e d by them to 2-keto s u g a r s - 7 5 X o C H O CC^Et I 43' -t I 0= C H N H C H 0-\~ C0 2 E t 44 The 2-deoxy-3-ketose 45 has ser v e d as s t a r t i n g m a t e r i a l f o r the s y n t h e s i s of hexopyranosyl g l y c i n e d e r i v a t i v e s v i a the az l a c t o n e c o n d e n s a t i o n . 7 6 The E and Z oxazolinones (46 and 47) were i s o l a t e d from the r e a c t i o n mixture both of which were sub j e c t e d to methanolysis f o l l o w e d by c a t a l y t i c r e d u c t i o n to give the ara b i n o and the r i b o branched-chain sugars, 12 respectively- Both compounds sere assigned the D-glycine configuration. / L L / " L i n / \\_JcH 3 \ | W O C H 3 0 V » x ° > 0 45. 46. 41 In addition to glycine, the terminal carbon of a-L-alanine has been attached to a furanose to give 48. 7 7 The synthesis, based on a method reported by Ogura and T s u c h i h a s a i 7 3 , proceeds from the addition of the anion of meth yl {methylthio) methyl sulfoxide to the n i t r i l e f u n c t i o n a l i t y of 3-C-cyanomethyl-3-deoxy-1,2:5,6-di-g-isopropylidene- a- D-allofuranose. "T -NH2 C02H 4£ The Bucherer hydantoin s y n t h e s i s 7 9 of glycine derivatives was used by Umezawa80 to prepare 49 from the corresponding ketose. Hydrolysis of 49 with base then afforded the novel 3-amino-3-C-carboxy-3-deoxy sugar 50. 13 BzO-i HO C0 2 H / 0 H 49 50 1-3.2 3 _ - Alanine 8 -Amino a c i d s , i n which the amino and c a r b o x y l i c f u n c t i o n s are separated by two carbons, are much more r a r e l y found as components of n a t u r a l l y - o c c u r r i n g s a c c h a r i d e s and n u c l e o s i d e s than are a-amino a c i d s . Coenzyme A . (5_) , an e s s e n t i a l c o f a c t o r f o r a c e t y l a t i o n r e a c t i o n s i n the l i v e r and b r a i n 8 1 3 2 and necessary i n the b i o s y n t h e s i s 8 3 — 8 4 and b i o d e g r a d a t i o n 8 5 - 8 6 o f f a t t y a c i d s , the metabolism of e r y t h r o c y t e s 8 7 - 8 8 and the p h o s p h o r y l a t i o n 3 9 - 9 l> of v a r i o u s b i o l o g i c a l l y important molecules, i n c o r p o r a t e s B - a l a n i n e as part of the diphosphate-l i n k e d s i d e - c h a i n a t C-5*. The s t r u c t u r e o f coenzyme A was e s t a b l i s h e d by a s e r i e s of s e l e c t i v e e n z y m i c . d e g r a d a t i o n s 9 1 — 9 3 and by t o t a l s y n t h e s i s 9 * - 9 6 Pantothenic a c i d {5 2) i s a 8 - a l a n y l - c o n t a i n i n g v i t a m i n {B3) 9 7 which has a l s o been obtained n a t u r a l l y as an a-D-g l u c o s i d e {53) p o s s e s s i n g m i c r o b i a l a c t i v i t y . 9 8 — 1 o o Recently, the 6-ureido 8-alan i n e purine n u c l e o s i d e 54 was s y n t h e s i z e d 1 0 1 and found t o be an i n h i b i t o r of adenosine 14 OH QH 9H3 fl CH,PO,PO-CH, | 2g '< I ^ ? ( C H 3>2 CHOH C=0 7 H O C H g C - W O H J C N H C r L C H X O O H C H 3 52 0,H(OH)2 OH NH 0 0 CH2CH2CNHCH2CH2SH Coenzyme A (51) NH'CNHCH2CH2C0OH HO-i / O CH, HO —/OCHjC-CHlOH) C NHCh^CHjCOOH OH Ch^ 0 53 CO 7 OH OH 54 k i n a s e . 1 0 2 B l a s t i c i d i n S (26) a l s o i n c o r p o r a t e s a 8 - a l a n i n e r e s i d u e i n i t s s i d e - c h a i n . 2- S ynthesis of Amino Acids The f i r s t l a b o r a t o r y s y n t h e s i s o f a n a t u r a l l y - o c c u r r i n g amino a c i d dates back to 1 8 5 0 1 0 3 when Stre a k e r produced a l a n i n e from acetaldehyde using the cyanohydrin method. Procedures f o r the s y n t h e s i s of other amino a c i d s , both n a t u r a l and u n n a t u r a l , were g r a d u a l l y taken up by E r l e n m e y e r 1 0 4 , F i s c h e r 1 0 5 , S o r e n s e n 1 0 6 and o t h e r s . T h e i r r e s u l t i n g methodologies, or v a r i a t i o n s thereon, were, u n t i l twenty years ago, the standard procedures f o r the p r e p a r a t i o n of amino a c i d s . Since then, a number of s y n t h e t i c methods have been developed, notably a l k y l a t i o n s . using the t r i a n i o n of h i p p u r i c a c i d 1 0 7 or the anion of methyl methylthiomethyl s u l f o x i d e 7 8 , a m i d o a l k y l a t i o n s with g l y o x y l i c a c i d 1 0 8 , condensations of c a r b o n y l compounds with 15 c a r b o x y l i c a c i d , amine and i s o c y a n i d e ' 1 0 9 - 1 1 2 , the use of t r i h a l o m e t h y l c a r b a n i o n s as n i t r i l e e q u i v a l e n t s 1 1 3 and r e a c t i o n s of copper g l y c i n a t e . 1 1 * The a p p l i c a t i o n of any of the c l a s s i c a l syntheses o f amino a c i d s to the production o f g l y c o s y l amino a c i d s (see S e c t i o n 1.3) has been l a c k i n g . The f o l l o w i n g then i s a b r i e f d i s c u s s i o n of three methods used i n the present work to produce g l y c o s y l amino a c i d s or t h e i r p r e c u r s o r s . 2.1 The Sorensen S y n t h e s i s of Amino A c i d s The f i r s t s y n t h e s i s o f g l y c i n e , developed by Goedeckemeyer 1 1 5 i n 1888, employed the r e a c t i o n of potassium phthalimide (55) with e t h y l c h l o r o a c e t a t e (56) to gi v e e t h y l p h t h a l y l g l y c i n a t e {57) which was then hydrolyzed with potassium hydroxide t o the di-potassium s a l t (58). Acid treatment o f the l a t t e r then gave g l y c i n e h y d r o c h l o r i d e (5_9) and p h t h a l i c a c i d (6_). r.__. „ _ _ : Th i s r e a c t i o n sequence was then developed a year l a t e r by G a b r i e l 1 1 6 as a gene r a l procedure f o r the s y n t h e s i s of amines from v a r i o u s o r g a n i c h a l i d e s , a r e a c t i o n which now bears h i s name. I t was then f i f t e e n years b e f o r e S o r e n s e n 1 " 6 1 , 7 - 1 2 0 was able to adapt the G a b r i e l s y n t h e s i s to make amino a c i d s . The 16 g e n e r a l scheme i n v o l v e d r e a c t i o n of the sodium s a l t of e t h y l phthalimidomalonate (6_) with an a p p r o p r i a t e organic h a l i d e to give the monoalkyl (or a r y l ) phthalimidomaionic e s t e r (62) from which the amino a c i d (63) was l i b e r a t e d by a c i d treatment. -hua' + R - X (C0 2 C 2 H ^ 2 IS-C—R 62 61 HBr R-CHC0 ,H NH2-HBr 63 Sorensen thus prepared p h e n y l a l a n i n e 1 1 7 , p r o l i n e 1 1 8 , o r n i t h i n e 1 1 7 and a- a m i n o a d i p i c a c i d 1 1 8 by r e a c t i o n of 6_ with benzyl c h l o r i d e , t r i m e t h y l e n e bromide, y-bromopropylphthalinside and Y - c h l o r o b u t y r o n i t r i l e , r e s p e c t i v e l y - In l a t e r y e a r s , the Sorensen method was used to s y n t h e s i z e t y r o s i n e 1 2 1 from a n i s y l bromide, s e r i n e 1 2 2 from monochlorodimethy1 e t h e r , m e t h i o n i n e 1 2 3 from 3 - c h l o r o e t h y l m e t h y l s u l f i d e , and a s p a r t i c a c i d 1 2 4 from c h l o r o a c e t i c e s t e r - Some lack of g e n e r a l i t y i n the Sorensen procedure was observed by Dunn and S m a r t 1 2 4 ; attempts to form glutamic a c i d from condensation of 55 with ethylene bromide, et h y l e n e c h l o r i d e , g - c h l o r o p r o p i o n i t r i l e or 3 - c h l o r o p r o p i o n i c e s t e r f a i l e d t o gi v e any s t a b l e products-Only minor i n n o v a t i o n s have been made i n the b a s i c Sorensen s y n t h e s i s over the years. , A more e f f i c i e n t method of generating the sodium s a l t 6_1 . from e t h y l phthalimidomalonate has been developed based on the use of toluene r a t h e r than ethanol as the r e a c t i o n s o l v e n t . 1 2 4 As w e l l , generation of the amino a c i d 63 17 f r o m 62 h a s been f a c i l i t a t e d by use o f h y d r o b r o m i c a c i d o r h y d r a z i n e 1 2 5 , t h e l a t t e r g i v i n g r i s e t o p h t h a l a z i n e r a t h e r t h a n p h t h a l i c a c i d (60) as t h e r e a c t i o n c o - p r o d u c t . More modern a p p l i c a t i o n s o f t h e S o r e n s e n method i n c l u d e t h e p r o d u c t i o n o f t r o p y l g l y c i n e , 1 2 6 a p o t e n t i a l l y t h e r a p e u t i c a n a l o g u e o f p h e n y l a l a n i n e , f r o m t r o p y l i u r a p e r c h l o r a t e and t h e s y n t h e s i s o f S - a l k y l - S - b e n z a m i d o b a r b i t u r a t e s 1 2 7 (65) f r o m d i e t h y l - a - a l k y l - a - p h t h a l i m i d o m a l o n a t e (64) a nd u r e a i n t h e p r e s e n c e o f s o d i u m e t h o x i d e . C l e a v a g e o f t h e p h t h a l i m i d e r i n g was o b s e r v e d i n t h e l a t t e r r e a c t i o n . T h a l i d o m i d e (67) ( N - ( 2 , 6 -(C0,C,H,), § ^STv^CO C.H.. R = CH3,CH2CH CH2 0 H 6A 65 d i o x o - 3 - p i p e r i d y l ) p h t h a l i m i d e ) 1 2 8 was p r e p a r e d by t h e a c t i o n o f ammonia on N - p h t h a l y l g l u t a m i c a c i d ( 6 6 ) . Q ^ - ^ X V-NH |[ £l-CHCH2CH2COOH .. COOH 0 o 66 62 2.2 The H y d a n t o i n S y n t h e s i s o f amino A c i d s . H y d a n t o i n s (69) w h i c h a r e 2 , 4 - d i k e t o t e t r a h y d r o i m i d a z o l e s , were f i r s t s y n t h e s i z e d by B a e y e r 1 2 9 when h e h e a t e d b r o m o a c e t y l u r e a (68) w i t h ammonia. N H 3 rA NH2CONH2COCH2Br — ) \ L ,>0 N 68 ° ' H 69 The v a l u e o f h y d a n t o i n . {§_9_) i n amino a c i d s y n t h e s i s i s 1 8 apparent when i t i s c o n s i d e r e d as a masked form of g l y c i n e ; h y d r o l y s i s 1 3 0 , u s u a l l y with aqueous barium hydroxide, f i r s t g i v e s hydantoic a c i d (29J as an i n t e r m e d i a t e v i a cleavage of the 3,4-bond. Further r e a c t i o n then gives g l y c i n e as the f i n a l NH 2 CONHCH 2 COOH j i 20 1 product. By s u b s t i t u t i n g one of the a c i d i c 1 3 1 - 1 3 3 protons a t the 5 - p o s i t i o n with an a l k y l or a r y l group <7_) a general method of forming v a r i o u s a-amino a c i d s (72.) i s achieved. Ingold and co-w o r k e r s 1 3 0 have shown that the ease of h y d r o l y s i s of the hydantoin r i n g (7_) depends on the nature of the 5 - s u b s t i t u e n t s . R •NH-, R _ U _ 0 H ^ R - | - ' o 71_R=H: R=Qlkyl,aryl Z2_ R=H; Ffcalkyl.aryl 73R=R'=alkyl.aryl 74 R= R= alkyl.aryl T The method was used e a r l y i n t h i s century to prepare a r y l -s u b s t i t u t e d a-amino a c i d s from aromatic aldehydes. Thus, r e a c t i o n 1 3 4 of benzaldehyde with hydantoin (69) under b a s i c c o n d i t i o n s a f f o r d e d the unsaturated condensation product 75 which was reduced and hydrolyzed to g i v e p h e n y l a l a n i n e (72, R=CH2 C ^  H ^  )- S i m i l a r l y , t y r o s i n e 1 3 5 and t r y p t o p h a n e 1 3 6 were obtained from a n i s a l d e h y d e (76) and 8 - i n d o l e aldehyde <77). O C H 3 C6' -CHO 0 " ^ " H CHO 75 76 11 Though many routes to 5 - s u b s t i t u t e d and 5 , 5 - d i s u b s t i t u t e d 19 hydantoins (71, and 73, r e s p e c t i v e l y ) have been developed over the y e a r s 1 3 7 , the s y n t h e t i c a l l y s i m p l e s t and most s u c c e s s f u l i s that i n t r o d u c e d by B e r g 1 3 8 and developed by B u c h e r e r . 1 3 9 - 1 4 0 I n t h i s procedure, an aldehyde or ketone i s heated i n a l c o h o l with potassium cyanide and ammonium carbonate g i v i n g d i r e c t l y the hydantoin 2 1 | i ' D the' case of an aldehyde) or 73 (f o r a ketone) . The mechanism as proposed by Bucherer though never e x p e r i m e n t a l l y v e r i f i e d i n v o l v e s i n i t i a l formation of the cyanohydrin 78 from the carbonyl compound f o l l o w e d by r e a c t i o n with ammonia (generated, together with carbon d i o x i d e , from the ammonium carbonate) to gi v e the a m i n o - n i t r i l e 79. Reaction of the l a t t e r with carbon d i o x i d e and ammonia then y i e l d s the N-s u b s t i t u t e d carbamic a c i d 8_0 which then c y c l i z e s to the imine 81. H y d r o l y s i s of B1_ a f f o r d s the hydantoin 7_ (or 73). c=o C N ' R V / ° H , / \ R XCN za NH, R \ / N H 2 X R x NCN za K O , 2 NH, 71 or 73 HN<^N R^ /NHC=0 81 8Q By t h i s method, Bucherer was a b l e to s y n t h e s i z e a v a r i e t y of new amino a c i d s . The g e n e r a l i t y of the o r i g i n a l Bucherer hydantoin s y n t h e s i s was l a t e r markedly enhanced by the use of acetamide as s o l v e n t 1 4 1 and by conducting the r e a c t i o n under s e v e r a l atmospheres of carbon d i o x i d e . 1 4 2 Hydantoins that are d i s u b s t i t u t e d at the 5 - p o s i t i o n d i s p l a y 20 hypnotic p r o p e r t i e s comparable to the s t r u c t u r a l l y r e l a t e d b a r b i t u r a t e s and moreover, are used as a n t i c o n v u l s a n t s i n the treatment o f e p i l e p s y . 1 3 7 1 4 3 In the carbohydrate f i e l d , the Bucherer s y n t h e s i s has been a p p l i e d by Umezawa and co-workers to prepare 3-amino-3-C-carboxy-3-deoxy s u g a r s 8 0 1 4 4 (50) (see S e c t i o n 1.3.1) and t h e i r adenine n u c l e o s i d e s . 8 0 No b i o l o g i c a l p r o p e r t i e s of t h i s compound were r e p o r t e d . 2.3 The Knoevenagel Condensation: Access t o 3-Amino Acids_ 2.3.1 - D e f i n i t i o n and Mechanism. The Knoevenagel c o n d e n s a t i o n 1 4 5 may be d e f i n e d as the r e a c t i o n between an aldehyde or a ketone (82) and a compound c o n t a i n i n g an a c t i v e methylene group (83), c a t a l y z e d by an or g a n i c base, ammonia or t h e i r s a l t s . The usual product i s the unsaturated a d d i t i o n compound 84. The methylene group of 83 i s i . I • . i • R R . ,x ; \=0 + X-CH—Y B g s e ) / C = C v + H 2 ° I 82 83 84 j i _ a c t i v a t e d by the presence of electron-withdrawing groups {X, Y), such as NOj , quaternary p y r i d i n i u r a , CN, COB, CONHB, CO2B, SO2, S, or Ar. G e n e r a l l y two such groups are r e q u i r e d f o r a c t i v a t i o n of 83 unl e s s a n i t r o or quat e r n i z e d p y r i d i n e group i s prese n t . The r e a c t i v i t y of 8_3 decreases i n the order N02>CN>COCH3 >COC 6H 5>C0 2 C 2H 5>C 6H 5. 1 4 8 I t i s a l s o • g e n e r a l l y accepted t h a t at l e a s t a c a t a l y t i c amount of a c i d , i n a d d i t i o n to the nitrogenous base, i s r e q u i r e d f o r s u c c e s s f u l 21 condensation 1 4 7 ~ 1 4 9 , although too much a c i d tends t o suppress the r e a c t i o n ; 1 5 0 - 1 5 3 The b a s i c c a t a l y s t s g e n e r a l l y employed are ammonia, primary or secondary amines, p y r i d i n e or ammonium s a l t s such as ammonium acetate- Ion-exchange r e s i n s , 1 5 4 1 5 5 metal f l u o r i d e s 1 5 6 - 1 5 7 and potassium c y a n i d e 1 5 8 have a l s o been used as c a t a l y s t s f o r the Knoevenagel condensation. In h i s o r i g i n a l i n v e s t i g a t i o n , Knoevenagel condensed formaldehyde with d i e t h y l ma Ion ate (85), using ethylamine as base, to give the b i s product 8 6 . 1 5 9 However, subsequent work showed t h a t condensations l e a d i n g to unsaturated compounds such as 84 were g e n e r a l l y a p p l i c a b l e . 1 6 0 Thus, benzaldehyde (87) and e t h y l a c e t o a c e t a t e (88) re a c t e d at f r e e z i n g temperatures i n the ' CH, —2 ) CH, 1 ! XC0 2C 2H 5 2 CH(C0 2C 2H 5) 2 • 85 86 presence of p i p e r i d i n e t o g i v e e t h y l b e n z y l i d e n e a c e t o a c e t a t e (89) • - -O , / W:H_C(COCH 3)CO 2C 2H 5 \ CHO ^ f + CH31!CH2CO2C2H5 - y i ^ j 87 88 83. The Knoevenagel condensation of a c t i v e methylene compounds such as nitromethane, methyl n i t r o a c e t a t e and e t h y l i s o c y a n o a c e t a t e with . ketoses as a route to branched-chain sugars has been d i s c u s s e d (see S e c t i o n s 1.1 and 1.3.1).,The Knoevenagel procedure a l s o provides access to s u b s t i t u t e d 3 - a l a n i n e d e r i v a t i v e s (92) by condensation of c y a n o a c e t i c esters{90) with a p p r o p r i a t e ketones or aldehydes (9_), f o l l o w e d by r e d u c t i o n of the unsaturated b o n d s . 1 6 1 - 1 6 2 22 R' R" R' U R" fl \' H ^ NCCH,,C0,R + RC R* > II —?-» I 2 2 C(CN)C02R H2NCH2CHC02R 90 91 22 The f o l l o w i n g then i s a d i s c u s s i o n of the proposed mechanisms o f the Knoevenagel condensation, the p a r t i c u l a r use of c y a n o a c e t i c e s t e r s i n t h i s reacton and a p p l i c a t i o n s of the l a t t e r to the f i e l d of carbohydrates. . 2.3 .1 .1 The Knoevenagel Mechanism. Knoevenagel observed, i n a s e r i e s of experiments, that both a S c h i f f base (93) and a b i s - ( d i a l k y l a m i n o ) compound (94) c o u l d r e a c t with malonic a c i d to g i v e the same a l k y l i d e n e product (2.5.), t h i s product, i n t u r n , being i d e n t i c a l to t h a t obtained by r e a c t i o n of malonic a c i d with the corresponding aldehyde (96) under c a t a l y s i s with ammonia, a primary amine or a secondary a m i n e - 1 6 3 - 1 6 4 T h i s v e r i f i e d his theory t h a t the r o l e of the j RCH=NR' i aa RCH(NR2>2 RCHO -) RCH=CICO2H)2 95_ amine was t o r e a c t with the aldehyde t o form the S c h i f f base 93 (in the case of ammonia or a.primary amine) or compound 94 ( i n the case of a secondary amine), these i n t e r m e d i a t e s then r e a c t i n g with the a c t i v e methylene component to y i e l d 95. Support f o r t h i s p r o p o s a l came mainly from the i s o l a t i o n of n i t r o g e n - c o n t a i n i n g compounds from r e a c t i o n s conducted under Knoevenagel c o n d i t i o n s - Moreover, f u r t h e r treatment of these 23 i n t e r m e d i a t e s gave the t y p i c a l Knoevenagel condensation products. For example, D i l t h e y and S t a l l m a n 1 6 5 - 1 6 , 5 were a b l e to i s o l a t e the p i p e r i d i d e 97 from the r e a c t i o n of benzaldehyde (87) , d i b e n z y l k e t o n e , and p i p e r i d i n e . Treatment of 97 with a c i d C 6H 5CH 2CCHC 6H 5 » C6 H5 C H2 Cjj C6 H5 + Q CH CHC6H5 H 97 i i then gave the u n s a t u r a t e d d i b e n z y l ketone 98 and p i p e r i d i n e . . T h e p o s s i b i l i t y t h a t 97 formed by a d d i t i o n of p i p e r i d i n e to the i n i t i a l l y formed unsaturated compound 98 was discounted t by the same i n v e s t i g a t o r s . 1 6 7 A more r a c e n t study by C h a r l e s 1 6 8 a l s o i n d i c a t e d t hat imines and N - s u b s t i t u t e d iraines c o u l d be used as s t a r t i n g m a t e r i a l s f o r Knoevenagel-type condensations with a c t i v e methylene compounds. Thus, r e a c t i o n of benzophenone imine (99) with cyanoacetamide (100) gave, without the use of c a t a l y s t , compound 1 0 1 . _ • I •| ( C 6 H 5) 2C=NH + NCCH2CONH2 > (C^J^CICNICON^ + NHj > -. ' 9J_ 100 101 1 In a d d i t i o n , the Knoevenagel mechanism has r e c e i v e d support from the r e s u l t s of r e a c t i o n r a t e s t u d i e s in which ammonia or a primary amine was used as c a t a l y s t ; aldehydes tending to form the most s t a b l e S c h i f f bases were a l s o those which formed Knoevenagel condensation products t h e most s l o w l y . 1 6 9 In cases where the a c t i v e methylene compound has an e n o l i z a b l e ketone, a m o d i f i c a t i o n of the Knoevenagel mechanism has been invoked wherein an enamine i s f i r s t formed which s e r v e s 24 as the n u c l e o p h i l e i n a t t a c k of another c a r b o n y l g r o u p . 1 7 ° — 1 7 1 For i n s t a n c e , the i n t r a m o l e c u l a r c y c l i z a t i o n of. compound JO 2 i s b e l i e v e d t o proceed by i n i t i a l r e a c t i o n with the c a t a l y t i c p y r r o l i d i n e to g i v e the enamine _03 which then f u r t h e r r e a c t s to give the charged imine 104. H y d r o l y s i s of 1.04 then generates the ketone 105. CH, t H 2 C H 2 & C H 3 102 Ch, -Au M H 20 OH 105 I C H 3 \ — ^ K C H,CH, Co \_ 2 l 2 103 H 2 C ~ S ? O 2.3.1.2 The Hann and Lapworth Mechanism The o b s e r v a t i o n by V e r l e y 1 7 2 and D o e b n e r 1 7 3 that p y r i d i n e , a t e r t i a r y amine, c o u l d be used t o e f f e c t i v e l y c a t a l y z e Knoevenagel condensations l e d Hann and L a p w o r t h 1 7 * t o propose t h a t the f u n c t i o n of the base i n these r e a c t i o n s was to remove a proton from the a c t i v e methylene compound t o give an anion (106) which then added to the c a r b o n y l compound. The r e s u l t i n g a l c o h o l (102) c o u l d then dehydrate to form the usual condensation product (84) . _ ' _ RCR Base B ^ * -H,0 n 83 ) X-CH-Y > H0C-CH 2—» 84. R' Y 106 Evidence f o r t h i s mechanism has come from the i s o l a t i o n of the hydroxy i n t e r m e d i a t e s 10.7. Thus, r e a c t i o n of nitromethane 25 with 2 - n i t r o b e G z a l d e h y d e and 2 , 4 - d i n i t r o b e n z a l d e h y d e gave compounds _Q8 and 19.9, r e s p e c t i v e l y - 1 7 5 S i m i l a r l y , N0 2 I CHCH,N0, i , 2 2 OH 1 R 108 R=H 109 R=NO. trichloroacetaldehyde ( H O ) and malonic acid yielded the g -hydroxy acid H I , decarboxylation occurring spontaneously- 1 7 6 CCI3CHO CCI3CHCH2C02H 110 6 h Ul Kinetic studies of the Knoevenagel reaction showed that, i n general, added acid decreased the rate of reaction while added s a l t s such as lithium chloride increased the rate, i n f e r r i n g that ionization of the active methylene compound (83) was the rate-determining s t e p - 1 5 0 - 1 5 3 The order of r e a c t i v i t y of active methylene compounds was determined to be CH^CCN)^ > C H 2(CN) CO^C^Hr^ > CH2(CN)CONH2 > CH-, (CC^C., H ^ ) . , . 1 5 3 The d i s s o c i a t i o n constants of these compounds follow a similar trend. A modified Hann and Lapworth mechanism has been suggested in which protonated amines are the active c a t a l y s t s i n the Knoevenagel condensation- 1 6 9 1 7 7 - 1 7 8 The introduction by Cope of ammonium acetate and other amine acetates as e f f e c t i v e c a t a l y s t s has reinforced t h i s p o s s i b i l i t y - 1 4 7 - 1 4 8 2-3-2 Knoevenagel Condensations with Cyan pace t i c Esters. 2. 3. 2. 1 Non-Carbohydrate Applications. Cyanoacetic esters generally condense with aldehydes and 26 ketones under Knoevenagel c o n d i t i o n s to g i v e the normal a ,8 -unsaturated cyanoacetates (112). O c c a s i o n a l l y dehydration does not occur and the 8-hydroxy a d d i t i o n compound (IJ3) i s i s o l a t e d . 1 7 9 I f excess c y a n o a c e t i c e s t e r i s used, Michael RCR + CH2(CN)C02R 0 RC(R')=C(CN)C02R"+ H2O 112 -* RC(OH)CH(CN)C02R R' 113 RC[CH(CN)C02R]2  R ' 114 a d d i t i o n t o the unsaturated bond of 112 can occur r e s u l t i n g i n formation o f s u b s t i t u t e d g l u t a r i c e s t e r s (H_ ). l a" Compounds of type 112 can a l s o add cyanide i o n 1 8 1 and Grignard r e a g e n t s 1 8 2 t o the double bond. Moreover, a l k y l i d e n e c y a n o a c e t i c e s t e r s such as 115 can be a l k y l a t e d to give 8 ,y-unsaturated e s t e r s (116). 1 8 3 R 1)NaOC,H„-i _ „ „ I CHjCHjCHjC-CtCNICOjCjHg 3 — C H ^ C H j C H — C NJCOJCJH^ j r i j 2)RI CH, j m C H 3 3 116 S u c c e s s f u l condensations of c y a n o a c e t i c e s t e r s with ketones have g e n e r a l l y employed ammonium a c e t a t e or acetamide and a c e t i c a c i d as c a t a l y s t s 1 4 7 - 1 4 8 while with aldehydes, p i p e r i d i n e has been widely used though ammonium ac e t a t e and weakly b a s i c i o n -exchange r e s i n s have been e q u a l l y e f f e c t i v e . 1 5 4 - 1 5 5 Ketones, u n l i k e aldehydes, o f t e n present s t e r i c f a c t o r s i n condensations with c y a n o a c e t i c e s t e r s which c o n t r o l the y i e l d of product and the r a t e of r e a c t i o n . For example, with the cycloalkanone 117, i n which there i s a s i n g l e a - s u b s t i t u e n t , 27 condensation occurred r e a d i l y , while with JJ.8, i n which t h e r e are two a-substituents, t h e r e was e s s e n t i a l l y no r e a c t i o n . 1 8 4 S t e r i c c o n s i d e r a t i o n s a l s o enter i n t o the e x p l a n a t i o n s of the observed s t e r e o s e l e c t i v i t y of the condensations of c y a n o a c e t i c e s t e r s with a l d e h y d e s . 1 8 5 To i l l u s t r a t e , 2-methoxybenzaldehyde r e a c t s with e t h y l cyanoacetate to g i v e e x c l u s i v e l y the t r a n s product 1 1 9 , 1 8 8 a geometry which a l l o w s the g r e a t e s t d i s t a n c e between the bulky phenyl and e s t e r groups. _ _ / C H 3 .C-C0,C H LtZ. R=H;R=CH3 NC 2 2 5 j 1J8 R=CH3!R'=C02C2H5 1J__ No such s t e r e o s e l e c t i v i t y i s g e n e r a l l y seen i n analogous condensations with k e t o n e s . 1 8 7 - 1 8 9 2.3.2.2. A p p l i c a t i o n s t o Carbohydrates. Zinner and c o - w o r k e r s 1 9 0 were ab l e to condense e t h y l cyanoacetate with 2,3:4,5-di-0-isopropylidene-D-arabinose using diethylamine as c a t a l y s t . The product was the unsaturated a c y c l i c heptose 120. Stereochemical a s p e c t s of the r e a c t i o n were CH,-CH-CH-CH-CH=C(CN)CO,C H, I I I I 1 ^ X 120 not d i s c u s s e d . C o n c u r r e n t l y with the present work, a r e p o r t has appeared d e s c r i b i n g the condensation o f the 3-ketose _4 with e t h y l cyanoacetate under ph a s e - t r a n s f e r c a t a l y t i c c o n d i t i o n s to g i v e 28 the branched-chain sugar 1.21. A M i c h a e l - a d d i t i o n of cyanide to the double bond of VJ.2 then y i e l d e d the _em-di-C-alkyl d e r i v a t i v e 122-191 xU N O - < o i - <rHCN \ 1 C0,Et C02Et 2 121 111 3- 1_3-Dithianes_ Two of the most d e s i r a b l e goals i n s y n t h e t i c o r g a n i c chemistry are the formation of carbon-carbon bonds and the i n t r o d u c t i o n i n t o molecules of v e r s a t i l e f u n c t i o n a l groups amenable t o f u r t h e r d e r i v a t i z a t i o n and m o d i f i c a t i o n . The anions of 1 , 3 - d i t h i a n e * 9 2 (123) and 2 - s u b s t i t u t e d 1,3-dithianes * 9 2 - i 9 5 ili.fi) have shown themselves i n the past decade to f u l f i l l both of these o b j e c t i v e s a t once by v i r t u e of t h e i r h i g h l y n u c l e o p h i l i c p r o p e r t i e s and t h e i r . a b i l i t y to be converted under mild c o n d i t i o n s to the s y n t h e t i c a l l y u s e f u l c a r b o n y l group.. The d i t h i a n e system i s a l s o t h e r m a l l y s t a b l e as s e l l as being r e l a t i v e l y i n e r t to a c i d s and bases, making i t even more val u a b l e as a s y n t h e t i c t o o l . Moreover, these t h i o a c e t a l s l a c k the overwhelming malodorousness g e n e r a l l y a s s o c i a t e d with organic mercaptans. 1,3-Dithiane (123) , f i r s t prepared and used s y n t h e t i c a l l y by Corey and S e e b a c h 1 9 2 i n 1965, i s an example of a masked carbonyl which allows f o r a r e v e r s a l , or umpolung 1 9 6, of the normal r e a c t i v i t y of t h i s l a t t e r group. That i s , whereas . the 29 12AR=CH3,i-C3H7,C6H5, normal c a r b o n y l (125) e f f e c t i v e l y c a r r i e s a p o s i t i v e charge on the carbon atom to which n u c l e o p h i l e s can a d d , 1 9 6 the masked c a r b o n y l , i n the form of i t s t h i o a c e t a l _26, i s capable o f supporting a negative charge on t h i s same carbon so t h a t i t can now a c t as a n u c l e o p h i l e . S t r e i f w e i s e r 1 9 7 and B e r n a r d i 1 9 8 have independently concluded that the p o l a r i z a b i l i t y of s u l f u r r a t h e r than the a v a i l a b i l i t y of empty d - o r b i t a l s i s r e s p o n s i b l e f o r the a c i d i t y of the a-hydrogens of the 1,3-dithiane system. For b r e v i t y , the f o l l o w i n g d i s c u s s i o n w i l l r e s t r i c t i t s e l f to the chemical p r o p e r t i e s of anions of the u n s u b s t i t u t e d 1,3-d i t h i a n e system 123 u n l e s s otherwise noted. The chemistry of both 123 and V2'± has been r e v i e w e d . 1 9 * 1 9 9 3.1 M u c l e o p h i l i c Reactions of the 1 t 3 - D i t h i a n e Anion. 2 - L i t h i o - 1, 3 - d i t h i a n e (126), c o n v e n i e n t l y p r e p a r e d 1 9 2 by r e a c t i o n of 1,3-dithiane with n - b u t y l l i t h i u m a t temperatures between -10° and -30<>, r e a c t s n u c l e o p h i l i c a l l y 1 9 9 with a l k y l h a l i d e s and benzenesulfonates, with epoxides, aldehydes, ketones, n i t r i l e s , amides, e s t e r s , and immonium s a l t s . These r e a c t i o n s and t h e i r products are summarized i n Table I. The d i t h i a n e anion r e a c t s with h a l i d e s more r e a d i l y than \ 30 with epoxides, as shown by the e x c l u s i v e formation o f the epoxide 133 when the bromo epoxide 132 i s t r e a t e d with one e q u i v a l e n t of anion 1 2 6 . 2 0 0 Though epoxides are g e n e r a l l y opened by d i t h i a n e t o g i v e the 3 - h y d r o x y a l k y l a t e d d e r i v a t i v e 128 (Table 1 3 2 1 2 6 I ) ,201-202 c y c l o a l k y l a t i o n 2 0 *-zo+ c a Q , be achieved by subsequently forming the p - t o l u e n e s u l f o n y l o x y d e r i v a t i v e J 3 4 . A d d i t i o n of one e q u i v a l e n t of n - b u t y l l i t h i u m then l e a d s t o i n t r a m o l e c u l a r c y c l i z a t i o n , y i e l d i n g the c y c l o p r o p y l compound (135) ^  Seebach and H i l k a 2 0 s have observed that while such i n t r a m o l e c u l a r displacements of N t o s y l a t e s proceed smoothly, benzenesulfonates are g r e a t l y s u p e r i o r f o r the analogous b i m o l e c u l a r r e a c t i o n by which compounds of type _27 are generated. - — | - „ A T . ~i I n-BuLi "RV^/^OTS 1 3 5 A c y l a t i o n of 1 , 3 - d i t h i a n e u s i n g amides or n i t r i l e s i s p r a c t i c a l only i f the l a t t e r two groups have no a - h y d r o g e n s . 2 0 6 In both cases, the a-hydrogens are more a c i d i c than those of 1 , 3 - d i t h i a n e so t h a t metal exchange r a t h e r than a d d i t i o n occurs, producing 136. The same r e s t r i c t i o n s apply t o r e a c t i o n s of the : 126_ + RCH2X X=CN,C0NH, 123 + RCHX 136 immonium s a l t s . 2 0 7 - 2 0 8 31 The a d d i t i o n of 2 - l i t h i o - 1 , 3 - d i t h i a n e to a , g - unsaturated c a r b o n y l s {1.37) g e n e r a l l y occurs i n a 1,2-fashion r a t h e r than i n the conjugate Michael-type 1 , 4 - f a s h i o n . 1 9 4 k t r a n s i t i o n s t a t e {___) i n which the carbanion center cannot reach the y-carbon 126. 137 l Q - / = ° / 139. atom of the unsaturated system has been p o s t u l a t e d i n order t o e x p l a i n t h i s phenomenon. 2 0 9 However, t h i s cannot account f o r the Q S-/-LI 140 f a c t that 2 - s u b s t i t u t e d d i t h i a n e anions Q2_, E=CO0CH 3, 1 9 9 SCH^ 2 1 0) o f t e n add e x c l u s i v e l y i n t h e 1,4-manner-I t has a l s o been suggested that an e q u i l i b r i u m e x i s t s between the 1,2 and 1,4 a d d i t i o n products (138 and J39, r e s p e c t i v e l y ) . 2 1 1 T h i s was d e m o n s t r a t e d 2 1 2 by the r e a c t i o n of 2-l i t h i o - 2 - p h e n y l - 1 , 3 - d i t h i a n e (124, R=Cgfl^) with 2-cyclohexanone; quenching of the r e a c t i o n mixture at room temperature gave e x c l u s i v e l y the 1,4-adduct 141 while quenching at -78° gave 65% of the 1,2-addition product 142. I t was thus concluded t h a t 1,4-a d d i t i o n i s a t h a r m o d y n a m i c a l l y - c o n t r o l l e d process while 1,2-a d d i t i o n i s k i n e t i c a l l y f a v o u r e d . In the case of a d d i t i o n of u n s u b s t i t u t e d 1,3-dithiane, the e q u i l i b r i u m would l i e f a r on the 32 s i d e of the 1,2-adduct. TABLE I: REACTIONS OF 2-LITHIO-V,3-DITHIANE (126) Type of Reaction Subst i tut ion Displacement Add i t ion A d d i t i o n -E l iminat ion Elect rophile R - X (X=CI,Br,I) (R=H C H 3 ) A R C R 0 (R = H, alkyl. aryl) RCN R 2 C = N R 2 R C N H , RCOR 0 Produc t 0« OH OH R C R ' S ' S Qy-U F L C - N R 2 o 127 127 129 130 131 130 1 30 3.2 Conversion of 1,_ 3- P i t h i an es t o Qarbonyls. The need to have g e n e r a l , e f f i c i e n t methods of h y d r o l y z i n g the 1 , 3 - d i t h i a n e group to a c a r b o n y l group under mild c o n d i t i o n s has produced s e v e r a l d i f f e r e n t approaches to t h i s problem. The t r a n s i t i o n metal-induced h y d r o l y s i s of d i t h i a n e i s an adap t a t i o n of F i s c h e r ' s 2 1 3 use of mercuric c h l o r i d e t o hydrolyze h i s sugar e t h y l S , S - a c e t a l s while the newer methods of o x i d a t i v e and a l k y l a t i v e h y drolyses of t h i o a c e t a l s r e p r e s e n t attempts to make the s u l f u r moiety a b e t t e r l e a v i n g group- These w i l l be 33 d i s c u s s e d i n t u r n while other methods, such as d i r e c t h y d r o l y s i s with a c i d , 2 1 4 w i l l be omitted s i n c e they cannot be c o n s i d e r e d as mild procedures. 3.2.1 T r a n s i t i o n Metal-Induced Hydro l y s i s - . The h y d r o l y s i s of t h i o a c e t a l s i s a r e v e r s i b l e r e a c t i o n which can be d r i v e n to completion only by removal of one of the products as i t i s formed (Scheme 1 ) . 2 1 S T h i s i s accomplished by use of a t r a n s i t i o n metal c h l o r i d e which i r r e v e r s i b l y binds with the t h i o l t o form a m e t a l l o t h i o l a t e C 1 M . 1 , Scheme 2}. The most + H,0 -* 0 = C + c N SH Scheme 1 commonly used reagent of t h i s type has been mercuric c h l o r i d e , 1 9 4 though c u p r i c c h l o r i d e 2 1 6 has a l s o been employed-The r e a c t i o n i s u s u a l l y performed i n aqueous p o l a r o r g a n i c s o l v e n t s , 2 1 7 n e u t r a l i t y being maintained by the a d d i t i o n of i n s o l u b l e carbonate s a l t s 2 1 7 - 2 1 8 or mercuric o x i d e 2 1 9 to remove the a c i d formed. I X 3 MCI, RV ,S R' R-C—<-V MCI H 2 ° . /R 0=C , 4- 2HCI R + CSMCI SMCI 143 Scheme 2 M = Hg,Cu Though t h i s method of h y d r o l y s i s appears to be g e n e r a l , i t f a i l s i n the case of a c y l 1,3-dithiane d e r i v a t i v e s ( 1 4 4 ) . 2 1 7 2 2 0 3. 2. 2. O x i d a t i v e H y d r o l y s i s 34 0 144 Oxidation o f a s u l f u r atom of a 1 , 3 - d i t h i a n y l d e r i v a t i v e to the S-oxide 145 permits mild a c i d i c h y d r o l y s i s to the corresponding ketone or aldehyde (Scheme 3). 2 2 1 - 2 2 2 T h i o l s are converted to the d i s u l f i d e 146 i n the process, e n s u r i n g complete r e a c t i o n . The h y d r o l y s i s of d i s u l f o x i d e s (1,47, Scheme 4) to the OC [o] Scheme 3 corresponding c a r b o n y l d e r i v a t i v e s with hydrogen c h l o r i d e has a l s o been shown to proceed v i a the monosulfoxides 148, some of which have been i s o l a t e d . 2 2 3 o li H 3 C S N / R C H,C Sy V 3 II 0 147 Scheme A HCI H 3 C S V R H,CS R 3 II 148 - 1 -) 0=C/ + HjCSSCR^CIj V Among the reagents used to e f f e c t S,S-acetal h y d r o l y s i s v i a the S-oxide i n t e r m e d i a t e 145 are b r o m i n e 2 1 7 , N - c h l o r o - 2 1 7 2 2 4 and N - b r o m o s u c c i n i m i d e . 2 1 7 The former i s o b v i o u s l y i n c o m p a t i b l e with the presence of double bonds i n the s u b s t r a t e to be hydrolyzed, a problem overcome by use of the N-halosucciaimides. The l a t t e r a l s o promote h y d r o l y s i s of d i t h i a n e s of type J44 t o 35 the d i - a c y l d e r i v a t i v e s - 2 1 7 C e r i c ammonium n i t r a t e i n aqueous a c e t o n i t r i l e converted the 5 - C - d i t h i a n y l r i b o f u r a n o s i d e 149 to the corresponding 5-C-for m y l d e r i v a t i v e 150 i n high y i e l d - 2 2 5 CH, ° x ° 149 OCH, CHO I CH. ° x ° 150 OCH, H y d r o l y s i s of the t h i o a c e t a l of acetone has been accomplished using s u l f u r y l c h l o r i d e and wet s i l i c a g e l - 2 2 6 Benzoyl peroxide was developed as an o x i d a t i v e h y d r o l y t i c reagent f o r the d i t h i a n e moiety of sgualenes when problems were encountered with the t r a d i t i o n a l mercuric c h l o r i d e p r o c e d u r e . 2 2 7 3-2-3- A l k y l a t i y e H y d r o l y s i s . A l k y l a t i v e h y d r o l y s i s of 1,3-dithiane d e r i v a t i v e s proceeds v i a the sulfonium s a l t s 151 {Scheme 5). Both the mono- and b i s -sulfonium i n t e r m e d i a t e s have been i s o l a t e d . 2 2 8 - 2 3 0 R y s _ A R"X A-/ 151 H20 Scheme 5 A l k y l a t i n g agents employed have i n c l u d e d methyl i o d i d e 2 3 1 i n aqueous acetone, a c e t o n i t r i l e or dimethylformamide. 36 t r i m e t h y l - or t r i e t h y l o x o n i u m t e t r a f l u o r o b o r a t e 2 2 8 - 2 3 0 as w e l l as methyl f l u o r o s u l f o n a t e . 2 3 2 The l a t t e r reagent can a l s o be used to promote conversion of t h i o a c e t a l s t o a c e t a l s , 2 3 3 a r e a c t i o n which has found value i n the formation of b e n z y l i d e n e d e r i v a t i v e s of c a r b o h y d r a t e s 2 3 4 (152) under n e u t r a l c o n d i t i o n s . • M°t)ocH+ CK>; - Xfc)0CHj: HON (0CH-, |® u I 3 i . I CH, OH i 3.2.4. M i s c e l l a n e o u s Methods of Hydrolysis.. Barton and c o - w o r k e r s 2 3 s used b e n z e n e s e l e n i n i c anhydride to achieve h y d r o l y s i s of 1,3-dithiolan d e r i v a t i v e s which, were i n e r t to other standard reagents. A s e l e n e n i c i n t e r m e d i a t e of type 153 was p o s t u l a t e d . I"""" " "I I Se=0 153 m i Mercuric oxide - boron t r i f l u o r i d e 2 8 1 has been developed as a h y d r o l y t i c system f o r the d i t h i a n e groups of s e n s i t i v e molecules and has been used by Paulsen i n the carbohydrate f i e l d . 2 3 8 D e t h i o a c e t a l i z a t i o n has a l s o been accomplished p h o t o l y t i c a l l y . 2 3 7 3-3 Reactions of 2-Litfaio-1 ,3-djthianes with Carbohydrates. 37 The n u c l e o p h i l i c p r o p e r t i e s of anions of 1,3-dithianes (123 and 124) have been advantageously u t i l i z e d i n the s y n t h e s i s of chain-elongated and branched-chain (A- and B- type) carbohydrates from, s u i t a b l y f unc t i o n a l i z e d p r e c u r s o r s . w. Such syntheses have been reviewed by S e e b a c h , 1 9 9 G e r o , 1 1 and Wander and H o r t o n 2 3 8 so that: the f o l l o w i n g d i s c u s s i o n w i l l be r e s t r i c t e d t o the s a l i e n t f e a t u r e s of these procedures. There have been no r e p o r t s of r e a c t i o n s between t h i o a c e t a l a n i o n s and n u c l e o s i d e d e r i v a t i v e s . 