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UBC Theses and Dissertations

Studies related to the synthesis of monomeric and dimeric vinca alkaloids Bylsma, Feike 1970

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STUDIES RELATED TO THE SYNTHESIS OF MONOMERIC AND DIMERIC VINCA ALKALOIDS  by  FEIKE BYLSMA B.Sc. Honours, McMaster U n i v e r s i t y , 1966  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE"REQUIREMENTS FOR THE DEGREE OF , DOCTOR OF PHILOSOPHY  i n the Department o f C h e m i s t r y  We a c c e p t t h i s t h e s i s as conforming, t o the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH A p r i l , 1970  COLUMBIA  In  presenting  this  an a d v a n c e d d e g r e e the I  Library  further  for  agree  in  at  University  the  make  tha  it  partial  freely  permission for  this  representatives. thesis  for  It  financial  gain  of  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, C a n a d a  of  of  Columbia,  British for  extensive by  the  Columbia  shall  not  the  requirements  reference copying of  Head o f  is understood that  written permission.  Department  fulfilment  available  s c h o l a r l y p u r p o s e s may be g r a n t e d  by h i s of  shall  thesis  I  agree  and this  be a l l o w e d  that  study. thesis  my D e p a r t m e n t  copying or  for  or  publication  w i t h o u t my  - i i ABSTRACT  The  f i r s t p a r t o f t h i s t h e s i s d e s c r i b e s a sequence which p r o v i d e s  a t o t a l s y n t h e s i s o f cleavamine catharanthinol  (12).  Dihydro-  (76) o b t a i n e d by l i t h i u m aluminum h y d r i d e r e d u c t i o n o f  dihydrocatharanthine The  (23) and c a t h a r a n t h i n e  (34) was c o n v e r t e d t o i t s t o s y l a t e  derivative.  l a t t e r i n t e r m e d i a t e upon h e a t i n g i n benzene c o n t a i n i n g two  e q u i v a l e n t s o f t r i e t h y l a m i n e underwent an i n t e r e s t i n g r e a c t i o n t o p r o v i d e a seco-diene system. tetrol  fragmentation  (78) c o n t a i n i n g t h e cleavamine  ring  R e a c t i o n o f t h i s d i e n e w i t h osmium t e t r o x i d e p r o v i d e d a (96) which c o u l d be c o n v e r t e d t o cleavamine  and t h e C . - f u n c t i o n a l i z e d cleavamine 4 treatment  on t h e one hand  d e r i v a t i v e s on t h e o t h e r .  o f t h e t e t r o l w i t h sodium b o r o h y d r i d e  Thus  allowed the hydrogenolysis  o f t h e c a r b i n o l amine f u n c t i o n and p r o v i d e d a t r i o l  (97).  The v i c i n a l  d i o l p r e s e n t i n 97 was c l e a v e d by means o f p e r i o d a t e and t h e r e s u l t a n t 2 - a c y l i n d o l e chromophore was f u r t h e r c o n v e r t e d by b o r o h y d r i d e 4,18-dihydroxy d i h y d r o c l e a v a m i n e  derivative  (99).  Reductive  to a removal  o f t h e C^g h y d r o x y l f u n c t i o n by means o f l i t h i u m aluminum h y d r i d e provided isovelbanamine y i e l d e d cleavamine  (100).  A c i d c a t a l y z e d dehydration o f the l a t t e r  (23) w h i l e i s o m e r i z a t i o n under aqueous a c i d i c  c o n d i t i o n s p r o v i d e d velbanamine ( 2 2 ) . To complete t h e t o t a l s y n t h e s i s o f c a t h a r a n t h i n e ( 1 2 ) ,  cleavamine  was r e a c t e d w i t h t - b u t y l h y p o c h l o r i t e and t h e r e s u l t a n t c h l o r o i n d o l e n i n e was then s u b j e c t e d t o n u c l e o p h i l i c a t t a c k by c y a n i d e i o n t o p r o v i d e 183-cyanocleavamine.  Basic h y d r o l y s i s o f the n i t r i l e  function followed  by e s t e r i f i c a t i o n p r o v i d e d 18g-carbomethoxycleavamine (60).  This  compound upon r e a c t i o n w i t h m e r c u r i c a c e t a t e was c y c l i z e d t o c a t h a r a n t h i n e .  - iii The second part of t h i s t h e s i s establishes the u t i l i t y of both the chloroindolenine and the C.--hydroxy analogues of the cleavamine systems to the synthesis of dimeric compounds s t r u c t u r a l l y s i m i l a r to the n a t u r a l dimeric a l k a l o i d s . Treatment of e i t h e r of these analogues with v i n d o l i n e under mild a c i d i c conditions y i e l d e d the appropriate dirners containing the indole and dihydroindole u n i t s present i n vincaleukoblastine. The d i m e r i z a t i o n r e a c t i o n was shown to be s t e r e o s p e c i f i c and l e d i n each case to the same stereochemistry dirners.  at C^g, of the r e s u l t i n g  - iv TABLE OF CONTENTS Page T i t l e page Abstract  11  T a b l e o f Contents  iv  List  o f F i g u r e s .,  List  of Tables  ...  