3.3.1. C h a i n - e l o n g a t i o n s of Carbohydrates. Gero and c o - w o r k e r s 2 2 S were a b l e t o d i s p l a c e the primary halogens of the methyl r i b o f u r a n o s i d e _J54 and the a c y c l i c e r y t h r i t o l J.55 with 2 - l i t h i o - 1 , 3 - d i t h i a n e i n hexamethylphosphoramide to a f f o r d r e a s o n a b l e y i e l d s of the d i t h i a n y l d e r i v a t i v e s 149 and 156, r e s p e c t i v e l y . Subsequent h y d r o l y s i s of the d i t h i a n e m o i e t i e s of the l a t t e r two compounds with c e r i c ammonium n i t r a t e (see S e c t i o n 3.2.2-) f o l l o w e d by sodium borohydride r e d u c t i o n of the r e s u l t i n g formyl f u n c t i o n a l i t i e s gave, r e s p e c t i v e l y , the one-carbon c h a i n -extended deoxy sugars _57 and _58. An attempted displacement of the primary t o s y l a t e of 159 gave only a 5% y i e l d of 149, a not s u r p r i s i n g r e s u l t i n view of l a t e r o b s e r v a t i o n s by Seebach and W i l k a 2 0 5 (see S e c t i o n 3.1). Chain-elongated deoxy-sugars were produced by displacement of the 5,6-epoxide of the p a r t i a l l y unblocked furanose _6Q with d i t h i a n e a n i o n . 2 3 9 Attack occurred e x c l u s i v e l y at the primary p o s i t i o n to g i v e the adduct 1.6 1.- H y d r o l y s i s of the d i t h i a n e 38 group using boron t r i f l u o r i d e - e t h e r a t e y i e l d e d the unusual t r i c y c l i c monosaccharide d e r i v a t i v e .162. One- and two-carbon e x t e n s i o n s could a l s o be obtained from the d i t h i a n y l compounds formed by r e a c t i o n of the e x o c y c l i c f o r m yl group of _63 with the anion of 2 - l i t h i o - 1 , 3 - d i t h i a n e 2 * 0 or 2 - l i t h i o - 2 - m e t h y l - 1 , 3 - d i t h i a n e . 2 * 1 - 2 * 2 Thus, while the L.-gl y c e r o - D - g a l a g t g isomer J6_ was produced e x c l u s i v e l y when the r e a c t i o n was run i n t e t r a h y d r o f u r a n with !23 2*o, 2-methyl-1,3-d i t h i a n e produced i n the same s o l v e n t both p o s s i b l e C-6 epimers _65 and _66 i n y i e l d s of U2% and 17% r e s p e c t i v e l y . 2 * 2 Only .the L-g l y c e r o d e r i v a t i v e 166 was formed when the r e a c t i o n was conducted i n h e x a m e t h y l p h o s p h o r i c t r i a m i d e . 2 * 1 C o n f i g u r a t i o n s 39 • " ^ CH, ' I ! P a ! j CHO H - C - O H R - C - R , 0O0 -0O0 0O0 ' i - f j i f 4 r t f 4 ^ - f : ! 163 164 1£5_ R=H;R=OH ; ' 166 R=OH;R=H were determined by c i r c u l a r d i c h r o i s m and by chemical c o r r e l a t i o n s . A p r e c u r s o r to C-nucleosides {see S e c t i o n 4) ( 1 6 8 ) was formed when 2 - l i t h i o - 2 - m e t h y 1 - 1 , 3 - d i t h i a n e was added t o the l a c t o n e sugar J.6.Z- 2 * 1 . 3.3. 2 . ,Synthesis of Type A Sugars. Paulsen and c o - w o r k e r s , 2 3 4 c o n c u r r e n t l y w i t h . Gero* s g r o u p , 2 4 0 prepared methyl D-haraameloside ( 1 2 2 ) by f i r s t adding 2 - l i t h i o - 1 , 3 - d i t h i a n e n u c l e o p h i l i c a l l y t o the 2 - k e t o g l y c o s i d e 169 and h y d r o l y z i n g the r e s u l t i n g product (170) to a f f o r d the formyl d e r i v a t i v e _7_ which was then reduced with sodium borohydride. The d i t h i a n e a d d i t i o n was s t e r e o s e l e c t i v e -171 R=CH0 172 R=CH2OH 40 A s i m i l a r s t e r e o s e l e c t i v i t y was observed i n the a d d i t i o n of d i t h i a n e anion t o the 3-ketoses 173 and 174 to give J 7 5 and 126* r e s p e c t i v e l y . 2 3 6 In both cases, the anion a t t a c k s from the l e a s t s t e r i c a l l y h indered s i d e of the sugar molecule. Compound 175 has served as a p r e c u r s o r i n the s y n t h e s i s of L - s t r e p t o s e (3) 2 3 6 and i t s a- and g - g l y c o s i d e s 2 * 3 , analogues of streptomycin. By r e a c t i n g 2 - l i thio-2-methy 1-1,3-dithiane with the 3-keto hexofuranose 177, the d i t h i a n y l adduct 178 was ob t a i n e d which, by the sequence of o x i d a t i o n , r e d u c t i o n , carbonate f o r m a t i o n and d e b e n z y l a t i o n , gave methyl 8-D-aldgaroside ( J 7 9 ) - 2 * *~ 2* 5 The c o n f i g u r a t i o n of the branched-chain of 179 was determined by comparison of i t s proton n.m.r. spectrum with those of the three other isomers obtained i n the same r e a c t i o n and from t h i s i n f o r m a t i o n the complete s t r u c t u r e of a l d g a r o s e , a sugar component of the a n t i b i o t i c Aldgamycin E 7 , was proven. Determination o f the c o n f i g u r a t i o n at the branching poin t of such sugars as 170, 175, 176, and J78 was hampered by the f a c t t hat, t h e r e being no hydrogen atoms at these quaternary c e n t e r s , no measurements of v i c i n a l proton-proton s p i n - c o u p l i n g v a l u e s c o u l d be determined.,Recourse was thus made to chemical 41 •0 OCH, and o p t i c a l c o r r e l a t i o n s with known compounds. 2 2 5 2 4 ° - 2 * 1 2 4 5 However, the use of s i n g l e - c r y s t a l x-ray c r y s t a l l o g r a p h y 2 * 6 allowed unambiguous assignment of c o n f i g u r a t i o n of the L-s t r e p t o s e d e r i v a t i v e 175. Gero and c o - w o r k e r s 2 3 9 2 * 7 - 2 4 3 have employed comparison of 1 3C-n.m.r. values of c l o s e l y r e l a t e d Type A branched-chain d i t h i a n e sugars to determine t h e i r s t e r e o c h e m i s t r y . A l s o , c o n f i g u r a t i o n a l assignments have been made using l a n t h a n i d e s h i f t reagents and 1H- n . m. r. 2 * 9 ~ 2 5 0 3.3.3. S y n t h e s i s of Tyge B Sugars. The s y n t h e s i s of Type B branched-chain sugars using 1,3-d i t h i a n e anions has proceeded mainly from displacement r e a c t i o n s with sugar epoxides.,The d i t h i a n e n u c l e o p h i l e g e n e r a l l y a t t a c k s i n a r e g i o s e l e c t i v e manner, as was s h o w n 2 3 9 i n the case of the t e r m i n a l epoxide 1.60 (Section 3^3-1-)-D i a x i a l opening of the epoxide r i n g of both the D - a l l o - and D-mannopyranosides {180 and J.81) by 2 - l i t h i o - 1 , 3 - d i t h i a n e was observed, g i v i n g , r e s p e c t i v e l y , 3-C-dithiany 1- and 2-C-d i t h i a n y l - a l t r o p y r a n o s i d e s (J82 and J83) . 2 4 7 2 5 1 , 42 S i m i l a r l y , Yamashita and Rosowsky, 2 5 2 i n t h e i r s t u d i e s on the s y n t h e s i s of a r a b i n o f u r a n o s y l branched-chain< sugars, d i s c o v e r e d that 1,3-dithiane attacked p r e f e r e n t i a l l y a t C-2 of the 2,3-anhydro sugar 184, presumably owing t o s t e r i c i n t e r f e r e n c e by the bulky C - 5 b l o c k i n g group to C-3 a t t a c k , t o give compound J.85. s ^ s RO 0 -0 ' OH 0 C H 3 18A R=#3c-,/2fcH2- 185 R=^3C->CH2-C-Nucleosides. Compounds i n which a h e t e r o c y c l e i s attac h e d to the anomeric carbon atom of a monosaccharide, u s u a l l y r i b o s e , by a C-C bond are r e f e r r e d to as C-nucleosides- The f i r s t example o f a C-nucleoside, pseu d o u r i d i n e £ 5 - { 3-D-ribof uranosyl) u r a c i l ] C 1 8 6 ) , was i s o l a t e d from an a l k a l i n e h y d r o l y s a t e of c a l f l i v e r RNA i n 1959 by C o h n 2 5 3 , who a l s o i d e n t i f i e d i t . 2 s * - 2 s s s i n c e then, a number of other C - n u c l e o s i d e s have been i s o l a t e d (see Fi g u r e I) from fermentation sources. A l l , except pseudouridine (186) possess a n t i b i o t i c p r o p e r t i e s and some <e.g. oxazinomycin 1 8 7 , showdomycin _ 8 8 , formycin J 8 9 , and pyrazomycin 1 9 2 ) d i s p l a y antitumour and a n t i v i r a l a c t i v i t i e s . 1 9 2 5 6 The b i o l o g i c a l a c t i v i t i e s of C- n u c l e o s i d e s stem from the enhanced h y d r o l y t i c s t a b i l i t y of the g l y c o s i d i c carbon-carbon bond compared to the more l a b i l e c a r b o n - n i t r o g e n bond of the common n u c l e o s i d e s . 2 5 7 Moreover, C - n u c l e o s i d e s , being s t r u c t u r a l l y r e l a t e d to the normal N-nucleosides can r e p l a c e t h e s e l a t t e r compounds i n the O H O H Formycin (189) O H O H Pyrazomycin (192) HiAo O H O H Oxazinomycin (187) O H O H Formycin B (190) H O H O O H O H Showdomycin (188) O H O H Oxoformycin B H O H O M h y m 2 Pyrazomycin B (193) OH • OH Indochrome B11 (194) Figure I: Naturally - Occurring C-Nucleosides 44 enzymic r e a c t i o n s a s s o c i a t e d with metabolism and tBNA s y n t h e s i s and consequently i n t e r f e r e with these p r o c e s s e s - 2 5 8 Because the b i o l o g i c a l p r o p e r t i e s ^ 2 5 6 of C - n u c l e o s i d e s , as well as the s y n t h e s i s 2 5 9 - 2 6 0 of both n a t u r a l C - n u c l e o s i d e s and t h e i r analogues, have been e x h a u s t i v e l y reviewed, a d e t a i l e d account of such t o p i c s i n these pages would be redundant. The f o l l o w i n g , then, i s a b r i e f d i s c u s s i o n of the general approaches t o C - n u c l e o s i d e s y n t h e s i s t h a t are r e l e v a n t to the present work. 4.1 S y n t h e s i s of C-Nucleosides and T h e i r Analogues. A great number o f a n a l o g u e s 2 5 6 2 6 0 of the n a t u r a l l y -o c c u r r i n g C - n u c l e o s i d e s have been s y n t h e s i z e d over the l a s t decade in an e f f o r t to o b t a i n more p h y s i o l o g i c a l l y e f f e c t i v e and s p e c i f i c compounds. The success i n t h i s endeavour has been h i g h l i g h t e d by the s y n t h e s i s 2 6 1 of p s e u d o - i s o c y t i d i n e [5-(g-D-r i b o f u r a n o s y l ) i s o c y t o s i n e J {_95) , the f i r s t s y n t h e t i c C-n u c l e o s i d e to d i s p l a y antitumour p r o p e r t i e s . 2 6 2 Pour s y n t h e t i c s t r a t e g i e s have been employed t o produce novel C - n u c l e o s i d e s . The f i r s t i n v o l v e s m o d i f i c a t i o n of n a t u r a l l y - o c c u r r i n g C - n u c l e o s i d e s . For i n s t a n c e , Sorm and a s s o c i a t e s 2 6 3 prepared 6-azapseudouridine (121) by o z o n o l y s i s of pseudouridine (186) f o l l o w e d by c y c l i z a t i o n of the d e r i v e d thiosemicarbazone. A second approach to C-nuclepside s y n t h e s i s i n v o l v e s the use of non-carbohydrate p r e c u r s o r s . Thus, by a s e r i e s of r e a c t i o n s , Sato and c o - w o r k e r s 2 6 * were a b l e to e l a b o r a t e the oxabicyclooctenone 198 i n a s t e r e o c o n t r o l l e d manner to give a v a r i e t y of pseudouridine d e r i v a t i v e s i n c l u d i n g p s e u d o - i s o c y t i d i n e (__5) . , 0 '" ' . HI^IH JL ' " x J 6 OH OH 1 J 2 1 9 8 _ • ' The d i r e c t c o u p l i n g of a preformed h e t e r o c y c l e with an a p p r o p r i a t e l y blocked sugar d e r i v a t i v e r e p r e s e n t s the t h i r d and most d i r e c t way of s y n t h e s i z i n g C-nucleosides- The i n t e r m e d i a r y of m e t a l l a t e d h e t e r o c y c l i c bases i s g e n e r a l l y r e g u i r e d 2 6 5 and t h i s w i l l be d i s c u s s e d more f u l l y i n the f o l l o w i n g s e c t i o n (see S e c t i o n 5 - 1 ) -By f a r the most p r a c t i c a l s y n t h e t i c r o u t e to modified C-n u c l e o s i d e s c o n s i s t s of f u n c t i o n a l i z a t i o n of a sugar d e r i v a t i v e at C-1 f o l l o w e d by a stepwise e l a b o r a t i o n of a h e t e r o c y c l i c base from t h i s f u n c t i o n a l group- Two methods of o b t a i n i n g such C-g l y c o s i d e s w i l l be d e s c r i b e d , the f i r s t proceeding from g l y c o s y l cyanides and the second from condensations of c a rbanions with g l y c o s y l h a l i d e s . 4 . 1 . 1 . G l y c o s y l Cyanides. Based on p r e v i o u s work by C o x o n , 2 6 6 Bobek and F a r k a S 2 6 7 prepared the t r i - O - b e n z o y l a t e d r i b o f u r a n o s y l cyanide 200 i n high y i e l d by r e a c t i n g the bromide J99 with mercuric cyanide i n nitromethane. Only the 6-isomer was o b t a i n e d , presumably owing to neighbouring-group p a r t i c i p a t i o n . The o r i e n t a t i o n of the C-1 s u b s t i t u e n t s of C - g l y c o s i d e s i s c r i t i c a l i n the s y n t h e s i s of C-n u c l e o s i d e s s i n c e , but f o r a few e x c e p t i o n s 2 6 8 — 2 6 9 only the 3-d e r i v a t i v e s of the l a t t e r compounds e x h i b i t t h e r a p e u t i c a c t i v i t i e s . The n i t r i l e group of _199 c o u l d be reduced with l i t h i u m aluminum hydride to the primary amine 201 which i n t u r n 46 , 19JL 2Q0 R-.CN : 201 R=CH2NH2 j 202 R=CHN2 ; . 203 R--CHO _ J was converted to the diazo d e r i v a t i v e 2 0 2 - 2 7 0 Compound 2 0 2 served as s t a r t i n g m a t e r i a l f o r s y n t h e s i s of formycin B 2 7 1 Q 9 0 ) and oxoformycin B 2 7 0 (191). A l t e r n a t i v e l y , the g l y c o s y l n i t r i l e c o u l d be r e d u c t i v e l y h y drolyzed to the c o r r e s p o n d i n g aldehyde ( 2 0 3 ) with Raney n i c k e l and sodium hypophosphite- 2 7 2 Because of troublesome 3 -e l i m i n a t i o n of benzoate groups during t h i s r e a c t i o n , the aldehyde 2 0 3 was trapped as the N , N • - d i p h e n y l i m i d a z o l i d i n e d e r i v a t i v e 2 0 4 as i t was formed- The aldehyde 2 0 3 c o u l d be 0 regenerated from 2 0 4 by mild a c i d h y d r o l y s i s . Compound 2 0 3 was a key i n t e r m e d i a t e i n a s i m p l i f i e d s y n t h e s i s 2 7 3 of showdomycin Q 8 8 . ) and has been e l a b o r a t e d i n t o a v a r i e t y of C-nucleoside a n a l o g u e s . 2 6 0 4 . 1. 2 Condensations with Carbanions. Hanessian and c o - w o r k e r s 2 7 * - 2 7 5 have r e p o r t e d the r e a c t i o n of d i e t h y l sodiomalonate ( 2 0 5 ) with d i f f e r e n t g l y c o s y l h a l i d e s ^ In t h e i r i n i t i a l study, r e a c t i o n of 2 0 5 with the a c e t y l a t e d glucopyranosy 1 bromide 2 0 6 i n 1 , 2-ldimethoxyethane 'gave t h e C-47 g l y c o s y l malonate 207. Only the 3-isomer of 207 was produced. AcO / CH C0 2C 2H 5 + C0 2C 2H 5 AcO 205 AcO NaH Br C2 H4 ( O C H3 )2 AcO 0 CH(C02C2H5)2 when a p o l a r s o l v e n t such as N,N-dimethylformamide was used as the r e a c t i o n medium, an a p p r e c i a b l e q u a n t i t y of compound 209 was i s o l a t e d , t h i s product a r i s i n g from a t t a c k of the carbanion at the dioxolenium carbon atom o f the i n t e r m e d i a t e acetoxonium i o n 208. Subsequent i n v e s t i g a t i o n s were thus concerned with the use of n o n - p a r t i c i p a t i n g b l o c k i n g groups i n the r e a c t i n g sugar h a l i d e i n order t o a v o i d t h i s competing s i d e r e a c t i o n . ACO-I A c 0 - i 1 l «<eCH(C0,C,H ) 0-C • 2 2 5 2 I CH3 208 ,0Ac AcON fO 0-C-CH(C02C2H5)2 CH, 209 6 Ohrui and F o x 2 7 6 used the 8-chloro r i b o f u r a n o s i d e 2J0 i n an extension of Hanessian's o r i g i n a l work, o b t a i n i n g an a,8-mixture of the malonates . (2J1) . . E q u i l i b r a t i o n of t h i s mixture i n ethanol-sodium ethoxide y i e l d e d e x c l u s i v e l y the a-isomer of 211. 2 7 7  TrO T r O CH(C0 2C 2H 5) 2 °x° 211 T r i e t h y l s o d i o e t h a n e t r i c a r b o x y l a t e 2 6 0 and e t h y l a c e t o a c e t a t e 2 7 6 have a l s o been r e a c t e d with r i b o f u r a n o s y l 4 8 h a l i d e s to give the corresponding C - g l y c o s i d e s -The attachment of a-amino a c i d s at the anomeric carbon o f sugars by a C-C bond has l a t e l y been of i n t e r e s t because such d e r i v a t i v e s are h i g h l y f u n c t i o n a l i z e d and can thus be c o n v e n i e n t l y e l a b o r a t e d to C - n u c l e o s i d e s . These compounds a l s o allow easy a c c e s s to those C-nucleosides i n which C-1 o f the aglycon i s a t t a c h e d to a carbon and a n i t r o g e n (for i n s t a n c e , compounds j.89-_93j.. The f i r s t s y n t h e s i s of such amino a c i d C-g l y c o s i d e s proceeded from the r e a c t i o n of the sodium s a l t of d i e t h y l 2-f ormamidomalonate (212) with the bromo.sugar 206 i n e t h a n o l to g i v e the C - g l y c o s i d e 2J.3 which was then converted to the g l y c i n e d e r i v a t i v e 21.4. 2 7 8 L a t e r attempts to repeat the work f a i l e d . 2 7 * "'. 212 213. 2H_ Rosenthal and B r i n k 2 7 9 obtained compound 21.4 by r e a c t i n g 206 with the anion of 2-phenyloxazol-5-one ( 2 1 5 ) f o l l o w e d by base h y d r o l y s i s of the product. o The s y n t h e s i s of C - g l y c o s y l g l y c i n e s was extended to a f u r a n o s y l sugar by H a l l and c o - w o r k e r s 2 8 0 by r e a c t i n g the potassium s a l t of e t h y l i s o c y a n o a c e t a t e with a blocked D-mannono-1,4-lactone to give 2_6. C a t a l y t i c hydrogenation of 216 f o l l o w e d by h y d r o l y s i s y i e l d e d the l y x o f u r a n o s y l p.- and L-49 g l y c i n e s 216a. 5. P a l l a d i u m - C a t a l y z e d S y n t h e s i s of M o d i f i e d N u c l e o s i d e s . The use of organopalladium i n t e r m e d i a t e s f o r the f o r m a t i o n of carbon-carbon bonds i s w e l l known and has been r e v i e w e d . 2 8 0 3 H e c k , 2 8 1 using a r y l m e r c u r i c s a l t s (217) and l i t h i u m palladium c h l o r i d e (21.8) was a b l e to a r y l a t e ; o l e f i n s i n varying y i e l d s . A '' H LLPdCl A r N / 217_X = Cl,OAc — Li jPdlCDH mechanism was p o s t u l a t e d (Scheme 6) i n which the i n i t i a l l y formed a r y l p a l l a d i u m i n t e r m e d i a t e 220 added to the o l e f i n i c double bond t o g i v e the sigma complex 221. Spontaneous decomposition of 221 then y i e l d e d the o l e f i n (219) and the metal hydride 222. The l a t t e r compound could then be converted to the c a t a l y t i c a l l y a c t i v e form (21.8) by i n c l u d i n g an o x i d i z i n g agent such as c u p r i c c h l o r i d e i n the r e a c t i o n mixture. T h i s g e n e r a l a r y l a t i o n r e a c t i o n was extended t o a l l y l i c a l c o h o l s , 2 8 2 - 2 8 3 , a l l y l i c h a l i d e s 2 8 4 , e n o l e s t e r s 2 8 5 , e n o l e t h e r s 2 8 5 , and carbon monoxide. 2 8 6 50 217 + P"X2 » [ArPdX] + HgX 2 218 220 , ' i ; H ; H / I I 220 + )C=C^ » Ar-C-C-PdX » 219. + [HPdX] I 221 222 ' Scheme 6 The a r y l a t i o n r e a c t i o n c o u l d be performed with a r y l h a l i d e s i n s t e a d of a r y l m e r c u r i c s a l t s (2J7) i f palladium metal was used as the c a t a l y s t , 2 8 7 the a c t i v e s p e c i e s 220 being formed by o x i d a t i v e a d d i t i o n of the metal to the h a l i d e - Moreover, i t was s h o w n 2 8 8 that the v i n y l hydrogen atom of methyl a c r y l a t e (224) co u l d be d i s p l a c e d by trans-B-bromostyrene (223) under these c o n d i t i o n s t o gi v e the diene 225 i n moderate y i e l d s . B e t t e r y i e l d s and more s t e r e o s e l e c t i v i t y were achieved i n these C=C 4- CH,=CHC0,CH. ; H X N B r 223 22A 225 - 2 ^ 3 , r e a c t i o n s when tr i p h e n y l p h o s p h i n a was used i n c o n j u n c t i o n with the palladium metal t o form t e t r a k i s t r i p h e n y l p h o s p h i n e p a l l a d i u m (0) (226) . 2 8 9 , :. ! ^ \ I X P d 226 The phosphine complex 226 a l s o c a t a l y z e s the c o u p l i n g of v i n y l h a l i d e s (e. g. 223) and a l k y l l i t h i u m compounds 2 9 1 (228) or Grignard r e a g e n t s 2 9 0 - 2 9 1 (229) to g i v e , i n both c a s e s , e x c l u s i v e l y the c i s or t r a n s product 230 i n high y i e l d s v i a the c- — — — organopalladium i n t e r m e d i a t e 227.. The g e n e r a l p r i n c i p l e s j u s t d e s c r i b e d have been s u c c e s s f u l l y employed i n the s y n t h e s i s of mod i f i e d n u c l e o s i d e s . 51 223 +226 •H C=C 227 , c = c 230 R T h i s i s d i s c u s s e d next. 5. 1 S y n t h e s i s of C-Nucleosides v i a Organopalladium IiL£ermedj.aJ_es_ The d i r e c t s y n t h e s i s of C-nucleosides (see S e c t i o n 4) by c o u p l i n g of a h e t e r o c y c l i c base with a s u i t a b l e sugar d e r i v a t i v e i s not yet an e n t i r e l y s a t i s f a c t o r y o p e r a t i o n . The f i r s t such attempt was r e p o r t e d by Shapiro and C h a mbers 2 9 2 who condensed the c h l o r o sugar 23_ with the 5 - l i t h i o u r a c i l d e r i v a t i v e 232.' Pseudouridine {_86) was obtained i n only 2% y i e l d a f t e r removal of the b l o c k i n g groups-S l i g h t improvements were made i n the y i e l d s of pseudouridine (186) by r e a c t i n g 5 - l i t h i o u r a c i l d e r i v a t i v e s (232, R=Me^C-, 0CHj) with a blocked aldopentose d e r i v a t i v e 2 9 3 and a r i b o n o l a c t o n e d e r i v a t i v e - 2 9 4 Recently the d i r e c t , p a l l a d i u m — c a t a l y z e d c o u p l i n g of the 5-m e r c u r i a c e t y l u r a c i l d e r i v a t i v e 233 with the t r i a c e t y l a t e d g l u c a l 234 was r e p o r t e d 2 9 5 t o g i v e the C - n u c l e o s i d e analogue 235 i n 20% y i e l d . Spontaneous d e a c e t y l a t i o n and opening of the pyranose r i n g were the main disadvantages of the r e a c t i o n sequence. 231 232 R=CH 52 5 * 2 S y n t h e s i s of Pyrimidine .Nucleosides Modified at C-5 usi_£ O s a S L B O E - i l - ^ i i i S Intermediates. Bergstrom and c o w o r k e r s 2 9 6 - 2 9 7 have r e c e n t l y d e s c r i b e d the p a l l a d i u m - c a t a l y z e d a l k y l a t i o n of the C-5 p o s i t i o n of u r i d i n e and 2'-deoxyuridine. For example, r e a c t i o n of 5-c h l o r o m e r c u r i u r i d i n e (236) with methyl a c r y l a t e <22_) i n the presence of the p a l l a d i u m c a t a l y s t 237 gave the t r a n s d e r i v a t i v e 238. " ~ " P y r i m i d i n e n u c l e o s i d e s s u b s t i t u t e d a t C -5 d i s p l a y i n many cases chemotherapeutic p r o p e r t i e s . 2 9 8 - 3 0 1 6 - M o d i f i e d P y r i m i d i n e Bases and T h e i r Nucleosides 53 U r a c i l d e r i v a t i v e s modified at C-5 (239) r e p r e s e n t an i n t e r e s t i n g c l a s s of compounds d i s p l a y i n g a n t i v i r a l , a n t i c a n c e r or mutagenic p r o p e r t i e s . 3 0 2 For example, 5 - f l u o r o u r a c i l {239, R=F) i s used c l i n i c a l l y i n the treatment of leukemia. Because the p h y s i o l o g i c a l a c t i v i t y o f 5-f l u o r o u r a c i l has been l i n k e d with the s t a b i l i t y of the carbon-rf 1 uorine b o n d 3 0 3 , the i n c o r p o r a t i o n of such s t a b l e l i n k a g e s i n the form of carbon-carbon bonds {239, R=alkyl, a r y l etc.) has been pursued i n the i n t e r e s t s of producing m e d i c i n a l l y v a l u a b l e analogues. Thus, pseudouridine (186, S e c t i o n 4) and i t s d e r i v a t i v e s may be consi d e r e d as C-5 modified u r a c i l compounds (239, S = r i b o f u r a n o s y l ) . 239 240 R=H,OH Though u r a c i l d e r i v a t i v e s of type 239 are p o t e n t i a l l y v a l u a b l e i n themselves they can a l s o be converted by c o n v e n t i o n a l techniques to C-5 s u b s t i t u t e d n u c l e o s i d e s (240), another c l a s s of c l i n i c a l l y u s e f u l compounds (see S e c t i o n 5 . 2 ) . 2 9 8 - 3 0 3 i n t h i s case, the n u c l e o s i d e s can d i s p l a y b i o l o g i c a l a c t i v i t i e s completely d i f f e r e n t from those of the parent base. For example, 5 - f l u o r o d e o x y u r i d i n e (240, R , = F , R=H) i s an a n t i v i r a l agent as w e l l as an a n t i c a n c e r a g e n t . 3 0 0 - 3 0 1 The b i o l o g i c a l s t u d i e s of n u c l e o s i d e s s u b s t i t u t e d a t C-2 (241) or C - 6 3 0 4 (242) have not r e c e i v e d the a t t e n t i o n accorded the C-5 analogues (240) mainly because problems encountered i n 54 t h e i r syntheses have made very few of t h e s e compounds a v a i l a b l e * However, the f i n d i n g that n a t u r a l l y - o c c u r r i n g o r o t i d i n e {242, B=C0OH) i s e s s e n t i a l f o r the b i o s y n t h e s i s of RNA p y r i m i d i n e n u c l e o s i d e s i n mammalian s y s t e m s 3 0 5 i s an i n d i c a t i o n that C-6 m o d i f i c a t i o n of t h i s compound may have important p h y s i o l o g i c a l i m p l i c a t i o n s - — -! The f o l l o w i n g , then i s a b r i e f d i s c u s s i o n of the more p r a c t i c a l methods of i n t r o d u c i n g carbon-carbon l i n k e d s u b s t i t u e n t s at C-5 of u r a c i l d e r i v a t i v e s (239) and C-2 and C-6 of p y r i m i d i n e n u c l e o s i d e d e r i v a t i v e s (241 and 242, r e s p e c t i v e l y ) -6.1 I n t r o d u c t i o n of C-C L i n k e d S u b s t i t u e n t s a t C-5 cf U r a c i l Deri y a t i yes. P y r i m i d i n e s s u b s t i t u t e d at C-5 (239) can be s y n t h e s i z e d by condensation of a p p r o p r i a t e l y f u n c t i o n a l i z e d components. Thus, r e a c t i o n of e t h y l i s o t h i o u r e a (243) with ethyloxymethylenecyanoacetate (244) i n the presence of base g i v e s a 5-cyano d e r i v a t i v e (245) which can be h y d r o l y z e d t o 5-c y a n o u r a c i l (239, R=CN). 3 0 6 T h i s method i s l i m i t e d by the a v a i l a b i l i t y of the necessary three-carbon p r e c u r s o r s -Aromatic s u b s t i t u e n t s can be p h o t o l y t i c a l l y attached t o C-5 of u r a c i l d e r i v a t i v e s - I r r a d i a t i o n of a s o l u t i o n of 5,6-diiodo-55 - - : , ^ r _L V / NaOEt t HN -V H A + C > j f M > 239 (R=CN) 5 NH, E t S ^ N ^ E t s 2 cVt « 243 241 2A5 1 , 3 - d i m e t h y l u r a c i l (246) i n benzene gave the 5-phenyl adduct 24 7 by a f r e e - r a d i c a l mechanism. 3 0 7 o O ^ N ^ I C6H. 0 ^ M > 0 ' ~ y ' *"6n6 " T CH3 CH3 246 247 The d i r e c t i n t r o d u c t i o n of a f u n c t i o n a l group a t C-5 t h a t can be f u r t h e r modified to give any type of s i d e - c h a i n i s perhaps the best approach to a l t e r i n g p y r i m i d i n e s a t t h i s p o s i t i o n . Toward t h i s end, the h i g h l y v e r s a t i l e 5 - f o r m y l u r a c i l (239, R=CHO) has been s y n t h e s i z e d i n high y i e l d by condensation of formaldehyde with u r a c i l (239, 8=H) under a c i d or base c a t a l y s i s , f o l l o w e d by manganese d i o x i d e o x i d a t i o n of the r e s u l t i n g 5-h yd roxymeth y l u r a c i l {239, F^CH^OH)- 3 0 8 The use of 5 - l i t h i o u r a c i l d e r i v a t i v e s (232) • as p r e c u r s o r s to C-5 r i b o s y l a t e d compounds has been d i s c u s s e d (see S e c t i o n 5. 1) . F i n a l l y , the s y n t h e s i s of a s t a b l e C-5 mercurated u r a c i l d e r i v a t i v e ( 2 4 8 ) 3 0 7 has opened the way t o m o d i f i c a t i o n of t h i s p o s i t i o n u s i n g the p a l l a d i u m - c a t a l y z e d r e a c t i o n s d i s c u s s e d p r e v i o u s l y (see S e c t i o n 5) . H3CN 0 .HgOAc i CH 3 248 6.2 Synthesis of Base-Modifled Pyrimidine Hucleosides. 6 . 2 . 1 . M o d i f i c a t i o n s at C-2 The s y n t h e s i s of m o d i f i e d n u c l e o s i d e s of type 24! by d i r e c t 56 condensation of a 2-substituted u r a c i l d e r i v a t i v e and a sugar would appear t o be s t e r i c a l l y unfavourable by analogy with the s y n t h e s i s of 6 - s u b s t i t u f e d n u c l e o s i d e s of type 242 (see S e c t i o n 6.2.2.1.).. The most convenient r o u t e to C-2 modified n u c l e o s i d e s i n v o l v e s the intermediacy of 2, 2'-anhydronueleosides {2 49), the chemistry of which has been reviewed by F o x . 3 0 9 Various n u c l e o p h i l e s are known to a t t a c k the anhydro l i n k a g e of 249 a t m 250 C-2 to give the 2-substituted a r a b i n o n u c l e o s i d e s of type 250. Thus, r e a c t i o n of 249 with hydroxide^ methoxide, ammonia or hydrogen s u l f i d e 3 1 0 g i v e s 250 i n which R i s r e s p e c t i v e l y OH, CH^O, NH2 or HS. I n t r o d u c t i o n o f a C-C l i n k e d s u b s t i t u e n t a t C-2 has been a c h i e v e d 3 1 1 by r e a c t i o n of an anhydronucleoside with 0 Q dimethyloxosulfonium methylide to give 250 (R=Me,§-CH). P y r i m i d i n e n u c l e o s i d e s having the arabino c o n f i g u r a t i o n (e.g. 250) are m e d i c i n a l l y v a l u a b l e compounds. 3 0 1 The main disadvantage of t h i s method of s y n t h e s i z i n g modified n u c l e o s i d e s l i e s i n the i n a b i l i t y to p r e d i c t the p o s i t i o n of a t t a c k of a p a r t i c u l a r type of a n i o n ; both a z i d e 3 1 2 and p h t h a l i m i d e 3 1 3 anion attack on the sugar p o r t i o n of the anhydro l i n k a g e of 249 to give C-21 modified n u c l e o s i d e s (25J_). 5 7 6,2.2. M o d i f i c a t i o n s at C-6.. 6. 2. 2. 1. . D i r e c t Condensation. The f i r s t s y n t h e s i s of o r o t i c a c i d (242, B=COOH) was achieved i n only 8% y i e l d by Curran and A n g i e r 3 1 4 , who condensed the mercury s a l t of n - b u t y l o r o t a t e with t r i b e n z o y l r i b o f u r a n o s y l c h l o r i d e . The main product (10%) was the s t e r i c a l l y favoured N-3 g l y c o s i d e 252. Other s t u d i e s 3 1 5 - 3 1 7 concerned with the d i r e c t c o u p l i n g of 6-methyluracil d e r i v a t i v e s with sugar h a l i d e s showed COOH OH OH 2 5 2 that the N - 3 g l y c o s i d e was again the favoured product, though 58 c o n d i t i o n s could be a l t e r e d to render a c c e p t a b l e y i e l d s of the N-1 g l y c o s i d e {242, R=CH 3). Proceeding from such a m o d i f i e d condensation r e a c t i o n , K l e i n and F o x 3 1 8 were a b l e to o x i d i z e the methyl group of 242 <R=CH3) with selenium d i o x i d e to g i v e 6 - f o r m y l u r i d i n e (242, fi=CHO), an important i n t e r m e d i a t e f o r f u r t h e r d e r i v a t i z a t i o n of the C-6 p o s i t i o n . 6.2.2.2. N u c l e o p h i l i c S u b s t i t u t i o n . The 5,6-double bond of u r a c i l and i t s d e r i v a t i v e s i s known to be s u s c e p t i b l e to n u c l e o p h i l i c a t t a c k . 3 0 3 For i n s t a n c e , sodium b i s u l f i t e adds to u r a c i l or u r i d i n e i n a r e v e r s i b l e manner to g i v e the 6 - b i s u l f i t e adducts 253 and 254, r e s p e c t i v e l y . 3 1 9 .253 R=H 2 54 R= yfl-g-ribofuranosyl By r e a c t i n g potassium cyanide with the blocked 5-. bromouridine d e r i v a t i v e 255 i n p y r i d i n e , U e d a 3 2 0 obtained the 6-cyano adduct 257. The r e a c t i o n was thought t o proceed by i n i t i a l n u c l e o p h i l i c a d d i t i o n o f the cyanide anion t o C-6 of the 5,6-double bond of 255 t o g i v e the i n t e r m e d i a t e 256. Spontaneous e l i m i n a t i o n of hydrogen bromide then gave 257. This a d d i t i o n -e l i m i n a t i o n mechanism was confirmed by d e u t e r a t i o n s t u d i e s o f the analogous potassium cyanide- 5-bromouracil s y s t e m 3 3 0 . Ueda was f u r t h e r a b l e to c o n vert the C-6 n i t r i l e group to a 59 AcO-O ^ N ^ HN 7 KCN, AcO V 255 v a r i e t y of other f u n c t i o n a l i t i e s by standard p r o c e d u r e s . 3 3 1 T h i s i s the only example of n u c l e o p h i l i c i n t r o d u c t i o n of a carbon u n i t a t C-6 of u r i d i n e . 6.2.2.3. Synthesis from Oxazolines. H o l y 3 3 2 has s u c c e s s f u l l y r e a c t e d , under base c a t a l y s i s , the 2-amino o x a z o l i n o sugar 258 w i t h . a l k y l 2-butynoates to gi v e the C-6 a l k y l a t e d 2,2'-anhydronucleoside 259. These HO-NH2 H0-RC^CC02C2H5^ OH 258 OH 259_R=CH3,C2H5 anhydronucleosides are e a s i l y converted to the 6 - a l k y l r i b o , arabino or 2-deoxy n u c l e o s i d e s . 3 3 3 S i m i l a r l y , H a l l and c o - w o r k e r s 3 3 4 were a b l e t o s y n t h e s i z e v a r i o u s novel 6 - s u b s t i t u t e d 2,2'-anhydro-5,6-dihydro n u c l e o s i d e s by r e a c t i n g 258 with a c t i v a t e d . a , B - u n s a t u r a t e d e s t e r s . Thus, 258 and dimethyl fumarate {259} gave the 6-carbomethoxy d e r i v a t i v e 260. _ ;  Hy /C0 2CH 3 A H J C O J C H 259 C02CH3 OH 260 60 6- 2. 2. 4 Mi s c e l l a n e o u s Methods. A l k y l groups have been attached t o C-6 of u r i d i n e by photochemical m e a n s 3 3 5 - 3 3 6 and by C l a i s e n rearrangement of 5-a l l y l o x y u r i d i n e . 3 3 7 6 1 I I I RESULTS AND DISCUSSION The work to be d e s c r i b e d has been d i v i d e d i n t o t h r e e b a s i c u n i t s . . These a r e : ( 1 ) The s y n t h e s i s of g l y c o s y l a - and e-amino a c i d s that are s t r u c t u r a l analogues of the sugar moiety of the p o l y o x i n s , (2) the s y n t h e s i s of C - n u c l e o s i d e s and t h e i r p r e c u r s o r s , and (3) the attachment of C-C l i n k e d s u b s t i t u e n t s at C-2 and C-6 of p y r i m i d i n e n u c l e o s i d e s . Each u n i t has been organized a c c o r d i n g to the f o l l o w i n g headings: 1. G l y c o s - 3 - y l Amino A c i d s : S t r u c t u r a l Analogues o f the Sugar Moiety of the P o l y o x i n s . 1 . 1 . S y n t h e s i s of D e r i v a t i v e s of G l y c o s - 3 - y l 3 - A l a n i n e : A p p l i c a t i o n o f the Knoevenagel Condensation of E t h y l Cyanoacetate with a 3-Ulose- , 1.2. S y n t h e s i s of D e r i v a t i v e s of G l y c o s - 3 - y l G l y c i n e : A p p l i c a t i o n o f the Bucherer Procedure v i a Condensation of 1,3-Dithiane Anion with a 3-Ulose. 2. S y n t h e t i c Approaches to C-Nucleosides. 2.1. S y n t h e s i s of F u n c t i o n a l i z e d P r e c u r s o r s to C-N u c l e o s i d e s . 2 . 1 . 1 . Knoevenagel Condensation of E t h y l Cyanoacetate with a 2,5-Anhydro-D-allose. 2.1.2. Condensation of D i e t h y l Sodium Phthalimidomalonate with a G l y c o s y l H a l i d e . 2.2. S y n t h e s i s of 5 - A l k y l U r a c i l . , Attempted One-Step S y n t h e s i s of a Pseudouridine D e r i v a t i v e . 3. M o d i f i c a t i o n s of the 2- and 6 - P o s i t i o n s of U r i d i n e Using 1,3-Dithiane Anion. 3.1. Reaction o f 1,3-Dithiane Anion with a 2,2'-62 Anhydroaucleoside: F u n c t i o n a l i z a t i o m of the 2- and 6 - P o s i t i o n s of P y r i m i d i n e N u c l e o s i d e s . 3.2. Reaction of 1 , 3 - D i t h i a n e Anion with Blocked 5-Bromouridine: Syn t h e s i s of a 6-8-Alanine D e r i v a t i v e of U r i d i n e . 1 . G l y c o s - 3 - y l Amino Aci d s : S t r u c t u r a l Analogues of the Sugar Moiety of the P o l y o x i n s . The s y n t h e s i s of branched-chain g l y c o s - 3 - y l amino a c i d s has been a s u b j e c t of c o n t i n u i n g i n t e r e s t i n our l a b o r a t o r y . 4 9 - 7 2 The o b j e c t i v e has been t o form analogues of the sugar moiety of the n a t u r a l l y - o c c u r r i n g p o l y o x i n s (see I n t r o d u c t i o n , S e c t i o n 1 . 3 . ) , the n u c l e o s i d e s of which might e x h i b i t i n t e r e s t i n g b i o l o g i c a l p r o p e r t i e s . 1 9 S i n c e p r e v i o u s s y n t h e t i c s t u d i e s have focussed on the attachment of a-amino a c i d s , notably g l y c i n e and a l a n i n e , 7 7 to s u i t a b l e carbohydrate d e r i v a t i v e s by carbon-carbon bonds, i t seemed n a t u r a l to extend t h i s work to the h i t h e r t o unknown B-amino a c i d sugar d e r i v a t i v e s . Such compounds c o u l d be of value i n e l u c i d a t i n g s t r u c t u r e - a c t i v i t y r e l a t i o n s h i p s of the v a r i o u s molecules s y n t h e s i z e d . I t was a l s o our g o a l to f i n d more e f f i c i e n t and convenient methods of s y n t h e s i z i n g those g l y c o s - 3 - y l a-amino a c i d s which had a l r e a d y been produced by v a r i o u s means i n our l a b o r a t o r y -Such new procedures, i t was f e l t , should y i e l d branched-chain d e r i v a t i v e s whose n u c l e o s i d e s could e a s i l y be formed. 1.1. S y n t h e s i s of D e r i v a t i v e s of Glycos- 3- y l B-Alanine; Jk E f i l i S ^ t i o n of the Knoevenagel Condensation of 63 E t h y l Cy.anoaceta.te with a 3-Ulose-1.1-1. 1 T 2 : ^ 5 # - & - D i - 0 ^ - i s g p r o p y l i d e n e - a-D M-r i b g -hexof uranos -3-u l o s e (1 fj ) „ . O x i dation of the f r e e hydroxyl group of 1, 2:5, 6-di-O-i s o p r o p y l i d e n e - a - D - g l u c o f uranose (261.) 3 3 8 was achieved by known procedures using ruthenium t e t r a o x i d e 3 3 9 ~ 3 * °, generated i n s i t u . . The r e s u l t i n g ketose hydrate (262) was dehydrated to 3-ulose J.4 by a z e o t r o p i n g with t o l u e n e immediately p r i o r to use. . ,0-, \0H_ 261 1 I OH 0-j-262 o" o f U 1.1.2. Knoevenagel Condensation of Ethy_l Cyanoacetate _(263}_ with 1,2: 5 f6-Di-0 -i s o p r o p y l i d e n e - g-p -riho-hexofuranost -3-ulose lJ_if_l=. The c o n d i t i o n s used by Rosenthal and C l i f f 7 2 i n t h e i r condensation of methyl n i t r o a c e t a t e with 1.4 were adapted f o r the present study. Thus, r e a c t i o n of the 3-ulose 14 with a s l i g h t molar excess of e t h y l cyanoacetate (263) i n N,M-dimethylformamide u s i n g ammonium acetate as the c a t a l y s t gave, a f t e r 2 hours a t room temperature, two major new products as shown by t . l . c . on s i l i c a g e l . Though t . l . c . , s t i l l . showed presence of some unreacted s t a r t i n g m a t e r i a l i n the r e a c t i o n mixture, i n c r e a s i n g the r e a c t i o n time r e s u l t e d i n the formation of a c o n s i d e r a b l e number of s i d e - p r o d u c t s so that 2 hours was c o n s i d e r e d the optimum r e a c t i o n time-64 m X rsl O O O z X <_> —<_>— n o o X -4-X -o c rH 4-1 OJ e /—s rH O • x> cn U rH CO O O Q £ ° O C .C -H u Q) /—^ w <T 0 vO C CN ca ^ o 11) 1 CO o t o C n Cfl ^ 3 , — i I o U |r-< I -H r o cd ^ An 6 7 3 0) M C 4-1 CD CJ TJ OJ -H O- r-l C/3 \ °< o o N CO o o rH rH Cfl •H 4-1 r-l cd P - t 0) M 3 60 •H 4' •H I vO CHCN C 0 2 C 2 H 5 2 6 8 H-1 i i i I i i i i I i i i i l i i i i I i i i i ' i j i ' ' . i , ' , i, l, \ ', ! j i i i i i i i i i i i r i 8 7 ' i i i I i i i i i I ~ I i i i i I I ' 1 I I I I I I I i i I I I I I I l U 3 2 1 o F i g u r e I I I . P a r t i a l 100 MHz PMR Spectrum of 3 - C - [ ( R , S ) - C y a n o ( e t h o x y c a r b o n y l ) m e t h y l e n e ] -3 - d e o x y - l , 2 : 5 , 6 - d i - 0 - i s o p r o p y l i d e n e - a - D - a l l o f u r a n o s e (268) i n CDCl^. ON 66 The r e s u l t i n g products were p a r t i a l l y separated by chromatography on s i l i c a g e l , a f f o r d i n g the h y d r o x y l a t e d d e r i v a t i v e 264 i n 25% y i e l d and a mixture of the dehydrated analogue of 264, compound 265, and the d i - a d d i t i o n compound 266 i n a combined y i e l d of approximately 10%-X ; 14 i f - f NCCH2C02C2H5 263 DMF NH^OAc CN >< • CHC02C2H5 •O-i o C N )K0-] CHC0,C,H 2^2r,5 OH i f /} I I C-CN 0-j— 264 C0 2C 2H 5 265 CHCN °" 2 266 C0 2C 2H 5 The n.m.r- spectrum of c r y s t a l l i n e 264 i n deuterochloroform (Figure II) c l e a r l y showed that a d d i t i o n of one molecule o f e t h y l cyanoacetate t o 1.4 had occurred, the e t h y l e s t e r s i g n a l s being v i s i b l e at 61.37 and 4.26. Moreover, a d d i t i o n of D^O to the n.m.r. sample r e s u l t e d i n the disappearance of the hyd r o x y l peak at 6 4.11. The i . r . spectrum of 264 c o r r o b o r a t e d t h i s s t r u c t u r e assignment; besides the n i t r i l e and c a r b o n y l a b s o r p t i o n s a t 2260 and 1730 cm - 1, a broad hydroxyl s t r e t c h i n g v i b r a t i o n was seen a t 3525 'cm-1. Both the chemical a n a l y s i s and mass spectrum of 264 were i n accord with a hydroxylated d e r i v a t i v e , the l a t t e r spectrum showing the t y p i c a l M+-CH^ peak of i s o p r o p y l i d e n e sugar d e r i v a t i v e s - 3 4 1 67 That compound 264 had the a l i o r a t h e r than the C-3 e p i m e r i c c o n f i g u r a t i o n was . based on p r e v i o u s work, i n our l a b o r a t o r y 7 2 i n which condensation of methyl n i t r o a c e t a t e with the same 3-ulose .14 i n the presence of ammonium a c e t a t e gave e x c l u s i v e l y the a l i o isomer, t h i s product a r i s i n g by a d d i t i o n of the anion from the l e s s s t e r i c a l l y h i n d e r e d s i d e of the k e t c s e . More d i r e c t evidence f o r the a l l o c o n f i g u r a t i o n of 264 was obtained from i t s d i l u t e - s o l u t i o n i . r . spectrum i n carbon t e t r a c h l o r i d e i n which, as j u s t mentioned, a s i n g l e OH a b s o r p t i o n peak a t 3525 cm - 1 was observed. S l e s s o r and T r a c e y 3 * 2 have shown t h a t the i . r . spectrum of 1, 2: 5,6-di-O-i s o p r o p y l i d e n e - a -D-glucof uranose <26 1) under these c o n d i t i o n s e x h i b i t s two hydroxyl peaks at 3485 and 3622 c r 1 , the former a r i s i n g from the C-3 OH t h a t i s i n t r a m o l e c u l a r l y bound to the C-5 oxygen and the l a t t e r peak a r i s i n g from that f r a c t i o n o f the C-3 OH i n which C-5 and C-6 are i n a rotamer t h a t cannot be hydrogen bonded. On the other hand, the d i l u t e - s o l u t i o n i . r . spectrum of the a l i o analogue 267 showed a s i n g l e OH a b s o r p t i o n at 3570 cm-* r e s u l t i n g from i n t r a m o l e c u l a r fl-bonding with the oxygen at C-2. W i : 267 j i The c o n f i g u r a t i o n a t the asymmetric c e n t r e of the C-3 branched-chain of 264 was not proven though, by analogy with the r e a c t i o n of methyl n i t r o a c e t a t e with ,14, a, mixture of the R and S isomers would be expected. T h i s was i n d i c a t e d by the 68 n.m.r. spectrum of 264 {Figure II) i n which minor side-bands were a s s o c i a t e d with most of the major peaks. The mixture of the two minor r e a c t i o n products 265 and 266 had an n. m. r. spectrum i n deuterochloroform t h a t was understandably complex but from which i t c o u l d n e v e r t h e l e s s be concluded that the products i n q u e s t i o n c o n t a i n e d the elements of e t h y l cyanoacetate (263) . I t a l s o seemed reasonable to assume that, based on the observed r e s u l t s of the Knoevenagel condensation of e t h y l cyanoacetate with some non-carbohydrate ketones (see I n t r o d u c t i o n , S e c t i o n 2.3.2.), t h i s mixture probably c o n t a i n e d the products a r i s i n g , r e s p e c t i v e l y , by dehydration of the i n i t i a l l y formed a d d i t i o n product 264 and M i c h a e l - a d d i t i o n of e t h y l cyanoacetate to the r e s u l t i n g unsaturated c e n t r e . , S i n c e compounds 265 and 266 c o u l d be separated n e i t h e r by f r a c t i o n a l c r y s t a l l i z a t i o n nor by pr e p a r a t i v e t . l . c , recourse was made to chemical t r a n s f o r m a t i o n s to achieve s e p a r a t i o n and c h a r a c t e r i z a t i o n o f these components. Thus, treatment o f the mixture of 26 5 and 266 i n methanol with sodium cyanoborohydride, a reagent known 3* 3 t o s e l e c t i v e l y reduce a c t i v a t e d double-bonds, gave 3-C-[ (B,S)-cyano (ethoxycarbonyl) methylene ]-3-deoxy- 1,2: 5,6-di-0-i s o p r o p y l i d e n e - a - D - a l l o f u r a n o s e (268) which was now e a s i l y s eparated by chromatography from the unreacted 3,3-C-bis-cyano{ethoxycarbonyl) methyl d e r i v a t i v e 266. Compound -268 analyzed f o r a s i n g l e e t h y l cyanoacetate moiety, and t h i s was s u b s t a n t i a t e d by i t s n.m.r. spectrum i n deuterochloroform (Figure I I I ) . Moreover, t h i s spectrum showed H-3 as a complex m u l t i p l e t c e n t r e d at 62.52, i r r a d i a t i o n of which caused the H-2 : 69 o—i NQCNBH 3 265 + 266 - — > MeOH V /0 }| + 266 (unchanged) CHC I C0 2C 2H 5 268 N 0-|— s i g n a l a t 6 4.76 t o c o l l a p s e from a m u l t i p l e t to a doublet of doublets with a c o u p l i n g constant {J- ) of 5.0 Hz. The two doublets presumably a r i s e from an approximately 1:1 mixture of S and S isomers a t the asymmetric centre of the C-3 branched-c h a i n . Since i t has been shown 3** that t r a n s H2~H3 °^ the furanose sugars have c o u p l i n g s of l e s s than 0.5 Hz,.whereas c i s H^-H^ have c o u p l i n g s of g r e a t e r than 2.5 Hz, then H-2 and H-3 of 268 must be i n a c i s o r i e n t a t i o n so t h a t 268 has the a l i o c o n f i g u r a t i o n . The sharpness of the doublet of the anomeric proton a t 6 5.78 was taken as evidence that none of the a l t e r n a t e q l u c o isomer was present i n the sample.. Chemical a n a l y s i s and n^aur. spectroscopy of c r y s t a l l i n e 266 i n d i c a t e d t h a t , as a n t i c i p a t e d , t h i s compound was the gem-d i - C - a l k y l d e r i v a t i v e formed by M i c h a e l - a d d i t i o n of e t h y l cyanoacetate to the double-bond of 265. Since no C-3 hydrogen c o u l d be seen i n the n.m.r. spectrum of 266, i t was concluded that a d d i t i o n of the second molecule of e t h y l cyanoacetate had occurred at the C-3 carbon of t h e furanose r i n g of 265 r a t h e r than at the other carbon atom of the double-bond. The r e s u l t s obtained i n t h i s Knoevenagel condensation of the 3-ulose J_4 with e t h y l cyanoacetate (263) are t o be c o n t r a s t e d with those c o n c u r r e n t l y obtained by A l l and S z a r e k 1 9 1 who reacted these two compounds i n benzene using aqueous potassium hydroxide as base under phase t r a n s f e r c o n d i t i o n s . In t h i s case, i t was r e p o r t e d t h a t o n l y the unsaturated d e r i v a t i v e 265 was obtained. The y i e l d was 85%. 70 1.1.3. C a t a l y t i c Hydrogenation of 3-C~t.iSx.Sl-Cyano(ethoxycarbonyl)methylene ^-1^2^5^6-di-0-isopropy l i d e n e - a - D - a l l o f uranose j264j_. Eeduction of the n i t r i l e group of the h y d r o x y l a t e d branched-chain sugar 264 was the next c r u c i a l step i n the planned s y n t h e s i s of sugar d e r i v a t i v e s of p-alanine. A l k y l cyanides have been reduced by metal h y d r i d e s 3 * 5 , by d i b o r a n e 3 * 8 and by c a t a l y t i c h y d r o g e n a t i o n . 1 6 1 - 1 6 2 3 4 7 - 3 * 8 only the l a t t e r method seemed compatible with - the presence of the e s t e r f u n c t i o n a l i t y of compound 264. Of the c a t a l y s t s that have been used f o r hydrogenation of n i t r i l e s , Raney n i c k e l seemed the l e a s t a t t r a c t i v e s i n c e i t r e g u i r e d both high pressures and t e m p e r a t u r e s . 3 4 7 The c a t a l y t i c r e d u c t i o n of a cyanomethyl branched-chain s u g a r 3 * 9 using 5% rhodium-on-alumina 3* 8 has been reported to g i v e the corresponding aminoethyl d e r i v a t i v e . More d i r e c t l y a p p l i c a b l e was the u t i l i z a t i o n by S e y g a a d 1 6 1 of platinum oxide (Adam's c a t a l y s t ) f o r hydrogenation of e t h y l cyanoacetate (26 3) to e t h y l g-alanate (26.9). ! NCCH2C02C2H5 NH 2CH 2CH 2C0 2C 2H 5 \ 263 269 j The c a t a l y t i c hydrogenation of n i t r i l e s i s hampered by the f o r m a t i o n of i n t e r m e d i a t e imines (Scheme 7, Equation(a)) which can r e a c t with the amine product t o form d i m e r s 3 * 8 (Equation ( b ) ) . S i d e r e a c t i o n s of t h i s s o r t can be prevented by conducting the hydrogenation i n an ammonia-saturated s o l u t i o n 3 * 8 , i n which case the e q u i l i b r i u m of Eguation (b) i s r e v e r s e d , or by t r a p p i n g the primary amine as i t i s formed, preventing i t s f u r t h e r 71 ! H H - - - - - -i RC=N 2-) RCH=NH —2—> RCH^NH^ • ( o) RCH=NH + RCH2NH2 ^ S R C H=N C H2R + N H ^  (b) . Scheme 7 r e a c t i o n - E i t h e r mineral a c i d 3 S 0 or a c e t i c anhydride can accomplish the l a t t e r . Thus, s i n c e compound 264 c o n t a i n s both a c i d - s e n s i t i v e i s o p r o p y l i d e n e groups and a b a s e - s e n s i t i v e e s t e r group, i t s hydrogenation was attempted i n anhydrous a c e t i c anhydride using platinum oxide as c a t a l y s t a t a pressure of 3 atmospheres. A f t e r 10 hours at room temperature, the N-acetamido d e r i v a t i v e 270 was CH2NHAC i X°H CHC0 2C 2H 5 H ?.Pt0 2 " 1 > ° \ I 264 2 n ) \] A ! Ac 20 \ / 0 OH 0-f-; 270 obtained i n 96% y i e l d by chromatography on s i l i c a g e l . The presence of peaks a t 1725 and 1750 cm - 1 i n the i . r . spectrum of 270 v e r i f i e d t h a t t h e r e were two c a r b o n y l groups i n t h i s compound while the n.m.r. spectrum of 270 i n deuterochloroform showed the r e q u i r e d two D^O-exchangeable protons, the NH and OH s i g n a l s appearing, r e s p e c t i v e l y , as a broad doublet centered a t & 6- 35 and a s i n g l e t a t 6 5-12..' The methyl group of the N-ace t a t e gave r i s e t o two s i n g l e t s around 6 1.90, a r e f l e c t i o n of the probable e x i s t e n c e of approximately e q u a l q u a n t i t i e s of E and S isomers of the blocked amino a c i d . A d d i t i o n a l proof o f s t r u c t u r e of 270 came from i t s low r e s o l u t i o n mass spectrum i n which the molecular i o n peak was seen a t m/e 417. 72 1.1- 4. Dehydration of 3-C-[_iE xS_L-^Y a.I>glgthoxyearbonyl^methylene]-1.2; 5,6-di-0~iso£ro2ylidene-_a-D-allofuranose _{26 4J_-^  Compound 270 i s a blocked Type A branched-chain sugar, the B - a l a n i n e moiety being attached to a carbon bearing a hydroxyl group. The Type B branched-chain analogue of 270, t h a t i s , the 3-deoxy d e r i v a t i v e , was a c c e s s i b l e by c a t a l y t i c r e d u c t i o n of the n i t r i l e group of compound 268. However, because t h i s compound was a v a i l a b l e only from the minor product 265 obtained i n an impure s t a t e by r e a c t i o n of e t h y l cyanoacetate with 3-ulose 14, dehydration of the major product 26 4 of t h i s r e a c t i o n seemed a more v i a b l e route to the d e s i r e d Type B sugar. A s t e r e o s e l e c t i v e dehydration of the C-3 branched-chain sugar 271. using t h i o n y l c h l o r i d e i n p y r i d i n e has been reported by E o s e n t h a l and Shudo 6 8 to g i v e the unsaturated d e r i v a t i v e 272, ON SOCI 1 0. 9H A Pyr id ine 5 /0 '2 "Jl- AcO-cf U_ I rn.ru 1 H i - ° A C ' -C0 2 CH 3 C 0 2 C H 3 L s 271 272 t r a n s e l i m i n a t i o n of the.hydrogen and the h y d r o x y l group being favoured. T h i s procedure was a p p l i e d t o 264. Thus, treatment of the l a t t e r compound «ith t h i o n y l c h l o r i d e i n p y r i d i n e at 0<> f o r 3 minutes gave, before work-up, a s t r o n g l y f l u o r e s c e n t product of i d e n t i c a l Rf on s i l i c a g e l as t h e dehydrated compound 265. However, a f t e r work-up, the r e a c t i o n showed a l o s s of f l u o r e s c e n c e though i t s R^  had not changed. That t h i s product, I 1 ! 1 1 i i i i i i i i i i i i I ' 1 i i i i i i i i i i i i i i i i i i i i i i i i I , c 7 6 5 4 1 i i i i I i i i i I i i I I I I l - l 2 1 f i g u r e IV. P a r t i a l 100 MHZ.PMR Spectrum of 3 - C - [ ( R , S ) - C y a n o ( e t h o x y c a r b o n y l ) m e t h y l e n e ] -3 - d e o x y - l , 2 : 5 , 6 - d i - 0 - i s o p r o p y l i d e n e - a - D - e r y ^ h r o - h e x - 3 - e n o f u r a n o s e (273_) i n C ^ . 74 i s o l a t e d by chromatography on s i l i c a g e l , was 3-C-[ ( J / S ) -i s o p r o p y l i d e n e - crD-erjrthro-hex-3-enofuranose (273) and not the expected compound 265 was i n d i c a t e d by i t s i . r . spectrum which showed a non-conjugated o l e f i n i c a b s o r p t i o n a t 1698 cm - 1 and by i t s n^m.r. spectrum i n deuterochloroform which e x h i b i t e d a t r i p l e t f o r H-5 centered a t 64.72. Ne i t h e r s p e c t r a showed evidence, of a h y d r o x y l group. Furthermore, compound 273 was not reduced by sodium cyanoborohydride, as was compound 265, and the u. v. spectrum of 273 i n methanol, which showed maxima at 212 and 263 nm d i d not correspond to the known absorbance of a double bond i n c o n j u g a t i o n with the e t h y l cyanoacetate group, the l a t t e r system having a maximum at 228 nm. 3 5 2 Though the R:S r a t i o of 273 co u l d not be estimated from i t s n.m.r. spectrum i n deuterochloroform, use of perdeuterobenzeae as the n.m.r- s o l v e n t unambiguously showed a 3:2 mixture of isomers with H-1, H-2 and methine proton of the e t h y l cyanoacetate moiety of each isomer c l e a r l y r e s o l v e d (Figure I V ) . A few examples ( 2 7 4 3 5 3 and 2 7 5 3 S 4 ) Q f 3,4-unsaturated furanoses have been repor t e d , the p h y s i c a l c h a r a c t e r i s t i c s of which resemble those of compound 273. I t i s l i k e l y , then, t h a t the. l a t t e r compound i s the r e s u l t of an a c i d - c a t a l y z e d i s o m e r i z a t i o n of the i n i t i a l l y formed e x o c y c l i c double-bond of cyano{ethoxycarbonyl)methylene]-3-deoxy-1,2:5,6-di-O-265 273 75 °x° y c + 274 R=H 275 R=OAC 265. This would account for the change i n fluorescence of the reaction product after work-up,enough acid being generated by hydrolysis of the thionyl chloride during t h i s procedure to cause the rearrangement. Direct elimination of the C-3 hydroxyl and C-4 hydrogen of 264 to give 273 i s unlikely since these two groups are c i s to each other-', ! . A s i m i l a r acid-catalyzed rearrangement of an exocyclic double-bond to the 3- y position was observed i n the decarboxylation of the cyanoacetic acid derivative 276. 3 5 6 V _ / \0M 276 C N C0,H - C O , 1.2 Synthesis of Derivatives of Glycos-3-y1 Glycine: AE£l±___42fi of the Bucherer Procedure via Condensation of __3- Dithiane Anion with a 3-0lose. 1.2. 1- 3_-.C_-i1j.3-Dithian- 2-yl_-Ix2l5_.6-d.i-0_-isopropylidene-g -D -a11ofuranose (1 7 6 ) . , Reaction of 2-lithio-1,3-dithiane (126) 1 9 2 with 1,2:5,6-di-O-isopropylidene- a-D-ribo-hexof uranos ,-3-ulose (1.4) 3 3 9 in tetrahydrofuran at -78« gave the 3-C-dithianyl adduct V76 i n 57% y i e l d . Compound _76 was i d e n t i c a l to that prepared and characterized by Paulsen and coworkers- 2 3 6 76 • V ° ~ l o *1 P 0 0 - J --78° THF OH 0 1 2 6 U 1 7 6 1.2.2. 3-C-Formyl- 1, 2: 5^  6 - d i - 0 - i s o p r o p y l i d e n e - _ - D -a 11ofuranose _278_ and i t s Semicarbazone 1279__ Paulsen and S t e n z e l 3 5 7 converted the d i - O - i s o p r o p y l i d e n e d e r i v a t i v e _76 to the 5,6-di-O-acetate 277 before h y d r o l y z i n g the d i t h i o a c e t a l with boron t r i f l u o r i d e e t h e r a t e , presumably to a v o i d p a r t i a l unblocking of the sugar during the l a t t e r s t e p . Since a c e t a t e b l o c k i n g groups would not withstand the s t r o n g l y b a s i c c o n d i t i o n s of our a n t i c i p a t e d Bucherer hydantoin s y n t h e s i s 1 3 9 - 1 4 0 on C-3, h y d r o l y s i s of the d i t h i o a c e t a l ; was attempted on compound _76 d i r e c t l y by the method of F e t i z o n and J u r i o n . 2 3 1 Thus, a s o l u t i o n of _76 i n aqueous acetone c o n t a i n i n g barium carbonate and methyl i o d i d e was heated at 55° f o r 12 hours. The r e a c t i o n was monitored by t - l . c . which showed that formation of the aldehyde (278) was accompanied by the 2 7 7 77 p r o d u c t i o n of a s u b s t a n t i a l q u a n t i t y of p o l a r , b a s e - l i n e m a t e r i a l . The l a t t e r was removed by aqueous work-up of the r e a c t i o n mixture, g i v i n g the pure 3-C-formyl d e r i v a t i v e 278 as a syrup i n 92% y i e l d . The n.m.r- of 278 i n deuterochloroform e x h i b i t e d a t y p i c a l l o w - f i e l d {& 9.86} s i g n a l f o r the a l d e h y d i c proton while the i . r . spectrum of t h i s compound showed a s t r o n g c a r b o n y l a b s o r p t i o n at 1720 cm - 1, i n d i c a t i n g t h a t the formyl group had not formed an a c e t a l during the h y d r o l y s i s . 3 5 7 P u l l X ° 0 - I . o . M e l B a C O , 1 7 6 , 3 ) \ C H=0 a q . a c e t o n e OH 0-j— OH 2 7 8 2 7 9 ^ N N H C N H 2 .0-'0 c h a r a c t e r i z a t i o n of 278 was achieved by i t s c o n v e r s i o n to the c r y s t a l l i n e semicarbazone d e r i v a t i v e 279. Besides a n a l y z i n g p r o p e r l y , semicarbazone 279 had an n.m.r. spectrum i n dimethyl s u l f o x i d e - d g c o n s i s t e n t with the assigned s t r u c t u r e , showing s i g n a l s f o r f o u r D2O-exchangeable protons and one l o w - f i e l d {<5 7.12) imine proton, a l l as s i n g l e t s . 1.2.3-, ^ - C - i J x J - d i k e t o t e t r a h y d r o i m i ^ y 1).-1 12: 5 t 6-di-0 ,,-isopropylidene - a -D_-a l l g f uranose 1 2 8 0 ^ The 3-C-formyl sugar 278 was converted t o the hydantoin (al s o known as 2,4 - d i k e t o t e t r a h y d r o i m i d a z o l e ) d e r i v a t i v e 280 by the method of Bucherer, as modified by floyer.142 Thus, a Figure V. P a r t i a l 100 MHz PMR Spectrum of 3-C-(2,4-Diketotetrahydroimidazol-5-(R,S)-yl)-.l,2:5,6-di-O-isopropylidene- a -D_-allof uranose (280) i n DMSO-d,. oo 79 s o l u t i o n of 27 8 i n methanol c o n t a i n i n g 4 e q u i v a l e n t s each of sodium cyanide and ammonium carbonate was s t i r r e d , f o r 3 hours a t room temperature under 3 atmospheres of carbon d i o x i d e . The temperature was then g r a d u a l l y r a i s e d t o 50° and r e a c t i o n continued f o r 12 hours, a f t e r aqueous work-up, 280 was obtained i n crude form, but was p u r i f i e d by chromatography on s i l i c a g e l and by r e c r y s t a l l i z a t i o n . ; T h e i . r - spectrum of 230 showed the r e q u i r e d two c a r b o n y l a b s o r p t i o n peaks a t 1700 and 1780 cm - 1 as we l l as a sharp NH s i g n a l a t 3400 cm - 1 superimposed over the broad hydroxyl band. The n.m.r. spectrum of 280 i n dimethyl s u l f o x i d e - d g (Figure V) showed t h r e e l o w - f i e l d , D^O-exchangeable s i n g l e t s , a t t r i b u t e d to the two non-equivalent NH protons of the hydantoin r i n g and the hydroxyl proton of C-3-1-2.4 L_-2 and {112z5,6-Di-O - i s o p r o p y l i d e n e - g -D - a l l o f u r a n o s - 3 - y l ) g l y c i n e J28 1) . When the 3-C-hydantoin sugar d e r i v a t i v e 280 was r e f l u x e d i n conce n t r a t e d aqueous barium hydroxide s o l u t i o n f o r 4 hours, a n i n h y d r i n - p o s i t i v e m a t e r i a l was produced which was p u r i f i e d by chromatography on w e a k l y - a c i d i c c a t i o n exchange r e s i n - That t h i s compound was the 3-C-glycine branched-chain sugar 28_ was demonstrated by comparison to a u t h e n t i c samples of t h i s substance p r e v i o u s l y prepared by Rosenthal and C l i f f 3 5 8 v i a the 80 methyl n i t r o a c e t a t e route. Both compounds e x h i b i t e d i d e n t i c a l i . r. s p e c t r a and Rf's on paper. The presence of two separate Ba(OH), 280 ^ NH, < 2 CH~C0,H OH 0-j— I 281 ' n-m.r. s i g n a l s f o r the anomeric proton of 281, each observed as a doublet, was evidence that t h i s compound was, as expected, a mixture of tha D- and L-amino a c i d s . Since Rosenthal and C l i f f 3 5 8 have shown t h a t the anomeric proton of the L-isomer of 281 resonates at lower f i e l d than that of the D-isomer, then i n t e g r a t i o n of these two s i g n a l s r e v e a l e d t h a t compound 281 obtained by the hydantoin route was a 2z1 mixture of the D- and L-amino a c i d s , r e s p e c t i v e l y . A preponderance of D-isomer was a l s o i n d i c a t e d by the o p t i c a l r o t a t i o n of 281 i n water; the mixture had a r o t a t i o n of 43.2°, a value c l o s e r t o t h a t of the pure D-isomer (+25°) than of the L-isomer (+89.2°) - 3 5 8 A s m a l l q u a n t i t y of the L - g l y c i n e isomer was obtained by f r a c t i o n a l c r y s t a l l i z a t i o n o f the syrupy 281. No other attempts were made t o s e p a r a t e the D and L diasteromers of 28_! s i n c e i t has been s h o w n 3 5 8 t h a t t h e i r r e s p e c t i v e methyl e s t e r s are e a s i l y s e parable on s i l i c a g e l . Thus, i n c o n t r a s t to the methyl n i t r o a c e t a t e s y n t h e s i s of 3 - C - g l y c y l - a l l o f u r a n o s e (281_) , i n which mainly the L o p t i c a l isomer was o b t a i n e d , 3 5 8 the present s y n t h e s i s of 28J. v i a the hydantoin p r e c u r s o r 280 makes the D-isomer a v a i l a b l e i n p r a c t i c a l q u a n t i t i e s . 8 1 2 « . S y n t h e t i c Approaches t o C-NNucleosides. The importance of C - n u c l e o s i d e s , both n a t u r a l and s y n t h e t i c , as antitumour and a n t i b i o t i c agents has been d e s c r i b e d 1 9 2 5 6 (see I n t r o d u c t i o n , S e c t i o n 4 ) . The s y n t h e s i s of analogues of these b i o l o g i c a l l y a c t i v e compounds has thus been pursued i n view of producing more potent or l e s s t o x i c d e r i v a t i v e s . 2 5 6 2 6 0 The present work d e s c r i b e s two approaches t o the s y n t h e s i s of C - n u c l e o s i d e s . The f i r s t i n v o l v e s f o r m a t i o n o f n o v e l f u n c t i o n a l i z e d p r e c u r s o r s to C - n u c l e o s i d e s by way of e i t h e r a Knoevenagel condensation or carbanion displacement of a s u i t a b l e group on an a p p r o p r i a t e l y d e r i v a t i z e d sugar- The second method c o n s i s t s of a p a l l a d i u m - c a t a l y z e d condensation of a pre-formed base with a carbohydrate and i s an attempt to form a C-n u c l e o s i d e i n one-step. No s a t i s f a c t o r y way of d i r e c t l y c o u p l i n g a base and a sugar by carbon-carbon bonds ye t e x i s t s . These approaches are d e s c r i b e d i n t u r n . . 2 - 1 - S y n t h e s i s of F u n c t i o n a l ! z e d P r e c u r s o r s to C-N u c l e o s i d e s . 2 . 1 . 1 . Knoevenagel Condensation of E t h y l Cyanoacetate with a 2,5-Anhydro-D, - a l l o s e . 2 . 1 . 1 . 1 . 2 , 5 - A n h y d r o - 3 . 4 , 6 - t r i - Q -benzoyl-D -a i l o s e J 2 0 3 1 Reductive h y d r o l y s i s o f 2 , 3 , 5 - t r i - O - b e a z o y l - B - D -r i b o f u r a n o s y l cyanide ( 2 0 0 ) 2 6 7 with excess Raney n i c k e l and sodium hypophosphite i n the presence of N,N'-82 diphenylethylenediamine (282) gave 1, 3-diphenyl-2-{2, 3 , 5 - t r i - O -b e n z o y l - B - D - r i b o f uranosyl) imida z o l i d i n e ( 2 0 4 ) . 2 7 2 4 2 3 The 2,5-anhydro-D-allose 203 was then generated i n high y i e l d by treatment of the i m i d a z o l i d i n e 204 with p - t o l u e n e s u l f onic a c i d monohydrate i n acetone. BzO CN OBz OBz 200 BzO- HC 1 CHjNH^ r R 0 n e y Ni^ CH 2NHjer NoH 2P0, 282 OBz OBz 204 p-TSA-H^O BzO X HC=0 OBz OBz 203 2-1.1.2- E t h y l IE or ZJ.-4 , 7-anh ydro-2-cyano-2^3 fc5-trideoxy-6f-8-di-0 -benzoyl-j? _-£Elthro-octpn-2,4-dieneate (2 8 3 ) . Reaction of e t h y l cyanoacetate (263) with the D - a l l o s e d e r i v a t i v e 203 i n N,N-dimethylformamide i n the presence of a c a t a l y t i c amount of ammonium a c e t a t e gave, as the major product, compound 283, i s o l a t e d by chromatography on s i l i c a g e l and f u r t h e r p u r i f i e d by r e c r y s t a l l i z a t i o n . . A number of other minor, lower Rf products were formed i n t h i s r e a c t i o n , as shown by t - l ^ c . of the mixture, but these were not c h a r a c t e r i z e d . The i . r . spectrum of 283 v e r i f i e d the presence of an e t h y l cyanoacetate moiety; peaks a t 1600, 1630, 1720, and 2270 cm - 1 r e p r e s e n t i n g the e t h y l e n i c , e s t e r carbonyl and n i t r i l e bonds F i g u r e VI. P a r t i a l 100 MHz PMR Spectrum of E t h y l (E or Z)-4,7-anhydro-2-cyano-2,3,5-trideoxy-6,8-di-0^-benzoyl-J)-ery_hrQ-octon-2,4-dieneate i n CDC1„. 84 ^ + N C C H 2 C0 2 C 2 H 5 — K 263 4 1 283 | OBz were observed. Moreover, no hydroxyl band was seen i n the i . r . , so t h a t dehydration of the i n i t i a l l y formed a d d i t i o n product had ob v i o u s l y o c c u r r e d . The n.m.r. spectrum of 2 83 i n deuterochloroform (Figure VI) provided the f i r s t i n d i c a t i o n t h at the elements of benzoic a c i d had been l o s t i n the course of the r e a c t i o n . T h i s spectrum i n t e g r a t e d f o r the presence of only two benzoate groups.,Because of the known p r o p e n s i t y f o r compound 203 t o B i - e l i m i n a t e the benzoate group of C - 3 , 2 7 2 the p o s i t i o n of u n s a t u r a t i o n i n the sugar r i n g of 283 was assigned at t h e C-4, C-5 p o s i t i o n . T h i s i s a l s o the geometry a f f o r d i n g the g r e a t e s t amount of resonance i n t e r a c t i o n . T h i s assignment was s u b s t a n t i a t e d by the n.m.r* spectrum of 283 ( F i g u r e VI), the two v i n y l i c protons a t C-3 and C-5 g i v i n g r i s e to superimposed s i g n a l s at 6 6.12. T h i s l a t t e r doublet c o l l a p s e d to a two-proton s i n g l e t when H-6 was i r r a d i a t e d . The mass spectrum and chemical a n a l y s i s of 283 provided f u r t h e r proof t h a t e l i m i n a t i o n of a benzoate group had oc c u r r e d d u r i n g the Knoevenagel condensation with 203. There was no i n d i c a t i o n by any of these methods of c h a r a c t e r i z a t i o n t hat 283 contained more than one e q u i v a l e n t of e t h y l cyanoacetate. Although no attempt was made to e s t a b l i s h whether compound 283 i s t h e E or the Z isomer about the 2,3-double bond, p r e v i o u s s t u d i e s 1 8 5 - 1 8 6 of Knoevenagel condensations of e t h y l cyanoacetate with non-carbohydrate aldehydes have shown t h a t the isomer i n which the two b u l k i e s t groups are trans i s favoured. 85 I t c ould thus be p r e d i c t e d that 283 i s the E isomer. 2.1-1.3. C a t a l y t i c Hydrogenation of Ethyl i J or Z) -4 , 7-anhy dr o-2-cyano-2, 3, 5-trideoxy-6,8—di-Q —benzoyl-D - e r y t h r o - o c t o n - 2 ,4-d i e n e a t e t(2 8 3 ). • Hydrogenation of compound 283 over platinum oxide i n a c e t i c anhydride, conditions previously shown to reduce a n i t r i l e function to the corresponding acetamido derivative (see Section 1.1.3) yielded mainly the product i n which both double bonds, as well as the n i t r i l e group, were saturated {284). The i - r . spectrum of 284 no longer showed the n i t r i l e and ethylenic absorption peaks seen in the precursor. Instead, peaks f o r an amide carbonyl and the associated NH were observed at 1660 and 3450 cm - 1 respectively. The n.m.r. spectrum of 284 (CDCl^) was consistent with a completely reduced system; no l o w - f i e l d v i n y l i c protons were observed and the N-acetate s i g n a l was v i s i b l e as a si n g l e t at 6 1.95. Though the mass spectrum of 284 displayed the required molecular ion peak at m/e 497, smaller signals at m/e 503 and 509 suggested that p a r t i a l reduction of the phenyl rings of the benzoate groups of 283 had also occurred. This was not r e f l e c t e d in the chemical analysis of 284. : Compound 284 i s a precursor to the little-known c l a s s of 2-OBz H 284 00 O N 87 deoxy-D-ribose C-nucleosides. 3 S 9 - 3 6° 2. 1.2- . Condensation of Diethyl S odium Phthalimidomalonate with a Glycosyl Halide. 2.1.2.1. 2 f 3-0, -IsopropYlidene-5-0 . - t r i t y l - e -D -ribofuranosyl chloride (210). Treatment of a solution of 2,3-0-isopropylidene-5-0-trityl-p_-ribof uranose (285) 3 6 2 in N,N-dimethylformamide with triphenylphosphine and carbon tetrachloride gave the corresponding g-glycosyl chloride 2_0.2 7 6 3 6 2 Though the moisture sensitive chloride 210 could be c r y s t a l l i z e d 3 6 2 , i t was more advantageous to u t i l i z e the pure syrup obtained after work-up f o r subsequent reactions. 285 210. i . l 2. 1.2.2. Diethyl sodium phthalimidomalonate JL6_J_L=. a variation of the known procedure 1 2* of forming the sodium s a l t of d i e t h y l phthalimidomalonate (286) was employed foe the present study. Thus, to a solution of 286* 2 0 i n anhydrous ether was added one equivalent of sodium hydride. The yellow 88 p r e c i p i t a t e which had formed a f t e r one hour of s t i r r i n g was f i l t e r e d o f f and shown to be the sodium s a l t 6_ by v i r t u e of the absence of a s i g n a l f o r the 3 - p r o t o n i n i t s n.m.r. spectrum, taken i n dimethyl s u l f oxide-d,- -« C 0 2 C 2 H 5 OCKH M C0,C,Hc 0 286 NaH C0,C,H, tl 5 (I N-Ce Na® C0 2 C 2 H 5 61 2.1-2.3- D i e t h y l 2*3-0 -i s p p r o p y l i d e n e - 5 - Q -t r i t y l - a - ( a n d _3 ) - D - r i b o f u r a n o s y l phthalimidomalonate i2_8_7_ and 2 8 8 ) . Reaction of the B - g l y c o s y l c h l o r i d e 210 with an e q u i v a l e n t of d i e t h y l sodium phthalimidomalonate (6_) i n anhydrous NfN-dimethylformamide f o r 18 hours at 90° gave a mixture of the anomeric> C - g l y c o s i d e s 287 ( a ) and 288 ( 3 ) i n a combined y i e l d 2 1 0 + 6 1 8 9 of 4 6 % . The isomers were not sep a r a t e d . The n.m.r. spectrum of the mixture of 2 8 7 and 2 8 8 i n deuterochloroform {Figure V I I ) c l e a r l y showed the presence of the phthalimidomalonate moiety, the e t h y l e s t e r s i g n a l s appearing as a t r i p l e t and a q u a r t e t at 6 1 . 2 0 and 4 . 2 0 , r e s p e c t i v e l y , while the phthalimido protons resonated a t 6 7 . 6 5 . An a p p r o x i a t e l y 1 : 1 anomeric mixture was a l s o i n d i c a t e d by the n.m.r. spectrum by the f a c t t h a t the anomeric proton gave r i s e to a s i n g l e t and a doublet {J^ ^  & H z ) at 6 5 . 10 and 5 . 0 3 , r e s p e c t i v e l y . ,A s i n g l e t f o r H - 1 i s g e n e r a l l y a s s o c i a t e d with t r a n s H - 1 , H - 2 of a furanose r i n g ( i . e . -i , 2 8 8 ) while a doublet with a c o u p l i n g constant (d^ 2 ^ gr e a t e r than 3 - 5 Hz l i e s w i t h i n the range r e q u i r e d f o r a c i s r e l a t i o n s h i p o f these p r o t o n s 3 6 3 ( i . e . a , 2 8 7 ) . The n.m.r. evidence f o r 2 8 7 and 2 8 8 was c o r r o b o r a t e d by high r e s o l u t i o n mass spectrometry, which e x h i b i t e d the t y p i c a l (M+-CH^) peak of i s o p r o p y l i d e n e d e r i v a t i v e s - 3 * 1 Moreover, a g l y c o s i d i c C-C bond was demonstrated by the absence of an a p p r e c i a b l e peak at m/e 4 3 1 {M+-aglycon). The 0 - g l y c o s i d e s are known to favour t h i s fragmentation p a t t e r n ^ 3 6 * The i - r - spectrum of t h i s C - g l y c o s i d e e x h i b i t e d the a p p r o p r i a t e c a r b o n y l a b s o r p t i o n s at 1 7 2 5 and 1 7 5 5 cm - 1. , A simple 5 ^ 2 displacement of the c h l o r i d e i o n of the e -g l y c o s i d e 2 1 0 by the d i e t h y l phthalimidomalonate anion 6 J , would be expected to give e x c l u s i v e l y the a-anoraer 2 8 7 . However, the f a c t t h a t a mixture o f the a and 6 anomers i s a c t u a l l y formed i n t h i s r e a c t i o n suggests that the mechanism has some S ^ 1 c h a r a c t e r . T h i s i s not unusual s i n c e n u c l e o p h i l i c displacements of C - 1 h a l i d e s of both p y r a n o s y l 3 6 S and f u r a n o s y l 3 6 6 sugars 90 having no p a r t i c i p a t i n g groups at C-2 have been shown t o proceed v i a the ring-oxygen s t a b i l i z e d carbonium i o n 239 to give mixtures of the a and 3 isomers, the p r o p o r t i o n s of each being dependent on the r e a c t i o n medium and the presence of added s a l t s . ' The C - g l y c o s i d e 288 may be co n s i d e r e d as a blocked d e r i v a t i v e of B - D - r i b o f u r a n o s y l g l y c i n e and, as such, i s a prec u r s o r not only of the n a t u r a l formycins {189-191) and pyrazomycins (12 2-_9 3} but a l s o of p o t e n t i a l l y c h e m o t h e r a p e u t i c a l l y v a l u a b l e analogues of these b i o l o g i c a l l y a c t i v e C - n u c l e o s i d e s . 1 9 2 S * The s y n t h e s i s , concurrent with the present work, of a C - g l y c y l f u r a n o s i d e v i a condensation of a 1,4-lactone sugar with e t h y l i s o c y a n o a c e t a t e (see I n t r o d u c t i o n , S e c t i o n 4.1.2., compound 216a) has been, r e p o r t e d 2 8 0 ; however, only molecules i n which the amino a c i d and the sugar hydroxyl groups have a c i s r e l a t i o n s h i p are a v a i l a b l e by t h i s route and so cannot be c o n s i d e r e d as p r e c u r s o r s t o the n a t u r a l C-n u c l e o s i d e s . 2.1-2.4. Attempted Unblocking of 287 and 288. An i n i t i a l attempt t o d e p r o t e c t the C - g l y c o s i d e s 287 and 288 has been u n s u c c e s s f u l . Thus, treatment of a mixture of 287 and 288 i n THF and 1N aqueous sodium hydroxide at r e f l u x i n g temperatures f o l l o w e d by a c i d h y d r o l y s i s <2M HCI) of the 9 1 b l o c k i n g groups of the r e s u l t i n g product gave t r i p h e n y l c a r b i n o l which c r y s t a l l i z e d from the r e a c t i o n mixture and a n i n h y d r i n -p o s i t i v e m a t e r i a l - The l a t t e r substance was i s o l a t e d by chromatography of the r e a c t i o n mixture on a cation-exchange r e s i n - However, an n.m.r- spectrum of the c o l l e c t e d n i n h y d r i n -p o s i t i v e f r a c t i o n s , obtained i n only 1631 y i e l d , d i d not c o n c l u s i v e l y i n d i c a t e the presence of a r i b o s y l moiety so t h a t i t appears t h a t the C - g l y c y l r i b o s e d e r i v a t i v e 289a does not HO-i n C0,H . „NOOH " V V - t « N H , i 287 + 288 W - * ^ ' 2)HCI OH OH 289a withstand the r i g o r o u s c o n d i t i o n s r e q u i r e d f o r d e p r o t e c t i o n of 287 and 288., 2.2. ., S y n t h e s i s of a 5-AjLky_l u r a c i l . Attempted 0ne-Step. Sy n t h e s i s of a Pseudouridine D e r i v a t i v e . 2.2-1- 5-Bromo-2,4-di-t-butoxypyrimidine {292) Though the use of methyl groups t o block the 2- and im-p o s i t i o n s of 5-bromouracil (290) would have been more s t e r i c a l l y advantageous t o the i n t r o d u c t i o n of s u b s t i t u e n t s a t C-5 of t h i s molecule, the v i g o r o u s a c i d i c c o n d i t i o n s r e q u i r e d to remove these b l o c k i n g g r o u p s 2 9 2 d i d not seem a t t r a c t i v e . I n s t e a d , 290 was p r o t e c t e d with the more e a s i l y - h y d r o l y z e d t - b u t y l group. Thus, by published p r o c e d u r e s , 3 6 7 290 was f i r s t c h l o r i n a t e d a t C -2 and C-4 using . p h o s p h o r u s j o x y c h l o r i d e , y i e l d i n g compound 2 9 J . Reaction of 291 with sodium t-butoxide then gave i n good y i e l d the blocked 5-bromopyrimidine 2 9 2 . 2 9 3 The mass spectrum of 92 292 e x h i b i t e d the a p p r o p r i a t e molecular i o n peak. 0 C, OBu' H N A ^ B r p 0 C ( N ^ r - B r ^ N ^ B r H 290 291 292 2.2. 2. 5 - i _ - P r o p e n - 2 - _ l i j i r a c i l _296_ v i a the G r i g n a r d Reagent c 2fi 4-Di-t-butoxy-5-magnesiumbromopyrimidine (294). The formation of Grignard reagents from 5 - h a l o u r a c i l s has not p r e v i o u s l y been rep o r t e d . Our i n i t i a l attempts to form the 5-bromomagnesium compound 294 by r e f l u x i n g a t e t r a h y d r o f uran s o l u t i o n of 292 c o n t a i n i n g magnesium metal were not s u c c e s s f u l . I nstead, the often-used method of e n t r a i n m e n t 3 6 8 was u t i l i z e d , wherein ethylmagnesium bromide (293) was f i r s t formed from e t h y l bromide and magnesium and which, by a presumed exchange r e a c t i o n with the added 5-brombpyrimidine 2.92, gave the d e s i r e d G r i g n a r d reagent, 294. _ __ I Mg ! CjHjBr C^HjMgBr • • 223 |. . • i OBu' 292 + 293 > L II + c 2H 5Br N l f M 9 B r B 294 To show t h a t .29 4 had, i n f a c t , been formed by t h i s procedure, acetone was added to the r e a c t i o n mixture. A f t e r work-up, an i . r . spectrum of the crude r e a c t i o n mixture showed a prominent a b s o r p t i o n at 3650 cm—1, a f i r s t i n d i c a t i o n t h a t the h y d r o x y l compound 295 had formed. Compound 295 was not f u r t h e r I ' l l I I I I I I I I I I I I I I I I I I I I I I I I M l I I I i i i I I i i i i I i i i I i i l l I I I I 9 8 7 6 i i i i i I [ i i i I i i i i i i I i i i i l i i i i I i I i i i i i i i i r i i i i i i i i i 5 4 i i i i l i i i 3 2 g F i g u r e V I I I . P a r t i a l 100 MHz PMR Spectrum of 5 - ( l - P r o p e n - 2 - y l ) u r a c i l (296) i n DMS0-d 6. 94 c h a r a c t e r i z e d but was immediately unblocked with * d i l u t e , methanolic h y d r o c h l o r i c a c i d to give the 5 - a l k e n y l u r a c i l 296. i -- - -i i? 2 9 A + CH3CCH3 > • 2 9 5 . 2 9 6 That 295 had undergone dehydration d u r i n g the a c i d treatment was obvious from the n. m. r. of the product 296 ( F i g u r e V I I I ) . T h i s spectrum g r e a t l y resembled t h a t of <*-methyl s t y r e n e 3 6 9 (297) i n that a peak corresponding t o only one methyl group was seen at 6 1.92, while the two v i n y l i c protons of the s i d e - c h a i n were v i s i b l e at 6 5.01 (two doublets) and 5.79 ( d o u b l e t ) . The proton a t C-6 gave r i s e t o the expected l o w - f i e l d s i n g l e t ( , <5 7.35). Although the chemical a n a l y s i s of 29 6 was not e n t i r e l y s a t i s f a c t o r y , the mass spectrum of t h i s compound was unambiguous, a strong molecular i o n peak at m/e 152 being observed. _ CH3 2 9 7 formation of 296 proved t h a t the 5-bromomagnesium 29 4 had indeed been .generated by the procedure j u s t With t h i s i n mind, the d i r e c t c o u p l i n g of the reagent 294 with, a blocked g l y c o s y l h a l i d e was 2.2.3. attempted Coupling of 2 9 4 and a G l y c o s y l Thus, prec u r s o r d e s c r i b e d . Grignard attempted. 