Acknowledgements  Vll  vm  Introduction  1  Discussion  ..  24  I .  24  Part  P a r t II  87  Experimental  124  Bibliography  159  - V  -  LIST OF FIGURES Figure 1.  Page Summary o f the pathway from mevalonate t o i n d o l e a l k a l o i d s of tryptamine +  2.  ^  Kutney's t o t a l s y n t h e s i s o f  type  .5  dl-dihydrocleavamine  (29)  .  3.  T o t a l s y n t h e s i s o f some Aspidosperma a l k a l o i d s  ....  4.  Mechanism proposed f o r t h e a c i d c a t a l y z e d r e a r r a n g e ment o f c a t h a r a n t h i n e  5.  Acid catalyzed isomerisation of dihydrocatharanthine 30  Reduction of c a t h a r a n t h i n e to the epimeric m e t h o x y d i h y d r o c l e a v a m i n e and  carbo-  18g-carbomethoxy-  cleavamine 7.  22  28  (34) t o c o r o n a r i d i n e (35) 6.  20  31  Proposed d e h y d r o g e n a t i o n - r e d u c t i o n  sequence u s i n g  t h e r i n g opened c a t h a r a n t h i n e i n t e r m e d i a t e ( 5 4 ) . . . .  33  8.  Partial  36  9.  Fragmentation  scheme o f the d e g r a d a t i o n o f a j m a l i n e ( 6 8 ) . o f v o a c a g i n o l - O - t o s y l a t e (71a)  conopharyngol-O-tosylate 10.  and  (71b)  Proposed scheme, f o r r i n g opening  37 of catharanthine to  t h e 5,18-seco-diene system (78) 11.  S y n t h e s i s o f cleavamine  (23) from t h e  39 seco-diene  (83) v i a osmium t e t r o x i d e o x i d a t i o n  54  12.  Mass spectrum o f the t e t r o l  56  13.  Mass spectrum o f t h e t r i o l  (97)  56  14.  Nmr  (96)  57'  spectrum o f the t e t r o l  (96)  - vi-  Figure  Page  15.  Nmr spectrum o f t h e t r i o l  (97)  59  16.  P a r t i a l nmr spectrum i l l u s t r a t i n g t h e p e r t i n e n t s i g n a l p a t t e r n s c o r r e s p o n d i n g t o t h e 183-hydroxymethyl f u n c t i o n  17.  Mass spectrum o f k e t o l  61 (98)  63  i (99)  1  63  ^  65  18.  Mass spectrum o f d i o l  19.  Nmr spectrum o f t h e d i o l  20.  Nmr o f i s o v e l b a n a m i n e (100)  68  21.  Mass spectrum o f i s o v e l b a n a m i n e (100)  70  22.  Mass spectrum o f 3 a - h y d r o x y - 4 3 - d i h y d r o c l e a v a m i n e . . .  70  23.  C o n v e r s i o n o f c l e a v a m i n e (23) t o c a t h a r a n t h i n e ....  72  24.  T a y l o r ' s r e a c t i o n scheme f o r f u n c t i o n a l i z a t i o n  (99)  using indolenine intermediates  72  25.  Nmr spectrum o f 18g-cyanocleavamine  (109)  75  26.  Nmr spectrum o f 3 a - a c e t o x y - 4 3 - d i h y d r o c l e a v a m i n e . . . .  81  27.  Mass spectrum o f dimer (118)  90  28.  Nmr spectrum o f dimer (118)  92  29.  Nmr spectrum o f v i n d o l i n e  93  30.  Nmr spectrum o f 4 g - d i h y d r o c l e a v a m i n e  94  31.  Mass spectrum o f dimer (119)  97  32.  Nmr spectrum o f dimer (119)  98  33.  Uv spectrum o f dimer (119) and v i n b l a s t i n e  34.  Nmr spectrum o f v i n b l a s t i n e  35.  Nmr. spectrum o f dimer (142)  H4  36.  Nmr spectrum o f dimer (146)  121 •  (11)  (16)  (16)....  102 103  J  - vii LIST OF TABLES Table I  Page S t r u c t u r e - a c t i v i t y studies  on v i n b l a s t i n e by  Hargrove^  II  The major d i f f e r e n c e s spectra  11  o b s e r v e d between the nmr  o f v i n b l a s t i n e and dimer (119)|  104  -  Vlll  -  ACKNOWLEDGEMENTS  I w i s h t o e x p r e s s my thanks t o P r o f e s s o r J.P. Kutney f o r h i s e x c e l l e n t guidance throughout t h e c o u r s e o f t h i s r e s e a r c h . H i s encouragement and unbounded optimism were o f t e n evoked and p r o v i d e d much o f t h e s t i m u l u s f o r t h i s work. I am v e r y g r a t e f u l t o my w i f e f o r h e r s u p p o r t and encouragement throughout t h i s s t u d y and a l s o f o r h e r h e l p i n t h e p r e p a r a t i o n o f this  manuscript. I am g r a t e f u l t o t h e N a t i o n a l Research C o u n c i l o f Canada and  the N a t i o n a l Cancer provided.  I n s t i t u t e o f Canada f o r t h e f i n a n c i a l  support  INTRODUCTION  The c o n s t a n t  and c o n t i n u i n g q u e s t f o r new t h e r a p e u t i c agents  and t h e i r development has been and remains t o be one o f t h e main o b j e c t i v e s of the n a t u r a l product chemist.  P r i m a r i l y h i s job i n  t h i s r e g a r d has been t h e s t r u c t u r a l e l u c i d a t i o n and s y n t h e s i s o f compounds o f known t h e r a p e u t i c v a l u e .  Knowledge o f t h e s t r u c t u r a l  d e t a i l s i s o f course e s s e n t i a l t o the understanding a c t i o n o f these drugs.  T h i s , coupled  o f t h e mode o f  with the synthetic c a p a b i l i t i e s  o f t h e chemist has l e d t o t h e use o f many s y n t h e t i c analogues o f t h e n a t u r a l l y o c c u r r i n g compounds i n modern m e d i c i n e . I t has been e s t i m a t e d  t h a t some f i f t e e n p e r c e n t  o r more o f a l l  v a s c u l a r p l a n t s c o n t a i n a l k a l o i d s . A v e r y l a r g e number o f d i f f e r e n t p l a n t s p e c i e s have been i n v e s t i g a t e d w i t h i n t h e p a s t two decades f o r alkaloidal constituents. pharmaceutical  Much o f t h i s work has been done by l a r g e  f i r m s who. a r e i n v o l v e d i n a s y s t e m a t i c  plants f o r s p e c i f i c pharmacological  activity.  1  screening of  A more d i r e c t b u t  l i m i t e d approach has been t h e s t u d y o f g a l e n i c a l s p r e s c r i b e d by f o l k l o r e and p r i m i t i v e m e d i c i n e . degree o f p h a r m a c o l o g i c a l  A l t h o u g h most a l k a l o i d s p o s s e s s some  a c t i v i t y , many a r e n o t m e d i c i n a l l y u s e f u l  e i t h e r because t h e i r a c t i v i t y i s t o o f e e b l e o r because t h e i r i s t o o marked.  toxicity  Thus o n l y a r e l a t i v e l y s m a l l number among a l l t h e known  - 2  a l k a l o i d s a r e c u r r e n t l y o f i m p o r t a n c e from t h e t h e r a p e u t i c  point of  view. A" d i v e r s i t y o f s t r u c t u r e i s e x h i b i t e d by t h e s e compounds. simplest  a r e perhaps t h o s e o f t h e p h e n e t h y l a m i n e group.  The  The Ephedra  a l k a l o i d e p h e d r i n e (1) r e s e m b l e s t h e a n i m a l hormone e p i n e p h r i n e (2) b o t h s t r u c t u r a l l y and i n i t s a d r e n e r g i c p r o p e r t i e s .  The Peyote a l k a l o i d  m e s c a l i n e (3) i s an h a l l u c i n o g e n i c agent used t o 'produce "model p s y c h o s e s " i n man f o r e x p e r i m e n t a l p u r p o s e s . OH  OCH, OH  OCH.  CH-OH I  CH-CH, I 3 NH-CH  (1)  (2)  In p a r t , t h e e a r l y b i o s y n t h e t i c p o s t u l a t e s  o f Robinson  and many  3 subsequent e x p e r i m e n t s  d e a l t w i t h t h e f o r m a t i o n o f t h e s l i g h t l y more  complex t r o p a n e a l k a l o i d s .  Important members o f t h i s f a m i l y a r e t h e  c h o l i n e r g i c b l o c k i n g agent a t r o p i n e anaesthetic  (hyoscyamine) (4) and t h e l o c a l  cocaine (5). .  Morphine  (6) and c o d e i n e (7) b o t h d e p r e s s a n t s o f t h e c e n t r a l  nervous system a r e even more complex and have been t h e o b j e c t o f 4 5 i n t e n s e s t r u c t u r a l , s y n t h e t i c and b i o s y n t h e t i c i n v e s t i g a t i o n . A v e r y l a r g e group o f a l k a l o i d s numbering about 600, have as t h e i r b a s i c s t r u c t u r a l u n i t , the indole moiety.  The c o m p l e x i t y o f t h e i r  s t r u c t u r e s range i n a manner s i m i l a r t o t h o s e c i t e d above, from t h e v e r y s i m p l e , f o r example, t h e neurohormone s e r o t o n i n (8) t o t h e v e r y complex such as the p o i s o n , s t r y c h n i n e ( 9 ) , and the h y p o t e n s i v e reserpine  (10).  agent,  The s y n t h e s i s o f compounds o f i n t r i c a t e s t r u c t u r e  6 7 such as the l a t t e r two ' of s y n t h e t i c o r g a n i c  r e p r e s e n t major achievements i n t h e f i e l d  chemistry.  Most o f t h e i n d o l e a l k a l o i d s can be c l a s s i f i e d  according to t h e i r  - 4 -  |  (10)  s t r u c t u r a l t y p e i n t o f o u r g r o u p s ; t h e s e a r e C o r y n a n t h e , Aspidosperma, Iboga and S t r y c h n o s .  Examples o f each o f t h e s e r e s p e c t i v e l y a r e  r e s e r p i n e ( 1 0 ) , v i n d o l i n e ( 1 1 ) , c a t h a r a n t h i n e ( 1 2 ) , and s t r y c h n i n e ( 9 ) .  (11)  (12)  I t has been e s t a b l i s h e d t h a t b i o s y n t h e t i c a l l y t h e s e s e e m i n g l y u n r e l a t e d s t r u c t u r e s are i n f a c t d e r i v e d from a common i n t e r m e d i a t e . 8 This intermediate, v i n c o s i d e (13), tryptamine  and  r e s u l t s from a c o n d e n s a t i o n between  a monoterpene u n i t , s e c o l o g a n i n  (15), derived  mevalonate t h r o u g h l o g a n i n (14) as shown i n f i g u r e 1.  Corynanthe  F i g u r e 1.  Iboga  from  The e l u c i d a t i o n  Aspidosperma  Summary o f the pathway from mevalonate t o i n d o l e a l k a l o i d s of tryptamine  + C  n  ..  