95 H a l i d e (210) _____ a Palladium _ I J J L C a t a l y s t (298). The use of palladium and i t s complexes to c a t a l y z e 2 8 0 * * the f o r m a t i o n of C-C bonds has been b r i e f l y d e s c r i b e d (see I n t r o d u c t i o n , S e c t i o n 5 ) . I n p a r t i c u l a r , our a t t e n t i o n was drawn to the f i n d i n g 2 9 0 that iodo (phenyl) b i s (triphenylphosphine) palladium ( I I ) (298) 3 7 0 could serve as a c a t a l y s t i n the c r o s s - c o u p l i n g of G r i g n a r d reagents and a r y l h a l i d e s . Thus, phenylethynylmagnesium bromide (29_) and phenyl i o d i d e (300) r e a c t e d i n t h e presence of c a t a l y s t 298 t o give an 8455 y i e l d of d i p h e n y l a c e t y l e n e { 3 0 1 ) 2 9 0 °3'2r jBfC-CMgBr + || | • x _ / 299 300 30L The mechanism p o s t u l a t e d f o r t h i s r e a c t i o n , d e p i c t e d i n Scheme 8, invoked the formation of the p a l l a d i u m complex 302 which, then r e a c t e d with phenyl i o d i d e (30.0.) t o form 30_ and , jfeCMgBr M g B r l I (299) \ / ( P C ^ P d ^ I < ) « p ^ 3 , 2 P d , ^ C s C ^ 298 ^ c - Q Q p 1 302 i m (300) Scheme 8 regenerate the c a t a l y s t 298.. An analogous r e a c t i o n sequence, i n which the pyrimidine Grignard reagent 294 r e p l a c e s 299 and the g l y c o s y l h a l i d e 210 r e p l a c e s 300, was envisaged as a p o s s i b l e r o u t e to a one-step s y n t h e s i s of blocked pseudouridine (303) . A c c o r d i n g l y , a s o l u t i o n of the G r i g n a r d reagent 294 i n THF was added t o a r e f l u x i n g s o l u t i o n of the r i b o f u r a n o s y l c h l o r i d e 2 1 0 2 7 6 c o n t a i n i n g a c a t a l y t i c amount of the palladium complex 298. However, even a f t e r 12 hours r e f l u x i n g of t h i s r e a c t i o n mixture, no c r o s s - c o u p l e d products resembling 303 c o u l d be d i s c e r n e d from an examination by n. m. r- of the s e v e r a l f l u o r e s c e n t r e a c t i o n OBu 210 + 294 303 components i s o l a t e d by chromatography. A p o s s i b l e e x p l a n a t i o n f o r the f a i l u r e of t h i s r e a c t i o n may l i e i n the i n a b i l i t y of the g l y c o s y l h a l i d e 210 to bind e f f e c t i v e l y with the c a t a l y s t . S e l f - c o n d e n s a t i o n of the G r i g n a r d reagent 294 c o u l d a l s o be a f a c t o r . T h i s approach to the s y n t h e s i s of C-nucleosides was abandoned with the p u b l i c a t i o n by A r a i and D a v e s 2 9 5 of a r e l a t e d , but s u c c e s s f u l , p a l l a d i u m - c a t a l y z e d C-C c o u p l i n g of a p y r i m i d i n e and a sugar {see I n t r o d u c t i o n , S e c t i o n 5.1..),. Nevertheless, the present work has r e s u l t e d i n a new method of a l k y l a t i n g the C-5 p o s i t i o n of u r a c i l (e.g. 296). 3. M o d i f i c a t i o n s of the 2- and 6- P o s i t i o n s of U r i d i n e Using 1,3-Dithiane Anion., The work to be p r e s e n t l y d i s c u s s e d was o r i g i n a l l y undertaken i n an attempt t o i n t r o d u c e f u n c t i o n a l i z e d C-C- l i n k e d s u b s t i t u e n t s a t the C-2 p o s i t i o n of the sugar moiety of the n a t u r a l n u c l e o s i d e s . Examples of so-modified n u c l e o s i d e s , e i t h e r 97 n a t u r a l or s y n t h e t i c , are not numerous and so, i n view of the known b i o l o g i c a l a c t i v i t i e s 1 9 of the C-3* and C-5* modified n u c l e o s i d e s (e. q. . puroraycin (28) and the p o l y o x i n s {29) , r e s p e c t i v e l y ) the development of a p r a c t i c a l s y n t h e t i c r o u t e t o these C-2* analogues seemed j u s t i f i e d . I n s p i r e d by the work of Yamashita and Rosowsky 2 5 2, who demonstrated t h a t the anion of 1,3-dithiane (126) a t t a c k e d r e g i o s e l e c t i v e l y a t C-2 of the 2,3-epoxide sugar 184 (see I n t r o d u c t i o n , S e c t i o n 3-3-3.) and, knowing that c e r t a i n n u c l e o p h i l e s (e-g- a z i d e . 3 1 2 , p h t h a l i m i d e 3 1 3 ) a l s o a t t a c k at C-2 of the sugar moiety of 2,2*-anhydrouridines {249) to give C-2' modified n u c l e o s i d e s (251), then i t seemed reasonable to expect t h a t the d i t h i a n e anion 126 would r e a c t with the anhydronucleoside 249 t o form 304 (Scheme 9), thereby y i e l d i n g the d e s i r e d C - 2 ' - f u n c t i o n a l i z e d n u c l e o s i d e . The r e a c t i o n of 249 and 126 d i d not, as d e s c r i b e d i n the f o l l o w i n g s e c t i o n , proceed as expected, but r a t h e r y i e l d e d a n o v e l method of modifying the e q u a l l y i n t e r e s t i n g and l i t t l e -s t u d i e d C-2 and C-6 p o s i t i o n s o f the n u c l e o s i d e - T h i s experiment was subsequently a l t e r e d , as d e s c r i b e d i n S e c t i o n 3.2- to allow the attachment of an amino a c i d at C-6 of u r i d i n e , thereby p 126 304 Scheme 9 98 extending our previous work ( S e c t i o n 1) on the s y n t h e s i s of g l y c o s y l amino a c i d s ( a l s o , see I n t r o d u c t i o n , S e c t i o n 6 f o r a d i s c u s s i o n of base-modified n u c l e o s i d e s ) -3.1 Raaction o f 1,3-Pithiane Anion with a 2,2'-Anhvdronucleosi.de: F u n c t i o n a l i z a t i o n of the 2- and 6- P o s i t i o n s of Pyrimidine Nucleosides-3.1-1. 2,2 t-Anhydro-1-(3-0 - a c e t y l - 5 - Q - t r i t y l - B - D -a r a b i n o f u r a n o s y l ) u r a c i l (308). Reaction of S ' - O - t r i t y l u r i d i n e C 3 0 5 ) 3 7 3 with 1one e q u i v a l e n t of t h i o c a r b o n y l d i i m i d a z o l e (306) i n r e f l u x i n g toluene gave, i n almost q u a n t i t a t i v e y i e l d , c r y s t a l l i n e 2,2'-anhydro-1-{5-0-t r i t y l - B - D - a r a b i n o f uranosyl) u r a c i l {307) . 3 7 4 Compound 307. was then t r e a t e d with a c e t i c anhydride i n p y r i d i n e to a f f o r d the 3'-O - a c e t y l d e r i v a t i v e 308., The s y n t h e s i s of 308 has been r e p o r t e d 3 7 5 though no p h y s i c a l c o n s t a n t s were given. 99 3-1.2- 2 - L i t h i o - 1 T 3 - D i t h i a n e 1126)-Reaction of 1,3-dithiane (123) i n anhydrous t e t r a h y d r o f uran (THF) with an e q u i v a l e n t of n - b u t y l l i t h i u m i n hexane at -78° under n i t r o g e n gave the anion 1 2 6 1 9 2 . The anion s o l u t i o n was g e n e r a l l y s t o r e d a t -20» f o r 2-5 hours p r i o r to use. S ^ ^ S n - B u L i S"^^, 123 126. 2. 1. 3- S y n t h e s i s of 2- (1,3-Ditfaian-2-yl) -1-( 5-0 -t r i t yl-B-D-arabinofuranosy 1)-U {IH) -pyrimidinone p09) and 2 t 2 1 -Anhydro-5,6-dihydro-6- (S)- (1 , 3 - d i t h i a n e - 2 - y l ) -1-(5-0-t r i t y l - g - D - a r a b i n o f u r a n o s y l ) u r a c i l (310). Hhen a s o l u t i o n of the blocked anhydronucleoside 308 i n anhydrous THF was added to a 5 molar excess of the anion J26 i n THF at -78°, two major products c o u l d be d i s c e r n e d by t . l . c . a f t e r , one hour of r e a c t i o n - Column chromatography on s i l i c a g e l of the worked-up r e a c t i o n mixture a f f o r d e d the two products 309 and 310 i n y i e l d s of 15 and 30%, r e s p e c t i v e l y . The e l u c i d a t i o n of the s t r u c t u r e s of 309 and 310 w i l l be d i s c u s s e d i n t u r n . The n.m.r. spectrum of 309 i n dimethyl s u l f o x i d e - d ^ showed, be s i d e s the h i g h - f i e l d s i g n a l s f o r the hydrocarbon protons of the d i t h i a n e moiety, two D20-exchangeable protons as d o u b l e t s a t 6 5-71 and 5.92- These were a t t r i b u t e d to the C-2» and C-3» secondary hydroxyl groups, the C-3 1 h y d r o x y l simply r e s u l t i n g from h y d r o l y s i s of the a c e t a t e group of 308 under the b a s i c 100 c o n d i t i o n s o f the r e a c t i o n . Moreover, the proton at the 2 - p o s i t i o n of the d i t h i a n e r i n g ( i . e . S-CH-S) gave r i s e t o a sharp s i n g l e t observed at 6 5.46, downfield from i t s u s u a l p o s i t i o n of ^  6 4.3, p o s s i b l y due to i t s p roximity t o t h e unsaturated imine. The l a t t e r group, as w e l l as the o l e f i n i c bond of 309, absorbed i n the a p p r o p r i a t e r e g i o n i n the i n f r a r e d (1635 and 1600 cm - 1, r e s p e c t i v e l y ) . Though a molecular i o n (M+) peak Iwas not observed i n the mass spectrum of 309, the c h a r a c t e r i s t i c s i g n a l a r i s i n g from cleavage of the g l y c o s i d i c c a r b o n - n i t r o g e n b o n d 3 7 * was seen a t m/e 375. T h i s corresponds t o the l o s s of 2 - { 1 , 3 - d i t h i a n ~ 2 - y l ) - 4 -pyrimidinone, t h a t i s , . M +-base, and proved that the d i t h i a n e group was not bonded to the sugar moiety. T h i s s p e c t r a l data, as w e l l as the chemical t r a n s f o r m a t i o n s of 309 (d e s c r i b e d below, S e c t i o n s 3.1.4-3.1.6), e s t a b l i s h e d that t h i s compound was that a r i s i n g by at t a c k of the d i t h i a n y l anion 1.26 at C-2 of the •I anhydronucleoside 308 with concomitant g e n e r a t i o n of an a r a b i n o sugar moiety. Based on the r e s u l t s of the a c t i o n of other n u c l e o p h i l e s 3 l 0 ~ 3 1 1 on anhydroimcleosides, the formation of the C-2 d i t h i a n y l adduct 309 from 308 and 126 was not unexpected (see I n t r o d u c t i o n , S e c t i o n 6.2.1..),... The s t r u c t u r e of the second major product (310) o b t a i n e d by r e a c t i o n of 3 08 and 126 was e s t a b l i s h e d by n.m.r. and 101 i . r. spectroscopy. F i r s t l y , the n.m.r. of 310 i n deuterochloroform showed, i n c o n t r a s t to t h a t of 309, only one D20-exchangeable h y d r o x y l proton { 6 5.50) and, s i g n i f i c a n t l y , disappearance of the l o w - f i e l d H-5 and H-6 doublets o f the p y r i m i d i n e r i n g , with g e n e r a t i o n of a two-proton m u l t i p l e t i n the 6 2.64-3.26 r e g i o n (H-5), p a r t i a l l y obscured by the l a r g e d i t h i a n e resonances. T h i s n.m.r- spectrum was thus c o n s i s t e n t with a pyrimidine n u c l e o s i d e i n which-the 5,6-double bond was s a t u r a t e d - 3 i 9 3 7 7 Moreover, the H-1 ' and H-2* resonances at 6 6-25 and 5-18, r e s p e c t i v e l y , and t h e i r c o u p l i n g constant of 5-0 Hz corresponded with the values obtained by H a l l and c o w o r k e r s 3 7 7 f o r these p r o t o n s i n the only other known re p o r t o f the s y n t h e s i s of C-6 s u b s t i t u t e d 2,2Lanhydro-5,6-d i h y d r o p y r i m i d i n e n u c l e o s i d e s (see I n t r o d u c t i o n , S e c t i o n 6.2.2-3. compound 260). The i . r . spectrum of 3_0 a l s o showed absorbances c h a r a c t e r i s t i c of an 0-C=N-C=0 s y s t e m , 3 7 7 with peaks at 1702, 1595 and 1460 cm- 1. The f o r m a t i o n of compound H O can be r a t i o n a l i z e d (Scheme 10) by i n v o k i n g a 1,4-Michael-type a d d i t i o n of the d i t h i a n e anion 1.26 to the unsaturated c a r b o n y l system of anhydronucleoside 308 to give the l i t h i u m s a l t 311. Upon aqueous work-up, the e n o l 3_2 forms which tautomerizes to the s t a b l e dihydro d e r i v a t i v e 3_0. Although the 5,6-double bond of u r i d i n e d e r i v a t i v e s i s known to be s u s c e p t i b l e to such. 1,4-additions by v a r i o u s n u c l e o p h i l e s to give the corresponding 6 - s u b s t i t u t e d - 5 , 6 - d i h y d r o compounds, 3 0 3 3 1 9 - 3 2 0 the behaviour of the d i t h i a n e anion 126 i n t h i s respect was somewhat unexpected s i n c e t h i s anion has been 10 2 g e n e r a l l y o b s e r v e d 1 9 9 to g i v e only non-conjugate 1,2-addition products i n r e a c t i o n s with a, g-unsaturated c a r b o n y l systems {see I n t r o d u c t i o n , S e c t i o n 3-1). Thus, i n a d d i t i o n to the m o d i f i c a t i o n of p y r i m i d i n e n u c l e o s i d e s a t C-2 ( i . e . , 309), f a c i l e f u n c t i o n a l i z a t i o n a t C-6 of , these n u c l e o s i d e s appeared f e a s i b l e i n view of the p o s s i b i l i t y of c o n v e r t i n g the d i t h i a n e moiety of 310 t o a fo r m y l g r o u p - 1 9 2 S i t h t h i s i n mind, the chemical p r o p e r t i e s of compounds 309 and 310 were studied,.The r e s u l t s are r e p o r t e d i n the f o l l o w i n g s u b - s e c t i o n s . 3.1.4. P e s u l f u r i z a t i o n o f 309 t o Give 2 - _ e t h _ l - _ -( 5 - 0 - t r i t y l - e - P - a r a b i n o f u r a n o s y l j - 4 (IH) -pyrimi d i n o n e (313). Treatment of the C-2 d i t h i a n y l n u c l e o s i d e 309 with a c t i v a t e d Raney n i c k e l 3 7 8 i n ethanol a t r e f l u x i n g temperatures gave the 2-methyl d e r i v a t i v e 3_3. Compound 313 had the same 103 p h y s i c a l c h a r a c t e r i s t i c s as t h a t prepared by Kunieda and W i t k o p 3 1 1 and thus provided unambiguous proof of s t r u c t u r e of the p r e c u r s o r , 309-Raney Ni 309 " 1 > 3-1-5- Acid H y d r o l y s i s of 3J09. , It was found that the n u c l e o s i d e 309 could be e a s i l y degraded i n r e f l u x i n g a c e t i c a c i d t o the corresponding f r e e base, 2 - { 1 , 3 - d i t h i a n - 2 - y i ) - 4 - p y r i m i d i n o n e (314), obtained i n a c r y s t a l l i n e s t a t e by a d d i t i o n o f e t h a n o l t o the r e a c t i o n mixture. The chemical a n a l y s i s and n.m.r. spectrum of 314 .-were completely c o n s i s t e n t with the proposed s t r u c t u r e . The sugar moiety of 309 was proven to be D-arabinose by comparison of Rf values on paper of the sugar component produced by h y d r o l y s i s of 309 with a u t h e n t i c a r a b i n o s e . 309 80V. HO Ac reflux N - f Arabinose + J2f C0H •S H 3 U 3.1.6. D e t r i t y l a t i o n of 309 to Give 2- f1 f 3 - D i t h i a n -2-yl) -1- B-D - a r a b i a o f uranosyl-4 (1H)-pyrimidinone 13,17),. D e t r i t y l a t i o n of 309 to give the corresponding unblocked n u c l e o s i d e was hampered by the extreme a c i d - l a b i l i t y o f the F i g u r e IX. P a r t i a l 100 MHz PMR Spectrum of 2 - ( 1 , 3 - D i t h i a n - 2 - y l ) - 1 - 3 - D - a r a b i n o f u r a n o s y l -4 ( I H ) - p y r i m i d i n o n e (317) i n DMSO-d . ~~ 105 g l y c o s i d i c C-N bond. Use of d i l u t e mineral or a c e t i c a c i d even at room temperature c o n s i s t e n t l y r e s u l t e d i n aglycon cleavage. Because the presence of e l e c tron-twithdrawing groups at C-2* and C-3' has been o b s e r v e d 3 7 9 to decrease the ease of h y d r o l y s i s o f the g l y c o s i d i c l i n k a g e i n n u c l e o s i d e s , compound 309 was a c e t y l a t e d i n a c e t i c a n h y d r i d e - p y r i d i n e to gi v e the 2',3 ,-di-0-a c e t y l - 5 * - 0 - t r i t y l d e r i v a t i v e 3_5. , Having v e r i f i e d by n. m. r. spectroscopy t h a t 315 was the a p p r o p r i a t e d i - a c e t a t e , t h i s compound,purified by chromatography on s i l i c a g e l , was allowed to s t i r i n 80% aqueous a c e t i c a c i d f o r 65 hours at room temperature. The r e s u l t i n g n u c l e o s i d e 3_6, a l s o p u r i f i e d by chromatography on s i l i c a g e l , was obtained i n U5% y i e l d , i n d i c a t i n g t h a t some g l y c o s i d i c cleavage had occur r e d . The n.m.r. spectrum of 3_6 i n dimethyl s u l f oxide-dg , c l e a r l y showed the presence of a O-exchangeable h y d r o x y l proton with no evidence of the t r i t y l group. The acetate b l o c k i n g groups of 316 were then e a s i l y removed by treatment of t h i s compound with methaaolic sodium methoxide to give the completely deprotected n u c l e o s i d e 3_7. . The n.m.r. spectrum of 3]7 i n DMSO-dg (Figure IX) v e r i f i e d t h a t t h i s was the f r e e n u c l e o s i d e ; the C-2' and C-3' h y d r o x y l groups gave r i s e to c l e a r l y r e s o l v e d doublets a t 6 5.52 and 5.83 while the primary hydroxyl group at C-5» appeared as a t r i p l e t { 65.15). 309 OAc OAc 315 316 106 These t h r e e s i g n a l s disappeared upon the a d d i t i o n of D^O to the n.m.r. sample. The high r e s o l u t i o n mass spectrum of 31,7 showed the a p p r o p r i a t e molecular ion peak at ra/e 347.074 1. NdOCH, 316  CH30H 3.1-7- Attempted H l d r o l y s i s of the D i t h i o a c e t a 1 of 3J5. A l l attempts t o h y d r o l y z e the d i t h i o a c e t a l group of 315 t o give the corresponding 2-formyl compound r e s u l t e d i n cleavage of the s e n s i t i v e g l y c o s i d i c bond. The methods employed were h y d r o l y s i s using mercuric c h l o r i d e - m e r c u r i c o x i d e , 1 9 * a l k y l a t i v e h y d r o l y s i s with methyl iodide-barium c a r b o n a t e 2 3 1 and use of b e n z e n e s e l e n i n i c a n h y d r i d e 2 3 5 . The reason f o r the l a b i l i t y of the g l y c o s i d i c bond of these C-2 s u b s t i t u t e d p y r i m i d i n e n u c l e o s i d e s i s u n c l e a r . The mechanism of the a c i d i c h y d r o l y s i s of n u c l e o s i d e s i s g e n e r a l l y a c c e p t e d 3 8 o - 3 8 1 t o i n v o l v e i n i t i a l p r o t o n a t i o n of the s u g a r - r i n g oxygen followed by f o r m a t i o n of an unstable S c h i f f base (Scheme 11). Attack of the l a t t e r by water then l e a d s to rupture of the N - g l y c o s i d i c bond. Thus, any s u b s t i t u e n t which decreases the ease of p r o t o n a t i o n of the r i n g oxygen i n c r e a s e s the s t a b i l i t y of the g l y c o s i d i c l i n k a g e 3 8 2 . For i n s t a n c e , the presence of an electron-withdrawing s u b s t i t u e n t a t C-2', such as an a c e t a t e group, i n s t e a d of a h y d r o x y l group makes the e l e c t r o n s of the 107 Scheme 11 ring-oxygen l e s s a v a i l a b l e f o r p r o t o n a t i o n with the r e s u l t that the g l y c o s i d i c bond i s s t a b i l i z e d - T h i s was shown to be true i n the case of compound 315. A l t e r n a t i v e l y , any s u b s t i t u e n t on the base or the sugar moiety of the n u c l e o s i d e which i n c r e a s e s the s u s c e p t i b i l i t y of the ring-oxygen t o p r o t o n a t i o n a l s o i n c r e a s e s the a c i d - l a b i l i t y of the compound. The d i t h i a n e group of 309 obv i o u s l y f a c i l i t a t e s the p r o t o n a t i o n step, the s u l f u r atoms o f the group perhaps a i d i n g i n the t r a n s f e r of protons. 3.1.8. Desul f u r i z a t i o n of 3_0 t o Give 2g_ 2_-Anh ydrp-5_5_- dihydrp-6-R-methy 1 - 5 * - O - t r i t y l u r i d i n e 13181-As mentioned above (Section 3.1.3-), the n.m.r. s i g n a l s of the p y r i m i d i n e r i n g of the dihydro-anhydro n u c l e o s i d e 31^ 0 were l a r g e l y obscured by the h i g h - f i e l d resonances o f the d i t h i a n y l protons- In order to o b t a i n c l e a r e r n.m.r- evidence of the presence of two C-5 protons, compound 3_0 was d e s u l f u r i z e d with Raney n i c k e l i n ethanol to give the 6-methyl d e r i v a t i v e 318- The n.m.r- spectrum of 3_8, taken i n dimethyl s u l f o x i d e - d ^ {Figure X) , d i s p l a y e d a three-proton doublet at 6 1.27 having a c o u p l i n g constant ( J . ) of 6.0 Hz. T h i s s i g n a l was a t t r i b u t e d t o the 6 , C H 3 I l i i I i i i i I i i i l I l l l I I I I I I I I M I I I I I I I I I I I I 1 I I I I 1 I M I I 1 ' 2 j 1 g | • I i i i I I L I I I I ,l ' I I I , I 7 6 5 F i g u r e X. P a r t i a l 100 MHz PMR Spectrum of 2 , 2 ' - A n h y d r o - 5 , 6 - d i h y d r o - 6 - R - m e t h y l - 5 ' - 0 - t r i t y l -u r i d i n e (318) i n DMSO-d,. o oo 109 methyl group while H—5 appeared as a two-proton p a i r of d o u b l e t s c e n t r e d a t 62.26 and H-6 as a one-proton m u l t i p l e t at 6 3.70. These assignments were v e r i f i e d by i r r a d i a t i n g the l a t t e r s i g n a l OH 318 (H-6); both d o u b l e t s (H-5, CH^) c o l l a p s e d t o ' s i n g l e t s as r e q u i r e d . Thus, the p o s i t i o n of the d i t h i a n y l group at C-6 o f 31.0 was f i r m l y e s t a b l i s h e d . 3- 1. 9. 5 f 6-Dihydro-6- (5)- (1,3- dithian-2-yl)_-1-B-D-a r a b i n o f u r a n o s y l u r a c i l J[3_19)_ and 3-£(5)_-1-(1,3-dithian-2-Yl),Jprogionamido-B-D -ar abinof urano-Q 1 * ,2V: 4,5 ")-2-oxazolidgne 13201=. When, i n an attempt at d e t r i t y l a t i o n , compound 31.0 was r e f l u x e d i n 80% aqueous a c e t i c a c i d f o r 10 minutes, two compounds, 3J.9 and 320, were unexpectedly produced. These products were separated c h r o m a t o g r a p h i c a l l y on a weakly a c i d i c c a t i o n i c exchange r e s i n . 0H OH 319 320 N H 2 F i g u r e X I I . P a r t i a l 100 MHz PMR Spectrum of 3 - [ ( S ) - - l - ( l , 3 - D i t h i a n - 2 - y l ) ] p r o p i o n a m i d o - 6 -D-a r a b i n o f u r a n o - [ l ' , 2 ' : 4 , 5 ] - 2 - o x a z o l i d o n e (320) i n DMS0-d 6. 112 The f a s t e r - r u n n i n g component, compound 319, obtained i n 5% y i e l d a f t e r c r y s t a l l i z a t i o n from agueous methanol, was shown to be 5,6-dihydro-6- (S)- (1 , 3 - d i t h i a n - 2 - y l ) -1- B-D-a r a b i n o f u r a n o s y l u r a c i 1 , t h a t i s , the compound a r i s i n g from d e t r i t y l a t i o n and h y d r o l y s i s of the 2,2'-anhydro l i n k a g e of 31.0. A c i d i c h y d r o l y s i s of 2,2'-anhydronucleosides to gi v e n u c l e o s i d e s with the arabino c o n f i g u r a t i o n i s w e l l known. 3 8 3 That compound 3J9 d i d not possess an anhydro s t r u c t u r e was shown by the presence i n i t s n. m. r spectrum (DHSO-dg , F i g u r e XI) of one primary h y d r o x y l proton at 6 4.85 and two secondary hydroxyl protons at 6 5.60 and 5.36 as w e l l as a l o w - f i e l d (.6 10.3 1), D20-exchangeable NH s i g n a l . The u.v. spectrum of 319 i n methanol showed a maximum a t 245 nm, the p o s i t i o n of a b s o r p t i o n of the d i t h i a n e r i n g , 3 8 * but no peaks above t h i s value. The i . r . spectrum of 3_19 no longer d i s p l a y e d the c h a r a c t e r i s t i c anhydro-dihydro p a t t e r n seen i n the pr e c u r s o r 310 but r a t h e r , c l o s e l y resembled t h a t of d i h y d r o u r i d i n e , 3 8 5 with peaks at 3400 (OH), 1710 (C=0) , 1690 (C=0) and 1600 cm-* <C=N of tautomer) . Moreover, the mass spectrum of 319 d i s p l a y e d an i n t e n s e peak a t m/e 133 corres p o n d i n g t o the M +-base fragment. No t y p i c a l anhydronucleoside fragmentation p a t t e r n s were observed. 3 8 6 F i n a l l y , the s t r u c t u r e o f 3,19 was confirmed by chemical means when i t was t r e a t e d with 1N h y d r o c h l o r i c a c i d f o r 4 hours a t 60°. H y d r o l y s i s of the g l y c o s i d i c bond o c c u r r e d under these c o n d i t i o n s to y i e l d g-arabinose, which was c h a r a c t e r i z e d by paper chromatography, and the corresponding f r e e base 5,6-dihydro-6- (S) - ( 1 , 3 - d i t h i a n - 2 - y l ) u r a c i l (321). The g l y c o s i d i c bond of 5,6-dihydropyrimidine n u c l e o s i d e s has been observed t o be much more s e n s i t i v e corresponding unsaturated to a c i d h y d r o l y s i s n u c l e o s i d e s . 3 8 5 than t h a t of the 319 HC! H O 321 Compound 321 was i n turn unambiguously c h a r a c t e r i z e d by i t s c o n v e r s i o n with Haney n i c k e l to the known. 6 - m e t h y l d i h y d r o u r a c i l (3 2 2 ) . 3 8 y ; v The s t r u c t u r e of the second and major (90%) product formed by a c i d treatment of 310, that i s , compound 320, was not so had to be made to chemical t r a n s f o r m a t i o n s of 320, t o be d i s c u s s e d below (S e c t i o n s 3. 1. 10-3. 1. 14) , to achieve t h i s end-N e v e r t h e l e s s , the i.r.,spectrum of 320 d i s c o u n t e d the p o s s i b i l i t y of a 2,2*-anhydro l i n k a g e i n t h i s compound; two c a r b o n y l s t r e t c h i n g peaks a t 1680 (amide) and 1740 cm - 1 (lactone) as w e l l as a p o s s i b l e amide I I peak at 1615 cm - 1 were observed. The proton-decoupled l 3C-n.m.r- spectrum of 320 i n c o r r o b o r a t e d the i . r . evidence of the presence of two c a r b o n y l groups; two weak s i n g l e t s a t 6\ 177.0 and 159-8 were a t t r i b u t e d to c a r b o n y l s of a primary amide and a carbamate group, r e s p e c t i v e l y , based on c o r r e l a t i o n s with the known 1 3 C resonances of these groups i n other m o l e c u l e s . 3 8 8 The lH-n.m.r. spectrum of 320 i n dimethyl s u l f o x i d e - d g (Figure XII) H 322 e a s i l y deduced by s p e c t r o s c o p i c means as was 319 and recourse 1 1 4 showed a primary hydroxyl proton as a t r i p l e t at 6 4.70 but only one secondary hydroxyl proton (6 5.66), both of which exchanged r a p i d l y with D^O, together with two broad one-proton s i n g l e t s a t 6 6.86 and 7.51 which, however, exchanged s l o w l y with D^O. These two broad peaks were assigned to the two m a g n e t i c a l l y non-e q u i v a l e n t protons of a primary amide group based on the s p e c t r a l data obtained f o r the f o l l o w i n g d e r i v a t i v e s prepared from 320. 3. 1. 10. 3-r (SI- 1- (1, 3 ) - D i t h i a n - 2 - y l ) Tpropionamido-3 ' , 5 ' - d i - O - t - b u t y l d i m e t h y l s i l y l - 3 - D -arabinofurano - r1*,2':4 f5 ]-2-pxazolido_e (323). When compound 320 was t r e a t e d with two e q u i v a l e n t s of t -b u t y l d i m e t h y l s i l y 1 c h l o r i d e i n N,N-dimethylformamide-pyridine f o r 24 hours, the f r e e h y d r o x y l groups were s e l e c t i v e l y s i l y l a t e d 3 8 9 to give 323, the i.r.,spectrum .of which c l e a r l y r e v e a l e d amide N-H s t r e t c h i n g v i b r a t i o n s , p r e v i o u s l y b u r i e d by the i n t e n s e hydroxyl a b s o r p t i o n s i n the spectrum of 320, a t 3420 and 3230 cm - 1. These primary amide protons appeared i n the n.m.r. spectrum of 323 as they had i n t h a t of the p r e c u r s o r 320, that i s , as two broad, s l o w l y exchangeable, l o w - f i e l d one-proton s i n g l e t s . • 3. 1. 11. 3-f <S)-1-f 1,3-Dithian-2-yl) Icyanoethyl-3-D-a rab i nof ura _g- f_ 11 & 2 *: 4 , 5 ]- 2- o xa zo 1 ido ne 13281. a p o s s i b l e mechanism to account f o r t h e . formation of the 115 Bu1(CH,),SiCI 320 — ) oxazolidone 320 from the t r i t y l a t e d anhydronucleoside 310 i s d e p i c t e d i n Scheme 12- I n i t i a l a c i d i c cleavage of the anhydro r i n g of 310, with concomitant d e t r i t y l a t i o n , g i v e s the a r a b i n o f u r a a o s y l u r a c i l d e r i v a t i v e 319 (which was i s o l a t e d ) -I n t r a m o l e c u l a r a t t a c k a t C-2 of the d i h y d r o p y r i m i d i n e r i n g of 319 by the a p p r o p r i a t e l y disposed C-2* h y d r o x y l group then d i s p l a c e s the amide group and produces the 2-oxazolidone 320. 310 H0-0 0*> N •\- sN Y 320 O H 319 Scheme 12 The intermediacy of 319 i n the f o r m a t i o n of 320 was e a s i l y demonstrated when a s o l u t i o n of 3.1.9 . i n water or a l c o h o l was allowed to stand f o r 3-4 days. Q u a n t i t a t i v e c o n v e r s i o n to the oxazolidone 320 occurred, as shown by n.m.r. spectroscopy and t . l . c . on s i l i c a g e l . . H , O ; 319 1 » 320 ; u doy5 ! An a l t e r n a t e s t r u c t u r e f o r 320 which would r e s u l t from s c i s s i o n of the 3,4-bond of 319 with concomitant l a c t o n i z a t i o n i s 325 (Scheme 13). I n f a c t , much evidence e x i s t s that t h i s bond r a t h e r than the 2,3-bond o f d i h y d r o p y r i m i d i n e s 3 9 0 and d i h y d r o p y r i m i d i n e n u c l e o s i d e s 3 8 5 i s c l e a v e d under a v a r i e t y of 116 c o n d i t i o n s t o g i v e g-ureido a c i d s . For i n s t a n c e , 3 9 1 treatment of 5 , 6 - d i h y d r o u r i d i n e {326) with potassium hydroxide causes .complete c o n v e r s i o n t o the u r e i d o p r o p i o n i c a c i d 327. However, 326 327 the absence of a ureide group i n compound 3 20 was demonstrated i n the f o l l o w i n g two experiments. F i r s t l y , 320 d i d not g i v e a p o s i t i v e t e s t with p-K,N-dimethylaminobenzaldehyde, a reagent known to r e a c t s e l e c t i v e l y with u r e i d e d e r i v a t i v e s of py r i m i d i n e s and p y r i m i d i n e n u c l e o s i d e s . 3 9 2 Secondly, treatment of 320 with t r i f l u o r o a c e t i c a n h y d r i d e - p y r i d i n e i n anhydrous dioxane, c o n d i t i o n s known to e f f e c t i n high y i e l d the dehydration of primary amides t o the corresponding n i t r i l e s , 3 9 3 f o l l o w e d by h y d r o l y t i c work-up of the r e a c t i o n mixture gave compound 328 as a c r y s t a l l i n e s o l i d , the i . r . spectrum of which c l e a r l y showed a n i t r i l e a b s o r p t i o n at 2260 cm - 1 as w e l l as the s i n g l e c a r b o n y l a b s o r p t i o n of the urethane s t r u c t u r e at 1740 cm—i. Though the p o s s i b i l i t y t h a t a u r e i d e f u n c t i o n a l i t y (as i n 325) can a l s o dehydrate to give the N-cyano d e r i v a t i v e has not been dismissed, such cyano groups absorb i n the i . r . i n the 2000 cm - 1 r e g i o n . 3 9 * 117 o C N 320 1) ( C F j C 2 0 / p y r i d i n e Thus, the tendency of the d i h y d r o p y r i m i d i n e r i n g of 3 19 to c l e a v e as i t does i n a c i d i c media i s no doubt due to the presence of the c i s C-2' hydroxyl group which can p a r t i c i p a t e i n the s c i s s i o n of the nearby 2,3-pyrimidine bond (Scheme 12} but not of the more d i s t a n t 3,4-bond. , The n e c e s s i t y of t h i s c i s r e l a t i o n between the h y d r o x y l group and the p y r i m i d i n e r i n g to e f f e c t 2,3-opening of the l a t t e r w i l l be shown by the behaviour of the r i b q analogue of 319 under a c i d i c c o n d i t i o n s , d e s c r i b e d below (see S e c t i o n 3.2-4-). In order to s i m p l i f y the n.m.r. spectrum of the d i t h i a n y l oxazolidone 320, the l a t t e r was d e s u l f u r i z e d with Eaney n i c k e l i n water to give the n o n - f l u o r e s c e n t methyl d e r i v a t i v e 329 as a syrup. The n.m.r. spectrum of 329 showed the expected doublet 3. 1. 12. 3- {R) - 1_-Met hylpropignamidg-B-D-a r a b i n o f urano - r 1' ,2l,;4f5 ]-2-oxazolidone 1 1 2 9 1 OH 329 f o r the methyl group (.6 1.18) while the C— 2 protons of the propionamide group appeared as a sharp doublet at 6 2-43 with a 118 c o u p l i n g c o n s t a n t ( J . ) of 7.0 Hz. The remaining s i g n a l s of the spectrum were s i m i l a r t o those of the s t a r t i n g m a t e r i a l 320. 3.1-13- Dehydration of 3_2_9_ to Give 3-iRJL-1-hethyIcyanoethyl-B-D-a r a b i n o f urano-[ 1 1 ,2' :4,5 ]-2-oxazolidone ! (330). The primary amide group of 329, l i k e t h a t of 320, was dehydrated using t r i f l u o r o a c e t i c a n h y d r i d e - p y r i d i n e t o y i e l d the n i t r i l e d e r i v a t i v e 330. .The i . r . spectrum of 330 showed the ! 329 expected n i t r i l e a b s o r p t i o n a t 2260 c m - 1 and a c a r b o n y l a b s o r p t i o n at 1740 cm - 1 while i n t h e n.m.r. spectrum (DMSQ-dg) , the two amide protons, seen at & 6.80 and 7.44 i n the spectrum °f 329, were no longer v i s i b l e . These r e s u l t s are completely c o n s i s t e n t with those obtained i n the analogous t r a n s f o r m a t i o n of the d i t h i a n y l compound 320 t o 328. In a d d i t i o n , the n.m.r. data showed a 0.49 ppm downfield s h i f t of the C-2 proton resonance i n going from the amide 3 29 to the more e l e c t r o n e g a t i v e n i t r i l e group of 330. T h i s i s p o s s i b l e only i f C-2 and the n i t r i l e group are adjacent so t h a t 320 must have the primary amide s t r u c t u r e r a t h e r than the a l t e r n a t i v e ureide s t r u c t u r e ( i . e . 325).., 3.1.14. Hydrogenation- of 330 to Give 3- j[B).-i-119 Methylace tamidopropyl - 3-D-a r a b i n o f u r a n o - f 1 1 , 2 * :4 £5 ]-2-oxazqlidone Because the i d e n t i f i c a t i o n of the d i t h i a n y l compound 3 20 as the 2-oxazolidone r a t h e r than t h e u r e i d e (325) hinged on i t s c o n v e r s i o n to the n i t r i l e (328), i t was deemed e s s e n t i a l t o v e r i f y the presence of the n i t r i l e f u n c t i o n a l i t y by chemical means as well as by the p r e v i o u s l y d e s c r i b e d p h y s i c a l methods and t h i s c o u l d e a s i l y be done by c a t a l y t i c hydrogenation of the n i t r i l e to the amine. Moreover, having shown that the methyl d e r i v a t i v e 330 d i s p l a y s chemical p r o p e r t i e s s i m i l a r to i t s precursor 320, then the former compound was chosen f o r r e d a c t i o n s t u d i e s because of i t s more e a s i l y i n t e r p r e t e d n.m.r. spectrum. Thus, hydrogenation o f 3 30 at 50 p . s . i . i n a c e t i c anhydride over platinum oxide f o r 24 hours gave 33% of the N-acetate 331, i s o l a t e d by chromatography on s i l i c a g e l (see S e c t i o n 1-1.3- f o r a b r i e f d i s c u s s i o n of n i t r i l e r e d u c t o n s ) . The i . r . spectrum of 330 331 331 showed the a p p r o p r i a t e c a r b o n y l a b s o r p t i o n of the N-acetate group a t 1640 cm - 1 as well as t h a t of the 2-oxazolidone moiety at 1740 cm - 1. No n i t r i l e peak could be seen. The n. m.r. spectrum of 331 1 B dimethyl s u l f o x i d e - d ^ v e r i f i e d the presence of an acetamide group; a broad, one-proton s i n g l e t , which exchanged s l o w l y with D 70, was seen a t 6 7.B8 while the a c e t a t e proton 1 2 0 s i g n a l appeared at 6 1 . 8 1 as a sharp s i n g l e t . The C - 2 protons, now adjacent to the newly-formed C - 3 methylene group i n s t e a d of to the h i g h l y e l e c t r o n e g a t i v e n i t r i l e f u n c t i o n a l i t y , d i s p l a y e d an expected u p - f i e l d s h i f t to 6 1 . 7 2 - The proton resonances of the arabinofuranose moiety of 3 3 1 were e s s e n t i a l l y i d e n t i c a l t o those of the s t a r t i n g m a t e r i a l 3 3 0 . Though c h e m i c a l a n a l y s i s of 3 3 1 showed the presence o f 1 . 5 moles of water of h y d r a t i o n , a high r e s o l u t i o n mass spectrum of the m a t e r i a l s u b s t a n t i a t e d the assigned formula of C ^ I ^ Q ^ O g . Furthermore, a base peak i n the mass spectrum a t 1 1 4 . 0 8 9 0 a r i s i n g from the acetamidobutane fragment was f u r t h e r proof that the d i h y d r o u r a c i l r i n g of the anhydronucleoside 3 1 , 0 had cleaved a t the 2 , 3 - p o s i t i o n during the a c i d - c a t a l y z e d d e t r i t y l a t i o n step. A c o n s i d e r a b l e amount {36%) of higher Rf m a t e r i a l was a l s o o b tained from the chromatography of the hydrogenation products of 3 3 0 and was i d e n t i f i e d by n. m. r . .. spectroscopy as a mixture of the 3 ' - 0 - and 5 « - O - a c e t a t e s of the acetamide 3 3 1 . These two mono-O-acetates could not be separated by chromatography and no f u r t h e r attempts were made to p u r i f y these compounds. Formation of O - a c e t y l a t e d by-products was prevented by hydrogenating a s o l u t i o n of compound 3 3 0 i n e t h a n o l and a c e t i c anhydride and by sho r t e n i n g the r e a c t i o n p e r i o d to 2 hours t o g i v e 33_1 as the s o l e product, thereby o b v i a t i n g the use of chromatography f o r p u r i f i c a t i o n . 3 . 1 . 1 5 . Attempted Formation of 2 , 2 , - A a h y d r o - 5 , 6 -d i h y d r o - 6 - ( S ) - (1 , 3 - d i t h i a n - 2 - y l ) u r i d i n e 11321. • 12.1 A l l attempts to d e t r i t y l a t e the anhydrodihydronucleoside 3_Q to give the unblocked d e r i v a t i v e 3 32 were u n s u c c e s s f u l - No r e a c t i o n was observed when, i n an attempt t o remove the t r i t y l group by h y d r o g e n o l y s i s , 3 9 5 compound 3_0 was h e l d under 50 p . s - i - of hydrogen f o r 48 hours i n the presence of p a l l a d i u m c a t a l y s t s - S i m i l a r l y , treatment of 310 with l i t h i u m i n - . l i q u i d ammonia r e s u l t e d i n recovery of s t a r t i n g m a t e r i a l - . Cleavage of the t r i t y l group using e i t h e r f e r r i c c h l o r i d e i n methylene c h l o r i d e 3 9 7 or hydrogen c h l o r i d e i n anhydrous c h l o r o f o r m 3 9 8 was p a r t i a l l y s u c c e s s f u l ; however, the d e t r i t y l a t i o n was, i n both cases, accompanied by a l a r g e amount of decomposition and s i d e r e a c t i o n s , making these approaches unviable- A supposedly mild m e t h o d 3 9 9 of d e t r i t y l a t i o n u s i n g t r i f l u o r o a c e t i c a c i d f o l l o w e d by treatment with a b a s i c ion-exchange r e s i n r e s u l t e d i n simultaneous h y d r o l y s i s of the anhydro r i n g and d i h y d r o p y r i m i d i n e r i n g of 310 to g i v e , as with a c e t i c a c i d , the oxazolidone 320. That the a c i d l a b i l i t y of the anhydro r i n g o f 3_0 i s a f u n c t i o n of the p o s i t i o n of attachment of the d i t h i a n y l moiety i n the d i h y d r o s t r u c t u r e r a t h e r than of any a s s i s t a n c e imparted o OH 3 32 122 by the s u l f u r atoms of that moiety was shown by s u b m i t t i n g the 6-methyl t r i t y l a t e d d e r i v a t i v e 3 1 8 , i n which the s u l f u r atoms are absent, to the same h y d r o l y t i c c o n d i t i o n s used on 3 1 0 , t h a t i s , 10 minutes r e f l u x i n 80% aqueous a c e t i c a c i d . Only compound 3 2 9 r e s u l t i n g from both anhydro and p y r i m i d i n e r i n g c l e a v a g e , was formed. .This product was i d e n t i c a l by n. m. r . , spec troscopy and t . l . c . on s i l i c a g e l to t h a t o b t a i n e d by Eaney n i c k e l d e s u l f u r i z a t i o n of 3 2 0 . OH Curiousy enough, none of the compound analogous to the a rabino n u c l e o s i d e 3 1 , 9 , i n which the d i t h i a n y l group i s r e p l a c e d by methyl, was i s o l a t e d , i n d i c a t i n g a p o s s i b l e i n h i b i t i n g i n f l u e n c e by the d i t h i a n y l group upon the h y d r o l y s i s of the d i h y d r o p y r i m i d i n e r i n g . 3 . 1 . 1 6 . Assignment of the C o n f i g u r a t i o n a t C - 6 of Compound 3J.0 and i t s D e r i v a t i v e s . Though the geometry a t C - 6 of 3_10 has not been u n e q u i v o c a l l y determined by d i r e c t c o r r e l a t i o n with a compound of known ster e o c h e m i s t r y at t h i s p o s i t i o n , i t would be expected t h a t , as P a u l s e n 2 3 6 has shown (see I n t r o d u c t i o n , S e c t i o n 3 . 3 . 2 . ) , the l a r g e d i t h i a n y l anion J 2 6 would approach from the l e s s s t e r i c a l l y hindered sid e of a molecule. Since t h i s corresponds to the exo s i d e of the t r i t y l a t e d anhydronucleoside 123 308 (Scheme 14) , then the 6-S isomer of 3_0 should r e s u l t - No diastereomeric mixtures of compound 31Q or i t s derivatives 3 1 8 -3 2 0 , 32 3 , 3 2 8 - 3 3 1 could be detected by n.m.r- spectroscopy or chromatography. The 6 - d i t h i a n y l arabinonucleoside 3 _ _ had a strong positive c d - spectrum with a maximum at 250 nm which corresponds to the position of absorption of the d i t h i a n y l group- 3 8* T h i s suggests that compound 319. and by inference i t s precursor 3 1 0 , are single isomers- As added proof that only one isomer about C - 6 was formed in the reaction of 308 and 1 2 6 , i t was found that the free base, 5 , 6 - d i h y d r o - 6 - d i t h i a n y l u r a c i l (321) i n which the only c h i r a l centre i s at C - 6 , exhibited a s p e c i f i c rotation of + 2 2 . 