n  type  o f t h e mechanism by which v i n c o s i d e  (13) i s c o n v e r t e d  s t r u c t u r a l t y p e s remains an a c t i v e a r e a o f r e s e a r c h a t  i n t o each o f present.  the  -  6  i  I  The b a s i c s t r u c t u r a l u n i t o f t h e a l k a l o i d s r e s u l t i n g from t h e above p r o c e s s , i s made up o f n i n e t e e n o r twenty carbon atoms and two n i t r o g e n atoms.  However, a number o f i n d o l e a l k a l o i d s have been  i s o l a t e d o v e r t h e l a s t f i f t e e n y e a r s which p o s s e s s a m o l e c u l a r f o r m u l a made up o f a p p r o x i m a t e l y two such u n i t s .  These " d i m e r i c a l k a l o i d s " , i n  p a r t i c u l a r , t h o s e i s o l a t e d from C a t h a r a n t h u s r o s e u s G. Don, have p r o v i d e d a tremendous s t i m u l u s t o a l l a s p e c t s o f t h e f i e l d o f i n d o l e a l k a l o i d c h e m i s t r y because o f t h e i r p r o v e n o n c o l y t i c . a c t i v i t y .  The  s t u d i e s i n o u r l a b o r a t o r y l e a d i n g t o t h e s y n t h e s i s o f t h e s e complex systems i s t h e s u b j e c t o f t h i s  thesis.  C a t h a r a n t h u s r o s e u s G. Don, a l s o r e f e r r e d t o as V i n c a r o s e a L i n n , i s a t r o p i c a l member o f t h e genus o f p l a n t s commonly known as t h e periwinkles.  The u s e o f t h i s s p e c i e s o f p l a n t t h r o u g h o u t t h e h i s t o r y  o f f o l k - m e d i c i n e has been v a r i e d , g a l e n i c a l s p r e p a r e d from i t have been used as an a b o r t i v e a g e n t , a n t i - d i a b e t i c a n t i - g a l a c t o g o g u e , m e n s t r u a l 9 r e g u l a t o r , p u r g a t i v e and a number o f o t h e r u s e s .  A recently published  a r t i c l e e n t i t l e d " P l a n t s used a g a i n s t Cancer - A S u r v e y " ^ , i s a 1  l i t e r a t u r e s u r v e y embracing t h e r e c o r d e d h i s t o r y o f m e d i c i n e , pharmacology, m a t e r i a medica, m e d i c a l b o t a n y , ethnobotany and f o l k l o r e t o 2800 B.C. I t i s i n t e r e s t i n g t o n o t e .that o f t h e more t h a n 3000 d i f f e r e n t p l a n t s p e c i e s r e p o r t e d t o have been used a g a i n s t growths and tumors, no mentioned i s made o f C_. r o s e u s G. Don. I n t e r e s t i n t h i s s p e c i e s a r o s e from i t s r e p o r t e d h y p o g l y c e m i c activity.  Noble and Beer c o u l d n o t s u b s t a n t i a t e t h i s a c t i v i t y b u t  o b s e r v e d i n s t e a d p e r i p h e r a l g r a n u l o c y t o p e n i a and bone marrow d e p r e s s i o n  - 7 -  i  ii in rats. VLB)  This  l e d t o the i s o l a t i o n o f v i n b l a s t i n e  (vincaleukoblastine, X2 (16) w h i c h was found t o produce s e v e r e l e u k o p e n i a i n r a t s .  I s o l a t i o n o f v i n b l a s t i n e and l e u r o s i n e  (17) and t h e i r a c t i v i t y  against 13  P-1534 l e u k e m i a i n mice was r e p o r t e d These p r e l i m i n a r y  s h o r t l y t h e r e a f t e r by Svoboda. I  i n v e s t i g a t i o n s marked t h e b e g i n n i n g o f a v e r y  active period of research  i n the Vinca a l k a l o i d s .  a l k a l o i d s have been o b t a i n e d  A t o t a l o f 61  from C. Roseus G. Don, 26 o f them a r e  d i m e r i c b u t o n l y 6 o f t h e s e have o n c o l y t i c a c t i v i t y .  These a c t i v e  compounds a r e a l l dimers o f t h e i n d o l e - i n d o l i n e t y p e .  The s t r u c t u r e s  o f f o u r o f them, v i n b l a s t i n e ( 1 6 ) ,  leurosidine ( 1 8 ) ^  and v i n c r i s t i n e  1 4  leurosine  (17),  1 5  14 ( l e u r o c r i s t i n e , VCR) ( 1 9 ) , have been e s t a b l i s h e d .  2 CH  (16)  l C0 CH 2  3  (17)  C0 CH 2  3  CH  (18)  C0 CH 2  3  C H  (19)  C0 CH  3  CHO  2  3 OH  4 H  R  R  R  3  •0  3  3  R  H  OH  OH  H  - 8 | V i n b l a s t i n e and v i n c r i s t i n e a r e the most a c t i v e and f o r t h i s r e a s o n have been s t u d i e d more e x t e n s i v e l y i n t h e i r c l i n i c a l use t h a n t h e o t h e r alkaloids.  Both have been shown t o be e f f e c t i v e i n t h e t r e a t m e n t o f 17  lymphomas and v a r i o u s  carcinomas  .  Vincristine i s also  effective  i n the treatment of acute leukemia p a r t i c u l a r l y i n c h i l d r e n . u s e f u l n e s s i s l i m i t e d , however, by t h e i r t o x i c i t y ; v i n b l a s t i n e l e u k o p e n i a w h i l e v i n c r i s t i n e e x h i b i t s neuromuscular  Their produces  toxicity.  The mode o f a c t i o n o f t h e s e drugs i s not p r o p e r l y u n d e r s t o o d . 18 recent review of t h i s subject  A  makes i t c l e a r t h a t a l t h o u g h t h e many  experiments conducted so f a r have p o i n t e d out a number o f p h y s i o l o g i c a l changes observed i n a v a r i e t y o f tumor systems s t u d i e d b o t h i n v i t r o and i n v i v o when s u b j e c t e d t o t h e s e d r u g s , i t has been d i f f i c u l t t o c o r r e l a t e t h e s e r e s u l t s , and t h e b i o c h e m i c a l mechanism o f t h e i r remains t o be d e t e r m i n e d .  action  I t does appear t h a t t h e V i n c a a l k a l o i d s  have a s i m i l a r i f not i d e n t i c a l mechanism o f a c t i o n t o t h a t o f t h e other m i t o t i c  p o i s o n s such as c o l c h i c i n e  (20) and p o d o p h y l l o t o x i n ( 2 1 ) .  - 9 The  f o l l o w i n g working hypothesis  i n c o r p o r a t i n g the observed  phenomena has been p r e s e n t e d by Armstrong a t t h e 'conclusion o f a r e c e n t 19 symposium on v i n c r i t i n e .  The p r i m a r y i n t r a c e l l u l a r m e t a b o l i c  effect  o f t h e V i n c a a l k a l o i d s seems t o be t h e i n h i b i t i o n o f t r a n s f e r RNA synthesis.  Because t h e f u n c t i o n o f t r a n s f e r RNA i s t o c a r r y amino  a c i d s from t h e c y t o p l a s m  i n t o t h e ribosomes where p r o t e i n s a r e formed,  i t i s thus t h e d e c r e a s e i n t r a n s f e r RNA s y n t h e s i s which causes a decrease i n p r o t e i n s y n t h e s i s .  The V i n c a a l k a l o i d s a r e p e r m i t t e d t o  e n t e r t h e c e l l s o n l y between prophase and metaphase and t h u s i n t r a c e l l u l a r p r o t e i n p r o d u c t i o n becomes d e c r e a s e d a t t h e v e r y time when p r o t e i n should  appear between t h e f i b e r s  o f the s p i n d l e apparatus t o  s p r e a d them a p a r t and s u p p o r t them i n t h e fanned o u t p o s i t i o n t h e y normally  adopt d u r i n g metaphase.  I n t h e absence o f t h i s s u p p o r t  s p i n d l e f i b e r s appear c o l l a p s e d and t a n g l e d phase by t h e a l k a l o i d .  the  i n c e l l s a r r e s t e d i n meta-  When t h e s p i n d l e a p p a r a t u s i s i n such a d i s a r r a y ,  the chromosomes cannot m i g r a t e from t h e metaphase p o s i t i o n .  The  i n h i b i t i o n o f DNA s y n t h e s i s o b s e r v e d , r e s u l t s from metaphase a r r e s t . Such an e x p l a n a t i o n p r o v i d e s account f o r t h e e x p e r i m e n t a l l y i n s i g h t i n t o the biochemical  an o r d e r e d sequence o f events t o  o b s e r v e d phenomena b u t p r o v i d e s no  mode o f a c t i o n ; f o r example what i n t e r a c t i o n  w i t h t h e a l k a l o i d s e x i s t s t h a t i n h i b i t s t h e s y n t h e s i s o f t r a n s f e r RNA. Having l i t t l e o r no knowledge o f t h e a c t u a l r e a c t i o n mechanism a s s o c i a t e d with the pharmacological  p r o p e r t i e s e x h i b i t e d by t h e s e compounds, t h e  c h e m i s t i s i n a p o o r p o s i t i o n t o model a compound w i t h t h e d e s i r e d t h e r a p e u t i c p r o p e r t i e s and l i t t l e o r no t o x i c i t y .  He need, o f n e c e s s i t y ,  use a r a t h e r e m p i r i c a l a p p r o a c h , t h a t i s , s t a r t w i t h a compound o f known  10  pharmacological properties  and a l t e r i t s t e p w i s e n o t i n g  or decrease i n a c t i v i t y associated  simply the increase  w i t h each s t r u c t u r a l m o d i f i c a t i o n .  In such a way knowledge can be g a i n e d o f t h e importance o f s t r u c t u r a l u n i t s as r e l a t e d t o a c t i v i t y . difficulties.  T h i s method i s f r a u g h t  w i t h two major  F i r s t , t h e chemist may have the m i s f o r t u n e o f c h o o s i n g  the wrong compound as h i s b a s i s f o r improvement and t h e r e b y p u t h i m s e l f i n t h e f a r from u n i q u e p o s i t i o n o f t r y i n g t o do t h e i m p o s s i b l e .  Second,  i f he chooses as we have, a compound w i t h a formula; such as C.,N.0_H , ' ^ 46 4 9 58' ro  he i s f a c e d w i t h a near i n f i n i t e number o f c h o i c e s o f how b e s t t o modify o r a l t e r the s t r u c t u r e .  