7 ° i n methanol. 3 . 1 . 1 7 . 3 - r (S ) - 1- ( 1 , 3 - D i t h i a n - 2 - y l ) Icyanoethyl-3__5_-dJ . - 0-_-nitroben^ a ra b i nof ur a no- _ 1 _ _ 2 ' : 41_ 5 ] - 2 - p xa zo 1 i do ne 1 J 3 3 1 and 3-(R)-1-Methylcyanoethyl - 3 ' , 5»-di-O-p-nitrpbenzoyl-B-D-arabinof urano-f 1 * t.2*_: 4 f 5 ] - 2-oxazolidone _ 3 3 4 _ _ , Before attempting hydrolysis of the di t h i o a c e t a l of 320 124 ( d e s c r i b e d i n the next s e c t i o n ) , i t was thought d e s i r a b l e to block the f r e e hydroxyl groups at the 3*- and 5'- p o s i t i o n s , a s w e l l as the primary amide group i n order to prevent c o m p l i c a t i n g s i d e - r e a c t i o n s . The p-nitrobenzoate group was c o n s i d e r e d s u i t a b l e f o r t h i s because of the c r y s t a l l i n i t y of the d e r i v a t i v e s and i t s ease of removal under m i l d l y b a s i c c o n d i t i o n s . However, when 320 was t r e a t e d with excess p-n i t r o b e n z o y l c h l o r i d e i n p y r i d i n e at room temperature, a s i n g l e c r y s t a l l i n e product was formed (333) whose n.m.r. spectrum showed the presence of o n l y two benzoate groups i n s t e a d of the expected t h r e e . No D20-exchangeable protons were observed. The i.r . , s p e c t r u m of 333 r e v e a l e d t h a t , j u s t as i n the case of the treatment of 320 with t r i f l u o r o a c e t i c anhydride and p y r i d i n e , dehydration of the primary amide to g i v e the n i t r i l e d e r i v a t i v e had o c c u r r e d . The c h a r a c t e r i z a t i o n of 333 was v e r i f i e d by 0Bz-p-N02 333 removal of i t s p - n i t r o b e n z o y l groups with methanolic sodium methoxide, generating 328, i d e n t i c a l i n a l l r e s p e c t s with the compound obtained d i r e c t l y from 320 v i a the t r i f l u o r o a c e t i c anhydride r o u t e . S i m i l a r l y , when the methyl d e r i v a t i v e 329 was p - n i t r o -benzoylated, the blocked analogue of the n i t r i l e compound 330 was obtained (334), as was evidenced by i . r . and n.m.r. spectroscopy. Such dehydrations of primary amides to the corresponding 125 0 CN _ 0 » \ O . N - Q - C C I p-0 2NBzO-j 9 \ / 329 — • > \ if CH 3 pyridine OBz-p-N02 334 cyano compounds using anhydrides or a c y l h a l i d e s i n p y r i d i n e have been w e l l d o c u m e n t e d - T h e mechanism i s t h o u g h t 3 9 3 t o i n v o l v e i n i t i a l t a u t o m e r i z a t i o n of the amide to the hydroxy imine - (Scheme 15), the h y d r o x y l group of which i s subsequently a c y l a t e d . P y r i d i n e - c a t a l y z e d e x p u l s i o n of the a c y l group, f a c i l i t a t e d by the presence of electron-withdrawing s u b s t i t u e n t s on the l a t t e r , then g i v e s the n i t r i l e compound. p C _ R ' 0 OH R'.£ x CJIK , R-C-NH, R-C=NH > R ~ % . ^ » R < = ^ P y r H <• pyridine N-H 5 ( X=halogen,-0C0R') Scheme 15 When compound 328 was r e f l u x e d f o r 1 hour i n 1N sodium hydroxide s o l u t i o n , complete h y d r o l y s i s of the n i t r i l e group to the primary amide oc c u r r e d , thereby r e g e n e r a t i n g 320. This compound was c h a r a c t e r i z e d by comparison of i t s s p e c t r a l data with that p r e v i o u s l y obtained f o r t h i s compound-328 > 320 reflux 3.1.18. H y d r o l y s i s of the D i t h i o a c e t a l of 33 3 t o Give 3-jS)_- J~ f o r myl cyano et hyl-3 * ^ ' - d i - P - p -n i t r p b e n z o y l - B-p-arabinof urano-f 1,2': 4 f5 •2-oxazolido.ae 1335JL/. C h a r a c t e r i z e d as the Semicarbazone 336-126 The f e a s i b i l i t y of converting, the d i t h i a n y l group of 333 t o the formyl f u n c t i o n a l i t y was s t u d i e d next. Though compound 333 i s a g r e a t l y a l t e r e d v e r s i o n of the n a t u r a l n u c l e o s i d e s , i t was hoped t h a t the pyr i m i d i n e r i n g of t h i s compound c o u l d be regenerated under the r i g h t c o n d i t i o n s (see S e c t i o n 3. 1- 18-) » Moreover, compound 333 would serve as a model system f o r the d i t h i o a c e t a l h y d r o l y s i s of r e l a t e d molecules, to be d e s c r i b e d l a t e r {see S e c t i o n 3.2). Quite unexpectedly, i t was di s c o v e r e d that 333 was completely i n e r t to t r a d i t i o n a l mercuric \ c h l o r i d e r - m e r c u r i c o x i d e 1 9 * S-S a c e t a l h y d r o l y s i s , complete recovery of s t a r t i n g m a t e r i a l being p o s s i b l e (see I n t r o d u c t i o n , S e c t i o n 3.2 f o r a b r i e f d i s c u s s i o n of the methods of h y d r o l y s i s ) . Other reagents such as copper (II) c h l o r i d e , 2 1 6 N - b r o m o s u c c i n i m i d e 2 1 7 and c e r i c ammonium n i t r a t e 2 2 5 a l s o gave no r e a c t i o n or l e d to e x t e n s i v e decomposition of s t a r t i n g m a t e r i a l . F i n a l l y , though i t was found that r e f l u x i n g a s o l u t i o n of 333 i n agueous acetone and methyl i o d i d e 2 3 1 had no e f f e c t on the d i t h i a n e group, use of agueous dimethyl s u l f o x i d e i n s t e a d o f acetone as the s o l v e n t l e d t o complete a l k y l a t i v e h y d r o l y s i s of 333 to the aldehyde (335) a f t e r 3 hours at 60°^ The aldehyde 335, which showed a l o w - f i e l d i? C N 333 1 HNCNH JJT\ 0 R 0 ' OR 336 doublet { < S 9„U5, DMSO-d^) f o r the formyl p r o t o n , was converted to the semicarbazone 336 by treatment with semicarbazide 127 h y d r o c h l o r i d e and p y r i d i n e i n methanol- The c r y s t a l l i n e d e r i v a t i v e (336) ., which analyzed c o r r e c t l y , had an i - r - spectrum and an n.m.r. spectrum which were completely i n accord with the proposed s t r u c t u r e . D. H. R. Barton has subsequently informed us t h a t benzene-s e l e n i n i c a n h y d r i d e 2 ' 3 5 • i s an e f f e c t i v e reaqent f o r the c o n v e r s i o n of 333 to the aldehyde 335-, 3- 1. 19- , Attempted Ring C l o s u r e of Compound 328..• I t was at f i r s t expected t h a t treatment of the cyano-2-oxazolidone 328 with methanolic ammonia would r e s u l t i n g e n e r a t i o n of the 5 , 6 - d i h y d r o - 6 - d i t h i a n y l a r a b i n o c y t o s i n e d e r i v a t i v e (337) by the mechanism o u t l i n e d i n Scheme 16. i 337 Scheme 16 However, when 328 was so t r e a t e d with ammonia i n a sealed bomb 128 at temperatures ranging from 20° t o 160°, no r e a c t i o n aas observed even a f t e r 24 hours, as shown by complete recov e r y of s t a r t i n g m a t e r i a l - T h i s behaviour of 328 i s not e n t i r e l y s u r p r i s i n g i n view of the known s t a b i l i t y of the 2-oxazolidone r i n g to a c i d s and b a s e s - * 0 1 3.2. Reaction of 1 f t3-Dithiane Anion with Blocked 5-B r o m o u r i d i n e i S y n t h e s i s o f a 6-8-Alanine D e r i v a t i v e of U r i d i n e -The s y n t h e s i s of p y r i m i d i n e n u c l e o s i d e s s u b s t i t u t e d at C-6 with a l k y l groups has been neglected f o r reasons d i s c u s s e d above (see Introduction> S e c t i o n 6.) d e s p i t e the knowledge that the C-5 s u b s t i t u t e d analogues o f t e n d i s p l a y potent chemotherapeutic p r o p e r t i e s . 2 9 8 - 3 0 3 The.foregoing r e s u l t s of the r e a c t i o n of 1,3-d i t h i a n e anion Q26J with the 2,2*-anhydronucleoside 308 suggested to us a novel and e f f i c i e n t method of i n t r o d u c i n g C-C bonded s u b s t i t u e n t s a t the 6 - p o s i t i o n of p y r i m i d i n e n u c l e o s i d e s by v i r t u e of a) the p r o p e n s i t y of the d i t h i a n e anion t o add i n a 1,4-fashion to the a, ^ -unsaturated c a r b o n y l system : of the p y r i m i d i n e r i n g , and b) the a b i l i t y of the d i t h i a n e group t o be e a s i l y converted to the v e r s a t i l e formyl g r o u p , 1 9 2 thereby p e r m i t t i n g f u r t h e r m o d i f i c a t i o n of the C-6 p o s i t i o n . The d i t h i a n y l - m o d i f i e d n u c l e o s i d e analogues prepared above, though i n t e r e s t i n g i n themselves p a r t i c u l a r l y 3 0 1 i n view of the arabino d e r i v a t i v e s which r e s u l t e d , were not c o n v e n i e n t l y amenable to f u r t h e r manipulation. The C-2 s u b s t i t u t e d n u c l e o s i d e 309 d i s p l a y e d an extremely a c i d - l a b i l e g l y c o s i d i c l i n k a g e while the anhydrodihydro nucleoside 3.10 c o u l d not be d e t r i t y l a t e d 129 without causing simultaneous rupture of the p y r i m i d i n e r i n g {to give 320} which, i n t u r n , r e s i s t e d attempts a t r e - c y c l i z a t i o n (see S e c t i o n 3.1.19.). The i n t e r e s t i n g 5,6-dihydro-6-d i t h i a n y l a r a b i n o u r a c i l d e r i v a t i v e 3_9, a v a i l a b l e only i n low y i e l d by the procedure d e s c r i b e d , a l s o d i s p l a y e d a tendency to p y r i m i d i n e - r i n g cleavage. Thus, prompted by the r e p o r t of Deda and I n o u e 3 2 0 i n which was d e s c r i b e d the a d d i t i o n of cyanide i o n to C-6 of 5-bromouridine {see I n t r o d u c t i o n , S e c t i o n 6.2.2.2.)., the r e a c t i o n of the l a t t e r n u c l e o s i d e with the d i t h i a n e anion 1.26 was s t u d i e d i n view of f i n d i n g a p r a c t i c a l method of s y n t h e s i z i n g a 6-f o r m y l u r i d i n e d e r i v a t i v e . The r e s u l t s o f t h i s study are d e s c r i b e d below. 3.2-1. 5-B.romq-2* ,3 1 - 0 - i s o p r o p y l i d e n e - 5 * - 0 -t r i t y l u r i d i n e (340). Although D e d a , 3 2 0 i n h i s study of the r e a c t i o n of potassium cyanide with 5-bromouridine, used a 5 * - 0 - a c e t y l d e r i v a t i v e of the l a t t e r compound ( i . e . , 255), i t was decided that f o r our present needs, a b a s e - l a b i l e b l o c k i n g group should be avoided. Thus, the known 2*,3'-0-isopropylidene d e r i v a t i v e ( 3 3 9 ) 4 0 2 of 5-bromouridine ( 3 3 8 ) 4 0 3 was f i r s t prepared by standard procedures using acetone, copper s u l f a t e and concentrated s u l f u r i c a c i d . Reaction of 339 with one e q u i v a l e n t of t r i p h e n y l m e t h y l c h l o r i d e i n p y r i d i n e a t 100° f o r 2 h o u r s 4 0 * then gave the c r y s t a l l i n e t r i t y l d e r i v a t i v e 34 0. Compound 340, which analyzed c o r r e c t l y f o r bromine, showed the a p p r o p r i a t e molecular i o n peak i n i t s mass spectrum (m/e 606 f o r 8 1 B r ) w h i l e the n.m.r. spectrum of Figure XIII. P a r t i a l 100 MHz PMR Spectrum of 5-(S)-Bromo-5,6-dihydro-6-(S)-(l,3-dithian-2-yl)-2',3'-0-isopropylidene-5'-0-trityluridine (342) i n CDC1 . 0 0 O F i g u r e XIV. P a r t i a l 100 MHz PMR Spectrum of 5 - ( R ) - B r o m o - 5 , 6 - d i h y d r o - 6 - ( S ) - ( l , 3 - d i t h i a n - 2 - y l ) -2 ' , 3 ' - 0 - i s o p r o p y l i d e n e - 5 ' - 0 - t r i t y l u r i d i n e (343) i n CDC1„. 132 340, i n a d d i t i o n to showing the i s o p r o p y l i d e n e and t r i t y l group s i g n a l s , d i s p l a y e d a s i n g l e t f o r H-6 at 6 7.86 (CDCl^). 3.2.2. Synthesis of 5,6-Dihydro-6- | B ) - ( 1 ^ 3 - d i t h i a n -2-yl) -2* ^ - Q - i s o p r o p y l i d e n e - S ' - C — t r i t y l u r i d i n e 134 1.1^  5-_[S_l- and 5~iE)_-Bromo-5 X 6 - d i h y d r o - 6 - ( S ) - { 1 , 3 - d i t h i a n - g - j l l - g i j J i -Q - i s o p r o p y l i d e n e - 5 ^ - 0 - t r i t y l u r i d i n e J[342 and 3 43) . A d d i t i o n of a s o l u t i o n o f the blocked 5-brcmouridine 3 40 i n anhydrous p y r i d i n e t o a s i x - f o l d molar excess of 2 - l i t h i o - 1 , 3 -d i t h i a n e (1.26) 1 9 2 i n t e t r a h y d r o f u r a n at -78° under dry n i t r o g e n gave, a f t e r a r e a c t i o n p e r i o d of 24 hours at -20°, the three d i t h i a n e a d d i t i o n products, 34_1, 342 and 343, i s o l a t e d i n y i e l d s of 37, 35, and 10%, r e s p e c t i v e l y , by column chromatography on s i l i c a g e l . The i d e n t i f i c a t i o n of these three products by p h y s i c a l means w i l l be d i s c u s s e d f i r s t , w h i l e t h e i r c h a r a c t e r i z a t i o n by chemical t r a n s f o r m a t i o n s i s reserved f o r subsequent s e c t i o n s . Neither the elemental a n a l y s i s nor the mass spectrum of 341 showed presence of bromine, but simple n u c l e o p h i l i c displacement of the bromide of 340 by the d i t h i a n e anion was precluded by the 133 340 + 126 T H F / p y r i d i n e 341 342 343 a b s e n c e i n t h e n.m.r. s p e c t r u m o f 3__, t a k e n i n d e u t e r o c h l o r o f o r m , o f a l o w - f i e l d s i n g l e t f o r H-6. I n s t e a d , a t w o - p r o t o n m u l t i p l e t was s e e n a t 6 2 - 4 8 - 2 . 7 1 , s u g g e s t i n g a 5,6-d i h y d r o s t r u c t u r e . 3 1 9 3 7 7 A s i m i l a r n.m.r. s p e c t r u m was o b t a i n e d f o r t h e 5 , 6 - d i h y d r o - 6 - d i t h i a n y l n u c l e o s i d e 3_0. The f o r m a t i o n o f compound 3_4_ f r o m t h e 5 - b r c m o u r i d i n e d e r i v a t i v e 340 can be e x p l a i n e d by a s s u m i n g an i n i t i a l v i n y l h a l o g e n - m e t a l e x c h a n g e between 34 0 and t h e a n i o n _26 t o g i v e t h e b l o c k e d 5 - l i t h i o u r i d i n e 344 (Scheme 1 7 ) . I t has been s h o w n * ° s t h a t i n t h e p r e s e n c e o f n - b u t y l l i t h i u m , 5 - b r c m o u r a c i l and i t s n u c l e o s i d e s e x i s t i n e q u i l i b r i u m w i t h t h e i r 5 - l i t h i o d e r i v a t i v e s . A 1 , 4 - M i c h a e l - t y p e a d d i t i o n a t C-6 o f a n o t h e r d i t h i a n e a n i o n {which i s i n e x c e s s ) would t h e n g i v e , a f t e r q u e n c h i n g , the 5 , 6 - d i h y d r o - 6 - d i t h i a n y 1 s p e c i e s 3 4 1 - The p r o p o r t i o n o f 34 0 t h a t i s n o t consumed by t h e e q u i l i b r i u m r e a c t i o n t h e n q o e s on t o g i v e p r o d u c t s 342 and 343 by a s t r a i g h t f o r w a r d c o n j u g a t e a d d i t i o n o f t h e d i t h i a n e a n i o n a t C-6. That compounds 342 and 3 4 3 b o r e a d i a s t e r e o m e r i c r e l a t i o n s h i p was i n i t i a l l y i n d i c a t e d by t h e b e h a v i o u r of t h e s e compounds on s i l i c a g e l . , W h e r e a s t h e r e a c t i o n m i x t u r e o f 3 4 0 and 134 Scheme 17 I _126 had shown, by t . l . c . on s i l i c a g e l , a preponderance o f compound 343 with r e s p e c t to 342, i t was found that a f t e r chromatography of t h i s same r e a c t i o n mixture on s i l i c a g e l , compound 342 was now the major product with r e s p e c t to 343. Both 34 2 and 343 were shown to c o n t a i n bromine by elemental a n a l y s i s . However, though 342 analyzed p r o p e r l y f o r the formula C 35H 37N2°6 S 2 B c ' t * i e a n a l y s i s of i t s isomer 343 d i d not show a complete mole of bromine, due, perhaps, to p a r t i a l e l i m i n a t i o n of HBr during d r y i n g of the a n a l y t i c a l sample i n vacuo at e l e v a t e d temperature. The chemical formula of 343 was thus confirmed by i t s high r e s o l u t i o n mass spectrum which showed an M+-CH3 peak at 711.1027, corres p o n d i n g to H 0 & S 2 8 1 B r . The peak, a r i s i n g from the 7 9 B r i s o t o p e was e q u a l l y obvious. A c a r e f u l study of the n.m.r. s p e c t r a of 342 (Figure XIII) and 343 (Figure XIV), both taken i n deuterochloroform, permitted the assignment of the r e l a t i v e c o n f i g u r a t i o n s of the bromine atom and the d i t h i a n y l group of these two compounds. For 34 2, H-135 5 was seen as a doublet at 6 5.12 with a c o u p l i n g constant (d^g) of 1.5 Hz, while f o r 343, H-5 was observed at s l i g h t l y h i g h e r f i e l d ( 6 4.80) but had a s i g n i f i c a n t l y l a r g e r J,- ^  value o f 6.0 Hz. Now, s i n c e i t has been shown by independent s t u d i e s that 5 , 6 - d i h y d r o u r a c i l (and i t s 5 , 6 - s u b s t i t u t e d d e r i v a t i v e s ) e x i s t s mainly i n a h a l f - c h a i r c o n f o r m a t i o n 4 0 6 - 4 0 9 (Figure XV) and furthermore, t h a t c i s hydrogens at these p o s i t i o n s g i v e r i s e t o c o u p l i n g c o n s t a n t s ( J Q e ) ranging from 5-2 to 7.23 Hz, 4 0 9 - 4 1 0 i t was then i n f e r r e d t h at 343 was the 5,6-cis isomer. ! '• H ! ' H i • ' HN-CCKNH-C.=O ,! ! F i g u r e XV. H a l f - C h a i r C o n f o r m a t i o n of D i h y d r o -p y r i m i d i n e R i n g s . Compound 342 must t h e r e f o r e be the 5,6-trans isomer. T h i s assignment i s a l s o c o n s i s t e n t with the observed c o u p l i n g c o n s t a n t (J^ ^ = J^- e = 1-6 Hz) of H-5 and H-6 i n t h i s compound s i n c e i t can be assumed that the bulky bromo and d i t h i a n e s u b s t i t u e n t s adopt the s t e r i c a l l y favoured 5 , 6 - d i a x i a l r e l a t i o n s h i p 4 0 7 4 0 9 so t h a t H-5 and H-6 are d i e g u a t o r i a l (Figure XVI). T r a n s - d i e q u a t o r i a l 5,6-hydrogens were observed to have | p ;• i S u g a r — N—CCN^NH —C=0 ! F i g u r e XVI. The 5 , 6 - D i a x i a l R e l a t i o n s h i p of the D i t h i a n y l and Bromo S u b s t i t u e n t s of Compound 342. J 5 e 6e 2 * 5 Hz i n the n.m.r. spectrum of 5-bromo-2'-deoxy-5,6-dihyd r o - 6 - h y d r o x y u r i d i n e ( 3 4 5 ) . 4 1 1 136 HO-HN "T-Br OH 345 The n.m.r- peak assignments of 342 and 343 were supported by. decoupling experiments. The a b s o l u t e c o n f i g u r a t i o n s of these two compounds were determined by chemical means discu s s e d l a t e r on (see S e c t i o n 3.2.7.). T h i s s t e r e o c h e m i c a l assignment of 342 and 343 as the t r a n s and c i s isomers, r e s p e c t i v e l y i s c o n s i s t e n t with the observed i n s t a b i l i t y of 343 on s i l i c a g e l , i n which t h i s a c i d i c medium c a t a l y z e s isomer i z a t i o n to the thermodynamically more s t a b l e 5,6-trans s p e c i e s (342), presumably v i a e n o l i z a t i o n of the C-4 c a r b o n y l (Scheme 18)-. 343 ( 5,6-cis) Scheme 18 silica gel ~* 342 (5,6-trans) I t i s i n t e r e s t i n g t o note t h a t , whereas the r e a c t i o n o f cyanide ion with 5-bromouridine gave a s i m i l a r 1,4-Michael-type a d d i t i o n product which, spontaneously dehydrobrominated to regenerate the 5,6-double b o n d , 3 2 0 no such e l i m i n a t i o n was observed i n t h i s case of M i c h a e l - a d d i t i o n of 1,3-dithiane t o give 342 and 343. T h i s can be a t t r i b u t e d t o the much g r e a t e r e l e c t r o n e g a t i v i t y of the cyanide group compared to the d i t h i a n e group with the r e s u l t i n g i n c r e a s e i n the a c i d i t y of H-6 and conseguent ease of e l i m i n a t i o n . 137 3.2. 3. Desulfurization of 341 to Give 5.6-Dihydro-2 ',3 1-0-isopropylidene-6- (S)-methyl-5'- O-t r i t y l u r i d i n e _346_. In order to simplify the h i g h - f i e l d region of the n.m.r. spectrum of the 6-dithianyl nucleoside 34_, the l a t t e r compound was desulfurized with Haney n i c k e l i n ethanol to give the 6-S-methyl derivative 346. The n.m.r. spectrum of 346 i n deuterochloroform showed the expected doublet for the C-6 methyl group at <$1.36._More importantly, H-5a, H-5e and H— 6 gave r i s e 346 to an ABX pattern i n the spectrum, the chemical s h i f t s and coupling constants ^ J 5 Q 5 b Hz) of which were again c h a r a c t e r i s t i c of a 6-substituted 5,6-dihydro system. 3 1 9 3 7 7 3.2. 4. 5,6-Dihydro-6- <B)— (1 ,3-dithianT2-yl) uridine 13421-Treatment of the dihydronucleoside 341 with 80% agueous acetic acid at refluxing temperatures yielded the completely unblocked compound 347. The n.m.r. spectrum of 347 {pMSO-d^) showed the appropriate doublets f o r the secondary hydroxyls <<5 5.02 and 5.25) and t r i p l e t for the primary hydroxyl group <6 4.84). The u.v. spectrum of 347 i n methanol exhibited only a peak due to absorption by dithiane (245 nm) ; the fact that there was no absorption in the 260 nm region was a further i n d i c a t i o n 138 OH OH 347 that the pyri m i d i n e r i n g was s a t u r a t e d a t the 5 , 6 - p o s i t i o n . 3 9 0 There was no evidence that the r i b o :nucleoside 341 had a, undergone cleavage of the p y r i m i d i n e r i n g d u r i n g the treatment with a c e t i c a c i d . T h i s i s to be c o n t r a s t e d with the a r a b i n o analogue of 34_1 ( i . e . compound 319) which d i s p l a y e d the anomalous tendency t o c l e a v e a t the 2 , 3 - p o s i t i o n under m i l d l y a c i d i c c o n d i t i o n s (see S e c t i o n 3-1.9.). T h i s behaviour o f the pyr i m i d i n e r i n g of 3J.9 can be r e l a t e d t o the a s s i s t a n c e provided by t h e nearby C-2* h y d r o x y l group, a s i t u a t i o n not p o s s i b l e i n the r i b o n u c l e o s i d e 347.. Compound 34 7 was assigned the 6-R c o n f i g u r a t i o n on the b a s i s of i t s c d . spectrum i n methanol which showed a s t r o n g l y negative Cotton e f f e c t with a maximum at 250nm (Ae -4.13}.^ p o s i t i v e Cotton e f f e c t a t t h i s wavelength was p r e v i o u s l y a s s o c i a t e d with the 5, 6-dihydro-6-S-dithiany 1 n u c l e o s i d e (319). The apparent s t e r e o s e l e c t i v i t y of the a d d i t i o n of 1.26 to the py r i m i d i n e moiety of 34 0 (and i t s 5 - l i t h i o d e r i v a t i v e 344) can be r a t i o n a l i z e d by assuming t h a t these n u c l e o s i d e s adopt the more s t a b l e a n t i conformation i n which, f o r s t e r i c reasons, the C-2 c a r b o n y l group of the py r i m i d i n e r i n g l i e s away from the plane of the sugar r i n g * 1 2 — * 1 * {Scheme 19). Endo at t a c k by the d i t h i a n e anion (126) at C-6 i s thus blocked by the bulky t r i t y l group while exo a t t a c k , with formation of the 6-R isomer, i s favoured. Such s t e r i c c o n t r o l s to the d i r e c t i o n of a d d i t i o n o f reagents at C-6 of p y r i m i d i n e n u c l e o s i d e s by the 5 f - 0 - t r i t y l 139 341 340 Scheme 19 group have been o b s e r v e d . 3 3 6 3.2.5. H y d r o l y s i s of 3 4 .7 to Give 5,6-Dihydro-6-(R)~ ( 1 . 3 - d i t h i a n - 2 - y l ) u r a c i l J348U. As a f i n a l chemical proof of s t r u c t u r e of 34_1, i t s unblocked d e r i v a t i v e 347 was hydrolyzed with 1M h y d r o c h l o r i c a c i d at 80° f o r 4 hours. White needles of the f r e e d i t h i a n y l base 348 formed upon c o o l i n g of the r e a c t i o n mixture. R e c r y s t a l l i z a t i o n of 348 gave a compound i d e n t i c a l by melting p o i n t and n. ra. r- spectroscopy t o 5, 6-dihydro-6-{S)~ (1 , 3 - d i t h i a n ~ 2-yl) u r a c i l {32!)i p r e v i o u s l y obtained by s i m i l a r treatment of the 6-S-arabinq analogue 3J9. However, as expected from the r e s u l t of the c.d. study of the i n t a c t molecule 347, compound 348 had an o p t i c a l r o t a t i o n of opposite s i g n to that of the 6-S isomer {322). Thus 348 and 32J are enantiomers. r o 348 3. 2. 6. 5,6-Ditiydro-6- {BT S ) - f ormyl-2 1 f3'-0 -i s o p r o p y l i d e n e - 5 ' - 0 - t r j t y l u r i d i n e (3 4 9 ) and I t s Semicarbazone 3 5 0 . Formation of the 5,6-dihydro-6-formyl n u c l e o s i d e 349 by 140 a l k y l a t i v e h y d r o l y s i s of the d i t h i a n e moiety of 34_ using methyl i o d i d e . and barium carbonate i n aqueous acetone proceeded smoothly at 55°. The 6-aldehyde 349 was c h a r a c t e r i z e d as i t s c r y s t a l l i n e semicarbazone 350 by i . r . and n.m.r. spectroscopy and by chemical a n a l y s i s . >' 349 350 The p o s s i b i l i t y of i s o m e r i z a t i o n of the aldehyde group of 349 about C-6 owing t o the a c i d i t y of the C-6 proton and the b a s i c h y d r o l y t i c c o n d i t i o n s employed has not been dismissed-T h i s would perhaps e x p l a i n the l a c k of r e s o l u t i o n observed i n the s i g n a l s of the n.m.r- spectrum of the d e r i v e d semicarbazone 350. 3.2.?. Debromination of Compounds 3 4 2 and ______ to Give 34J_ , B r i e f treatment of e i t h e r the 5,6-trans compound 342 or i t s 5,6-c i s diastereomer 343 with a t h a n o l i c Haney n i c k e l * 1 5 at r e f l u x i n g temperatures gave the debrominated product 341_, i d e n t i c a l by R^  ( s i l i c a gel)§ n.m.r. sp e c t r o s c o p y , mass spectrometry and, most i m p o r t a n t l y , o p t i c a l r o t a t i o n with t h a t compound obtained d i r e c t l y from the r e a c t i o n of 340 with the d i t h i a n e anion 12.6, the c o n f i g u r a t i o n of which was shown above to be R a t C-6- Thus, compounds 342 and 343 must d i f f e r only i n 141 j 342 (5.6-trons) 343 (5,6-cis) 341 t h e i r c o n f i g u r a t i o n s a t C-5 so t h a t 342, p r e v i o u s l y e s t a b l i s h e d as the t r a n s isomer must have the 5S, 6S c o n f i g u r a t i o n while 343 must be the 5R, 6S isomer. Although both 342 and 343 a p p a r e n t l y underwent some d e s u l f u r i z a t i o n during the Raney n i c k e l treatment, as shown by t . 1 . c . of the r e a c t i o n mixture, these secondary products were not c h a r a c t e r i z e d . 3.2. 8. 6-Formyl-21 x3.1-0-isopropylidene-51-0-t r i t y l u r i d i n e (351) and 6-Formyl-2 1,3*-Q-i s o p r o p y l i d e n e - 3 - m e t h y 1 - 5 ^ - 0 - t r i t y l u r i d i n e <353) , C h a r a c t e r i z e d as T h e i r Semjcarbazones 352 and 354, R e s p e c t i v e l y . I t was f e l t , in view of Ueda's observation 3 2° that 5-bromo-5,6-dihydro-6-cyanouridine spontaneously dehydrobrominates to give 6-cyanouridine, t h a t h y d r o l y s i s of the d i t h i o a c e t a l of 342. (or 343) to the 6-aldehyde d e r i v a t i v e would a l s o r e s u l t i n concomitant e l i m i n a t i o n of HBr because of the i n c r e a s e d a c i d i t y of the C-6 proton. In t h i s way, the d e s i r e d 5,6-double bond would be regenerated. To t e s t t h i s h y p o t h e s i s then, the t r a n s isomer 342 was t r e a t e d with methyl i o d i d e and barium carbonate i n agueous acetone c o n t a i n i n g 10% dimethyl s u l f o x i d e . An n.m.r. spectrum of the crude worked-up r e a c t i o n mixture showed, 142 i n deuterochloroform, a s i n g l e t f o r the f o r m y l proton at 6 9.53, the same.position r e p o r t e d by K l e i n and F o x 3 1 8 f o r the f o r m y l proton of 2\3 • ,5»-tri-0-acetyl-6~formyluridine {242, R=CHO) -S i n c e the same authors a l s o s t a t e d t h a t the last-named compound was u n s t a b l e , the aldehyde 35_ was c h a r a c t e r i z e d as i t s semicarbazone 352. The n.m.r. spectrum of 352 i n d i m e t h y l 342 (or 343) s u l f o x i d e - d g d i s p l a y e d , i n a d d i t i o n to f o u r D2O-exchangeable protons {NH) , a s i n g l e t f o r H-5 at 6 5.96 {superimposed on H-1', a l s o a s i n g l e t ) as w e l l as a sharp s i n g l e t a t 5 7.57 a t t r i b u t e d to the imine p r o t o n . T h i s , i n a d d i t i o n to the proper elemental a n a l y s i s and mass spectrum of 352 was c o n v i n c i n g proof that HBr had been e l i m i n a t e d from 342 to g i v e 35_ and thence 352. a few p o i n t s about the a l k y l a t i v e h y d r o l y s i s of 342 t o the aldehyde 351 deserve mention. When the r e a c t i o n was conducted i n 10% agueous acetone a t 55°, o n l y p a r t i a l h y d r o l y s i s was observed by t . l . c . even a f t e r seven days of r e a c t i o n . Hhen 10% by volume of DMSO was i n c l u d e d i n the r e a c t i o n mixture, complete t h i o a c e t a l h y d r o l y s i s was accomplished w i t h i n f o u r days at 55°C. However, i n a d d i t i o n to t h e 6-aldehyde 35_, a minor, higher Rf compound was a l s o formed.,This compound was shown to be the N-3 methylated 6-aldehyde 35 3, a l s o c h a r a c t e r i z e d as i t s semicarbazone, 354. The n.m.r. spectrum of 354 showed only three D•>0-exchangeable protons but now, a three-proton s i n g l e t due to 143 353 354 the N-m e t h y l group was seen at 6 2-98. A l s o , the mass spectrum of 354 i n d i c a t e d a mass of 14 u n i t s g r e a t e r than the un methyl a ted d e r i v a t i v e 352. Both the r a t e of h y d r o l y s i s and the amount of N-methylated product 353 and s i d e - p r o d u c t s i n c r e a s e d with i n c r e a s i n g DMSO c o n c e n t r a t i o n , u n t i l , i f only 10% aqueous DM SO was used as the r e a c t i o n s o l v e n t , a l l s t a r t i n g n u c l e o s i d e had disappeared w i t h i n 30 minutes with, however, l i t t l e formation of 353, as shown by t . l . c . on s i l i c a g e l . The N-methylation of p y r i m i d i n e s and purines with methyl i o d i d e under b a s i c c o n d i t i o n s has been r e p o r t e d . 4 1 6 When the c i s 5-bromo-6-dithianyl d i h y d r o n u c l e o s i d e 343 was subjected to a l k y l a t i v e h y d r o l y s i s with methyl i o d i d e , and semicarbazones formed of the products, compounds 352 and 354 were i s o l a t e d , i d e n t i c a l i n a l l r e s p e c t s with the semicarbazones d e r i v e d from 342. T h i s provided f u r t h e r proof that compounds 342 and 343 are c o n f i g u r a t i o n a l isomers about C-5 and C-6. 3.2.9. 6-Hydroxymethyluridine (3 5 ,6 )_-_ Sodium borohydride r e d u c t i o n of the 6-aldehyde 35_1 i n e t h a n o l gave 6-hydroxymethyl-:2»,3'-0-isopropylidene-5'-0-t r i t y l u r i d i n e (355) • i n 72% y i e l d from 342. The n.m.r. spectrum of 355 i n deuterochloroform showed a D20-exchangeable h y d r o x y l proton at 61-54, the N-3 proton at 68.06 and the 6-methylene group as a s i n g l e t at 6 4-58. The l a t t e r changed to a doublet 144 upon a d d i t i o n of D^O, win a geminal c o u p l i n g constant of 6.4 Hz. The i . r , spectrum of 355 i n chloroform s o l u t i o n showed a sharp N-H a b s o r p t i o n a t 3420 cm- 1 superimposed on a broad O-H band. When compound 355 was r e f l u x e d i n 80% agueous a c e t i c a c i d f o r 25 minutes, 6-hydroxymethyluridine (356) was i s o l a t e d as a c l e a r syrup a f t e r p u r i f i c a t i o n by chromatography on Bio-Bex 70 c a t i o n exchange r e s i n (H + form).,The n.m.r. spectrum of 356 i n d i m e t h y l OH OH 355 356 s u l f o x i d e - d g was completely c o n s i s t e n t with the assigned s t r u c t u r e , having a t o t a l of f i v e D 2O-exchangeable protons. The C-6 methylene s i g n a l was observed as a broad s i n g l e t which sharpened a f t e r D 20 a d d i t i o n . . The u.v. spectrum of 356 i n methanol e x h i b i t e d a maximum at 258 nm due to the unsaturated py r i m i d i n e m o i e t y . 4 1 7 3. 2. .10. 6-Hy d r o x y m e t h y l u r a c i l {357) . Although U e d a 3 3 1 has r e p o r t e d a melting p o i n t f o r 5*-0-a c e t y l - 6 - h y d r o x y m e t h y l - 2 * , 3 ' - O - i s o p r o p y l i d e n e u r i d i n e , no other p h y s i c a l c o n s t a n t s f o r 6-hydroxymethyluridine (356) or i t s d e r i v a t i v e s are known. A c c o r d i n g l y , i n order to c o n f i r m the s t r u c t u r a l assignments of 355 and 356, the l a t t e r compound was s u b j e c t e d to a c i d h y d r o l y s i s using 1M h y d r o c h l o r i c a c i d a t 90° f o r 12 hours, y i e l d i n g the known 6-hydroxymethyluracil 3 5 7 . * 1 8 145 356 HCI 0 HN + D - R i b o s e 357 3. 2- 11- attempted S y n t h e s i s of i - i i _ 4 d i k e t o t e t r a h y d r o i m i d a z o l - 5 - y l ) -2*,3'-0 -Since, as mentioned p r e v i o u s l y , our u l t i m a t e goal was to a t t a c h a C-C l i n k e d amino a c i d s i d e - c h a i n a t C-6 of u r i d i n e , a p p l i c a t i o n of the Bucherer hydantoin s y n t h e s i s 1 * 2 to the aldehyde 35_ was c o n s i d e r e d a convenient route to such a compound- T h i s r e a c t i o n was p r e v i o u s l y used to s y n t h e s i z e the 3-C-hydantoate 280 (see S e c t i o n 1.2.3.) from which the 3-C-g l y c y l a l l o f u r a n o s e 281 was s u c c e s s f u l l y formed. However, when the n u c l e o s i d e 351 was submitted t o the same c o n d i t i o n s , that i s , heating at 50° f o r 12 hours i n methanol i n the presence of sodium cyanide and ammonium carbonate under three atmospheres of carbon d i o x i d e , t . l . c . of the r e a c t i o n mixture showed t h a t at l e a s t e i g h t d i f f e r e n t compounds had formed i n a d d i t i o n to decomposition products, the l a t t e r appearing as b a s e - l i n e m a t e r i a l on the p l a t e - No attempt was made to i s o l a t e any of these products. I t thus appeared t h a t the s e n s i t i v e 3 1 8 6-aldehyde 35_ was not ab l e to withstand the s t r o n g l y b a s i c c o n d i t i o n s r e g u i r e d f o r hydantoin s y n t h e s i s . 358 146 3.2-12. E - I o r Z )-6-f (2-Carboethoxy-2-cya no)_et. h y 1 i d e ne J - 2 1 A 3|_- 0_- i s o p r o p y l i d e n e -5 ' - 0 - t r i t y l u r i d i n e 1359)_ and E - l o r Z L - f H L l l -c a r b o e t a g x y - g - c y a n o ^ e t h y l i d e n e ] - ^ 1 , 3 * - 0 -isoprojjy l i d e n e - 3- methyl- 52.-0- t r i t y l u r i d i n e 13_6_0_I-S i n c e a p p l i c a t i o n of the hydantoin s y n t h e s i s to the 6-aldehyde 352 f a i l e d , i t was decided to attempt s y n t h e s i s of a C-6 3-amino a c i d d e r i v a t i v e by the somewhat milder Knoevenagel condensation of e t h y l cyanoacetate (263) with the 6-formyl n u c l e o s i d e 351. „ The r e a c t i o n s of 263 with the 3-ketose 1_4_ (Sec t i o n 1.1.2.) and the 2, 5-anhy dro-|)-allose 203 (Section 2.1.1.2.) were used as models f o r the present study. Thus, because i t was thought best not to attempt s e p a r a t i o n of the s e n s i t i v e aldehydes, a s o l u t i o n of a mixture of 351. and 353, and e t h y l cyanoacetate (263) i n anhydrous N - -dimeth y l f ormamide was s t i r r e d f o r 2 hours at room temperature i n the presence of a c a t a l y t i c amount of ammonium a c e t a t e as base. Two products,, 359 and 360, were i s o l a t e d by column chromatography on s i l i c a g e l . i n y i e l d s of 38% and 10%, r e s p e c t i v e l y . The n.m.r. s p e c t r a of both these compounds i n deuterochloroform were e s s e n t i a l l y i d e n t i c a l , showing the e t h y l e s t e r s i g n a l s as a c l e a n t r i p l e t (CH^) and qu a r t e t (Ch^) around <5 1.40 and 4.40, r e s p e c t i v e l y , as w e l l as a l o w - f i e l d (5 8.1) s i n g l e t f o r the branched-chain v i n y l proton. However, whereas 359 showed a broad, l o w - f i e l d , D2 0-exchaagea.ble s i g n a l f o r the N-3 proton (Figure X V I I ) , no such s i g n a l was seen i n the spectrum of 360. Instead, a sharp 3-proton s i n g l e t a t <5 3.14 F i g u r e XVII. P a r t i a l 100 MHz PMR Spectrum of E - ( o r Z ) - 6 - [ ( 2 - C a r b o e t h o x y - 2 - c y a n o ) e t h y l i d e n e ] -2 ' , 3 ' - 0 - i s o p r o p y l i d e n e - 5 ' - 0 - t r i t y l u r i d i n e (359) i n CDC1 . 148 i n d i c a t e d t h a t 360 was the N-3 methyl d e r i v a t i v e - The 351 4- 353 NCCH 2C0 2C 2H 5(__) NH40Ac DMF CH,-N" T r O -0 ^ N ' i k C H = c ' 2 _ 0 < N > - C H = ( ( XCN TrO-+ y 359 V 360 i . r - spectrum of 360 i n carbon t e t r a c h l o r i d e s o l u t i o n s u b s t a n t i a t e d the absence of the N-H group and moreover, d i s p l a y e d three c a r b o n y l s i g n a l s at 1745, 1725, and 1680 c r 1 which served as proof t h a t 360 as w e l l as the p r e c u r s o r 353 and i t s semicarbazone 354 were N-methylated r a t h e r methylated. The l a c k of m u l t i p l i c i t y i n the s i g n a l s n.m.r. s p e c t r a of 359 ( F i g u r e XVII) and 360 was evidence t h a t o n l y one of the p o s s i b l e E and Z isomers had been formed i n each case. I t has been demonstrated (see I n t r o d u c t i o n , S e c t i o n 2.3.2.1.} t h a t e t h y l cyanoacetate (263) g e n e r a l l y r e a c t s with aldehydes i n a s t e r e o s e l e c t i v e manner to give the g e o m e t r i c a l isomer i n which the two b u l k i e s t groups are t r a n s . 1 8 5 - 1 8 6 a c c o r d i n g l y , i n both compounds 359 and 360, the isomer i n which the c a r b o x y e t h y l and n u c l e o s i d e moiety are t r a n s would be p r e f e r r e d . No attempt was made to v e r i f y t h i s t e n t a t i v e than 0-of the taken as 149 assignment s i n c e the next s t e p (hydrogenation) i n the planned s y n t h e s i s of u r i d i n y l 8' - a l a n i n e was expected t o dest r o y t h i s c e n t e r of g e o m e t r i c a l isomerism. 3-2.13. Hj_drp_ienation of 359 t o Give §_-L12-±R or SJ_-Carboethoxy-2-acetamidqn;ethyl) eth y l 1-21 ,3'-0 .-lsopropy.lidene-5*-»0-tr i t y l u r i d i n e (36,1) -No f u r t h e r work was done on the N-3 methyl d e r i v a t i v e 360. Compound 359, however, was hydrogenated f o r 20 hours a t 50 p. s - i - i n a c e t i c anhydride using platinum oxide as the c a t a l y s t to give the N - a c e t y l d e r i v a t i v e 361- Though 361 analyzed i Y 361 p r o p e r l y f o r C^gH^N^Og, i t s mass spectrum showed, i n a d d i t i o n to the molecular ion peak at m/e 697, s e v e r a l higher mass peaks centered at m/e 709, i n d i c a t i n g t h a t p a r t i a l r e d u c t i o n of the t r i t y l group had o c c u r r e d . T h i s . was confirmed by the n.m.r. spectrum of 361 i n deuterochloroform which showed a very complex patt e r n of high f i e l d s i g n a l s a r i s i n g from the reduced phenyl r i n g s . However, from t h i s spectrum i t could s t i l l be concluded t h a t a) the e x o c y c l i c v i n y l i c proton seen a t 6 8-1 i n the n-m-r- spectrum of the unreduced compound 359 was no l o n g e r present so that the e x o c y c l i c double-bond was now s a t u r a t e d , b) the n i t r i l e group was converted to the N-acetamide as shown by 1 5 0 the appearance of an a d d i t i o n a l D2O-exchangeable NH s i g n a l and a sharp s i n g l e t at <$ 1-95 and c) the p y r i m i d i n e r i n g of 361 was not reduced s i n c e the C-5 proton was observed as a sharp s i n g l e t at 55-64. S e l e c t i v e r e d u c t i o n of unsaturated s i d e - c h a i n s of p y r i m i d i n e n u c l e o s i d e s i s not uncommon. 2 9 7 3.2.14. 