Unfortunately  o r f o r t u n a t e l y he i s  l i m i t e d i n h i s c h o i c e by h i s s y n t h e t i c c a p a b i l i t i e s and t h e amount o f time a v a i l a b l e . The  v e r y s l i g h t s t r u c t u r a l d i f f e r e n c e between v i n b l a s t i n e and  v i n c r i s t i n e and t h e r e l a t i v e l y l a r g e d i f f e r e n c e i n t h e r a p e u t i c and  properties  t o x i c i t y s e r v e s t o i n d i c a t e t h a t perhaps o n l y a minor change i s  necessary t o e f f e c t the synthesis  o f an improved d r u g .  An attempt t o  20 a c h i e v e t h i s has been r e p o r t e d  by Hargrove.  V i n b l a s t i n e was c o n v e r t e d  d i r e c t l y i n t o a number o f analogues by r e a c t i o n s h y d r o g e n a t i o n and a c e t y l a t i o n .  such as h y d r o l y s i s ,  The r e s u l t s a r e summarized i n t a b l e I .  The  numbered arrows on t h e s c h e m a t i c i n d i c a t e t h e p o s i t i o n a f f e c t e d by  the  reaction. As r e f e r e n c e  f o r f u r t h e r d i s c u s s i o n , t h e numbering system  commonly used f o r t h e Iboga and Aspidosperma a l k a l o i d s i s g i v e n below.  T a b l e I.  S t r u c t u r e - a c t i v i t y studies  on v i n b l a s t i n e by Hargrove.  Activity relative t o VLB  Modification  1)  reduction  of vindoline  portion  2)  reduction  (hexahydro)  3)  acid hydrolysis  4)  LiAlHj  5)  acid hydrolysis  6)  a c e t y l a t i o n u s i n g ketene  7)  acetylation using Ac 0  (desacetyl)  reduction o f VCR  2  (triacetate) (diacetate)  (6) (7)  | 1/3  less  none  --  none  10X  none  —  j  (desformyl)  none  --  none  --  none  (4)  toxicity  —  - 12 -  Iboga  Aspidosperma  More p r o m i s i n g r e s u l t s were o b t a i n e d from t h e p r o d u c t i o n o f 4 - a c y l analogues r e a d i l y p r e p a r e d by t h e r e a c t i o n o f d e s a c e t y l VLB w i t h a series of simple a l i p h a t i c acids.  The b e s t o f t h e s e , v i n g l y c i n e  ( d e s a c e t y l VLB 4 - ( N , N - d i m e t h y l a m i n o a c e t a t e ) )  produced from d e s a c e t y l  V L B - 4 - c h l o r o a c e t a t e and d i m e t h y l a m i n e , e q u a l s v i n c r i s t i n e i n i t s a c t i o n a g a i n s t P-1534 l e u k e m i a i n mice.  T h i s compound proved t o be much l e s s  t o x i c t h a n v i n b l a s t i n e and c o u l d thus be t o l e r a t e d a t h i g h e r dose l e v e l s . A l t h o u g h a t t h i s p o i n t VLB has been t r a n s f o r m e d i n t o an "improved"  drug,  t h i s was no s o l u t i o n t o t h e problem s i n c e i t s a c t i v i t y seemed t o be s i m i l a r to that of v i n c r i s t i n e . Changes o t h e r t h a n i n t h e f u n c t i o n a l groups on the m o l e c u l e a r e much more d i f f i c u l t t o i n t r o d u c e . Two  p o s s i b i l i t i e s present themselves:  a) p a r t i a l l y degrade v i n b l a s t i n e and b u i l d i n s t r u c t u r a l m o d i f i c a t i o n s o r b) attempt t o s y n t h e s i z e analogues u s i n g the a p p r o p r i a t e Iboga Aspidosperma  and  type u n i t s .  Some d e g r a d a t i o n o f v i n b l a s t i n e has been r e p o r t e d and the work i n d i c a t e s t h a t t h e dimer i s r e a d i l y c l e a v e d i n t o i t s monomeric u n i t s . I t was  the i d e n t i f i c a t i o n o f t h e s e c l e a v a g e p r o d u c t s which p r o v i d e d much  - 13 -  o f t h e i n i t i a l e v i d e n c e f o r t h e s t r u c t u r e o f VLB. under a c i d i c r e d u c i n g  c o n d i t i o n s , t h e p r o d u c t s i s o l a t e d were  v i n d o l i n e and velbanamine (22) . conditions  When VLB was t r e a t e d desacetyl  P r o l o n g e d t r e a t m e n t under t h e above  a l s o produced some c l e a v a m i n e ( 2 3 ) .  (22)  Desacetyl  (23)  v i n d o l i n e was r e a d i l y i d e n t i f i e d by comparison w i t h an 21  authentic  sample produced by m i l d h y d r o l y s i s o f v i n d o l i n e (11) •  The  s t r u c t u r e o f velbanamine was e s t a b l i s h e d v i a c l e a v a m i n e , i t s d e h y d r a t i o n product. obtained  Cleavamine had been i s o l a t e d from a m i x t u r e o f p r o d u c t s from c a t h a r a n t h i n e  (12) t r e a t e d under c o n d i t i o n s i d e n t i c a l t o 22 t h o s e used f o r t h e dimer c l e a v a g e . I t s s t r u c t u r e had been c o r r e c t l y 23 a s s i g n e d based on mass s p e c t r a l d a t a and was l a t e r s u b s t a n t i a t e d by 24 X-ray a n a l y s i s o f c l e a v a m i n e m e t h i o d i d e . Treatment o f v i n b l a s t i n e under n o n - r e d u c i n g a c i d i c - c o n d i t i o n s a l s o c l e a v e d i t ; t h e p r o d u c t o f 14 t h i s r e a c t i o n was d e s a c e t y l v i n d o l i n e and t h e e t h e r e t h e r when s u b j e c t e d  t o reducing  (24).  This  a c i d i c c o n d i t i o n s y i e l d e d velbanamine.  I t i s n o t s u r p r i s i n g t h a t t h e bond j o i n i n g t h e s e two u n i t s i n t h e dimeric The  system s h o u l d be so l a b i l e , p a r t i c u l a r l y under a c i d i c c o n d i t i o n s ,  v i n d o l i n e aromatic p o r t i o n i s e s s e n t i a l l y a meta-methoxyaniline  - 14 -  (24)  system which would be e x p e c t e d t o undergo f a c i l e substitution.  electrophilic  I n t h i s case p r o t o n a t i o n a t C^,_ would l e a d t o a r e s o n a n c e -  s t a b i l i z e d carbonium i o n s i n c e b o t h t h e ortho-methoxy and p a r a - a n i l i n o n i t r o g e n atom can make c o n t r i b u t i o n t o i t s s t a b i l i t y .  Bond f i s s i o n i s  t h e n m e r e l y a p r o c e s s which would l e a d t o n e u t r a l i z a t i o n o f t h e p o s i t i v e charge. T h e o r e t i c a l l y , any r e a c t i o n mechanism i s r e v e r s i b l e .  Thus the  problem i n s y n t h e s i z i n g t h e d i m e r i c system from i t s two components i s one o f making i t e n e r g e t i c a l l y f a v o u r a b l e f o r the r e v e r s e o f t h e above process t o occur.  Because Kutney and coworkers had d e v e l o p e d a g e n e r a l  s y n t h e t i c r o u t e t o b o t h the Iboga and Aspidosperma t y p e s o f a l k a l o i d , t h e two h a l v e s o f t h e d i m e r , t h i s approach was adopted and i s o u t l i n e d in this  thesis.  The key s t e p i n t h e s y n t h e s i s o f t h e Aspidosperma and Iboga a l k a l o i d s 25 i s a t r a n s a n n u l a r c y c l i z a t i o n which was p o s t u l a t e d i n 1962 by Wenkert i n a b i o s y n t h e t i c scheme l e a d i n g t o t h e s e compounds.  The  Aspidosperma  system was p r o p o s e d t o r e s u l t from t h e t r a n s a n n u l a r c y c l i z a t i o n o f t h e a p p r o p r i a t e b i o s y n t h e t i c p r e c u r s o r (25 -»- 26) and t h e Iboga c o u l d v i a a s i m i l a r p r o c e s s (27 -*• 28) .  arise  - 15 -  (27)  (28)  The f i r s t e x p e r i m e n t a l v e r i f i c a t i o n f o r t h i s scheme was p r o v i d e d by Kutney.  26  Dihydrocleavamine  (29) a v a i l a b l e from c a t h a r a n t h i n e ( 1 2 ) ,  p r o v i d e d a c o n v e n i e n t model system. gave t h e r e q u i r e d iminium, s a l t  2  Oxidation with mercuric acetate  (30) which on r i n g c l o s u r e f o l l o w e d by  r e d u c t i o n r e s u l t e d i n t h e Aspidosperma s k e l e t o n ( 3 1 ) . When c a r b o m e t h o x y d i h y d r o c l e a v a m i n e conditions pseudovincadifformine  (32) was o x i d i z e d under  27 (33) was i s o l a t e d 28  c a t h a r a n t h i n e (34) and c o r o n a r i d i n e ( 3 5 ) .  similar  along with dihydro-  Whereas t h e c y c l i z a t i o n '  t o t h e Aspidosperma s k e l e t o n i n t h e d i h y d r o c l e a v a m i n e  case must i n v o l v e  -  16  -  H (29)  H  H  the e l e c t r o n s i n h e r e n t i n the i n d o l e system as i n the i n t e r m e d i a t e ( 3 0 ) , i n t h e c a r b o m e t h o x y d i h y d r o c l e a v a m i n e c a s e , t h e d r i v i n g f o r c e comes from t h e l o s s o f a, hydrogen a l p h a t o the carbomethoxy i n t e r m e d i a t e (36) .  group i n the  The p r e s e n c e o f b o t h c o r o n a r i d i n e and d i h y d r o -  c a t h a r a n t h i n e i n d i c a t e s t h a t the i m i n i u m s a l t  (37) i s i n e q u i l i b r i u m  w i t h i t s enamine i s o m e r . The Aspidosperma s k e l e t o n as s y n t h e s i z e d i n t h e e x p e r i m e n t s c i t e d above i s o f an u n n a t u r a l s t r u c t u r e b e a r i n g t h e e t h y l s i d e c h a i n a t r a t h e r t h a n a t C^.  The c o r r e c t s t r u c t u r e was o b t a i n e d by t r a n s a n n u l a r -  c y c l i z a t i o n o f quebrachamine aspidospermidine  ( 3 8 ) , which l e d t o the s y n t h e s i s o f  (39).  I t i s o f i n t e r e s t t o note t h e s t e r e o c h e m i c a l d e t a i l s o f t h i s work. The Aspidosperma s k e l e t o n c o n t a i n s f o u r asymmetric c e n t e r s w h i l e t h e s t a r t i n g c i e a v a m i n e o r quebrachamine  systems have o n l y one.  