6-f 3-Amino-2-(R or S ) - c a r b o x y p r o p y l j u r i d i n e Treatment of the blocked n u c l e o s i d e 361 with t r i f l u o r o a c e t i c a c i d at room temperature gave the p a r t i a l l y unblocked d e r i v a t i v e 3_62. The n.m.r, spectrum of 362 i n dimethyl s u l f o x i d e - d ^ i n d i c a t e d t h a t the i s o p r o p y l i d e n e and t r i t y l groups °f 361 had been removed, generating one primary and two secondary hydroxyl groups. The h i g h - r e s o l u t i o n mass spectrum of HN n CO2C2HB 0<kN-^CH HO I CF,C00H H U1 / 0 \ | 361 — > K V CH2NHCCH3 OH OH 362 362 d i d not show a molecular i o n peak; i n s t e a d , the highest mass fragment was t h a t corresponding to the protonated base moiety (BH+) , a t y p i c a l fragmentation p a t t e r n f o r N - g l y c o s i d e s . Removal of the b a s e - l a b i l e b l o c k i n g groups of the amino a c i d moiety of 362 was accomplished by r e f l u x i n g a s o l u t i o n of the l a t t e r compound i n c o n c e n t r a t e d aqueous barium hydroxide f o r 6 hours. The n i n h y d r i n - p o s i t i v e m a t e r i a l so obtained {363} was p u r i f i e d by chromatoqraphy on a weakly a c i d i c c a t i o n (H +) 151 exchange r e s i n . While the n.m.r. spectrum of 36 3 i n dimethyl 363 d i s p l a y e d the a p p r o p r i a t e molecular i o n peak (M+H) at m/e 346, the chemical a n a l y s i s of t h i s substance i n d i c a t e d the presence of barium s a l t s . When a s t r o n g l y - a c i d i c c a t i o n exchange r e s i n (Dowex 50W-X2) was used to attempt removal of the barium i o n s from 363, the o r g a n i c m a t e r i a l recovered was no l o n g e r n i n h y d r i n - p o s i t i v e . ^ . . __ The c d . s p e c t r a of n u c l e o s i d e s 362 and 363 i n water showed extremely weak negative Cotton e f f e c t s i n the 260 nm r e g i o n . T h i s i s c o n s i s t e n t with the o b s e r v a t i o n t h a t 6^-substituted p y r i m i d i n e n u c l e o s i d e s i n the 3 — c o n f i g u r a t i o n adopt the syn c o n f o r m a t i o n 4 2 8 (see S e c t i o n 3.2.4)., The 3 - a l a n y l n u c l e o s i d e 363 i s a s t r u c t u r a l isomer o f N 3-{3-L-amino-3-carboxypropyl) u r i d i n e {364), f o u n d 4 2 9 a t p o s i t i o n 47 i n the e x t r a loop of E. c o l i tfiNA. Compound 364 has been s y n t h e s i z e d by S e e l a and C r a m e r . 4 3 0 s u l f o x i d e - d g no longer showed the presence of e i t h e r the N-ac e t a t e group or the e t h y l e s t e r group and the mass spectrum of OH OH 363 p 364 15.2 IV BIOLOGICAL ASSAY 3-n i n v i v o t e s t s , compounds 3 1 7 and 320 were f o u n d t o be i n a c t i v e a g a i n s t L e u k e m i a 1 2 1 0 . * 2 6 Compounds 3 1 7 , 3 1 9 , 3 2 0 , and 347 e x h i b i t e d , r e s p e c t i v e l y , 24, 13, 8 and 2 4 % i n h i b i t i o n o f L1210 c e l l s a t a c o n c e n t r a t i o n o f 10-* M and c a n t h u s be c o n s i d e r e d m a r g i n a l l y a c t i v e i n v i t r o . * 2 7 153 V.. EXPERIMENTAL 1. General Methods., P.m.r. spectra were determined in chloroform-d or dimethyl sulfoxide-dg with tetramethylsilane as the standard (set at 6=0) by using a Varian T6Q., Varian XL-100 or Bruker 270 spectrometer. Values given f o r coupling constants are f i r s t order- Carbon-13 n.m.r- spectra were determined i n deuterium oxide with tetramethylsilane as the i n t e r n a l standard by using a Varian CFT-20 spectrometer. Optical rotations were measured at ambient temperature with a Perkin-Elmer Model 141 automatic polarimeter. The c-d. , measurements were performed on a Jasco J-20 automatic recording spectropolarimeter and i . r . spectra were recorded on a Perkin-Elmer 710 or 727B spectrometer. A l l melting points were done on a L e i t z microscope heating stage. Model 350, and are corrected. Mass spectra were determined on a HMS-9 spectrometer. U l t r a v i o l e t spectra were recorded on a Cary 15 spectrometer. Elemental analyses were performed by Mr. P. Borda of the Microanalytical Laboratory of the University of B r i t i s h Columbia. 2- Chromatography 2. 1. Column Chromatography S i l i c a gel column chromatography was performed using s i l i c a gel H for t . l . c . (Merck). I f not stated, the r a t i o of material to absorbent was approximately 1:100 and the r a t i o of column length to diameter was approximately 10:1. Columns were pressurized above the solvent reservoir at 5-10 p . s . i . providing 154 flow r a t e s of 70-140 ml h " 1 . 2.2. Thin Layer Chroma tog ra phy A l l t h i n l a y e r chromatography was performed using s i l i c a g e l (Camag) c o n t a i n i n g 5% c a l c i u m s u l f a t e . Compounds were detected by u l t r a v i o l e t a b s o r p t i o n , by s p r a y i n g with 50% s u l f u r i c a c i d f o l l o w e d by heating on a hot p l a t e , or by spraying with a 0.3% s o l u t i o n of n i n h y d r i n i n n-butanol f o l l o w e d by warming a t 110° i n an oven. 3. A b b r e v i a t i o n s . The a b b r e v i a t i o n s used i n the f o l l o w i n g d e s c r i p t i o n s are as f o l l o w s : n.m.r. (nuclear magnetic resonance), u. v. ( u l t r a v i o l e t ) , i . r . ( i n f r a r e d ) , m.p. (melting p o i n t ) , t . l . c . ( t h i n l a y e r chromatography), c d . , ( c i r c u l a r dichroism) , DMF (N,N-dimethylformamide) , DMSO (dimethyl s u l f o x i d e ) , THF ( t e t r a h y d r o f uran) , MeOH (methanol), s ( s i n g l e t ) , d ( d o u b l e t ) , d d (doublet of d o u b l e t s ) , t ( t r i p l e t ) , g ( q u a r t e t ) . 4- Synthesis of G l y c o s - 3 - y l Amino Acids 1,2:5,6-Di-O-isopropylidene - a-D-ribo-hexofuranos-3-ulose (14).. - To a m e c h a n i c a l l y - s t i r r e d s o l u t i o n of 1,2:5,6-di-Q-i s o p r o p y l i d e n e - a - D - g l u c q - f u r a n o s e 3 3 8 (261, 20g) i n carbon t e t r a c h l o r i d e (100 ml) and water (100 ml) c o n t a i n i n g sodium hydrogen carbonate (1g) and ruthenium d i o x i d e (hydrate, 0.2g), was very s l o w l y added a 5% s o l u t i o n of sodium metaperiodate (1 ml every 10 min) u n t i l the c h a r a c t e r i s t i c yellow-green c o l o u r a t i o n of ruthenium t e t r a o x i d e was observed. When the 155 s o l u t i o n had completely r e v e r t e d to the b l a c k , d i o x i d e stage the a d d i t i o n was repeated as above. A f t e r 1 h, the rate o f a d d i t i o n was i n c r e a s e d to 1 ml per minute and a f t e r 4 hours the s o l u t i o n c ould be s t i r r e d with an excess of p e r i o d a t e present. The pH of the mixture was maintained at gr e a t e r than 6 by the a d d i t i o n of sodium hydrogen carbonate. A f t e r 10-20 hours the r e a c t i o n was complete as evidenced by t - l . c. on s i l i c a g e l e l u t e d with 95:5 dichlo r o m e t h a n e - e t h y l a c e t a t e . Excess ruthenium t e t r a o x i d e was decomposed by the a d d i t i o n of i s o p r o p a n o l {1 ml). The r e a c t i o n mixture was f i l t e r e d and the carbon t e t r a c h l o r i d e l a y e r separated from the agueous s o l u t i o n . The l a t t e r was then e x t r a c t e d with c h l o r o f o r m (10 x1G0 ml). The combined o r g a n i c s o l u t i o n s were washed with 5% sodium t h i o s u l f a t e s o l u t i o n (50 ml), d r i e d over anhydrous sodium s u l f a t e , f i l t e r e d and evaporated to a f f o r d c r y s t a l l i n e ketose hydrate 262 (19.5 grams, 97%) . Compound 262 was r e c r y s t a l l i z e d from water-saturated e t h y l a c e t a t e and hexane; m.p. 109-110° { l i t . * 1 9 m. p. 109-1 11°) . Immediately b e f o r e use, the anhydrous ketose _14 was prepared by a z e o t r o p i c d i s t i l l a t i o n with toluene. 3-C-f (8, S) -Cyano (ethoxycarbonyl) methylene 1-1 T2:5,6-di—0-i s o p r o p y l i d e n e - a - D - a l l o f u r a n o s e (264). A mixture of 1,2:5,6—di-O- i s o p r o p y l i d e n e - a - p - r i b o - h e x o f u r a n o s - 3 - u l o s e (_14) (6.2 g, 24 mmol) , e t h y l cyanoacetate {263,.2.7 g, 24 mmol), and ammonium ac e t a t e (5 mg) i n anhydrous DMF {100 ml) was s t i r r e d f o r 2 hours at room temperature. The re a c t i o n - m i x t u r e was then poured i n t o ice-water (1 1) and e x t r a c t e d with c h l o r o f o r m (6x100 ml) . The combined c h l o r o f o r m e x t r a c t s were d r i e d with magnesium s u l f a t e 156 and evaporated, l e a v i n g a crude syrup which was chromatographed on s i l i c a g e l (200 g) using 2:1 benzene-ethyl a c e t a t e as developer- A f l u o r e s c e n t compound of R^  0.54, c o n s i s t i n g of a mixture of 265 and 266 (0.9 g) was f i r s t e l u t e d f o l l o w e d by compound 264 (E f 0.44, 875 rug,. 26%). The l a t t e r was c r y s t a l l i z e d from ether-hexane, m.p.. 97-99°; [ a ] 2 3 • 80.4° (c 3.4, c h l o r o f orm) ; v ^ l A 3525 (-OH) , 2260 (-C=N) , and 1730 cm~i (es t e r C=0) ; n. m-r. , (CDC13} ; 6 1.37 ( t , 3H, CH 2C_ 3) '•, 1-30, 1-34, 1.50, 1-62 (s, 1 2 H , 4 X C H 3 ) , 4-07 (d, 1H, J Q H C H 1 - 0 Hz, OH, exchanges i n D 20) , 4.57 (d, 1H, J 1 - 2 4.0 Hz, H-2), 5.93 (d, 1H, H-1) ; mass spectrum: m/e 356 (M +-CH 3) . A s a i i c a l c . f o r C 1 7H 2 5NO g^ C, 54-99; H, 6-74; N, 3.77., Found: C, 54.67; H, 6.49; N, 3.64. 3 t3-C-Bisr {RS,SS #RR)-cyano {ethoxycarbonyl). methyl 1-3-deoxy-l i . J l 5 x 6 - d i - 0 - i s o g r o p y l i d e n e - a - D - a l l o f uranose (266) and 3-C-f(R rS) -cyano(ethoxycarbonyl)methylene 1-3-deoxy-1,2:5,6-di—0-isoPEOEYli^g^Qza-D-allofuranose (268). - To the syrupy mixture of 265 and 266 (600 mg} i n methanol (15 ml) was added Analar I n d i c a t a r i a H^Oto t u r n the s o l u t i o n yellow (pH 4.0). Sodium cyanoborohydride (100 mg) , d i s s o l v e d i n methanol, was then added at room temperature and the yellow, c o l o u r of the r e a c t i o n mixture maintained by i n t e r m i t t e n t a d d i t i o n of 1% HCI i n methanol- A f t e r the r e a c t i o n mixture was s t i r r e d f o r 30 min, t . l . c . monitoring of the product on s i l i c a u s i ng 10:1 benzene-e t h y l a c e t a t e as developer showed two n o n - f l u o r e s c e n t compounds of R j ' s 0.15 and 0.20. The s o l u t i o n was n e u t r a l i z e d with agueous sodium hydrogen carbonate. The aqueous f r a c t i o n was e x t r a c t e d 157 with chloroform (3x20 ml), and the combined o r g a n i c f r a c t i o n s were d r i e d with sodium s u l f a t e , and the s o l v e n t s evaporated under reduced pressure. The r e s i d u a l syrup was chromatographed on a column of s i l i c a g e l (200 g) using 10:1 benzene-ethyl a c e t a t e as developer, y i e l d i n g 266 (268 mg) which was c r y s t a l l i z e d from ether-hexane, m.p. 136-140°; n.m.r- (CDCl^): 5 1.20- 1- 58 (m, 18 H, 4xCH 3, 2xCH 2CH 3) , 6.02 (d, IH, J 1 2 5-0 Hz, H-1); and 268 as a s o l i d (220 mg) m. p. 50-52°; [ a ] " + 79. 4° (c 1.2, c h l o r o f o r m ) ; n.m . r . (CDCl^) : .6 1.30 (t, 3H, CH^H^) , 1.25, 1.40, 1-50, 1- 55 (s, 12H, 4xCH 3), 2.34-2. 70 (m, 7H, H-4, H-5, H-6, CH 2CH 3 # CHCN) , 4.78 (pseudo-t, 1H, J 2 3 5. 0 Hz, H-2), 5-78 (d, 1H, J 1 7 4.0 Hz, H-1) . .. Anals... of 266.Calc. f o r C ^ H ^ ^ O g : C, 56.66: H, 6.44; N, 6.00. Found: C, 56.58; H, 6.65; N, 5.85. Aaai.=.- o f 268. C a l c . f o r C ^ H ^ N 0 ? : C, 57. 47; H, 7.04; N, 3.94. Found: C, 57.18; H, 7.19; N, 3.68. 3-C-f (R y S) - Acetamidomethyl jethoxycarbonyl) methylene 1, 2: 5, 6 - d i - O - i s o p r q p y l i d e n e - a-D-a 11 of uranose (270). - A s o l u t i o n of compound 264 (0.31 g» 0.85 mmol) i n dry a c e t i c anhydride (6 ml) was hydrogenated at 3 atra f o r 10 h i n the presence o f platinum oxide (Adam's catalyst,; 20 mg)..The c a t a l y s t was then removed by f i l t r a t i o n , xylene {10 ml) added to the f i l t r a t e , and the s o l u t i o n evaporated under reduced pressure. The r e s i d u e was chromatographed on a column of s i l i c a g e l (30 g) using 9:1 benzene-ethanol as developer g i v i n g 270 as a syrup (0.34 g, 96%); [ a ] " + 62.6° (c 2.7, c h l o r o f o r m ) ; n.m.r. (CDCl-O : 6 1-08-D ^ 1.58 (m, 15H, 4xCH 3, CH 2CJ 3) , 1.92- 1. 94 (d, 3H, C0CH 3) , 4.40 (d, 1H, J . , 3.8 Hz, H-2), 5.73 (d, 1H, H-1), 6.10-6.52 (d(broad), 158 1 H , NH) ; m a s s s p e c t r u m ; m / e 4 1 7 (M+) , 3 4 5 ( M . + - C H 3 C O N H C H 2 ) . . . i a a l _ C a l c . f o r . C i g H 3 1 N O g : C , 5 4 . 6 8 ; H , 7 . 4 3 ; N , 3 . 3 6 . F o u n d : C , 5 4 . 3 8 ; H , 7 . 2 0 ; N , 3 . 1 3 . , 3 - C - f ,<Rjf.S) 7 C y a n o ( e t h o x Y c a r b q n Y ^ i l g ^ h y l e n e J 7 i . 3 - d e p x y - 1 , 2 : 5 , 6 -d i - O - i s q p r o g y l i d e n e - a i P z e r y t h r o ^ h e x - 3 - e n o . f u r a . n o s e ( 2 7 3 ) . - T o a s o l u t i o n . o f c o m p o u n d 2 6 4 ( 2 1 6 mg) i n a n h y d r o u s p y r i d i n e ( 8 m l ) a t 0 ° w a s a d d e d a s o l u t i o n o f f r e s h l y d i s t i l l e d t h i o n y l c h l o r i d e ( 0 . 5 m l ) i n p y r i d i n e ( 2 m l ) . . . T h e r e a c t i o n m i x t u r e w a s s t i r r e d f o r 3 m i n a t 0 ° a n d t h e n p o u r e d i n t o a m i x t u r e o f i c e w a t e r -c h l o r o f o r m . T h e c h l o r o f o r m l a y e r w a s d r a w n o f f , t h e w a t e r l a y e r w a s h e d o n c e w i t h c h l o r o f o r m a n d t h e c o m b i n e d c h l o r o f o r m e x t r a c t s w a s h e d o n c e w i t h w a t e r a n d d r i e d w i t h s o d i u m s u l f a t e . T h e o r g a n i c s o l v e n t s w e r e e v a p o r a t e d i n v a c u o , t r a c e s o f p y r i d i n e b e i n g r e m o v e d b y a z e o t r o p i c d i s t i l l a t i o n w i t h x y l e n e a t r e d u c e d p r e s s u r e , l e a v i n g a y e l l o w s y r u p ( 1 8 8 mg) . T h e l a t t e r w a s c h r o m a t o g r a p h e d o n s i l i c a g e l ( 2 0 g ) u s i n g 1 5 : 1 b e n z e n e - e t h y l a c e t a t e a s d e v e l o p e r , y i e l d i n g c o m p o u n d 2 7 3 a s • a c l e a r s y r u p ( 6 0 m g , 3 0 % ) ; [a ] « + 1 1 0 . 6 ° ( c 1 . 9 , c h l o r o f o r m ) ; v J^J^ l3 2 2 4 0 { -MeOH C_N) , 1 7 4 0 ( e s t e r - C = 0 ) , 1 6 9 8 c m - * ( - C = C - ) ; 2 1 2 , 2 6 3 nm ( c 0 . 0 2 ) ; n . m . r . ( C D C 1 3 ) z 6 1 . 2 6 - . 1 . 6 2 ( i (9 l i n e s ) , 1 5 H , 4 x C H 3 » C H 2 C _ 3 ) , 3 . 8 8 - 4 . 4 4 (m , 4 H , H - 6 , C _ 2 C H 3 ) , 4 . 6 0 - 4 . 8 2 ( t , 1 H , 6 6 . 5 H z , H - 5 ) , 5 . 4 0 ( d , 2 H , H - 2 , C H C = 0 ) , 6 . 0 2 - 6 . 1 2 ( d d , 1 H , H - 1 ) ; n . m . r . ( b e n z e n e - d g ) : 6 0 . 8 4 - 1 . 0 8 ( d d , 3 H , C H 2 C _ 3 ) , 1 . 2 4 - 1 . 6 2 ( m ( 6 l i n e s ) , 1 2 H , 4 x C H 3 ) , 3 . 8 0 - 4 . 1 8 ( m , 4 H , H - 6 , C _ 2 C H 3 ) , 4 . 3 4 - 4 . 5 2 ( t ( b r o a d ) , 1 H , H - 5 ) , 5 - 2 0 ( d , J . , 2 6 H z , 0 . 6 H , R ( o r S ) H - 2 ) , 5 - 3 0 ( s , 0 . 6 H , R ( o r S) - C H C = 0 ) , 5 . 4 0 ( d , 0 . 4 H , S ( o r R) H - 2 ) , 5 . 4 5 ( s , 0 . 4 H , S ( o r R) - C H C = 0 ) , 5 - 5 7 ( d , 0 . 6 H , R ( o r S ) H - 1 ) , 5 - 7 0 ( d , 0 . 4 H , S ( o r R) H - 1 ) . 159 Mai-.., C a l c . . f o r . C 1 7 H 2 3 N 0 7 3 C, 57. 79; H, 6.52; N, 3-97. Found: C, 57.69; H, 6.39; N, 4.10., 2- L i t h i o - 1 , 3 - d i t h i a n e 1 9 2 (126). - To a s o l u t i o n of 1,3-d i t h i a n e (123, d r i e d by a z e o t r o p i c d i s t i l l a t i o n with benzene) i n anhydrous THF at -78° under n i t r o g e n was added dropwise a s o l u t i o n of 1.6 M n - b u t y l l i t h i u m i n hexane (1 equivalent) . A f t e r completion of the a d d i t i o n , the mixture was s t i r r e d at -78° f o r 30 min and then s t o r e d at -20° f o r 3-4 h p r i o r to use i n other r e a c t i o n s . 3- C-(1 y 3- P i t h i a a- 2- y 1) -1 y 2 : 5,6 ~d i - 0- i s o p r o p y l i d e n e - a - D -a l l o f u r a n o s e (176). -A s o l u t i o n of the ketose JI4 (4.95 g) i n THF (50 ml) was added at -78° under n i t r o g e n to a s o l u t i o n o f the d i t h i a n e anion 1.26 (2.64 g) i n THF (40 ml). A f t e r 2-5 h at -20°, the r e a c t i o n mixture was quenched with water (200 ml) and the s o l u t i o n was e x t r a c t e d with chloroform (3x200 ml).,The combined org a n i c e x t r a c t s were d r i e d with sodium s u l f a t e and evaporated l e a v i n g a crude syrup (5.8 g)- Unreacted 1,3-dithiaae was removed by s u b l i m a t i o n and the . r e s i d u e was c r y s t a l l i z e d from ether-hexane y i e l d i n g c o l o u r l e s s c r y s t a l s of 176 (3-8 g, 57%); m.p. 96-97° ( l i t . 2 3 * m.p. 9 7 ° ) ; n.m.r- (60 HHz, CDC1 3) : « .5.82 (d, 1H, H-1), ( l i t . 2 3 6 6 5.98, d, H-1). , i 3-C-Formyl-1,2:5,6-di-Q-isoprqpylidene-a-D-allofuranose (2 7 8 ) and i t s semicarbazone 2_7_9_ r - A mix ture of the d i t h i a n y l compound 176 (40 mg) , methyl i o d i d e (1 ml), and barium carbonate (60 mg) i n 10% aqueous acetone (10 ml) was h e l d a t 55° f o r 12 h a f t e r which i t was cooled aad f i l t e r e d to remove the 160 barium s a l t s - The f i l t r a t e was evaporated under reduced pressure. The r e s u l t i n g s o l i d was then d i s s o l v e d i n chlo r o f o r m (30 ml) and washed with water (5 ml). A f t e r the ch l o r o f o r m l a y e r was d r i e d with sodium s u l f a t e , the s o l v e n t was evaporated to y i e l d a crude syrup {28 mg, 92%) i d e n t i f i e d as the aldehyde 278; 3400 (OH), 1720 cm-* (C=0) ; n.m.r. (100 MHz, C D C l 3 ) : 6 9.86 (s, 1H, HC=0) . Without, f u r t h e r p u r i f i c a t i o n , 278 was d i s s o l v e d i n methanol (2 ml) and p y r i d i n e (0-5 ml) f o l l o w i n g which semicarbazide h y d r o c h l o r i d e (0.5 ml of a 2M aqueous s o l u t i o n ) was added to the s o l u t i o n . The mixture was heated on a steam-bath f o r 5 min, d i l u t e d with water (20 ml) and e x t r a c t e d with e t h y l a c e t a t e (3x15 ml)- The combined o r g a n i c e x t r a c t s were then d r i e d with sodium s u l f a t e , evaporated i n vacuo and the re s i d u e chromatographed on a column of s i l i c a g e l (20 g) using 9:1 benzene-ethyl a c e t a t e as the developer, y i e l d i n g a major component (279) as a s o l i d {15 mg, 42%) which was c r y s t a l l i z e d from benzene-ethanol; m.p. 227-228°; L a3p 3 +78.3° (c 0.84, methanol); n.m.r. (100 MHz, DMSO-d&) : 6 1.28, 1-32, 1. 49 (s, 12H, 4xCH 3) , 3.63 (dd, 1H, 6 t ) 9.0 Hz, ^ 5 6 q 6.0 Hz, H-6a) , 3.86 (dd, 1H, J & 6 b 5.0 Hz, H-6b) , 4.02-4.16 (m, 2H, H-4, H-5), 4-63 (d, 1H, J . ? 4.0 Hz, H-2), 5.58 (s, 1H, OH, exchangeable with D^O) , 5,83 (d, 1H, H-1), 6.40 (broad s, 2H, NH.,, exchangeable with D^O) , 7.12 (s, 1H, CH=N) , 10.04 (broad s, IH, NH, exchangeable with D 2 O ) . A n a l i C a l c . f o r C^H^NgOy: c ' 48.?0; H, 6.67; N, 12.17. Found: C, 48.73; H, 6.67; N, 11.92. , 3-C- ( 2 , 4 - D i k e t o t e t r a h y d r o i m i d a z o l - 5 - (B, S) - y l ) - 1 ,2: 5,6-di-O-i§°££°£Yii^§Il§Z^Z_zaliof uranose ______ -A mixture of the 161 aldehyde 278 (0.67 g) , f r e s h l y - r e c r y s t a l l i z e d ammonium carbonate (1-11 g) and sodium cyanide (0.53 g) i n methanol (30 ml) was s t i r r e d under 3 atmospheres o f carbon d i o x i d e f o r 3 h a t 20° and then f o r 18 h a t 55°. The r e a c t i o n mixture was then c o o l e d , f i l t e r e d and the f i l t r a t e was evaporated under reduced pressure. The r e s i d u a l s o l i d was then d i s s o l v e d i n water (20 ml) and the s o l u t i o n was a c i d i f i e d to pH 6.5 by a d d i t i o n of 3N h y d r o c h l o r i c a c i d . E x t r a c t i o n of the aqueous s o l u t i o n with e t h y l a c e t a t e (3x20 ml), d r y i n g of the combined o r g a n i c e x t r a c t s with sodium s u l f a t e and ev a p o r a t i o n of the s o l v e n t s l e f t a crude s o l i d which was chromatographed on s i l i c a g e l (30 g) us i n g 9:1 benzene-ethyl a c e t a t e as the developer. The component of 0.06 (280) was thus i s o l a t e d as a s o l i d (440 mg, 53%) which was c r y s t a l l i z e d from benzene-ethanol, m.p. 282-283°; [ a3Q 3 +29.0° (c 0.?, methanol)'; v j ^ ^ 3400 (broad, OH, NH) , 1780 (C=0) , 1700 c r > (C=0) ; n. m, r. , (100 MHz, DMS0-d6) : 6 1.2-8, 1. 32, 1. 50 (s, 12H, 4xCH 3) , 3.80-4.10 (m, 2H, H-6), 4.20-4-34 (m, 2H, H-4, H-5), 4-26 (s, IH, H-1», sharpens upon a d d i t i o n of D^O) , 4.44 (d, IH, J 1 2 3.5 Hz, H-2), 5.66 (d, 1H, H-1), 7.60, 7.86, 8. 16 (broad s, 3H, GH, NH, a l l exchangeable with D j O ) . , Anal. Calc. f o r C 1 cH. oN.0 0: C, 50-28; H, 6.15; N, 7.82. l b 2 2 2 o Found: C, 50.73; H, 6.23; N, 8-07. IH and L-2-(1,2:5^6-Di30-isopropYlidene-a-D-allofuranos-37 yl) g l y c i n e (2 8 1 ). -A suspension of the hydantoate 280 (4 7 mg) i n s a t u r a t e d aqueous barium hydroxide (6 ml) was r e f l u x e d at 125° f o r 4 h. Ammonium carbonate (1 g) was added i n p o r t i o n s and the s o l u t i o n was r e f l u x e d f o r another 30 min. The barium s a l t s were then removed by f i l t r a t i o n , the f i l t r a t e was concentrated 162 under reduced pressure and a p p l i e d to a column {31x2.25 cm) of Bio-Rex 70 (H+) c a t i o n exchange r e s i n . E l u t i o n with water and c o l l e c t i o n of the n i n h y d r i n ..positive f r a c t i o n s y i e l d e d 28T as a hard g l a s s (32 mg, 7 4%); £ a ] 2 3 +43.2° (c 2. 13, water), ( l i t . [ a ] Q S °'f k~ isomer: +89.2° (water); D-isomer +25° (water)); Rf 0.65 (Whatman #1 paper, 10:4:3 e t h y l a c e t a t e - p y r i d i n e - w a t e r , n i n h y d r i n d e t e c t i o n ) ; v j ^ j j j 3400 (OH, NH 2), 1725 (C=0) , 1600 cm-* (NH2) ; n.m.r. .,{100 MHz, D 20 ) : < 5 1. 42, 1.48, 1.60 (s, 12H, 4xCH 3) , 5.88 (d, 2/3 H, J 1 2 3.5 Hz, H-1 of D-isomer), 5.93 (d, 1/3 H, J ' L 2 3.5 Hz, H-1 of L-isomer) { l i t . « B 6 6.07 (H-1 of p_-isomer) , 6.08 (H-1 of L-isomer), J ^  2 3.5 Hz f o r L and D) ; mass spectrum: m/e 318 (H*-CH3) , 260 (M+-glycine) . A s a l . C a l c . f o r C 1 4H 2 3MOg*H 20: C, 47.86; H, 7.12; N, 3.99.. Found: C, 48. 13; H, 7.40; N, 4.11. C r y s t a l l i z a t i o n of 28_1 from ethanol-ethy1 a c e t a t e gave a sm a l l g u a n t i t y of the L - g l y c i n e isomer (2 mg), m.p. 192-193° ( l i t . 3 5 8 m.p. 189-191°). j>=. S y n t h e s i s of P r e c u r s o r s t o C-Nucleosides^, 2 15 T&nhYdro- 3^ 4,. 6 - t r i - O - b e n z o y l - D - a l i o s e (203) . - A s o l u t i o n of p - t o l u e n e s u l f o n i c a c i d monohydrate (0.92 g) i n acetone (25 ml) was added dropwise t o an i c e - c o o l e d s o l u t i o n o f 1,3-diphenyl-2-(2,3,5-tri-O-benzoy1-3 -D-r i b o f uranosyl) i m i d a z o l i d i n e 2 7 2 * 2 3 (204, 1-5 g) i n methylene c h l o r i d e (75 ml). A f t e r 5 min at room temperature, the r e a c t i o n mixture was g r a d u a l l y allowed t o come to room temperature and was s t i r r e d f o r another 30 min. T . l . c . (2:1 ether-hexane) o f the product at t h i s time showed complete r e a c t i o n . The mixture was 163 then f i l t e r e d , the p r e c i p i t a t e was washed with methylene c h l o r i d e and the combined f i l t r a t e s were evaporated under reduced pressure a t a temperature not exceeding 30°. The r e s i d u e was d i s s o l v e d i n methylene c h l o r i d e (100 ml), washed with water (3x20 ml), and the o r g a n i c l a y e r was d r i e d with magnesium s u l f a t e . E v a p o r a t i o n of the s o l v e n t s l e f t 203 as a syrup (1-02 g, 96%); n.m.r. . (60 MHz, CDCl^) s .6 9.72 (d, approx 1H, 1-5 Hz, H-C=0), ( l i t . 2 7 2 6 9.77, J 1 2 1.5 Hz). E t h y l i E or Zjziit-lzanhydro-2-c yano- 2^3, 5-trideoxy-6,8-di-Q-benzoyl-erythro-octon-2,4-dleneate ! (283)_. - A - mixture of 2,5-anhy d r o - 3 , 4 , 6 - t r i - g - b e n z o y l - D - a l l o s e (203, 1.02 g, 2.15 mmol), e t h y l cyanoacetate (263_, 250 mg, 2 . 2 mmol) and ammonium a c e t a t e (30 mg) i n anhydrous DMF (20 ml) was s t i r r e d at 0° f o r 6 h. A f t e r the r e a c t i o n mixture was poured i n t o i c e - w a t e r (100 ml), the mixture was e x t r a c t e d with c h l o r o f o r m (3x50 ml).' The combined organic e x t r a c t s were d r i e d with .: sodium s u l f a t e and evaporated under reduced pressure. The r e s u l t i n g crude syrup (1.35 g) was chromatographed on a s i l i c a g e l column (130 g) using 10:1 benzene-ethyl a c e t a t e as developer. Compound 283 (300 mg, 31%) was c r y s t a l l i z e d from e t h e r , m.p. , 124-127°; [ a j 2 3 + 244.4° (c 0 . 7 , c h l o r o f o r m ) ; 3 2270 (C= N), 1720 (es t e r C=0) , 1630 and 1600 cm - i (C=C) ; n. m. r. (CDCl 3) : 6 1.38 ( t , 3H, CH 2CH 3), 4.30 ( g , 2H, CJ^CH^, 4. 60-4.75 (d, 2H, H-8), 5.04 (m, 1H, H-7), 6.12 (2s, 2H, H-3, H-5) ; mass spectrum: m/e 325 (M+-C^COOH) , 204 (M+-2C6H5COOH) . Anal. .Calc. f o r C^H^NOy:: C, 67.11; H, 4.70; N, 3.13. Found: C, 66.83; H, 4.78; N, 3.07. 164 E t h y l 4 g7-anhydro-2-(R,5)-acetamidomethyl-6,B-di-Q^beflZOYl-J^J^5-trideoxy.-4- (R,S)-D-'ervthro rP-octqnate j284). - A s o l u t i o n of compound 283 (710 mg, 1.6 mmol) i n dry a c e t i c anhydride (30 ml) was hydrogenated over platinum oxide (140 mg) at 3 atm f o r 20 h at room temperature. The c a t a l y s t was removed by f i l t r a t i o n and the f i l t r a t e evaporated a t reduced pressure t o y i e l d an o i l which was chromatographed on a s i l i c a g e l column (130 g) using 9:1 benzehe-ethanol as developer. The product having R^ 0.25 (284) was i s o l a t e d as a syrup (250 mg, 31%); f a ] 2 * +2.3° (c 0.4, chloroform) ; v C H C I 3 1720 (ester C=0) , 1660 (amide C=0); n.m.r. max (CDC1 3) : <5 1.14-1.37. (q, 3H, CH^H^) , 1.95 (s, 3H, A c ) , 5.45-6.10 (d(broad), IH, NH) , 7.39-8.06 (m, 10, 2xCgH 5) ; mass spectrum: m/e 497 (M+), 375 (M+-C6H5COOH); a l s o seen i n the mass spectrum were peaks at m/e 503 and 509 i n d i c a t i n g s a t u r a t i o n of one and two phenyl r i n g s of 284. Anal. C a l c . f o r C-,„H ,,, N00 : C, 65.19; H, 6.24; N, 2-82-2 / 3 1 o Found: C, 65.27; H, 6.30; N, 2.60. 2f 3-p-I^opr opylidejne-5-O-tr B~P- r i b o f u r a n o s y l c h l o r i d e (210). - A s o l u t i o n of 2 , 3 - 0 - i s o p r o p y l i d e n e - 5 - 0 - t r i t y 1 - D - r i b o -f u r a n o s e 3 6 2 (285, 13. 4 g) i n anhydrous N,N-dimethylf ormamide (20 ml) was t r e a t e d with carbon t e t r a c h l o r i d e (15 g) and t r i p h e n y l p h o s p h i n e (7 g) f o r 14 h a t room temperature. The s o l u t i o n was then poured i n t o a r a p i d l y s t i r r i n g mixture of d i e t h y l e t h e r (50 ml), hexane (50 ml) and ice-water (100 ml) . The suspension was g u i c k l y f i l t e r e d through a C e l i t e pad to remove i n s o l u b l e t r i p h e n y l p h o s p h i n e oxide and the aguecus l a y e r was separated. The organic l a y e r was d r i e d over sodium s u l f a t e and evaporated i n vacuo to g i v e a c l e a r syrup. A d d i t i o n of 1 6 5 benzene to the syrup p r e c i p i t a t e d r e s i d u a l t r i p h e n y l p h o s p h i n e oxide which was removed by f i l t r a t i o n . Hexane was then added to the f i l t r a t e u n t i l c l o u d i n e s s was observed whereupon c r y s t a l l i z a t i o n commenced, f i n a l l y y i e l d i n g the g l y c o s y l c h l o r i d e 2_0_ (5.6 g, 40%) i n two crops; m. p. , 113-116°, ( l i t . 3 * 2 m.p., 114-115°); n.m.r. (60 MHz, CDC1 3):.5 6.08 (s, 1H, H-1)., ( l i t . 3 6 , 2 S 6-10, s, H-1). The c h l o r i d e 210 was g e n e r a l l y used i n i t s syrup form r a t h e r than i t s c r y s t a l l i n e form i n subsequent r e a c t i o n s i n order t o avoid l o s s e s due t o decomposition. D i e t h y l sodium phthalimidomalonate (61). - A s o l u t i o n o f d i e t h y l phthalimidomalonate* 2° (286, 15 g) i n anhydrous d i e t h y l ether (50 ml) was added slowly under n i t r o g e n to a r a p i d l y s t i r r i n g suspension of sodium hydride (2.4 g of a 50% d i s p e r s i o n i n o i l ) i n d i e t h y l e ther (200 ml). A f t e r one hour, the yellow p r e c i p i t a t e of 6_ which had formed was c o l l e c t e d by f i l t r a t i o n , washed c o p i o u s l y with dry e t h e r , and s t o r e d i n a d e s i c c a t o r ( 1 3.5 g, 84%); n.m.r. (60 MHz, DMSO-dg):60.80 ( t , 6H, CH 2C_ 3}, 3.65 {q, 4H, Cj^CH^ , 7.60 ( s , 4H, A r ) . D i e t h y l 2 , 3 - 0 - i s o p r o p y l i d e n e - 5 - 0 - t r i t y l - a - (and £ )_-D-£ifeof uranosy_l phthalimidomalonate _287 and 288, r e s p _ _ t i y e l _ _ _ ,-A s o l u t i o n of the g l y c o s y l c h l o r i d e 21.0 (0.62 g) and d i e t h y l sodium phthalimidomalonate (61., 0-44 g) i n anhydrous N, N— dimethylformamide (100 ml) was maintained a t 90° f o r 5 h under an atmosphere of dry n i t r o g e n . The r e a c t i o n mixture was c o o l e d , poured i n t o r a p i d l y - s t i r r i n g ice-water (100 ml) and the water was e x t r a c t e d with chloroform (3x100 : ml). The combined chloroform e x t r a c t s were d r i e d with magnesium s u l f a t e , the 166 s o l v e n t s were evaporated under reduced press u r e , and the r e s i d u e was chromatographed on s i l i c a g e l (130 g) u s i n g 10:1 benzene-e t h y l a c e t a t e as the developer, y i e l d i n g a 1:1 mixture o f 287 and 288 as a white foam (0.45 g, 46%); [ a ] 2 3 +12.5° (c 0.9, C H C l c h l o r o f o r m ) ; v m Q x 3 1755 ( e s t e r ) , 1725 c r 1 (amide); n.m.r- (60 MHz, CDClj) : <51.21 ( t , 6H, CH 2CH 3) , 1-29, 1.37 (s, 6H, 2xQCH 3), 3.10 (m, 2H, H-5'), 3.80-4-60 (m, 7 H # H-2', H-3', H-4', CH^CH^ , 5-03 (d, approx. 0.5 H, ^ 3.5 Hz, H-1* of a-anomer) , 5.08 J (s, approx., 0.5 H, H-1« of 8-anomer), 6-90-7.40 (m, 15H, t r i t y l ) , 7.60 (m, 4H, p h t h a l y l ) ; mass spectrum: 705.254 (MH*-C H 3 ) »'..C41 H 3 Q 0 1 Q N r e q u i r e s 705-257.,, Anal. C a l c . f o r H/,1 N0 1 Q : C, 7 0 . 1 0 ; H, 5.70; N, 1.95. Found: C, 70. 27; H, 5-84; N, 1.78. Attempted Unblocking of 287 and 288..,- A mixture of 287 and 288 (424 mg) i n methanol (10 ml) c o n t a i n i n g 1N aqueous sodium hydroxide (1 ml) was r e f l u x e d f o r 3 h. The r e a c t i o n mixture was c o o l e d , 2N h y d r o c h l o r i c a c i d (2 ml) was added and the s o l u t i o n was r e f l u x e d f o r another 4 h.,Cooling of t h i s r e a c t i o n mixture r e s u l t e d i n the p r e c i p i t a t i o n o f t r i p h e n y l c a r b i n o l (15 mg) which was c o l l e c t e d by f i l t r a t i o n , m-p. 155-159°, ( l i t - * 2 5 m.p. 164.2°); n.m.r. (100 MHz, MeOH-d^) : 5 7.80-8. 12 (m, Ar)...; The f i l t r a t e was n e u t r a l i z e d with 1N sodium hydroxide and concentrated under reduced pressure. The residue was then chromatographed on a column of Bio-Rex 70 (H +) r e s i n (30x2.75 cm) using water as the de v e l o p e r . The n i n h y d r i a - p o s i t i v e f r a c t i o n s were c o l l e c t e d and evaporated. An n.m.r. spectrum o f the r e s i d u e (20 mg, 16%) i n D2O showed only a complex m u l t i p i e t at 6 3.40-4. 10. 167 6... Attempted S y n t h e s i s of C-Nucleosides Using a Palladium C a t a l y s t . 5-Bromq—2 f4-dichloropyrifflidine (291..)..- - A suspension of 5-b r o m o u r a c i l 3 6 7 (290, 4.4 g) i n ' phosphorus j o x y c h l o r i d e {15 ml) was heated at 125° f o r 5 days. The homogeneous r e a c t i o n mixture was then c o o l e d and the s o l v e n t was removed by d i s t i l l a t i o n under reduced pressure. Ice-water {100 ml) was c a r e f u l l y added to the r e s u l t i n g syrup and the mixture was e x t r a c t e d with e t h e r {2x50 ml). The ether e x t r a c t s were d r i e d w i t h ; sodium s u l f a t e , the ether evaporated and the remaining yellow syrup was d i s t i l l e d a t 60° at 0.2 t o r r to a f f o r d 29_ as a c l e a r o i l (3.17 g, 61%), ( l i t . b. p. 145- 147° (78 mm)). 5-Brqmo-2,4-di-t-butoxypyrimidine (292). - Dry t - b u t a n o l (25 ml) i n anhydrous hexane (10 ml) was added to a s t i r r e d suspension of sodium h y d r i d e (1 -4 g of a 50% d i s p e r s i o n i n o i l ) i n hexane {15 mi). A f t e r 5 min r e a c t i o n a t room temperature, the s o l u t i o n was r e f l u x e d f o r 10 min. The r e s u l t i n g suspension of sodium t - b u t o x i d e was c o o l e d and a s o l u t i o n of 5-bromo-2,4-d i c h l o r o p y r i m i d i n e (29_, 3 g) i n hexane (10 ml) was added s l o w l y to maintain r e f l u x . After' complete a d d i t i o n of 291, the r e a c t i o n mixture was r e f l u x e d f o r 2 h before i t was c o o l e d and evaporated- Hater was added to the residue and the mixture was e x t r a c t e d with ether (5x20 ml}- The combined ether e x t r a c t s were d r i e d with magnesium s u l f a t e , the ether evaporated and the r e s i d u e d i s t i l l e d a t 0-2 t o r r . , The f r a c t i o n d i s t i l l i n g a t 60° was d i s c a r d e d while that d i s t i l l i n g a t 80-100° was c o l l e c t e d . The l a t t e r f r a c t i o n c r y s t a l l i z e d spontaneously a t room temperature to give pure 292 (2.55 g, 65%); m-p. 55-57°, 168 ( l i t « m.p. 63-64°) ; n.m.r.,(60 MHz CDCl ) 6 1.55 ( s , 9H, 3xCH 3), 1.60 (s, 9H, 3xCH 3) , 8. 10 ( s , 1H, H-6) ; mass spectrum; m/e 302 (M+) . . 2__-_i-t_b_tox_____a___s (294) and 5 - j 1 -p r o p e n - 2 - y l ) u r a c i l 1296_. - A s o l u t i o n of the bromo d e r i v a t i v e 292 (375 mg, 1.24 mmol) and e t h y l bromide (1-35 mg, 1.24 mmol), i n anhydrous t e t r a h y d r o f u r a n (THF, 4 ml) was added over 30 min to a mixture of magnesium powder (90 mg, 3.72 gr. at.) i n r e f l u x i n g THF (2 ml) under an atmosphere of dry n i t r o g e n . T h i s s o l u t i o n o f the 5-magnesiumbromo d e r i v a t i v e 294 was r e f l u x e d f o r 1 h a f t e r completion: of the a d d i t i o n and then cooled before acetone (230 mg, 4 mmol) i n anhydrous ether (5 ml) was added dropwise. A f t e r the vigorous r e a c t i o n had subsided, the mixture was r e f l u x e d f o r an a d d i t i o n a l 30 min, c o o l e d , and poured i n t o water (100 ml) to which had been added h y d r o c h l o r i c a c i d (5 ml of a 0.2M s o l u t i o n ) . The aqueous mixture was e x t r a c t e d with e t h e r (3x50 ml), the combined o r g a n i c e x t r a c t s washed with s a t u r a t e d aqueous sodium hydrogen carbonate, d r i e d with magnesium s u l f a t e and evaporated under reduced pressure. The r e s u l t i n g crude syrup, c o n t a i n i n g unreacted 292 as evidenced by 1.1. c. on s i l i c a g e l was d i s t i l l e d (60°, 0.2 t o r r ) , l e a v i n g a CHCl r e s i d u e (295, v m a x ^ 3650 cm-1 (OH) ) which, without f u r t h e r p u r i f i c a t i o n , was h y d r o l y z e d by r e f l u x i n g f o r 5 min i n methanol c o n t a i n i n g cone., HCI (0.2 ml). Evaporation of the s o l v e n t s then l e f t a y e l l o w i s h s o l i d which was c r y s t a l l i z e d from e t h a n o l t o a f f o r d 296 (82 mg, 43%); m. p. , 300-3 15° (decomp. } ; n.m.r. (100 MHz, DMSO-dg).: 5 1-92 (s, 3H, CH^) , 5-01 . (dd, 1H, J L A 1 B 2 Hz, J 1 q C H 1Hz, H-1a) , 5-79 (d, 1H, H-1b),7-35 (s, 1H, H-6), 11.00 169 (broad s, 2 N H , exchangeable with D20) ; inass spectrum: m/e 152 (M+) , 137 (M+-CH3) . A_ a l _ C a l c . f o r CyHg N ^ * 1/3 H2<3: C, 53.11; H, 5.48; N, 17.72. Found: C, 53.12; H, 5.20; N, 18.30-Iqdp„_phenyl)_bis{tr^ palladium _ I I _ (298) . A s o l u t i o n of f r e s h l y - d i s t i l l e d phenyl i o d i d e (300 mg) i n benzene (50 ml) was added dropwise to a r a p i d l y s t i r r e d suspension of t e t r a k i s ( t r i p h e n y l p h o s p h i n e ) p a l l a d i u m ( 0 ) 4 2 4 (226, 1.5 g)- The r e s u l t i n g dark orange s o l u t i o n was s t i r r e d f o r 10 min a f t e r completion of the a d d i t i o n , a f t e r which the s o l v e n t s were evaporated- The r e s i d u a l s o l i d was then t r i t u r a t e d with ether and the p r e c i p i t a t e was c o l l e c t e d by f i l t r a t i o n . C r y s t a l l i z a t i o n of t h i s s o l i d from methylene chloride-hexane gave orange needles o f 298 (320 mg, 30%); m.p. 195-197° (decomp.), ( l i t . 3 ™ m . p , 171-186° {decomp.)), Attempted Palladium ( I I ) - c a t a l y z e d C o u p l i n g of 2 1 0 and 294. - To a r e f l u x i n g s o l u t i o n of the g l y c o s y l c h l o r i d e 210 (610 mg) i n anhydrous THF (10 ml) c o n t a i n i n g the palladium (II) c a t a l y s t 298 (20 mg) was added, under an atmosphere o f dry n i t r o g e n , a s o l u t i o n of the Gri g n a r d reagent 294 (350 mg) i n THF (8 ml). The r e a c t i o n mixture was r e f l u x e d f o r 12 h by which time a l l s t a r t i n g sugar had been consumed as shown by t . l . c . on s i l i c a g e l . The s o l v e n t s of the mixture were next evaporated, e t h e r was added t o the r e s i d u e and the i n s o l u b l e m a t e r i a l removed by f i l t r a t i o n . , T . l . c . of the f i l t r a t e using 10:1 benzene-ethyl a c e t a t e showed many components, only two of which were f l u o r e s c e n t and c h a r r i n g . These were i s o l a t e d by column 170 chromatography on s i l i c a g e l using 10:1 benzene-ethyl a c e t a t e as the developer i n y i e l d s of 30 mg and 40-mg- However, n e i t h e r of the n- m. r . ' s of these two sugar components d i s p l a y e d peaks a s s o c i a t e d with the blocked p y r i m i d i n e 303, i n d i c a t i n g that c o u p l i n g had not o c c u r r e d . 7. Synthesis of 6 - S u b s t i t u t e d N u c l e o s i d e s . 2,2' -Anhydr o-1-7 (5-0 - t r i t yl-g - D- ar abinof uranosyl) u r a c i l (307). - F o l l o w i n g the method of Fox and Wempen37*, a mixture of 5 ' - 0 - t r i t y l u r i d i n e 3 7 3 (305, 13-6 g) and t h i o c a r b o n y l d i i m i d a z o l e ' (306, 5.6 g) i n anhydrous toluene (500 ml) was r e f l u x e d a t 120° f o r 1 h. The p r e c i p i t a t e which formed was c o l l e c t e d by f i l t r a t i o n , washed with t o l u e n e , d r i e d i n vacuo and r e c r y s t a l l i z e d from methanol, y i e l d i n g 307 as shiny p l a t e s (11-5 g, 88%); m.p. 222-223°, ( l i t - 3 7 * m. p. 219-22 1 9} . 2 , 2« - Anh y d r 0 - 1 - { 3-0 - ace t y 1- 5- 0 -1 r i t y 1- ft - D-ar abinof uranosyl) u r a c i l (30 8) . , - In a m o d i f i c a t i o n of the procedure of O g i l v i e and Iwaclia,* 2* a s o l u t i o n of the t r i . t y l a t e d anhydronucleoside 3 07 (10 g) and a c e t i c anhydride (30 ml) i n anhydrous p y r i d i n e (100 mi) was s t i r r e d at room temperature f o r 18 h, f o l l o w i n g which t h e s o l v e n t s were evaporated a t reduced pressure, the temperature of the mixture never exceeding 35°. R e s i d u a l a c e t i c anhydride was removed from the crude product by repeated a z e o t r o p i c d i s t i l l a t i o n with xylene. The g l a s s y r e s i d u e was then passed through a s h o r t column of s i l i c a g e l (200 g) using 5:1 benzene-ethyl a c e t a t e as the e l u t i n g s o l v e n t s . The acetate 308 was thus obtained as a white foam (10.5 g, 96%); 1 7 1 [ a ] 2 3 -28.9° (c 1.5, methanol}'; n.m.r. (100 MHz, CDC1 ) : 6 2.10. (s, 3H, CH 3) , 3.01 (dd, 2H, 5» 7.0 Hz, J 5'Q &' b 0.5 Hz, H-5 » ) , 4.45 (t of doublets, 1H, J 3< ^ 1.5 Hz, H-4»), 5.30 (d , IH, J y 2- 6.0 Hz, H-2') , 5.40 Cd, 1H, H-3'), 5.8 4 (d, 1H, J 5 6 8.0 Hz, H-5), 6.25 (d, 1H, H-1'), 7.15-7.50 (m, 16H, H-6, Ar)-Inal^ C a l c . f o r C30 B26 N2 O6" 1 / 3 fl20: C ' 69.77; H, 5.16; N, 5.42. Found; C, 70.05; H, 4.94; N, 5.36. . Synt h e s i s of 2- f1 , 3 - d i t h i a n - 2 - y l ) -1- C 5 - 0 - t r i t y l - e - D -a r a b i n o f uranosyl) -4 {IH) -pyr i m i d i n o n e j309)_ and 2. 2'-anhydro-5,6-<lihlilEo::£:iisiziIi^^ ar abinof uranosyl) u r a c i l (310)_. - A s o l u t i o n of anhydronucleoside 308 <1.2 g, 2.5 mmole) i n anhydrous THF (20 ml) was added by s y r i n g e t o a s o l u t i o n of the d i t h i a n e anion • T26 (1-5 g, 12.5 mmoles) i n THF a t -78° under n i t r o g e n . A yellow p r e c i p i t a t e formed immediately and the mixture was s t i r r e d at -78° f o r an a d d i t i o n a l hour a f t e r which water (0.5 ml) i n THF (5 ml) was s l o w l y added. S t i r r i n g of the mixture was continued at -78° f o r 30 min before i t was allowed to come t o room temperature. The s o l u t i o n , n e u t r a l i z e d with d i l u t e h y d r o c h l o r i c a c i d , was then e x t r a c t e d with chloroform (5x40 ml), the combined o r g a n i c e x t r a c t s d r i e d (magnesium s u l f a t e ) and the s o l v e n t s evaporated, l e a v i n g a crude orange syrup (1-8 g ) . Chromatography of t h i s syrup on s i l i c a g e l (200 g) using 9:1 benzene-ethanol as e l u t i n g s o l v e n t s gave 309 (183 mg, 15%) ; Rf 0.10; m.p. 155-156°; O J 2 3 + 38.8° (c 1.28, methanol) ; v * ^ 3380 (OH), 1725 (C=0) , 1635 (C=N) , and 1600 c u r 1 (C=C) ; n.m.r. (100 MHz, DMSO-dg): <$ 1.74-2.20 (m, 2H, SCH 2CH 2) , 2.95-3.21 (m, 4H, SCH 2CH 2), 3.42 (m, H-5'), 3.80-4-51 (m, 3H, H-2',3',4'), 5.46 (s, 1H, SCHS) , 5.?1 (d. 172 1H # OH, exchangeable with D_0) , 5.73 (d, 1H, J c c 8.0 Hz, H-5), L 5, b 5.92 (d, 1H, OH, exchangeable with D 2 0 ) , 6.31 (d, 1H, J 2' 5 * 0 Hz, H - 1 V ) , 7 . 3 1-7.46 {m, 15H, Ar) , 7.91 (d, IH, H-6); mass spectrum: m/e 375 (M + - base).. Anal. Calc- f o r C 3 2 H 3 2 N 2 ° 5 S 2 * a 2 ° : C / 63.36; H, 5-61; N, 4-62. Found; C, 63.13; H, 5-52; H, 4.49-, The f a s t e r running compound 31.0 was i s o l a t e d as a non-c r y s t a l l i z a b l e g l a s s (392 mg, 30%) ; Rf 0.15; [ a ] 2 3 -109. 3° (c PH0I 0.66, chloroform) ; 3 3 3 5 0 (OH), 1702 (C= 0 ) , 1595 (C=N) ; and 1460 cm-1; n.m-r-.(100 MHz, CDC1 3) : 6 1.80r2.38 (m, 4H, S C 3 2 C _ 2 # H-5), 2.64-3.26 (m, 6H, SC_ 2, H-5») , 3.88-4-05 (m, 1H, H-6), 4-36-4.46 (m, 3H, SCHS, H-3«, H-4«), 5-18 (d, 1H, J ^  2' 5.0Hz, H-2 « ) , 5.50 (s(broad) , 1H, OH, exchangeable with D . ,0) , 6-25 (d, 1H, H-1') , 7. 18-7.58 (m, 15H, Ar) . M a l i C a l c . . f o r C 3 2 H 3 2 N 2 0 5 S 2 : C, 6 5 . 3 1 ; H, 5.44; N, 4.76., Found; C, 65.31; H, 5.64; N, 4.58. 2-Methyl-1~ ( S - O ^ t r i t y l - g - Q - a r a b i n o f u r a n o s y l ) - 4 C 1 H ) -pyrimidinone _3_3_. - F r e s h l y - a c t i v a t e d Raney n i c k e l (100 mg) i n eth a n o l (2 ml) was added to a s o l u t i o n of compound 3 09 (42 mg) i n e t h a n o l (5 ml) and r e f l u x e d f o r 1 h by which time t . l . c . of the r e a c t i o n mixture on s i l i c a g e l using 5:1 e t h y l a c e t a t e -e t h a n o l as developer showed complete disappearance of 309 and formation of a . s i n g l e new lower Rf compound. The r e a c t i o n mixture was then f i l t e r e d , the n i c k e l washed r e p e a t e d l y with hot etha n o l and the c o l l e c t e d f i l t r a t e and washings evaporated, l e a v i n g a c l e a r syrup (26 mg). A d d i t i o n of et h a n o l to the syrup r e s u l t e d i n formation of white c r y s t a l s o f 313 (26 mg, 33%), m-p- 234-235°, ( l i t . 3 1 1 m.p. 238-239°) ; n. m. r- (100 MHz, DMSO-173 a 6) : 6 2-39 {s, 3H, CH ) , 3.83-4.33 (m, 3H, H-2', 3 V, 4 » ) , 5.67 (d, 1H, OH, exchangeable w i t h DjO) , 5.64 {d, 1H, J 5 & 8.0 Hz, H-5), 5.79 (d,. 1H, OH, exchangeable with D 20), 6.02 (d, IH, -J.gg 8.0Hz, H-6); ^ a ^ " _ i } 0 - 4 ° (£ 0.65, N, N-dimethylf ormamide) ( l i t - 3 * i [ a ] 2 5 -43.2° (c 0.22, N,N-dimethy If ormamide) ) ;• mass spectrum: m/e 375 (M+-base), 241 (M+-{CgHg) 3 C) . Anal. C a l c . . f o r C29 H28 N2°5*^2 H5 O B : C' 7 0 " 1 8 ; H' 6- 4 1» M' 5.28. Found: C, 70.21; H, 5.97; N, 5.30. A c i d h y d r o l y s i s of 309 t o give a r a b i n o s e , 2- ( 1 , 3 - d i t h i a n - 2 -y l ) - 4 - p y r i m i d i n o n e (314) and t r i p h e n y l c a r b i n o l . - A s o l u t i o n of 309 (20 mg) i n methanol (2 ml) and 80% aqueous a c e t i c a c i d (0.5 ml) was r e f l u x e d f o r 10 min. The r e a c t i o n mixture was seen t o c o n t a i n by t . l . c . using 5:1 e t h y l a c e t a t e - e t h a n o l as developer a high Rf (0.90), f l u o r e s c e n t compound ( t r i p h e n y l c a r b i n o l , yellow when t . l . c . p l a t e was sprayed with 50% s u l f u r i c a c i d and heated), a f l u o r e s c e n t , n o n - c h a r r i n g component (31.4, .Rf 0 . 7 0 ) and a c h a r r i n g , n o n - f l u o r e s c e n t m a t e r i a l ( a r a b i n o s e , Rf 0.10). The l a t t e r was c h a r a c t e r i z e d by paper chromatography (No. 1 Whatman, descending e l u t i o n with water-saturated n-butanol) of the degradation mixture a g a i n s t a u t h e n t i c a r a b i n o s e (Rf 0.11, a l k a l i n e s i l v e r n i t r a t e d e t e c t i o n ) . A d d i t i o n of agueous e t h a n o l t o the r e a c t i o n mixture caused c r y s t a l l i z a t i o n of the 2-s u b s t i t u t e d base component 314 (1 mg) , m.p- 210-215° (decomp) ; n.m.r. (100 MHz, DMSO-dg):6 1-87-2-12 (m, 2H, S C ^ C j ^ ) , 2.68-3.44 (m, 4H, SCfJ 2) , 4.92 (s, 1H, SCHS) , 6^31 (d, 1H, J g 6 8,0 Hz, H-5), 8.11 (d# 1H, H-6), 12.51 (s (broad) , 1H, NH, exchangeable with D 20). Anal.. C a l c . f o r CgH^N^S.^: C, 44.85; H, 4.67, N, 13.08. 174 Found: C, 44.60; H, 4.99; N, 13.28., 2 - ( 1 , 3 - P i t h i a n - 2 - y l ) - 1 - ( 2 , 3 - d i - Q - a c e t y l - 5 - 0 - t r i t y l - B - D -a r a b l n o f u r a n o s _ l _ ~ 4 ( 1 H ) - p y r i m i d i n o n e (315).. - A s o l u t i o n of the n u c l e o s i d e 309 (2.04 g) i n p y r i d i n e (20 ml) and a c e t i c anhydride (5 ml) was maintained at 0° f o r 12 h by which time t . l . c . o f the a c e t y l a t i o n mixture on s i l i c a g e l using 9:1 benzene-ethanol as developer showed a s i n g l e product (Rf 0.43). The s o l v e n t s were removed by t h r e e a z e o t r o p i c e v a p o r a t i o n s with xylene and the r e s i d u a l syrup chromatographed on s i l i c a g e l (200 g) using 10:10:1 benzene-ethyl a c e t a t e - e t h a n o l as e l u t i n g s o l v e n t s , y i e l d i n g the d i a c e t a t e 3_5 as a white foam (2.33 g, 100%); .[<*.]* 5 +45.1° (c 1.62, c h l o r o f orm) ; n.m.r. (100 MHz, DMSO-dg): <5 1.90 (S, 3H, Ac), 2.11 (s, 3H, Ac), 2.98-3.20 (m, 4H, SC_ 2) , 3.39-3.52 (m, 2H, H-5'), 4.16-4.36 (m, 1H, H-4») , 5.34-5.50 (pseudo-t , 1H, H-3') / 5.63 (s, 1H, SCHS), 5.68-5.82 (pseudo-t, 1H, H-2*), 5-91 (d, 1H, J 5 6 8.0 Hz, H-5), 6.53 (d, Ml, J y 2< 5.6 Hz, H-1»), 7.23-7-53 (m, 15H, Ar) , 7. 83 (d, 1H, H-6). Anal, C a l c - f o r C -,CH -_H_ OnS.: C, 64.29; H, 5-36; N, 4.17. ; 3 b 36 2 / 2 Found: C, 64.58; H, 5.50; N, 4-11.-.. 2____3_Dithian_2_^ a r a b i n o f u r a n o s y l ) - 4 ( 1 H _ - p y r i m i d i n o n e ______ - A s o l u t i o n of 3_5 (1-24 g) i n 80% aqueous a c e t i c a c i d (35 ml) was s t i r r e d f o r 65 h f o l l o w i n g which e v a p o r a t i o n of the s o l v e n t s of the r e a c t i o n mixture at room temperature and chromatography of the r e s u l t i n g syrup on s i l i c a g e l (60 g) using 9:1 benzene-ethanol as developer y i e l d e d the d e t r i t y l a t e d compound 316 as a white g l a s s (356 mg, 45%) ; Rf 0.13; [ a]2s +48.3° (c 1.0, c h l o r o f orm) ; n. m. r . 175 <100 MHz, DHSO-dg)s <S 1.91 (s, 3H, Ac), 2.12 {s, JH, Ac), 2-94-3.22 (m, 4H, SCH 2) , 3.64-3.82 {m, 2H, H-5») , 3.98-4.16 {m, ' IH, H-4'), 5.20-5.31 (pseudo-g, 2H, H-3', OH, p a r t l y exchanges with D 20), 5.55 (s, 1H, SCHS), 5.68-5. 82 (pseudo-t, 1H, H ~ 2 » ) , 6.12 (d, IH, J 5 g 8.0 Hz, H-5), 6.51 (d, 1H, J y 2 ' 5-8 Hz, H-1'), 8.04 (d, IH, H-6) . Anal. C a l c . f o r C, y H ^ I ^ Q y S ^ 1/2H20: C, 46.47; H, 5.24; N, 6.38. Found: C, 46.68,' H, 5.23; N, 6.10. 2- {1,3-D i t h i a n - 2 - y l ) -1- g-D-a r a b i n o f uranosyl-4 f IH) -pyrimidinone (317). - To a s o l u t i o n of t h e d i a c e t a t e 316 <290 mg, 0.67 mmoles) i n anhydrous methanol (15 ml) was added a 0.04 M s o l u t i o n of sodium i n methanol {70 y l ) . A f t e r the r e a c t i o n mixture, had been s t i r r e d f o r 1 h a t room temperature, i t was n e u t r a l i z e d with Bio-Rex 7 0 (H +) w e a k l y - a c i d i c cation-exchange r e s i n , the r e s i n was f i l t e r e d o f f and washed with methanol. The f i l t r a t e and washings were evaporated under reduced pressure, l e a v i n g a white foam (237 mg, 100%); £ a ] 2 3 +82. 1° (c 1.1, methanol) ; 3350 {OH), 1725 (C=0) , 1625 {C=N) , 1600 c r » MeOH (C=C) ; * m u X 245 nm ( e 15,700); n.m.r-. {100 MHz, DMSO-d 6):5 1- 55-2. 29 (m, 2H , SCH 2CH 2) , 2.9 1-3. 21 (m , 4H, SCH 2) , 3.57-3.79 {m, 3H, H-4', 5») , 3.79-4.05 (m, IH, H-3»), 4.37 (g, 1H, H-2'), 5.15 <t, 1H, CH 20H, exchangeable with D20) , 5.41 (s, 1H, SCHS), 5.52 (d, 1H, CHOH, exchangeable with D 20) , 5.83 {d, 1H, -CHOH, exchangeable with D 20), 6.00 (d, 1H, J-,. & 7.5 Hz, H-5) , 6.24 (d, 1H, 3 y 2' 5 * 2 H z ' H-1 •) , 0.01 (d, 1H, H-6) ; mass spectrum: m/e 347.0741 (M+). Anai^ C a l c . f o r C 13 H18 N2°5 S2 3 C ' 4 5 * 0 9 ; H » 5.20; N, 7.91. Found: C , 44.80; H, 5.45; H,'' 7,91-.., 1 7 6 Attempted H y d r o l y s i s of the P i t h i o a c e t a l of Compound 3 , 1 5 . . -(a) A mixture of 3 1 5 ( 1 5 mg) , mercuric c h l o r i d e (1.2 mg) and mercuric oxide ( 9 . 5 mg) i n 9 0 % aqueous a c e t o n i t r i l e ( 3 ml) was r e f l u x e d under n i t r o g e n f o r 3 0 min. T . l . c . of the r e a c t i o n mixture using 5 : 1 e t h y l a c e t a t e - e t h a n o l as the developer showed a high R ^ ( 0 - 8 6 ) c h a r r i n g component as w e l l as a f l u o r e s c e n t , n on-charring component of R^  0 . 7 0 , the l a t t e r c orresponding to 2 - { 1 , 3 - d i t h i a n ^ 2 - y l ) u r a c i l ( 3 1 4 ) , thus i n d i c a t i n g t h a t g l y c o s i d i c cleavage was the major r e a c t i o n pathway. (b) A mixture of 3 , 1 5 ( 2 5 mg) , methyl' i o d i d e ( 0 . 5 ml), and barium carbonate ( 3 0 mg) i n 9 0 % aqueous acetone was heated at 5 5 ° f o r 4 h. T . l . c . of the r e a c t i o n mixture using 9 : 1 benzene-ethanol as the developer showed some lower R^  ma t e r i a l { 0 . 10) but the major component was the f r e e base 3 1 4 (R^ 0 . 2 5 ) . (c) A s o l u t i o n of 3 . 1 5 ( 7 5 mg) and b e n z e n e s e l e n i n i c a n h y d r i d e * 2 2 ( 1 2 1 mg) i n anhydrous THF ( 1 0 ml) was r e f l u x e d under n i t r o g e n f o r 3 0 min. T - l ^ c . of the r e a c t i o n mixture showed the presence of a t l e a s t f i v e components as w e l l as b a s e - l i n e m a t e r i a l . Shortening of the r e a c t i o n time or a decrease i n the r e a c t i o n temperature had no n o t i c e a b l e e f f e c t on the t . l . c . r e s u l t s . 2 f 2 ' - A n h y d r o - 5 , e - d i h y d r o - e - R - m e t h y l - S ' - O - t r i t y l u r i d i n e J_3_18]_. - A mixture of compound 3 J . 0 (1 .g) and f r e s h l y - a c t i v a t e d Raney n i c k e l ( 2 g) i n e t h a n o l ( 5 0 ml) was r e f l u x e d f o r 2 h. The n i c k e l was removed by f i l t r a t i o n ^ washed c o p i o u s l y with e t h a n o l and the combined f i l t r a t e and washings evaporated under reduced pressure. The s o l i d r e s i d u e was c r y s t a l l i z e d from e t h a n o l y i e l d i n g a white powder ( 3 4 0 mg, 41%) ; m.p-. 2 4 5 - 2 4 7 ° ; [ a ] 2 3 -177 101.1° <c 0.8, methanol) ; v j ^ 3350 (OH), 1700 (C=0) , 1570 (C=N) , 1450 c r > ; n.m.r. ,,{100 HHz, DMSQ-dg): 6 1.26 {d, 38, J6 CH3 6 , 0 H z ' C H 3 ^ ' 2 * 2 0 ( d / 1 H' J 5 Q 6 4 , 0 H z ' H ~ 5 a ) ' 2 , 2 8 *d' 1H, J 5 b 5 1Hz, H-5b), 2.82-3.16 (m, 2H, H-5'), 3.39 {broad s, 1H, OH, exchangeable with D 20), 3.60-3.84 (pseudo-g, 1H, H-6), 4.15-4.28 (m, 1H, H-4'), 4.33 ( b r o a d s , 1H, H-3'), 5.11 (d, IH, 2- 5.6 Hz, H-2'), 6.05 (d, 1H, H-1'), 7.38 (s, 15H, Ar) -I r r a d i a t i o n of the m u l t i p l e t at 6 3.60 c o l l a p s e d the doublets a t 6 2. 20 and 1.26 to s i n g l e t s -M a i - C a l c . f o r C29 H28 N2°5 : C ' 71-?°5 H ' 5.79; N, 5-79-Fbund: C, 71.80; H, 5.87; N, 5.75. 5,6-Dihydro-6- (S) - { 1,3-dithian- 2-y 1) - 1-B -p-a r a b i n o f u r a n o s y l u r a c i l (3 1 9 ) and 3-T (S) - 1- ( 1 , 3 - d i t h i a n - 2 -y l ) lpropionamido-8 -D-arabinof urano-^ 1 1 f 2': 4, 5 ]- 2- oxaz o l i d one (320). -A s o l u t i o n of the t r i t y l a t e d anhydronucleoside 310 (2 g) i n 80% aqueous a c e t i c a c i d ( 5 0 ml) was r e f l u x e d f o r 10 min, c o o l e d and d i l u t e d with water (50 ml}- The r e s u l t i n g p r e c i p i t a t e of t r i p h e n y l c a r b i n o l was f i l t e r e d o f f and washed c o p i o u s l y with water- The f i l t r a t e and c o l l e c t e d washings were then evaporated, the r e s i d u a l syrup d i s s o l v e d in? water and washed twice with e t h e r to remove r e s i d u a l t r i p h e n y l c a r b i n o l . The water l a y e r was concentrated, a p p l i e d to a column (3x30 cm) of Bio-Sex 70 (H+) cation-exchange r e s i n and e l u t e d with water- The f i r s t f r a c t i o n s y i e l d e d the d e t r i t y l a t e d n u c l e o s i d e 3_9 (50 mg, 10%) as a s o l i d which was r e c r y s t a l l i z e d from aqueous methanol, m-p- 245-247°; H f 0.42 ( s i l i c a g e l , 5:1 e t h y l a c e t a t e - e t h a n o l ) ; [ a ] * 3 +11-4° {c 0.25, methanol) ; 3400 (OH) ,1710 - (C=0) , 169.0 • (C=0).# and M e O H 1600 cm-1; X m Q X 245 nm ( e 1700) ; c.d. (c 3.5 x 10-*, methanol) 178 £e +4-80; n.m.r. (100 MHz, DMSO-d,-): & 1-47-2-21 (m, 2H, 250 - . o SCH 2C_ 2) , 2.59-3.01 (m, 6H, SCH^, H-5), 3.47-3.73 (m, 3H, H-5', H-6) , 3.76-3.90 (m, 1H, H-4'},.3.93-4.15 (m, 2H, H-2', 3») , 4.76 {d, 1H, J^.g 4.0 Hz, SCHS), 4.85 ( t , 1H, CH^H, exchangeable with D-,0) , 5.60 (d, 1H, CHOH, exchangeable with D 20) , 5.99 (d, IH, J y 2' 5.0 Hz, H-1'), 10.31 (s, 1H, NH, exchangeable with D 20) ; mass spectrum: m/e 245 (M +-dithiane) , 133 (M+-base) . Anal. C a l c . f o r C n H, ~N. 0r S.: C, 42.85; H, 5.49; N, 7.69. I J 2 U 2 b 2 Found; C, 42.90; H, 5.68; N, 7.78. Further e l u t i o n of the chromatography column with water gave the d e t r i t y l a t e d 2-oxazolidone d e r i v a t i v e 320 (0. 5 g, 90%) which was c r y s t a l l i z e d from aqueous methanol, m.p. 185-188°; Rf 0.23 ( s i l i c a g e l , 5:1 e t h y l acetate-ethanol) ; [ a ] p S -32.3° (c K R r 0.65, methanol); v m Q x 3400 (OH), 1740 (carbamate), 1680 (amide) MeOH and 1615 cm-» (amide II). 225 (e 3500), 232 ( e 3000) and 245 nm { e 1500) ; c. d. (c 1.92x10-*, methanol) Ae. +2.41; *H-22 6 n.m-r. (100 MHz, DMSO-dg) ; <S 1.73- 2. 1 2 (m, 2H, SCH 2C_ 2) , 2.55-3,19 (m, 6H, -C_ 2C=0, SCR^ , 3.25-3-58 (m, 2H, H-5'), 3-63-3.90 (m, 1H, -CHCH2C=0) , 4.04 (d, 1H, J ] y, 10.6 Hz, SCHS), 4.15 (broad s, 1H, H-3') , 4.37-4.61 (m, 1H, H-4'), 4.68 (d, 2H, J y 2' 5.8 Hz> H-2'), 4.70 (t ( p a r t l y b uried under H-2») , 1H, CH 20H, exchangeable with D^O), 5.66 (d, 1H, CHOH, exchangeable with D 20) , 5. 80 (d, 1H, H-1'), 6.86 (broad s, IH, NH, exchanges s l o w l y with: D 20), 7.51 (broad s, 1H, NH, exchanges s l o w l y with D 20) ; i 3 C n.m.r. (D 20) : 6 177.0 (amide), 159-8 (carbamate), 90.5 (anomeric) ; mass spectrum; m/e 227 (Mt-dithiane) . . Anal. C a l c . f o r C. - H.AN. Oc S. : C, 42.85; H, 5.49; N, 7.69. I 5 2U L 0 2 Found: C, 42.78; H, 5.66; N, 7.87. 179 Acid h y d r o l y s i s of 3T9 to cjive arabinose and 5,6-dihydro-6-(S)- ( 1 . 3 - d i t h i a n - 2 - y l ) u r a c i l !3_2_J_J__ - A suspension of n u c l e o s i d e 319 (5 mg) i n 1N h y d r o c h l o r i c a c i d (1 ml) was s t i r r e d at 70° f o r 4 h. The r e a c t i o n mixture was then c o o l e d and the white p r e c i p i t a t e which formed was f i l t e r e d o f f . The p r e c i p i t a t e was washed s e v e r a l times with water and shown to be the f r e e base 321 (2 mg, 62%); m.p. 260-261°; [ a ] g 3 +22 - 7 ° (c 0.1, methanol) ; v ^ x 3420 (OH of tautomeric form), 3230 (NH) , 1720 MeOH (broad, C=0) , 1600 cm-* (C=N of tautomer) ; A m Q x 245 nm ( e 700) ; n.m.r. (100 MHz, DMSO-dg) t 6 1. 48-2. 18 (m, 2H, SCH 2CH 2) , 2.58-2.98 Im, 6H, H-5, SCH 2), 3.63-3. 92 (m, 1H, H-6), 4.24 (d, 1H, J y 6 6.0 Hz, H-1 1), 7.6 1 (broad s, 1H, NH, exchangeable with D 20) , 10.01 (broad s, 0.5H, NH, exchangeable with DO)'. , Anal_ C a l c . f o r Cg H 1 2 N ^ ^ : C, 41.38; H, 5.17; N, 12.07. Found: C, 41.38; H, 5.31; N, 12.20. The f i l t r a t e was spotted on Whatman No. 1 paper a g a i n s t D-a r a b i n o s e , the paper e l u t e d i n a descending manner with water-s a t u r a t e d 4:1 n - b u t a n o l - a c e t i c a c i d and the chromatogram developed by s p r a y i n g with a l k a l i n e s i l v e r n i t r a t e s o l u t i o n which r e v e a l e d two spots of i d e n t i c a l Bf (0.31). 5,6-Dihydro-6-methyluracil (322). - A s o l u t i o n of the d i t h i a n y l compound 321 (12 mg) i n N,N-dimethylformamide (1 ml) was heated f o r 2h at 80° i n the presence of f r e s h l y - a c t i v a t e d Baney n i c k e l (50 mg) i n e t h a n o l (3 ml). The n i c k e l was then removed by f i l t r a t i o n and washed with hot N,N-dimethylformamide. Evaporation of the combined f i l t r a t e and washings l e f t an o f f -white s o l i d (5 mg, 75%) which was c r y s t a l l i z e d from methanol, KBr m.p. 218°, ( l i t . 217-218°) ; v ' 3200 (NH, OH), 1725 (C=0), 180 1695 (C=0), 1605 cm- i (0=N of tautomer) ; n. m. r- (100 MHz, DM SO-o d c ) : 6 1.12 (d, 3H, J c r u 6-0 Hz, CH ) , 2-10-2.62 (oct e t b b , L n ^  — 3 ( p a r t i a l l y obscured by DMSO) , approx. 2H, J ^ Q ^ 16 Hz, g 5.6 Hz, H-5), 3.50-3-68 (m, 1H, H-6), 7.52 (broad s, 1H, NH, exchangeable with D 20) , 9.96 {broad s, 1H, NH, exchangeable with D 20) -D i - s i l y l a t i o n of 3_2_0_ to g i v e 3-f (S) -1- (1 , 3 - d i t h i a n ~ 2 -yl) ]propionamido-3', S ' - d i - O - t - b u t y l d i m e t h y l s i l y l - 8,-D-arabinofurano-£!f^2^:jf t 5 J-2-oxazolidpne 1323|_,- - A s o l u t i o n of the dihydroxy compound 320 .{44 mg, 0.12 mmoles) and t -b u t y I d i m e t h y l s i l y l c h l o r i d e {50 mg, 0.3 mmoles) i n anhydrous N, N-dimethylf ormamide (2 ml) and p y r i d i n e (0.5 ml) was s t i r r e d f o r 24 h under n i t r o g e n . Water (0-5 ml) was then added t o the r e a c t i o n mixture and s t i r r i n g o f t h e s o l u t i o n was continued f o r 15 min. The s o l u t i o n was then evaporated to dryness under reduced pressure, the r e s i d u e d i s s o l v e d i n chloroform (30 ml) and washed with water (2x15 ml). Drying of the chloroform s o l u t i o n with sodium s u l f a t e f o l l o wed by e v a p o r a t i o n , l e f t a syrup (97 mg) which was chromatographed on s i l i c a g e l [15 g) using 1:1 benzene-ethyl a c e t a t e as developer y i e l d i n g 323 as a white g l a s s (53 mg, 75%); [ a ] 2 3 -50.9° (c 1 . 4 , c h l o r o f o r m ) ; n.m.r. (100 MHz, CDCl 3) : 6 0. 04 (s, 6H, 2xCH 3) , 0.10 (s, 3H, CH^) , 0.12 (s, 3H, CH^) , 0.88 ( s , 18B, 2xt-Bu) , 1.84-2. 20 (m, 2H, SCH 2CH 2), 2. 40-3. 42 (m, 6H, SCH 2, CH 2C=0), 3.52-3.68 (m, 2H, H-5«), 3.82-3. 98 (m, 1H, NCH) , 4.07 (d, 1H, J 1 2" 10 Hz, SCHS), 4 . 4 0 (broad s, 1H, H - 3 » ) , 4. 49-4.60 (m, 1H, H-4») , 4.69 (d, 1H, J l' 2' 6 " ° H z * H ~ 2 ' ) ' 5 * 7 9 < d' 1 H ' H-tl) , 5-68-6 .30 (broad d ( p a r t l y b u r i e d under H-1'), 2H, NH,, exchangeable with D 70) ; 181 C H C l vmax 3 3 4 2 0 a n d 3 5 4 0 <NH2) , 1760 (carbamate), 1695 (amide carbonyl) and 1598 cm - 1 (amide I I ) . Anal. C a l c . f o r C 2 5 H 4 8 N 2 ° 6 S 2 S i 2 : C ' 5 0 * 6 8 » H * 8 - 1 1 . N, 4.73; Found: C, 50.85; H, 8.08; N, 4.81. . Conversion of 31.9 t o the oxazolidone 320_._ - A s o l u t i o n o f the n u c l e o s i d e 3J.9 (20 mg) i n water (1 ml) was kept at room temperature f o r 4 days. Evaporation o f the water under reduced pressure l e f t a s o l i d (20 mg) i d e n t i f i e d as 320 by t . l . c - (5:1 e t h y l acetate-ethanol) and n. m- r- , sp e c t r o s c o p y - . Dehydration of 320 to g.ive 3-f (S)-1- ( 1 , 3 - d i t h i a n - 2 -yl) Ic Yanoethyl-3-D-ar abinof urano - r 1 1 ,2':4,5 1-2-oxazolidone {328j. - To a suspension of the amide 320 (43 mg, 0.12 mmoles) i n anhydrous 1,4-dioxane (3 ml) and p y r i d i n e (0.08 ml, 8 eg.) at 0° was added t r i f l u o r o a c e t i c anhydride (0.14 ml, 8 eg.)... The mixture was then s t i r r e d a t room temperature f o r 2 h by which time a l l s t a r t i n g m a t e r i a l had d i s s o l v e d . Methanol (1 ml) was added to the s o l u t i o n and the l a t t e r was s t i r r e d f o r 30 min before the s o l v e n t s were evaporated i n vacuo. ,The r e s i d u a l syrup was d i s s o l v e d i n a s m a l l g u a n t i t y of water, a p p l i e d to a column (11x1 .5 cm) of Bio-Rex 70 (H +) r e s i n and e l u t e d with water, y i e l d i n g the n i t r i l e 328 (32 mg, 77H) as a syrup which was c r y s t a l l i z e d and r e c r y s t a l l i z e . d from chloroform; m.p. 184-185°; [ a ] 2 3 -40.2° (c 0.99, methanol) ; . v * ^ 3400 (OH), 2260 (C=N) , 1740 cm-i (C=0) ; n. m. r. , (100 M Hz, DM SO- dg) : 6 1.72-2.10 (m, 2H, SCH 2CJ 2) , 2. 60-3. 65 (m, 8H, SCH 2, H-5', CH2CN) , 3.77-4.01 (m, 1H, H-4'), 3.99 (d, J l f 11.0 Hz, SCHS), 4.01 (broad s, 1H, H-3'), 4.45-4.71 (m, 1H, -CHCH2CN) , 4.82 (t, 1H, CH^OH, 182 exchangeable with D^O) , 4.79 {dd a f t e r a d d i t i o n of D.,0, J^' 2 ' 6.0 Hz, J 2' 3' 1-5 Hz, H-2') / 5 . 7 4 (d, 1H, -CHOH, exchangeable with U^O), 5.86 Cd, 1H, H-1'.)., _____ C a l c . f o r C 1 3 H l g N 2 0 5 S 2 : C, 45.09; H, 5.20; N, 8.09. Found; C, 44.57; H, 5-26; N, 7.91. 3- (R) -1-Met hylpropionamido- g-rj-arabino£urano-i" 1 1 ,2 1:4, 5 ]-2-oxazclidone 13_2_9__- ,- F r e s h l y - a c t i v a t e d Raney n i c k e l (1-7 g) i n water (5 ml) was added to a s o l u t i o n of the d i t h i a n y l compound 320 (314 mg) i n water (10 ml) and the mixture heated at 75° f o r 4 h. The mixture was then f i l t e r e d , the n i c k e l washed c o p i o u s l y with water, the f i l t r a t e and c o l l e c t e d washings concentrated and the r e s i d u a l syrup passed through a column (2.?x18 cm) of Bio-Rex 70 (H+) cat ion-ex change r e s i n (water e l u t i o n ) y i e l d i n g 329 as a c l e a r syrup (190 mg, 85%)., The m a t e r i a l c o u l d not be c r y s t a l l i z e d , though i t was shown t o be pure by paper chromatography {Rf 0.36,. descending e l u t i o n on Whatman No. 1 paper with water-saturated n-butanol) ; £ a j 2 3 -78.8° (c 1.1, methanol) ; v ^ ' j j 3375 (OH), 1740 {carbamate}, 1670 (amide c a r b o n y l ) , 1625 (amide I I ) ; .n.m.r. (100 Hflz, DMSO-dg); 6 1-18 (d, 3H, J 1 C H ^ 6.0 Hz, CH^) 2.43 (d, 2H, J 1 2 7.0. Hz, -CH 2C=0), 3.28-3. 4 3 ( o c t e t , 2H, J 5' Q 5' b 12.0 Hz, J ^  5'Q 6.0 Hz, J A' 5' b 7.0 Hz, H-5') , 3.80-4-14 (m, 2H, H-4*, ~CHCH3) , 4-18 (broad s, 1H, H-3»), 4.67 (d, 1H, J \> ^ 5.0 Hz, H-2'), 4.89 ( t , IH, CHjOH, exchangeable with D 20) , 5.62 (d, 1H, CHOH, exchangeable with D 20) , 5-81 (d, IH., H-1*), 6-86 (broad s, IH, NH, exchanges slowly with D 20), 7-44 (broad s, 1H, NH, exchanges s l o w l y with D 20) ; mass spectrum: m/e 152 (M + -base). Anal. C a l c . f o r C. a H N.0c • 1/2 H 0: C, 44.60 ; H, 6.32; N, 10 16 2 b 183 10.41. Found: C, 44.50; H, 6.30; N, 10.46., Dehydration of 329 to give 3 - j R)_- 1 - m e t h y 1 c y a n o e t fa y 1 - ft- D-ar abinof urano-£1 f.f.,21 :4 f 5 ]-2-oxazolidone J 3 3 Q L - Compound 329 (41 mg) was t r e a t e d with p y r i d i n e - t r i f l u o r o a c e t i c anhydride i n e x a c t l y the same manner used i n the c o n v e r s i o n of the amide 320 to the n i t r i l e 328, y i e l d i n g 330 as a syrup {23 mg, 60%); £ ° ^ Q 3 -67.5° (c 1-2, methanol) ; v ^ 3390 {OH), 2230 (C=N) , 1740 cm-'-(C=0) ; n.m.r. {270 MHz, DMSO-dg): 6 1.35 {d, 3H, J 1 C H 6.75 Hz, CH^) , 2.92 ( o c t e t , 2H, J 2 Q ^ 15.3 Hz, 3^ 2 q 7.5 Hz, J 1 2 b 6.7 Hz, CHjCN) 3. 27-3.44 {m, 2H, H-5«), 3.95 (broad t , 1H, J ^( 5 ' 5.75 HZ, H-4-), 4.07 (g, 1H, CHCH3) , 4.24 (s, 1H, H-3'), 4.77 (d, IH, 2' 5 - ° H z ' H-21) , 5.03 (d, 1H, -CH2OH, exchangeable with D 20), 5.85 (d, 1H, —CHOH, exchangeable with D 20), 5.89 (d, 1H, H-1'). A n a l . C a l c . f o r C "H.,N.,Oc: C, 49.59; H, 5.79; S, 11.57. IU I 4 2 5 Found: C, 49.35; H, 5.55; M, 11.26., HYJESaenation of 330 to g i v e 3^j[R).- 1-methylacetamidopropyl-8-D-arabinof urano-f 1' , 2 1: 4 4 5 ]- 2-oxazolidone (331) . - A s o l u t i o n of compound 330 (28 mg) i n anhydrous a c e t i c anhydride (3 ml) was hydrogenated at 55 p. s. i . at room temperature f o r 20 h i n the presence of platinum oxide (21 mg) as c a t a l y s t . The c a t a l y s t was then removed by f i l t r a t i o n and washed c o p i o u s l y with methanol. The f i l t r a t e and c o l l e c t e d washings, were evaporated under reduced p r e s s u r e , t r a c e s of a c e t i c anhydride being removed a z e o t r o p i c a l l y with p-xylene. The crude r e s i d u e was chromatographed on s i l i c a g e l using 5:1 e t h y l a c e t a t e - e t h a n o l . A minor component of Rf 0.26 was f i r s t e l u t e d and appeared t o be 1 8 4 an i n s e p a r a b l e syrupy mixture of the 3'-0- and 5 ' - 0 - a c e t y l acetamido d e r i v a t i v e s (14 mg, 36%) ; 3320 (OH), 1750 (carbamate) , 1650 (amide c a r b o n y l ) , 1555 c r 1 (amide I I ) ; n.m.r. (270 MHz, DMSO-dg) : 6 1.80 (s, NAc), 2.02 (s, -CHjOAc) , 2.08 (s, CHOAc), 7.86 (broad s, NH, exchangeable with D 20)-,The r a t i o of C-5' a c e t a t e to C-3* a c e t a t e was approximately 2:1.., Fu r t h e r e l u t i o n of the chromatography column gave the acetamido compound 3 3 J as a syrup (11.mg, 33%); 0.16; £ A ] Q 3 ~ 78.8° (c 0.52, methanol) ; v|^1™ 3320 (OH) , 1740 (carbamate) , 1640 (amide carbonyl) , 1560 (amide II) ;• n.m.r- (270 MHz, DMSO-dg) : 6 1.18 (d, 3H, J ., C H 6 . 0 Hz, CHCH^), 1.72 (m, 2H, N-CH 2Cfl 2) , 1.81 ( s , 3H, NAc), 3.03 ( t , 2H, «3 2 3 6 * 8 H z ' NHCH2) , 3.18-3.32 (ra, 2H, H-5'), 3-70 (broad g, 1H, CH^CH) , 3.90 (broad t , 1H, H-4*), 4.22 ( b r o a d s , 1H, H - 3 « ) , 4.71 (d, 1H, J y 2' 5-5 Hz, H - 2 ' ) , 4.96 ( t , 1H, -CH^OH, exchanges with DjO) , 5.67 (d, 1H, -CHOH, exchanges with D 20) , 5. ?9 (d, 1H, H-1'), 7.88 (broad s, 1H, NH, exchanges s l o w l y with D.,0) . Anal.. C a l c . f o r C. . H, nN,0 c.«3/2 H.Q: C, 45.71; H, 7.30; N, ~ 1 L IU I o 2 8.88- Found: C, 45-80 ; H, 6.79; N, 8.40. Molecular weight, by mass spectrometry 288. 1328. C 1 2 H 2 0 N 2 ° 6 (M+) r e q u i r e s 288. 1321. The base peak was observed a t 114.0890., CgH1 2 NO r e q u i r e s 114.0919. Hydrogenation of a s o l u t i o n of compound 330 (31 mg) i n anhydrous methanol ( 3 ml) and a c e t i c anhydride (0.5 ml) a t 55 p.s. i . at room temperature f o r 2 h i n the presence . of platinum oxide ( 2 3 mg) fol l o w e d by removal of the c a t a l y s t by f i l t r a t i o n and removal of the s o l v e n t s o f the f i l t r a t e by c o - d i s t i l l a t i o n with xylene, gave compound 3 3 1 ( 3 5 mg, 9 5 % ) with no observable 185 formation of O-acetates. Attempted D e t r i t y l a t i o n of 310 t o Give 2 f 2_-Anhydro-5,6-dihydro-63iS)-J1 f 3 - d i t h i a n - 2 ~ y l ) u r i d i n e (332) . - (a) A mixture of 3J0 (118 mg) and 5% p a l l a d i u m on c h a r c o a l (64 mg) i n methanol (3 ml) was hydrogenated at 50 p . s . i . f o r 24 h. T . l . c - of the r e a c t i o n mixture showed the presence of only s t a r t i n g m a t e r i a l . The mixture was f i l t e r e d and the f i l t r a t e was evaporated, l e a v i n g a r e s i d u e whose n-m.r. spectrum (100 MHz, CDCl-^) i n d i c a t e d t h a t i t was unchanged _10-(b) When the above procedure (a) was repeated using palladium h y d r o x i d e 3 9 5 on carbon as the c a t a l y s t , t h e r e was again no d i s c e r n i b l e d e t r i t y l a t i o n of 310 as evidenced by e i t h e r t- 1. c- or n. m. r. spectroscopy. (c) To a s o l u t i o n of 3_0 (111 mg) i n anhydrous THF (4 ml) and l i q u i d ammonia (20 ml) at -78° was added l i t h i u m powder (15 mg). The s o l u t i o n was s t i r r e d at -78° f o r 30 min b e f o r e ammonium c h l o r i d e (275 mg) was added to d e s t r o y the l i t h i u m . The r e a c t i o n mixture was then allowed to come t o room temperature, n i t r o g e n was bubbled through f o r 15 min and r e s i d u a l s o l v e n t s were removed by r o t a r y e v a p o r a t i o n . The r e s i d u a l syrup was shown to c o n s i s t mainly of 3_0 by 1.1. c. and n.m.r. spectroscopy though the presence of s e v e r a l h i g h e r Rf i m p u r i t i e s was a l s o i n d i c a t e d . (d) A s o l u t i o n of 310 (10 mg) and f e r r i c c h l o r i d e (1 . mg) i n anhydrous dichloromethane (2 ml) and methanol (5 yul) was s t i r r e d f o r 24 h at room temperature. T . l . c . .of the r e a c t i o n mixture on s i l i c a g e l using 9:1 benzene-ethanol as developer i n d i c a t e d t h a t some d e t r i t y l a t i o n Chad occurred as evidenced by the presence of a high R^  f l u o r e s c e n t component. However, at 186 l e a s t f i v e other sugar components were observed on the t . l . c . p l a t e so t h a t t h i s method was abandoned as a p r a c t i c a l method of d e t r i t y l a t i o n . . (e) A s o l u t i o n of 310 (30 mg) i n anhydrous c h l o r o f o r m (5 ml) was added to c h l o r o f o r m (15 ml) s a t u r a t e d with HBr gas at 0°. A f t e r 5 min at 0°> t . l . c . o f the r e a c t i o n mixture (5; 1 e t h y l acetate-ethanol) showed complete d e t r i t y l a t i o n accompanied by the formation of at l e a s t 4 other sugar components and much b a s e - l i n e m a t e r i a l . (f) A s o l u t i o n of 310 (67 mg) i n 2:1 n-butanol-t r i f l u o r o a c e t i c a c i d (3 ml) was s t i r r e d f o r 3 min at room temperature. The r e a c t i o n mixture was then poured i n t o a r a p i d l y s t i r r i n g mixture of Bexyn 201 (OH-) i n methanol (120 ml) at 0°. A f t e r 5 min, the r e s i n was removed by f i l t r a t i o n and the f i l t r a t e was evaporated under reduced pressure y i e l d i n g a gummy r e s i d u e . Chromatography of the l a t t e r on a column (20x2-5 cm) of Bio—Bex 70 (H*) r e s i n u s i n g water as the e l u t i n g s o l v e n t a f f o r d e d the d e t r i t y l a t e d oxazolidone 320 (32 mg, 80%), i d e n t i f i e d by n. m- r- , spectroscopy. D e t r i t y l a t i o n of compound 318 to g i v e 329. - A s o l u t i o n of compound 31§ (94 mg) i n 80% agueous a c e t i c a c i d (10 ml) was r e f l u x e d f o r 10 min, the r e a c t i o n mixture c o o l e d and the s o l v e n t s evaporated under reduced pressure a t room temperature. The r e s i d u e was suspended i n water and washed twice with e t h e r . Evaporation of the water f r a c t i o n l e f t a syrup (50 mg) which was a p p l i e d t o a column (1-5 x 11 cm) o f Bio-Bex 70 (H +) r e s i n and e l u t e d with water, y i e l d i n g compound 329 as a c l e a r syrup (26 mg, 52%) . 187 3-r (S)-1- (1 ,3-Dithian-2-yl) Icyanoeth yl-3 ' ,5 «-di-0 -p-nitrobenzoyl-g-D-arabinofurano-_1 *,21:4,5 1-2-oxazolidone (333) - To a s o l u t i o n of compound 320 (285 mg) i n anhydrous p y r i d i n e (10 ml) was added at room temperature f r e s h l y r e c r y s t a l l i z e d p_-n i t r o b e n z o y l c h l o r i d e (458 mg, 3 eguiv) i n p y r i d i n e (5 ml) - The s o l u t i o n was s t i r r e d f o r 2 h, water added (1 ml) and the mixture s t i r r e d f o r another hour-.The s o l v e n t s were then .. evaporated i n vacuo, the r e s i d u e was d i s s o l v e d i n c h l o r o f o r m (60 ml) and the l a t t e r washed s u c c e s s i v e l y with .4% h y d r o c h l o r i c a c i d (2 x 30 ml), s a t u r a t e d agueous sodium hydrogen carbonate (2 x 30 ml) and water (.3 x 30 ml). The c h l o r o f o r m l a y e r was d r i e d with sodium s u l f a t e and evaporated, l e a v i n g a crude s o l i d (517 mg) which was chromatographed on s i l i c a g e l (30 g ) . E l u t i o n with 3:1 c h l o r o f o r m - e t h y l a c e t a t e y i e l d e d t h e d i e s t e r 333 as a s o l i d (422 mg, 85%) a f t e r removal of s o l v e n t s . Compound 33_3 was r e c r y s t a l l i z e d from a c e t o n i t r i l e - w a t e r , m.p. 201-20 2°; £ a 3 _ , 3 42.9° (c 1.3, c h l o r o f o r m ) ; n.m.r. (100 MHz, CDCl^) : « 1.90-2 -10 (m, 2H, S C I N C H ) , 2. 40-3. 30 (m, 6H, SCH 2, ~CH2C=0) , 4 . -02-4.38 (m, 2H, -CHCH2C=0, SCHS), 4.64 (broad s, 2H,. H-4» , 5 » ) , 5.23 (d, 1H, J y 2' 6 - ° H 2 / H-2 1), 5.70 (s, 1H, H-3'), 5.90 (d, 1H, H-' CHCl 1*), 8-25 (m, 8H, Ar) ; v m a x 3 2260 (CN) , 1780 (carbamate) , 1740 ( e s t e r ) , 1615 and 1535 cm-* (NQ 2). Anal. C a l c . f o r C2 7 H2 A^A °11 S 2 * C ' 5 0 * 3 1 ; K ' 3 - 7 3 » N ' 8 . 7 0 . . Found: C, 50.17; H, 3.69; N, 8.66., Conversion of compound 333 to compound 328_ - To a s o l u t i o n of compound 333 (190 mg) i n anhydrous methanol (25 ml) and t e t r a h y d r o f u r a n (3 ml) was added with s t i r r i u g under n i t r o g e n a s o l u t i o n of 0 -1N sodium i n methanol (20 u l ) . A f t e r one hour, the 188 r e a c t i o n mixture was n e u t r a l i z e d with Bio-Rex 70 (H +) r e s i n , the r e s i n was removed by f i l t r a t i o n and the f i l t r a t e evaporated. The re s i d u e was suspended i n water (30 ml) and washed with ether (3x20 ml) . The water l a y e r was then;evaporated under reduced pressure l e a v i n g a s o l i d (328, 90 mg, 88%) which was c r y s t a l l i z e d from ethanol-water, m.p- 186- 1.86.5°; [ a ] 2 * - 4 4 . 2 ° K P r (c 0.94, methanol) ; 3400 (OH), 2260 (C=N) , 1740 cm-* (C=0); n.m.r- (100 MHz, DMSO-dg).: 6 1.72-2.10 (m, 2H, .SCINCH ) # 2.60-3.65 (m, 8H, SCjJ 2, H-5« , CH^CN) , 3.77-4.01 (m, IH, H-4«), 3.99 (d, J 1 C H 11.0 Hz, SCHS), 4.01 (broad s, 1H, H-3*),: 4.45-4 . 7 1 (m, IH, -CHCH 2CN), 4.79 (dd a f t e r a d d i t i o n of DjO, 1H, J y 2' 6.0 Hz,  3 2' l' 1 * 5 H z ' H ~ 2 ' ) ' 4.82 (t ( p a r t l y b u r i e d by H-2» ) , 1H, CH2OH, exchangeable with D-,0), 5.74 (d, 1H, CHOH, exchangeable with D 2 0^ » 5. 86'. (d, 1H, H-1») ; mass spectrum: m/e 346 (M+) , 315 (M+-CH2OH). toaL Ca l c . ,for 3 F ^ g N ^ - O g ^ ^ ' O s C, 42. 86; H, 5.49; N, 7.69. Found: C, 42.88; H, 4.93; N, 7.52. 3- (R) - 1-Methylcyanoethyl-3 * ^5 ' - d i - Q - p - n i t r o b e n z o y l - 3-D-ara b i n o f urano-r 1* ,2*V: 4,5 ]-2-oxazolidone (334) . - To a s o l u t i o n of compound 329 (60 mg) i n anhydrous p y r i d i n e (3 ml) was added p.-nitrobenzoyl c h l o r i d e (214 mg, 5 eguiv) i n p y r i d i n e (2 ml). The s o l u t i o n was s t i r r e d f o r 2 h by which time t . l . c . of the r e a c t i o n mixture: on s i l i c a g e l u s i n g 2:1 benzene-ethyl a c e t a t e as developer showed consumption of a l l . s t a r t i n g m a t e r i a l and formation of a s i n g l e component of 8^ 0.37. Water (0-5 ml) was added to the s o l u t i o n and the l a t t e r s t i r r e d f o r another hour. The mixture was then evaporated, the r e s i d u e d i s s o l v e d i n methylene c h l o r i d e (6 0 ml) and s u c c e s s i v e l y washed with 4% 1 8 9 h y d r o c h l o r i c a c i d (2x30 ml)., s a t u r a t e d aqueous sodium hydrogen carbonate (2x30 ml) and water (3x30 ml). The organic l a y e r was d r i e d with sodium s u l f a t e and evaporated, l e a v i n g a yellow g l a s s (146 mg) which was chromatographed on s i l i c a g e l (15 g ) . E l u t i o a with 3:1 benzene-ethyl a c e t a t e gave 334 as a white g l a s s (124 rag, 98%) . A f i r s t c r y s t a l l i z a t i o n o f t h i s g l a s s from e t h y l acetate-methylene chloride-hexane gave o f f - w h i t e powder, m.p. 81-82°. R e c r y s t a l l i z a t i o n from the same s o l v e n t s r e s u l t e d i n c r y s t a l s melting at 86-87°; £ a ] 2 3 -45,2° (c 0.8, c h l o r o f o r m ) ; C HOI vmax 2 2 6 0 * C - N ) ' 1 7 8 0 f c a r b a r a a t e ) # 1 7 i j 0 ( e s t e r carbonyl) , 1615 and 1537 cm- 1 (N0 2) ; n.m.r. (100 MHz, CDC1 3) : < S 1.52 (d, 3H, J r u 7.0 Hz, CH ) , 2.56-3.04 ( o c t e t , 2H, J . 17.0 Hz, J , l , L H 3 ~3 2a, 2b 1,2 5.8 Hz, -C_2C=0) , 4.10-4.32 (pseudo-g, 1H, -CHCH^), 4.46-4.70 (m, 3H, H-4», H-5«), 5.23 <d, 1H, J ^ ^ 5.5 Hz, H - 2 « ) , 5.70 (s, 1H, H-3«) , 6.10 (d, 1H, 2' 5.5 Hz, H-1'), 8.30 (m, 8H, Ar) . I r r a d i a t i o n of the q u a r t e t at 6 4.10 c o l l a p s e d the o c t e t a t 6 2.56 to two doublets having J gem 16..0 Hz and the doublet a t <$ 1.52 to a s i n g l e t ; mass spectrum: m/e 373.0952 (M+-02NC6HZfCOOH) . AnaJU Calc. f o r C ^ H ^N^O,^ : .:C,' 53.33; H, 3.70; N, 10.37. Found: C, 53.31; H, 3.60; H, 10.06. Conversion of compound 328 to compound 320. - A suspension of compound 328 (31 mg) i n 1N sodium hydroxide (3 ml) was r e f l u x e d f o r 5 min by which time t . l . c . on s i l i c a g e l using 5:1 e t h y l a c e t a t e - e t h a n o l as developer showed consumption of a l l s t a r t i n g m a t e r i a l (R ^  0.56) and formation of a major product of R f 0.26. A f t e r n e u t r a l i z a t i o n of the r e a c t i o n mixture with B i o -Rex 70 (H +) r e s i n , the l a t t e r was removed by f i l t r a t i o n , the f i l t r a t e evaporated under reduced pressure and the r e s i d u a l 190 syrup was a p p l i e d t o a column of Bio-Sex 70 {H+) r e s i a and e l u t e d with water, y i e l d i n g compound 320 {12 mg, 40%) i d e n t i c a l by n.m.r. and i . r - with t h a t obtained from compound 310. U n s u c c e s s f u l attempts a t H y d r o l y s i s of the D i t h i o a c e t a l of 333. - (a) A mixture of 333 (7.8 mg) , mercuric c h l o r i d e (7 mg) and mercuric oxide (5.4 mg) i n 5% aqueous a c e t o n i t r i l e was r e f l u x e d f o r 24 h under an atmosphere of n i t r o g e n . No r e a c t i o n was seen by t . l . c . of the r e a c t i o n mixture (2:1 benzene-ethyl a c e t a t e ) . (b) A mixture of 333 (12 . 3 mg) , c u p r i c c h l o r i d e (5.7 mg) and c u p r i c oxide (6.7 mg) i n 99% aqueous acetone (3 ml) was r e f l u x e d f o r 2 h with no observable h y d r o l y s i s of s t a r t i n g m a t e r i a l by t . 1 . c. (c) To a s o l u t i o n of f r e s h l y - r e c r y s t a l l i z e d N-bromosuccinimide (24.2 mg) and 2 , 4 , 6 - t r i m e t h y l p y r i d i n e (33 mg) i n 80% aqueous a c e t o n i t r i l e (2 ml) was added a s o l u t i o n of 333 (11 mg) i n a c e t o n i t r i l e (1 m l ) . , A f t e r the r e a c t i o n mixture had s t i r r e d f o r 10 min, t . l . c . showed t h a t consumption of a l l s t a r t i n g sugar had o c c u r r e d with g e n e r a t i o n of two lower Rf spots (5:1 benzene-ethanol). The s o l u t i o n was d i l u t e d with chloroform (6 ml) and washed s u c c e s s i v e l y with s a t u r a t e d aqueous sodium s u l f i t e (6 ml), s a t u r a t e d aqueous sodium hydrogen carbonate (6 ml), 3M aqueous c u p r i c - n i t r a t e (6 ml) and water (2x6 ml). The o r g a n i c l a y e r was d r i e d with magnesium s u l f a t e and evaporated, l e a v i n g a crude s o l i d (13 mg). An n.m.r- spectrum of t h i s mixture i n deuterochloroform d i d not show a l o w - f i e l d s i g n a l a s s o c i a t e d w i t h t h e formyl proton, i n d i c a t i n g that h y d r o l y s i s of 333 had not occurred. ., ' 191 fd) To a s o l u t i o n of 333 ( 1 2 - 3 mg) i n 75% aqueous a c e t o n i t r i l e (2 ml) was added c e r i c ammonium n i t r a t e (42 mg) . A f t e r the s o l u t i o n had s t i r r e d f o r 5 min, t . l - c . (5: 1 benzene-e t h y l acetate) showed mainly b a s e - l i n e m a t e r i a l which could not be r a i s e d using more p o l a r s o l v e n t s (9:1 benzene-ethanol)-3- (S) - 1-Formylcyanoethyl-3. i , i ,5* - d l - Q - p - n i t r o b e n z o y l - & 7 D -a r a b i n o f u r a n o - f 1 1 , 2 ' : 4 , 5 1 - 2 - o x a z o l i d o n e (335),. Jas semicarbazone 336)_- - A mixture of 333 (43 mg) and barium carbonate (47 mg) i n dimethyl s u l f o x i d e ( 4 ml) and water (0-5 ml) was heated at 55° f o r 15 min. The mixture was c o o l e d before methyl i o d i d e was added (1 ml). Heating of the mixture a t 55° was resumed f o r 3 h a f t e r which i t was c o o l e d , d i l u t e d with acetone ( 2 0 ml) and the mixture evaporated to h a l f volume to remove excess methyl i o d i d e . More acetone (20 ml) was added to p r e c i p i t a t e the barium s a l t s , the mixture f i l t e r e d , and the f i l t r a t e evaporated. The r e s i d u e , d i s s o l v e d i n c h l o r o f o r m , was washed with water, the chloroform l a y e r was d r i e d with sodium s u l f a t e and evaporated l e a v i n g an orange syrup (335) ; n.m.r. (100 MHz, DMSO-dg) x <S 9.45 (d, J 14 . 0 Hz, H-C=0).. Without f u r t h e r p u r i f i c a t i o n , the f o r e g o i n g syrup was d i s s o l v e d i n methanol ( 2 ml), to which was added p y r i d i n e (0.5 ml) < and 0.5M agueous semicarbazide h y d r o c h l o r i d e ( 0 - 4 ml). The r e a c t i o n mixture was evaporated, the r e s i d u e d i s s o l v e d i n water, the l a t t e r e x t r a c t e d with e t h y l a c e t a t e , the o r g a n i c e x t r a c t d r i e d with, sodium s u l f a t e and evaporated, l e a v i n g a crude s o l i d (41 mg) from which the semicarbazone 336 (15 mg, 37% from 333) was obtained i n pure form by two r e c r y s t a l l i z a t i o n s from e t h y l acetate-methanol, m.p. 192 192-194°; [ a]23 -86.9° (c 0.35, 9:1 methanol-ethyl a c e t a t e ) ; n.m.r. (100 KHz, DMS0~dg):6 3. 10-3.28 (m, 2H, -C_2C=0) , 4,40-4.60 (m, 2H, H-5»), 4.65-4-96 (m, 2H, H-4', -CHCH2C=0) , 5.49 (d, 1H, J y 2' 6.0 Hz, H-2'), 5.68 (s, 1H, H-3»), 6.10 (d, IH, H-1 f ) , 6-37 (broad s, 2H, WH^ , exchangeable a i t b D^O) , 7.23 (d, 1H # J 1 c H 3- 0 Hz, CH=N), 8.20-8.50 (m, 8H, Ar) , 10.23 (broad s, K Rr 1H, N-NH, exchangeable a i t h D^O) ; v | ^ ° x 3450 (NH) , 2270 (C=N) , 1765 (carbamate), 1735 ( e s t e r C=0) , 1690 (NHC=0) , 1585 (HC=N-) , 1615 and 1535 cm-i (NC>2) . Anal_, C a l c . . f o r C- c B_, H^O, , : • C, 49.10; H, 3.44; N, 16.04-~ 2 b 21 V 12 Found: C, 48. 98; H, 3.30; N, 15.68. Attempted S y n t h e s i s of 5,6-Dihydro-6-(1,3-dithian-2-yl) c y t i d i n e (33 7).. - A s o l u t i o n of the unblocked 2-oxazolidone 328 (30 mg) i n anhydrous methanol (20 ml) . t h a t was p r e v i o u s l y s a t u r a t e d with ammonia a t 0° was heated f o r 24 h at 160° i n a se a l e d g l a s s tube- The r e a c t i o n mixture was . cooled and the s o l v e n t evaporated l e a v i n g a s o l i d the n-m-r- spectrum o f which i n DMSO-dg i n d i c a t e d t hat i t was unchanged s t a r t i n g m a t e r i a l 328, 5-Bromo-2 * , i.3_-0-isgprqpylldeneuridine (339) . - A suspension of S-bromouridine 1* 0 3 (338, 8. 5 g) and c u p r i c s u l f a t e (35 g) i n anhydrous acetone (1 1) c o n t a i n i n g c o n c e n t r a t e d s u l f u r i c a c i d (1 ml) was s t i r r e d f o r 24 h a t room temperature. The r e a c t i o n mixture was f i l t e r e d , the p r e c i p i t a t e was washed with acetone (75 ml) and the f i l t r a t e was n e u t r a l i z e d with c o n c e n t r a t e d ammonium hydroxide (0.2 ml). The s o l v e n t was evaporated under reduced pressure and the r e s i d u e was d i s s o l v e d i n hot acetone 193 (200 ml). Hexane (150 ml) was added to the s o l u t i o n and c r y s t a l l i z a t i o n was induced i n . the c o l d , y i e l d i n g 339 as c o l o u r l e s s needles i n two crops (7.9 g, 83%); m.p. 224-227°^ { l i t . * 0 2 m. p. . 23 1-232°, ethanol-cyclohexane) . 5 - B r o m o - 2 * , 3 ' - 0 - i s o p r o p y l i d e n e - 5 ' - 0 - t r i t y l u r i d i n e (340). -A s o l u t i o n of 5-bromo-2',3'-Q-isopropylideneuridine (339, 7.8 g, 21.5 mmole) and f r e s h l y r e c r y s t a l l i z e d c h l o r o t r i p h e n y l m e t h a n e (6.14 g, 22 mmole) i n anhydrous p y r i d i n e (150 ml) was heated a t 100° f o r 4 h. The r e a c t i o n mixture was then cooled and poured i n t o r a p i d l y s t i r r i n g water {1200 ml). The water l a y e r was decanted and the remaining gummy p r e c i p i t a t e was d i s s o l v e d i n chloroform (1 1) and washed with water (2x250 ml). The organic l a y e r was d r i e d with sodium s u l f a t e , the s o l v e n t s were evaporated and the residue, was c r y s t a l l i z e d from ether-hexane to give 340 as c o l o u r l e s s needles (12.5 g, 96%), m.p., 201-202-5°; [ a ] 2 3 -25.5° (c 1.1, c h l o r o f o r m ) ; n.m.r (100 MHz, CDCl-,}: 6 1.31 D ^ (s, 3H, C H 3 ) , 1.54 {s, 3H, CH^) , 3.40 {d, 2H, 3^> 5< 3-6 Hz, H-5*), 4-33 (g, 1H, J 3< A- 7.0 Hz, H-4 1), 4.73 {dd, 1H, J 2' 3' 3.0 HZ, H-3»), 4.86 (dd, 1H, • J y 2.4 Hz, H-2' ) , 5.87 (d, 1H H-1'), 7.18-7.50 (m, 15H, Ar) , 7.86 (s, 1H, H-6), 9-06 ( b r o a d s , 1H, NH, exchangeable with D 20); mass spectrum: m/e 606 (M+ f o r B r 8 1 ) , 604 (M+ f o r B r 7 * ) . M a l-L C a l c . f o r C 3 1 H 2gN 20 6Br: C, 61,. 50; H, 4-79; N, 4.63. Found: C, 61.57; H, 4.59; N, 4.90., S y n t h e s i s of 5.6-dihydro-6-(R) - ( 1 , 3 - d i t h i a n - 2 - y l ) - 2 ' f 3'-0-i s o p r o p y l l d e n e - 5 ' - 0 - ' t r i t y l u r i d i n e (341), 5- (S)-bromo-5,6-dihydro-6- (S) - ( 1 , 3 - d i t h i a n - 2 - y l ) -2' ,3'.-03isopropylidene-5'-0-194 t r i t y l u r i d i n e 1342). and 5- (R) - bromo-5, 6 - dihydro-6- (S)- j 1 f 3-ditfaian - f 2 - x l L ~ 2 1 i.3 t-0-isopr idpYlid'ene-5*--0-trityluridine 134-3J... -A s o l u t i o n of n u c l e o s i d e 340 (5.56 g, 9 . 2 mmole) i n anhydrous p y r i d i n e (50 ml) was added dropwise over 45 min to a s o l u t i o n of the d i t h i a n e anion 126 (6.9 g, 57.6 mmole) i n THF (150 ml) a t -78° under nitrogen..The deep red r e a c t i o n mixture was s t o r e d at -20° f o r 24 h. The s o l u t i o n was then poured i n t o a r a p i d l y s t i r r e d mixture of ether and s a t u r a t e d agueous sodium c h l o r i d e s o l u t i o n (800 and 100 ml, r e s p . ) , the aqueous l a y e r was drawn o f f and the o r g a n i c l a y e r washed to n e u t r a l i t y with s a t u r a t e d s a l t s o l u t i o n . , A f t e r drying of the o r g a n i c l a y e r with sodium s u l f a t e and e v a p o r a t i o n of the s o l v e n t s , there remained a syrupy m a t e r i a l which was chromatographed on s i l i c a g e l (500 g) using 10:1 benzene-ethyl a c e t a t e as developer, y i e l d i n g compound 342 as a foam (2.3 g, 35%) which was c r y s t a l l i z e d from methanol, m.p. 193-195°; Rf 0.42 ( s i l i c a g e l , 4:1 benzene-ethyl a c e t a t e ) ; [ a j 2 2 -138.9° (c 0.72, chloroform) : v C H C l3 3400 (NH) , 1720 cr> D max ( c a r b o n y l ) ; n. m. r. (100 MHz, CDClg)-: -6 1-27 (s, 3H, CH 3) , 1-50 (s, 3H, CH 3) , 1.73-2.01 (m, 2H, SCH2-CB_2) , 2.49-2.65 (m, 2H, S~CH2) , 2.79-2.96 (m, 2H, S-CH2) , 3.17 (dd, IH, J^'5'a'- 4.6 Hz, J 5a 5b • 9 " * E z > H-.5»a), 3.45 ( t , 1H, J ^ ^ 8.0 Hz, H-5b) , 3.99 (dd, 1H, J & 6 1.5 Hz, J 2» 6 4.0 Hz,. H-6), 4. 13- 4.35 (m, 1H, H-4*), 4.63 (d ( p a r t i a l l y obscured by H-2"), 1H, J 3' ^' 6.0 Hz, H-3'), 4.69 (d, 1H, S-CH-S) , 4.81 (s, 1H, H-2')* 5.07 (s, 1H, H-1') , 5.12 (d, 1H, H-5'), 7.13-7.53 (m, 15H, A r ) , 7.86 (broad s, 1H, NH, exchangeable with D 20). I r r a d i a t i o n of the doublet at 6 4.69 c o l l a p s e d the doublet of doublets at 6 3. 99 to a broad s i n g l e t . I r r a d i a t i o n of the. m u l t i p l e t a t 6 4. 13-4. 35 c o l l a p s e d 195 the doublet at 54.63 t o a s i n g l e t w h ile the t r i p l e t a t 6 3.45 and the doublet of doublets a t 6 3. 17 c o l l a p s e d to two doublets with J 5Q 5b 9 * 4 'Hz;.mass spectrum: m/e 726 {B* with B r 8 1 ) , 724 (M* with B r ™ ) , 711 (M+-CH3) , 481 and 483 (M+-trityl) . Anal. C a l c . f o r C, CH._M,O cS,Bri C, 57.93; H, 5.10; N, 3.86; So i I I o I Br, 11.02. Found: C, 57.59; H, 5.50; N, 3-58; Br, 10.65. Continued e l u t i o n of the chromatography column gave compound 343 as a white foam {0.66 g, 10%), which was c r y s t a l l i z e d from carbon t e t r a c h l o r i d e - h e x a n e , m.p. 145-150° {amorphous); R ^  0.30 { s i l i c a g e l , 4; 1 benzene-ethyl a c e t a t e ) ; [ o ] 2 2 +0.84° (c 1.7, chloroform) ; v ^ l 3 3400 (NH) , 1720 cm- 1 {carbonyl); n.m.r. (100 HHz, CDC1 3): 6 1.34 (s, 3H, CH 3) , 1-52 (s, 3H, CH ) , 1.80-2.15 (m, 2H, SCH Cfl ) , 2.76-3.03 (m, 4H, S-CH 2) , 3.33 (d, 2H, J^< ^  4.0 Hz, H-5»), 4.06 (dd, 1H, J 2" 6 3 " 6 Hz, J c c 6.0 Hz, H-6), 3-96-4.14 (m (buried under H-6), 1H, H-b , b 4») , 4.50 (d, 1H, S-CH-S) , 4.73 (dd, 1H, J 2' 3' 6.5 Hz, J 3< ^ 5.6 Hz, H-3'), ^-80 (d, 1H, H-5), 5.30 (dd, 1H, H-2'}, 5.81 (d, 1H, H-1'), 7,16-7.54 (m, 15H, Ar) , 7.65 (broad s, 1H, NH, exchangeable with DjO). I r r a d i a t i o n of the doublet a t 6 4.50 c o l l a p s e d the doublet of doublets a t 6 4,06 to a doublet ( J ^ ^  6,0 Hz); mass spectrum: m/e 711.102-7. C-^H^N-^OgS^VBr (M+-CH3) r e q u i r e s 711.1022.. Anal . C a l c . f o r C- CH .^ N O. S. Br.: C, 57.93; H, 5.10; N, 3.86. io 37 2 o 2 Found: C, 57.59; H, 4.94; N, 3.97., Further e l u t i o n of the column with 4:1 benzene-ethyl acetate gave compound 341 as a white g l a s s (2.2 g, 37%) which was c r y s t a l l i z e d from carbon t e t r a c h l o r i d e - h e x a n e , m.p. 138-139°; Rf 0.20 ( s i l i c a g e l , 4:1 benzene-ethyl a c e t a t e ) ; I 0 1 ] " ~ 196 16.7° (c 0.6, c h l o r o f orm) ; 3 3410 (NH) , .1710 era-* (carbonyl) ; n.m.r. (100 MHz, CDC1 3) .: . 6 1.27 (s, 3H, C H 3 ) , 1.49 <s, 3H, CH 3) , 1.73-2,03 (m, 2H, SCH 2C_ 2), 2.48-2.71 (m, 2H, H-5), 2.73-2.97 (m, 4 H, SC_ 2) , 3.18 (dd, 1H, J 5» Q 5' b 9.4 Hz, J ^ 5'a 3.6 Hz, H-5'a), 3.46 ( t , 1H, J ^ 5' b 7.4 Hz, H~5*b), 3.67-3.95 (m, 1H, H-4'), 4-11-4.27 (m, 1H, fl-6) , 4.61 (d, 1H, J 2' 3' 6-6 Hz, H-3«) , 4.70 (d, 1H, J 2" S 3 " 2 H z * S ~ C S ~ S ) > 5.09 (dd, 1H, J .j' 2' 2.0 Hz, H - 2 » ) , 5.24 (d, 1H, H-1«), 7.13-7.53 (m, 15H, A r ) , 8.03 (broad s, 1H, NH, exchangeable with D 20); mass spectrum: m/e 646 (M*), 631 (M+-CH3) , 403 ( M + - t r i t y l ) -Anal. C a l c - f o r C 1 r H , o K . 0 , S , « 3 / 2 H-O: C, 62- 40 ; H, 6.09; N, 35 i'o 2 b Z L 4.16. Found: C, 62.72; H, 5.80; N, 4.42. D e s u l f u r i z a t i o n of compound 34_ t o g i v e 5,6-dihydro-2 1,3'-0-isopropYlidene-6~i?lri§;thYi~5' n-0- i346|__ - A s o l u t i o n of the d i t h i a n y l compound 34J (132 mg) i n e t h a n o l (15 ml) and THF (2 ml) was r e f l u x e d f o r 4 h i n the presence of f r e s h l y a c t i v a t e d Raney n i c k e l . T . l . c . of the r e a c t i o n mixture on s i l i c a g e l u s i n g 3:1 benzene-ethyl .acetate as developer showed a major f l u o r e s c e n t component of Rf 0.32 contaminated with minor q u a n t i t i e s of higher and lower Rf m a t e r i a l . The r e a c t i o n mixture was then f i l t e r e d , the n i c k e l r e p e a t e d l y washed with hot e t h a n o l and the combined f i l t r a t e and washings evaporated, l e a v i n g a crude syrup (80 mg) which was chromatographed on s i l i c a g e l (15 g) using 3:1 benzene-ethyl a c e t a t e as developer. The major component (346) was thus i s o l a t e d as a white foam which c o u l d not be c r y s t a l l i z e d (40 mg, 37%); [ a ] " -32.0° (c 0.9, c h l o r o f orm) ; n.m.r. (100 MHz, CDC1-) :.• 6 1-30 (s, 3H, i s o p r o p y l i d e n e ) , 1.36 (d, 3H, J 6 C H 6.6 Hz CH 3 197 of C-6), 1.52 (s, 3H, i s o p r o p y l i d e n e ] , 2.32 (d, IH, J g Q ^ 16.6 Hz, J 5 q g 0 Hz, H-5a) , 2.80 (dd, 1H, J 5 b g 6 . 0 Hz, H-5b) , 3.33 (dd, 2H, 5' Q 1.2 Hz, .-J ^  ^ 3.2 Hz, H-5! a, B-5»b), 3.84-3.98 (broad t , 1H, H-6) , 4.12-4.28 (broad g, 1H, H-4'), 4.70 (dd, 1H, J 2 ' 3 - 4.0 Hz, J ^ , 6.4 Hz, H-31 ) , 4.96 (dd, 1H, J y 2' 3.0 Hz, H-2'), 5.46 (d, 1H, H-1'), 7.16-7.52 (m, 15H, Ar) , 7.68 (broad s, 1H, NH, exchangeable with D^O) ; mass spectrum; m/e 527 (M+-CH3), 2-99 ( M * - t r i t y l ) . Anal;., C a l c . f o r C^H^N^Og: C, 70.85; H, 6.27; N, 5.1.7. Found: C, 70.68; H, 6.40; N, 5.10. 5.6-Dihydro-6- (R) - f 1 , 3 - d i t h i a a - 2 - y l ) u r i d i n e 1147)_. - A suspension of the blocked n u c l e o s i d e 341 . (1.3 g) i n 80% agueous a c e t i c a c i d was r e f l u x e d f o r 30 min, the r e s u l t i n g s o l u t i o n was cooled and the s o l v e n t s removed by repeated a z e o t r o p i c d i s t i l l a t i o n with xylene under reduced pressure. The r e s i d u e was p a r t i t i o n e d between water (100 ml) and c h l o r o f o r m (50 ml) , the ch l o r o f o r m l a y e r drawn o f f and the water l a y e r was then washed with chloroform (2x40 ml). The water l a y e r was evaporated to dryness, the r e s u l t i n g r e s i d u e a p p l i e d t o a column of Bio-Rex 70 (H*) c a t i o n exchange r e s i n (42x2.2 cm) and the column e l u t e d with water y i e l d i n g compound 347 as a foam (425 mg, 60%) which was c r y s t a l l i z e d from methanol-ethy 1 a c e t a t e , m.p. 190-19 1°; Rf 0.29 ( s i l i c a g e l , 10: 10:3 benzene-ethyl acetate-ethanol) ; [cx] 2 3 -46-5° (c 0.9, methanol); x M e 0 H 245 nm { e 1700); c. d. (c - ' max • *-5.23x10-*, methanol) A e 2 5 Q -4.13; n.m.r. , ( 100 MHz , DMSO-tdg) ; 6 1.90-2.20 (m, 2H, S-CH 2-CH 2), 2.66-3.00 (ra, 6H, H-5, S-CEJ2) , 3.50 (broad d, 2H, J ^, ^ 3.2 Hz, H-5'), 3-71 (d, 1H, H-4'), 3.90-4-20 (m, 3H, H-2', H-3«, H-6), 4.55 (d, 1H# .J ,« c 3.6 Hz, 1 , D 198 S-CH-S) , 4.84 ( t , 1H, J 5 ' Q H 5.6 Hz, CH O H , exchangeable with D 20) , 5.02 (d, 1H, CHOH, exchangeable with D 2 0 ) , 5. 25 (d, IH, CHOH, exchangeable with DO) , 5.67 (d, 1H, J y y 6.8 Hz, H-1») , 1 10.42 i s , 1H, NH, exchangeable with D 20). Anal_ C a l c . f o r C ^  ^  H 2 Q N 2 ^5^2 * C # 4 2 * ? 6 « H * 5.49; N, 7.69.., Found: C, 42.62; H, 5.54; N, 7.61. 5,6-Dihydrq-6- (£) - ( 1, 3-dit hian-2-y 1) u r a c i l i_48)__ - A s o l u t i o n of nu c l e o s i d e 347 (35 tag) i n 1N h y d r o c h l o r i c a c i d (4 ml) was heated a t 80° f o r 4 h. The r e a c t i o n mixture was then c o o l e d r e s u l t i n g i n the f o r m a t i o n of c o l o u r l e s s needles which were i s o l a t e d by f i l t r a t i o n and r e c r y s t a l l i z e d from methanol, y i e l d i n g pure 348 (10 mg, 45%), m.p. 258.5-259°; [° ] * 2 -60.4° (c 0.2, methanol); n. m. r . (100 MHz, DMSO-dg): 6 1.48-2. 18 (m, 2H, S-CH 2-CH 2), 2.58-2.98 (m, 6H, H-5, SC_ 2) , 3.63-3.92 (m, 1H, H--6), 4.24 (d, 1H, J y , 6.0 Hz, H-1«), 7.58 (broad s, 1H, NH, j exchangeable with D 20), 10.08 (broad s, IH, NH, exchangeable with D20) . 5 f f6-Dihydro-6-(R,S) -formyl-2*,3'-O-isopropylidene-S'-O-t r i t y l u r i d i n e J349_ _as semicarbazone 350^_ - A mixture of n u c l e o s i d e 34J[ (380 mg) , barium carbonate (325 mg) and methyl i o d i d e (2 ml) i n 15% agueous acetone (17 ml) was heated a t 55° f o r 48 h. The co o l e d mixture was then f i l t e r e d to remove the barium s a l t s , the f i l t r a t e evaporated and the r e s i d u e was d i s s o l v e d i n ch l o r o f o r m (200 ml). The chloroform s o l u t i o n was washed with- water (3x40 ml), d r i e d with sodium s u l f a t e and evaporated, l e a v i n g a pale yellow syrup which, without f u r t h e r p u r i f i c a t i o n , was d i s s o l v e d i n methanol (10 ml) and p y r i d i n e 199 (0.5 ml) before a d d i t i o n of 0 . 5 M aqueous semicarbazide h y d r o c h l o r i d e (1 ml). The s o l u t i o n was then heated on a steam bath f o r 10 min, the s o l v e n t s evaporated, the residue suspended i n e t h y l a c e t a t e (75 ml) and washed with water (3x20 ml). The o r g a n i c l a y e r was d r i e d with sodium s u l f a t e and evaporated, l e a v i n g a crude syrup which was p u r i f i e d c h r o m a t o g r a p h i c a l l y on s i l i c a g e l (30 g) using 9:1 benzene-ethanol as developer y i e l d i n g the semicarbazone 350 (100 mg, 30% from 34_) as a s o l i d which was r e c r y s t a l l i z e d twice from toluene-hexane, m. p. , 160-162°; B f 0.22 ( s i l i c a g e l , 9:1 benzene-ethanol); [ A 3 * 3 +23.5° (c 0.84, methanol) ; v C H C l 3 3495 (NH.), 3340 (N-NH) , 3210 (CO-NH-max I CO), 1725 (pyrimidine C=0) , 1700 (~C0NH 2), 1640 (C=N) , 1590 cm-* (amide I I ) ; n.m.r (100 MHz, CDCl^) : 6 1.30 (s, 3H, CH 3) , 1.54 (s, 3H, CH 3) , 2.56 (dd, 1H, 0 5 a 6 6.0 Hz, 5 b 17 .0 Hz, H-5 a) , 2.86 (d, 1H, J 5 b 6 0 Hz, H-5b), 3.33 (broad s, 2H, H-5'), 4 . 1 5 (d, IH, ^3'^' 3.0 Hz, H-4'), 4.4 7-4.86 (m, 3H, H-2« , H-3 *, H-6), 5.99 >{d, 1H, J Y 2' 4 , 0 H z ' H ~ 1 "•) » 6 * 0 6 <br°ad s, 2H, NH 2, exchangeable with D2G) , 6.98 (d, 1H, J fe 1 0.0 Hz, CH=N) , 7.12-7 .50 (m, 15H, A r ) , 9.12 (broad s # 1H, NH, exchangeable with D 20) , 10.31 (broad s, 1H, NH, exchangeable with D 20). Anal. C a l c . f o r C 3 3H 3 5N 50 7*1/2H 20: C, 63.67; H, 5.79; N, 11.25. Found: C, 63.6 4; H, 5.68; N, 11.16., Debromination of compound 342 to g i v e compound 34 __ - A s o l u t i o n of compound 342 (140 mg) i n e t h a n o l (10 ml) and THF (2 ml) c o n t a i n i n g f r e s h l y a c t i v a t e d Raney n i c k e l was heated a t 90° f o r 1 h. T . l . c . of the r e a c t i o n mixture on s i l i c a g e l using 4:1 benzene-ethyl a c e t a t e as developer showed that a s i n g l e new compound of R^  0.20 had formed. The r e a c t i o n mixture was 200 f i l t e r e d , the n i c k e l washed r e p e a t e d l y with e t h a n o l , the combined f i l t r a t e and washings evaporated and the r e s i d u a l syrup chromatographed on s i l i c a g el {17 g) . E l u t i o n with 4:1 benzene-e t h y l a c e t a t e gave compound 341 as a foam (54 mg, 44%) ; [ a ] 2 3 -13.0° (c 1.0, c h l o r o f orm) . The i . r . , n.m.r. and mass s p e c t r a of 341 obtained from 342 were i d e n t i c a l t o those of 341 obtained d i r e c t l y from 340. , Debromination of compound 343 to j i v e compound 341. - When compound 343 {100 mg) was t r e a t e d with Haney n i c k e l i n a manner i d e n t i c a l t o that of compound 342, compound 341 was obtained (30 rag, 33%); [ a ] 2 3 -14.2° (c 0.95, c h l o r o f o r m ) . Compound 34_I obtained by t h i s route was i d e n t i c a l by Bf and n.m.r. as that obtained from compound 342 and compound 340. 6 - F o r m Y l - 2 ' , ^ ' - Q - i s o p r o p y l i d e n e - S ' - O - t r i t y l u r i d i n e (351) and 6 - f o r m y l - 2 * , 3 f - 0 - i s o p r o p y l i d e n e - 3 - m e t h y l - 5 ' - 0 - t r i t y l u r i d i n e ,(3.53) ^ c h a r a c t e r i z e d as the semicarbazones 3 5 2 and 3_5_4_iL r e s p e c t i v e l y ) from compound 3 4 2 . - A mixture of compound 342 (300 mg), barium carbonate (660 rag), methyl i o d i d e {1 ml. added at 12 h i n t e r v a l s ) , and dimethyl s u l f o x i d e (1.5 ml) i n 10% agueous acetone (17 ml) was heated at 55° under a n i t r o g e n atmosphere f o r 72 h. T . l . c . of the r e a c t i o n mixture on s i l i c a g e l using 4:1 benzene-ethyl a c e t a t e showed complete consumption of s t a r t i n g m a t e r i a l with the formation of two components of Bf 0.13 and 0.23 (compounds 351 and 353, r e s p e c t i v e l y ) . The r e a c t i o n mixture was worked-up as before (see compound 349), leaving, a yellow syrup, n.m.r- (100 MHz, CDCl^): 5 9.53 (s, CH=0). Without f u r t h e r p u r i f i c a t i o n , the aldehyde was t r e a t e d 201 with semicarbazide hydrochloride as before (see compound 350}-In t h i s case, two semicarbazones were formed which were separated by preparative t - l - c . o n s i l i c a gel using 15:1 benzene-ethanol as developer- The slower moving component was shown to be compound 352 (22 mg from 48 mg of crude 6-aldehyde, 41%) which was c r y s t a l l i z e d from ethanol-benzene-hexane, m.p. 211-212°; E f 0-21 ( s i l i c a gel, 9:1 benzene-ethanol) ; [ a 3 ^ 2 ~ 17-52° (c 0-51, acetone) ; v ^ l 3 , 3540 ( N ^ ) , 3400 (NH), 3200 (NH), 1700 (broad C=0 s t r e t c h ) , 1580-1620 cm-* (complex pattern, C=C, C=N, amide I I ) ; n.m.r-, (100 MHz, DMSO-dg):6 1.04 (s, 3H, CH 3), 1.26 (s, 3H, CH3) , 2.7 3-3. 42 (m, 2H, H-5«) , 3.78-4.02 (m, 1H, H-4») , 4.48 (broad t , 1H, J y ,• 5.0 Hz, H-3«), 5.00 (d, 1H, 3 2' 3' 6 - ° H z » H-21) , 5.96 (s, 2H, H-5, H-1'), 6.56 (broad s, 2H, NH2, exchangeable with D 20), 7.06-7.30 (m, 15H, Ar) , 7.56 (s, IH, -CH=N), 10.54 (s, IH, NH, exchangeable with D2Q) , 11.20 (s, 1H, NH, exchangeable with B^O) -Anal. Calc- for C 3 3 H 3 3 N^Oy* 1/2H20: C, 63.87; H, 5-48; N, 11-29. Found: C, 63.85; H, 5.42; N, 11.19. The faster running component (compound 354) was obtained as a s o l i d (7 mg, 13%), m.p.. 213-215°, which could not be c r y s t a l l i z e d owing to the formation- of a gel i n organic solvents; E ^  0.30 ( s i l i c a gel, 9: 1 benz ene-ethanol) ; J > ] 2 3 -5.6° run ^ (c 0-23, methanol) ; 3 3540 (NH2 ) , 3375 (NH) , 3200 (NH) , 1700 (pyrimidine C=0), 1675 (amide C=0), 1620-1565 cm-1 (complex pattern due to C=C, C=H, amide I I ) ; n.m.r. (100 MHz, DMSO-dg): 6 1.28 (s, 3H, CH3) , 1-48 (s, 3H, CH 3) , 2.98 (s, 3H, N-CH3), 3-00-3.54 (m (obscured by water peak), 2H, H-5») , 4.00-4.34 (m, 1H, H-4«), 4.77 (broad t , J ^  ^ 5-0 Hz, H-3«), 5.24 (d, 1H, J 2 ' 3 ' 202 6-0 Hz, H-2'), 6 - 2 6 (s, 1H, H-1 « ) , 6-34 ( s , IH, H-5), 6-80 (broad s, 2H, NH.,, exchangeable with B^Q) , 7.20-7-60 (m, 15H, Ar) , 7-80 (s, 1H, CH=N) , 10.82 (s, 1H, NH, exchangeable with D 20); mass spectrum: m/e 567 (J!+-acetone) , 539 (H+-CH=NNHCONH2 ) , 415 (M*-base) , 382 ( 0 + - t r i t y l ) . , M a l i . C a l c , f o r C ^ H^N^Oy *H 20: C, 63-45; H, 5-,75; N, 10-88- Found: C, 63-87; H, 5-47; N, 10.58. Comp_ounds 351 and 353 ( c h a r a c t e r i z e d as semicarbazones 352 and 354^ r e s p e c t i v e l y ) from compound 343. - Treatment of 343 (136 mg) with methyl i o d i d e i n the same manner as d e s c r i b e d f o r compound 342 gave, a f t e r f o r m a t i o n and p u r i f i c a t i o n of the semicarbazones, compound 352 (34 mg, 30%); m-p. 209-211°; [ a ] 2 3 -19.4° (c 0-9, acetone) . The R^ , i . r - , and n.m.r- s p e c t r a were i d e n t i c a l t o those obtained f o r 352 d e r i v e d from 342-Semicarbazone 354 was a l s o i s o l a t e d (6 mg, 5%), m.p. ,209-214°; [ a ] 2 3 -4.0° (c 0.25, methanol). The R f and n.m.r spectrum °f 354 were i d e n t i c a l t o those d e s c r i b e d p r e v i o u s l y . 6 - H y d r o x y m e t h y l - 2 * L 3 ' - O ^ i s o p r o p y l i d g n e ^ S ' - 0 - t r i t y l u r i d i n e (355). - To a s o l u t i o n of the 6-aldehyde 35J[ . (232 mg) i n e t h a n o l (8 ml) was added dropwise a s o l u t i o n of sodium borohydride (20 mg) i n e t h a n o l (4 ml). The r e a c t i o n mixture was s t i r r e d f o r 1 h a t room temperature, c o n c e n t r a t e d to o n e - t h i r d volume under reduced p r e s s u r e , d i l u t e d with ether (150 ml) and s u c c e s s i v e l y washed with 1N h y d r o c h l o r i c a c i d (2x20 ml), s a t u r a t e d agueous sodium hydrogen carbonate (2x20 ml) and water (3x15 ml). The ether l a y e r was then d r i e d over sodium s u l f a t e and evaporated t o a f f o r d a c l e a r syrup (202 mg). B o r i c a c i d complexes were removed 203 f r o m t h i s c r u d e p r o d u c t by r e p e a t e d l y d i s s o l v i n g i t i n m e t h a n o l a n d e v a p o r a t i n g i t u n d e r r e d u c e d p r e s s u r e . The s y r u p t h u s o b t a i n e d was c h r o m a t o g r a p h e d on s i l i c a g e l . {60 g) u s i n g 1:1. b e n z e n e - e t h y l a c e t a t e as d e v e l o p e r . The component o f Bf 0.21 {355) was i s o l a t e d a s a c o l o u r l e s s o i l w h i c h c o u l d n o t be c r y s t a l l i z e d {168 mg, 7 2 % ) ; [ a ] 2 3 +14. 11° ( c 0.73, c h l o r o f o r m ) ; V ' f a a x 3 3 5 0 ° - 3 3 0 0 ( b r o a d , OH) , 3420 (HH) , 1700 (C=0) , 1610 cm~» (weak C=C) ; n.m.r. (100 MHz, CDCl^} : .6 1.26 ( s # 3H, CH^) , 1.50 ( s , 3H, C H ^ ) , 1.54 ( s , 1H, OH, e x c h a n g e a b l e w i t h D 2 0) , 3.16 ( d d , 1H, J g. 5'Q 4.0 H z , J 5 ' Q 5« b • 9.6 H z , H-5«a) , 3-44 ( d d , 1H, J A' 5'b 8 " ° H 2 ' H - 5 ' b ) , 4.22-4.38 (m, 1H, H - 4 « ) , 4.58 ( s , 2H, CH^OH, c h a n g e s t o d o u b l e t w i t h J g e m 6 . 4 Hz upon a d d i t i o n o f D^O) , 4 . 7 2 ( d d , 1H, J ^ y 7.0 Hz, J <^ ^ 4.0 Hz, H - 3 * j , 5.15 ( d , 1H, H - 2 » ) , 5.74 ( s , 1H, H - 1 « ) , 5-86 ( s , 1H, H-5), 7.12-7.50 (m, 15H, Ar) , 8.06 ( b r o a d s , a p p r o x . 1H, NH, e x c h a n g e a b l e w i t h D 20) ; mass s p e c t r u m : m/e 541 (M+-CH 3), 313 ( M + - t r i t y l ) , 126 (H + base) . Afi&.I=. C a l c . f o r C32H32N2°7 * V 2 H 2 0 : C, 6 7 . 9 6 ; H, 5-84; N, 4.96. F o u n d : C, 6 8 . 1 0 ; H, 5.73; N, 4.93-6 - H y d r o x y m e t h y l u r i d i n e ( 3 5 6 ) . - A s o l u t i o n o f t h e b l o c k e d n u c l e o s i d e 355 (68 mg) i n 8 0 % a q u e o u s a c e t i c a c i d (3 ml) was r e f l u x e d f o r 25 m i n , c o o l e d a n d e v a p o r a t e d . T r a c e s o f a c i d were removed b y a z e o t r o p i c d i s t i l l a t i o n w i t h x y l e n e a t r e d u c e d p r e s s u r e . The r e s u l t i n g c r u d e s o l i d was s u s p e n d e d i n w a t e r (30 ml) and washed w i t h c h l o r o f o r m (3x15 m l ) . The w a t e r l a y e r was t h e n c o n c e n t r a t e d , a p p l i e d t o a c o l u m n o f B i o - R e x 70 (Ht) c a t i o n e x c h a n g e r e s i n ( 3 0 x 1 . 6 5 cm) and e l u t e d w i t h w a t e r y i e l d i n g t h e u n b l o c k e d - n u c l e o s i d e 356 as a c l e a r s y r u p (23 mg, 6 9 % ) ; f a ^ Q 3 2 0 4 3 1 . 8 ° ( c 1 . 5 , m e t h a n o l ) ; 2 5 8 nm ( e 6 0 8 0 ) ; n . m . r . ( 1 0 0 M H z , D H S G - d g ) ; <5 3 . 4 0 - 3 . 6 4 ( m , 2 H , H - 5 * ) , 3 . 6 7 - 3 . 8 2 { m , 1 H , H - 4 » ) , 4 . 0 2 - 4 . 2 1 ( m , 1 H , c o l l a p s e s t o a t r i p l e t u p o n a d d i t i o n o f I ^ O , J 3 - 4 ' 6 . 0 H z , H - 3 ' } , 4 . 3 9 ( s , 2 H , C H 2 o f C - 6 ) , 4 . 5 0 - 4 . 7 1 ( m , 2 H , p a r t l y e x c h a n g e s w i t h D 2 0 l e a v i n g d d , J 2 * 3' 6 . 0 H z , J ^ ' 2 ' 4 - 0 H z , H - 2 * , C - 5 * , O H ) , 4 . 9 2 ( d , 1 H , O H , e x c h a n g e a b l e w i t h D 2 0 ) , 5 . 1 6 { d , 1 H , e x c h a n g e a b l e w i t h D 2 0 ) , 5 . 4 1 ( d , 1 H , H - 1 ' ) , 5 . 7 5 ( b r o a d s , 2 H , p a r t l y e x c h a n g e s w i t h r>2Q l e a v i n g a s h a r p s i n g l e t , H - 5 , C H 2 O H o f C - 6 ) , 1 1 . 2 9 ( b r o a d s , 1 H , N H , e x c h a n g e a b l e w i t h D 2 0 ) . A n a l . C a l c . f o r C l Q H 1 ^ N 2 0 7 * 1 / 2 H 2 0 : .. C , 4 2 . 4 0 ; H , 5 . 3 0 ; H , 9 . 8 9 . . F o u n d ; C , 4 2 . 6 6 ; H , 5 . 2 1 ; N , 9 . 7 5 . . §ZHydroxymethyluracil ( 3 5 7 ) . - A s o l u t i o n o f n u c l e o s i d e 3 5 6 ( 1 5 mg) i n 1M h y d r o c h l o r i c a c i d ( 2 m l ) w a s h e a t e d a t 9 0 ° f o r 1 2 h , c o o l e d a n d n e u t r a l i z e d w i t h a n e x c e s s o f s o l i d b a r i u m c a r b o n a t e . T h e u n d i s s o l v e d s a l t w a s r e m o v e d b y f i l t r a t i o n , t h e f i l t r a t e w a s e v a p o r a t e d t o d r y n e s s a n d t h e c r u d e r e s i d u e c h r o m a t o g r a p h e d o n a c o l u m n o f B i o - S e x 7 0 ( H t ) r e s i n w h i c h w a s d e v e l o p e d w i t h w a t e r . T h e f i r s t c o m p o n e n t t o b e e l u t e d w a s r i b o s e w h i c h w a s c h a r a c t e r i z e d b y c h r o m a t o g r a p h y oa* N o . 1 S h a t m a n p a p e r ( d e s c e n d i n g e l u t i o n u s i n g w a t e r - s a t u r a t e d n -b u t a n o l ) a g a i n s t a u t h e n t i c r i b o s e (B ^ 0.W, a l k a l i n e s i l v e r n i t r a t e d e t e c t i o n ) . C o n t i n u e d e l u t i o n o f t h e r e s i n c o l u m n g a v e c o m p o u n d 3 5 7 a s a w h i t e p o w d e r (6 m g , 7 6 % ) w h i c h w a s c r y s t a l l i z e d f r o m w a t e r , m . p . , 2 6 9 - 2 7 0 0 ( d e c o m p . ) , ( I i t . * 1 8 m . p . 2 7 4 ° ) ; n . m . r . ( 1 0 0 M H z , D M S O - d g ) : 6 4 . 19 ( s , 2 H , CH_2) , 5 . 5 0 ( s , 1 H , H - 5 ) , 1 0 . 6 0 - 1 1 . 0 4 ( b r o a d b a n d , a p p r o x . 2 H , N H , e x c h a n g e s w i t h D ? 0 ) , [ l i t . * * 8 n . m . r - ( 6 0 M H z , D-,0) : 6 4 . 1 7 ( C H , ) ] . 20 5 Attempted S y n t h e s i s of 6 - f 2 , 4 - d i k e t o t e t r a h y d r o i m i d a z o l - 5 -y l ) - 2 1 f 3 * - 0 - i s o p r o p y l i d e n e - 5 ^ - 0 - t r i t y l (358). - A mixture of the crude 6-carboxaldehyde 35_ (80 mg) , f r e s h l y -r e c r y s t a l l i z e d ammonium carbonate (56 mg) , and sodium cyanide (37 mg). i n .methanol (10 ml) and dimethyl s u l f o x i d e (1 ml) was s t i r r e d under 50 p . s . i - o f carbon d i o x i d e a t 23° f o r 2 h and then at 65° f o r 14 h. The s o l u t i o n was then evaporated under reduced pressure, the r e s i d u e was suspended i n water (10 ml) and the mixture was brought t o pH 6-7 with 1N h y d r o c h l o r i c a c i d - ,The water was e x t r a c t e d with e t h y l a c e t a t e (.3x10 ml) and the combined o r g a n i c e x t r a c t s were washed with water (10 ml). Drying of the o r g a n i c l a y e r with sodium s u l f a t e and e v a p o r a t i o n . o f the s o l v e n t s l e f t a crude orange syrup the t . l . c . (9:1 benzene-ethanol) of which showed the presence of at l e a s t s i x d i f f e r e n t components which were not pursued., E- or Z-6-r ( 2 - C a r b o e t h o x y - 2 - c y a n o ) e t h y l i d e n e j - 2 1 t 3 ' - 0 -isoEropyl.idene-5 * - 0 - t r i t y l u r i d i n e (35.91 and • E or Z-6-f, 12-c a r b o e t h o x y - 2 - c y a n o ) e t h y l i d e n e ] - 2 ' f 3 ' - O - i s o p r o p y l i d e n e - 3 - m e t h y l -5 _ - 0 - 1 r i t _ 1 u r i d i n e (360). - A s o l u t i o n of the crude carboxaldehyde mixture (351 and 353, 1.42 g ) , e t h y l cyanoacetate (263, 3-5 ml) and ammonium a c e t a t e (20 mg) i n anhydrous N,N-dimethylformamide (50 ml) was s t i r r e d at room temperature under nit r o g e n f o r 2 h. The r e a c t i o n mixture was then d i l u t e d with ether (300 ml) and washed with water (3x40 ml). The ether l a y e r was d r i e d (magnesium s u l f a t e ) and evaporated l e a v i n g a yellow syrup which was chromatographed on s i l i c a g e l (200 g) using 5:1 benzene-ethyl a c e t a t e as developer. The f a s t e r moving minor component was shown to be 360 (168 .mg, 10%) and was c r y s t a l l i z e d 20 6 from ether-hexane, m.p. 104-105°; [ a ] J 3 +2.79° (c 0.61, ch l o r o f o r m ) ; 0.35 ( s i l i c a g e l , 4:1 benzene-ethyl a c e t a t e ) ; Vmax 1 7 4 5 < e s t e r c = ° ) ' 1 7 2 5 (Pyrimidine C=0), 1680 {pyrimidine C=0) , 1630 c m - » . (C=C) ; nw m , r - .. (10.0 MHz, CDC1 3): 6 1.31 (s, 3H, CH 3) , 1-44 ( t , 3H, J C H C H ^ 7.2 Hz, CH^H^) , 1-54 (s, 3H, CH 3) , 3-14 (s, 3H, N-CH3) , 3.26 (dd, 1H, J ^  4-0 Hz, J 5» Q ^ 10-5 Hz, H-5'a), 3.46 (t, 1H, J ^  &' b 8-0 Hz, H-5»b), 4-25-4.50 (m, 1H, H-4') , 4.46 (g ( p a r t i a l l y obscured by H-4»), 2H, CH^CI^) , 4.81 (dd, 1H, J 2' 3' 6.0 Hz, J 3' ^  4.0, Hz, H-3»), 5.18 (d, 1H, H-2*), 5.44 (s, 1H, H-1'), 6.20 ( s , 1H, H-5), 7. 1 8-7. 60 (m, 15H , A r ) , 8.12 ( s , 1H, CH=C-CN) ; mass spectrum: m/e 663 (M+) , 648 {M+-CH3), 420 ( H + - t r i t y l ) , 415 (M+-base)-Anal_ C a l c . .for C3gH 3 7N 3Gg*1/2H 20: C, 67-85; H, 5-65; N, 6-25- Found: C, 68.21; H, 5-49; N, 6.16-., The major and slower moving component, compound 359 was i s o l a t e d as a foam (0.69 g, 38%) and c r y s t a l l i z e d from e t h e r -hexane, m. p. 122-123°; [ a j " +0.18° (c 1,1, c h l o r o f o r m ) ; 8 f 0.16 ( s i l i c a g e l , 4:1 benzene-ethyl acetate) ; v j ^ > 3420 (MH), 3200 (NH) , 1725 (ester C=0) , 1715 (pyrimidine C=0) , 1705 {pyrimidine C=0) , 1635 cm-* (C=C) ; n.m.r. (100 MHz, CDCI3): 6 1.26 {s, 3H, CH 3) , 1.38 ( t , 3H, J C H C H ^ 7.0 Hz, CH^CH^) , 1.52 (d, 3H, CH3) , 3.22 (dd, 1H, J^' 5' Q 5.0 Hz, J 5» Q 5' b 10.0 Hz, H-5* a ) , 3.40 ( t , 1 H ' JA' 5'b 8 * ( ) Hz, H-5'b), 4- 20-4- 39 (m, 1H, H-4*), 4.41 (g ( p a r t i a l l y obscured by H-4*) , 2H, CH^-CH^, 4-71 (dd, 1H, J 2' 3' 6.8 Hz, J o * ' / ' 3.-6 Hz, H-3*), 5-12 (d, TH, H-3'), 5.36 (s, 1H, H-1»), 6.08 (s, 1H, H-5) , 7-14-7.54 (m, 15H, Ar) , 8.05 ( s , 1H, CH=C-CN) , 8.82 (s, 1H, NH, exchangeable with D 20) ; mass spectrum; m/e 649 (M + ) , 635 {M + ~CH 3) , 415 (M+-base) , 406 (M +-207 t r i t y l ) . . Mai-. C a l c . f o r C^H^N-^Og: C, 68.41; H, 5-39; N, 6.47., Found: C, 67.95; H, 5.36; N, 6.19. 6z.Li2z.lR 2£ S) -Carboethoxy-2-acetamidomethyl) e t h y l 1-2 » ,3'-0 - i s p p r q p y l i d e n e - 5 ' - 0 - t r i t y l u r i d i n e (361)... ,- A s o l u t i o n of the cyano d e r i v a t i v e 359 (150 mg) i n anhydrous a c e t i c anhydride (20 ml) was hydrogenated a t 50 p . s . i . a t room temperature f o r 20 h i n the presence of platinum oxide (20 i g ) as c a t a l y s t . The r e a c t i o n mixture was then d i l u t e d with c h l o r o f o r m {150 ml) and f i l t e r e d through a C e l i t e pad to remove the c a t a l y s t . The f i l t r a t e was evaporated under reduced p r e s s u r e , and t r a c e s o f a c e t i c anhydride were removed by repeated a z e o t r o p i c d i s t i l l a t i o n s with t o l u e n e . The r e s i d u e was then . a p p l i e d to a column of s i l i c a g e l (30 g), the column developed with 9:1 benzene-ethanol and the component of B ^  0.29 was i s o l a t e d as a white foam (80 mg, 50%); [ e t ] 2 3 + 2-..91 ° (c 0.8, c h l o r o f o r m ) ; n.m.r. (100 MHz, CDCl^) : 6 0.92-1.28 (m, approx. , 6H,. CH 2 CH^, CH 3 of i s o p r o p y l i d e n e ) , 1.40 {d, approx. 3H, CH^ of is o p r o p y l i d e n e ) 1. 80 , 1.90, 1.95 (:3s, 3H, N-Ac) , 2. 32-3.62 {m, approx. 7H, H-5», CH_2CHCH2) , 3. 82-4.37 (m, 3H, H-4', CH 2CH 3), 4.62-4-74 (m, 1H, H-3«)# 4 .94-5.28 (m, 1H, H - 2 » ) , 5.64 (s, 1H, H-5), 5 . 7 0 (d, 1H, H-1*}^ 5.85 (broad s, 1H, NH, exchangeable with D-,0) , 7.08-7.48 (m, approx. .. 15H, A r ) , 8.10 (broad s, IH, NH, exchangeable with D-,0) ; mass spectrum: m/e 697 (M + ) , 682 (M+-CH3) , 454 {Mt-t r i t y l ) . A s i g n a l was a l s o seen a t m/e 709 i n d i c a t i n g p a r t i a l s a t u r a t i o n of the t r i t y l group-Ana l . C a l c . f o r C 3gH / ( 3 N30g.: C, 67.14; H, 6.17; N, 6.03.. Found: C, 66.88; H, 6 . 4 7 ; N, 5.80. 208 §_zLllzlR 2E S) -Car boethoxy-2- acet amidomethy 1) e t h y l ] u r i d i n e (362). - A s o l u t i o n of the blocked n u c l e o s i d e 361. (80 mg) i n 80% agueous . t r i f l u o r o a c e t i c a c i d (4 ml) was s t i r r e d a t room temperature f o r 15 min- The yellow s o l u t i o n was then d i l u t e d with methanol (30 ml) and toluene (100 ml) and evaporated t o near dryness under reduced pressure- A z e o t r o p i c e v a p o r a t i o n with toluene was repeated (5x30 ml) i n order to remove t r a c e s of a c i d , y i e l d i n g f i n a l l y a c l e a r syrup which was p u r i f i e d by chromatography on a column of Bio-Eex 70 (H*) r e s i n (29x1.7 cm) -E l u t i o n with water a f f o r d e d the pure n u c l e o s i d e d e r i v a t i v e 362 as a syrup (34 mg, 72%); [ a ] 2 3 -19- 1° (c 1.4, methanol); B f 0.16 M e O H ( s i l i c a g e l , 5:1 e t h y l acetate-ethanol) ; ^ m Q X 260 nm (e 12,540); c. d- (c 4. 1x10-s, water) -0.29; n-m-r. , (100 MHz, DMSO-d &): 6 1.21 ( t , 3H, J 7.0 Hz, CH 2CH 3), 1.87 (s, 3H, NHAc), 2.87 (broad s, 3H, CE^CHCC^) , 3.23-3.89 (m, 5H, H-5', H-4', CH 2NH), 4.14 (g, 3H, CH^CH^, H-3'), 4.55 (dd, 1H, J 2' 3' 6.0 Hz, J |« ? ' 4.0 Hz, H-2'), 4 . 7 3 ( t ( p a r t i a l l y obscured by H-2'), 1H, CH2OH, exchangeable with D 2 0 ) , 5.01 (broad s, 1H, OH, exchangeable with D 2 0 ) , 5.23 (broad s, 1H, OH, exchangeable with D 20) , 5. 43 (pseudo-t, IH, H-1'), 5.55 (s, 1H, H-5), 8.08 (d, IH, NH-Ac, exchangeable with D 20), 11.39 (broad s, 1H, NH of p y r i m i d i n e , exchangeable with r>20) ; mass spectrum; m/e 283- 1180. C l 2 H 1 7 N 3 0 5 (BH+) r e q u i r e s 283. 1168. M § J L = . C a l c . , f o r C 1 y ^2SU3 O^-H^z C, 47.11; H, 6.23; N, 9.69. Found; C, 47.03; H, 6.00; N, 9-11., 6~l 3-Amino- 2- (R or S) -carboxypropyl j u r i d i n e 1 3 6 3 ) _ . - A s o l u t i o n of compound 363 (20 mg) i n c o n c e n t r a t e d aqueous barium hydroxide (2 ml) was r e f l u x e d f o r 6 h. The s o l u t i o n was c o o l e d 209 and n e u t r a l i z e d with d i l u t e s u l f u r i c a c i d - The p r e c i p i t a t e of barium s a l t s was removed by f i l t r a t i o n , the f i l t r a t e was evaporated and the r e s i d u e was chromatographed on a column of Bio-Sex 70 (H + ) r e s i n (30x2.5 cm) . The column was developed with water and the n i n h y d r i n - p o s i t i v e f r a c t i o n s were combined y i e l d i n g 36 3 (13 mg, 56%) mainly as i t s barium s a l t ; [a J 2 3 25.5° (c 0.8, water) ; 260 ( e 7,000), 254 (e 7,900), 248 nm (e. 7,500); c. d. , (c 1.07x10~3, w a t e r ) A e 2 5 5 -0.02; n.m.r. (80 MHz, DMS0-d 6): 6 1.20 (d, 2H, J 7.0 Hz, C H 2 ) , 1.25 (m, 2H, CH 2NH 2 # c o l l a p s e s t o doublet upon a d d i t i o n of D 20 with J 9.0 Hz), 3.25-3.60 (m, 2 H, H-5'), 3. 85-4.25 (m, 3H ( a f t e r D 20 a d d i t i o n ) , H-3', 2', 1»), 4.40 (s, 1H, H-5), 4.10-4.80 (broad band, OH, exchangeable with D^O), 6.50, 7. 15, 7.80 (s, 3H, NH, exchangeable with D^O).; mass spectrum: m/e 346 (MH+). Anal._ C a l c . for. C ^  ^  H^  g Og N^8a: C, .32-41; H, 3.74; N, 8.72. Found: C, 27.15; H, 5.04; N, 3.33. When compound 363 was s t i r r e d f o r 10 min i n water i a the presence of Dowex 50W-X2 s t r o n g l y - a c i d i c c a t i o n exchange resin> no n i n h y d r i n - p o s i t i v e m a t e r i a l was recovered. 210 VI BIBLIOGRAPHY E- Vongerichten, L i e b i g s Ann. Chem., 3_18, 121 (1901). 0. Th. Schmidt, L i e b i g s Ann. Chem. , 483, 1 15 (1930). E. F i s c h e r and K. Freudenberg, Ber- Dtsch. Chem. Ges. , 45, 2709 (1912) . 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