I t has been  - 17 -  (33)  (34)  R=H, R =C H  (35)  R=C H ,R =H  1  2  5  2  1  - 18 -  (38)  (39)  e s t a b l i s h e d by c h e m i c a l and X-ray s t u d i e s t h a t t h e lone asymmetric center i n the s t a r t i n g m a t e r i a l r e s u l t s i n a s t e r e o s p e c i f i c  cyclization 29  and d e t e r m i n e s t h e s t e r e o c h e m i s t r y a t t h e o t h e r t h r e e c e n t e r s . Thus b o t h o f t h e s t e r e o c h e m i c a l s e r i e s known i n t h e n a t u r a l A s p i d o sperma a l k a l o i d s can be o b t a i n e d by t h e p r o p e r c h o i c e o f s t a r t i n g material. Having e s t a b l i s h e d t h e u t i l i t y o f t h e t r a n s a n n u l a r  cyclization  approach t o t h e s y n t h e s i s o f b o t h t h e Aspidosperma and Iboga systems, a g e n e r a l approach t o t h e s y n t h e s i s o f t h e a p p r o p r i a t e n i n e r i n g i n t e r m e d i a t e was d e s i r a b l e .  The d i f f i c u l t y o f s y n t h e s i z i n g  m e d i a t e s i z e r i n g systems i s w e l l known.  quaternary  inter-  I n t h i s case t h e d i f f i c u l t y  was o b v i a t e d by advantageous u s e o f t h e n i t r o g e n atom p r e s e n t r i n g system.  membered  i n the  The key i n t e r m e d i a t e f o r t h i s s y n t h e t i c approach i s t h e  salt  ( 4 0 ) . Ring opening o f t h i s i n t e r m e d i a t e i s r e a d i l y  a c h i e v e d under r e d u c i n g c o n d i t i o n s t o g i v e dl-quebrachamine (38) (when R=C2H^ and R^=H) 30,31,32  and d l - d i h y d r o c l e a v a m i n e (29) (when R=H and R^= The s y n t h e s i s o f t h e i n t e r m e d i a t e (40) was a c h i e v e d i n  - 19 -  a s t r a i g h t f o r w a r d manner as shown f o r the i n t e r m e d i a t e f i g u r e 2.  31  Intermediate  Having obtained  (40a) was  obtained  dihydrocleavamine,  e x t e n d t h e s y n t h e t i c sequence t o a C  (40b)  in  i n a s i m i l a r manner.  i t was  30  then d e s i r a b l e to  -carbomethoxydihydrocleavamine  d e r i v a t i v e s i n c e t h i s would t h e n g i v e a t o t a l s y n t h e s i s o f d l - d i h y d r o catharanthine  and d l - c o r o n a r i d i n e v i a the t r a n s a n n u l a r  a l r e a d y mentioned.  Use was  cyclization  made o f the t e r t - b u t y l h y p o c h l o r i t e  o x i d a t i o n o f i n d o l e systems t o the c o r r e s p o n d i n g  chloroindolenine  as  33 employed by B u c h i serves  i n h i s voacangine s y n t h e s i s .  an i m p o r t a n t  T h i s r e a c t i o n which  r o l e i n the work f o r t h i s t h e s i s , w i l l be  i n d e t a i l when t h a t work i s p r e s e n t e d . formed from d i h y d r o c l e a v a m i n e was  The  chloroindolenine  l c  position.  This, followed  t r e a t m e n t w i t h m e t h a n o l i c h y d r o c h l o r i c a c i d produced the 31  by  required  (32).  Subsequent work c a r r i e d out t o extend the t o t a l s y n t h e s i s dl-quebrachamine and  (41)  reacted with potassium cyanide to  i n t r o d u c e the n i t r i l e group a t the C  18-carbomethoxydihydrocleavamine  discussed  aspidospermidine  of  t o the more complex members o f  - 20 -  (29)  F i g u r e 2.  Kutney's t o t a l s y n t h e s i s o f d l - d i h y d r o c l e a v a m i n e  (29).  - 21 -  0C1" (29).  (32)  (42)  (41)  t h e Aspidosperma a l k a l o i d s r e s u l t e d i n t h e improved  sequence as o u t -  32 l i n e d i n f i g u r e 3.  C o n d e n s a t i o n o f t r y p t a m i n e w i t h t h e aldehyde  p r o v i d e d the r e q u i r e d t e t r a c y c l i c i n t e r m e d i a t e d i r e c t l y  thereby  e l i m i n a t i n g t h e low y i e l d i n g o x i d a t i v e s t e p i n h e r e n t i n the approach.  first  T h i s sequence l e d t o the s y n t h e s i s o f the q u a t e r n a r y  i n a g r e a t l y improved  over-all yield.  (43)  mesylate  N u c l e o p h i l i c a t t a c k by c y a n i d e  on t h i s i n t e r m e d i a t e e f f e c t e d b o t h t h e r i n g opening and f o r m a t i o n o f the d e s i r e d n i t r i l e  i n a single step.  t h e carbomethoxy group produced isomeric at C . 1C>  Conversion o f the n i t r i l e  d l - v i n c a d i n e and  to  dl-epivincadine,  T h i s work a l s o p r o v i d e d a t o t a l s y n t h e s i s o f d l -  v i n c a m i n o r e i n e and d l - v i n c a m i n o r i n e , t h e c o r r e s p o n d i n g i n d o l e N-methylanalogues.  T r a n s a n n u l a r - c y c l i z a t i o n o f t h e above nine-membered r i n g  n a t u r a l p r o d u c t s p r o v i d e d t o t a l s y n t h e s e s o f d l - v i n c a d i f f o r m i n e and i t s N-methyl a n a l o g u e , d l - m i n o v i n e . An e x t e n t i o n o f t h i s sequence t o encompass a l k a l o i d s b e a r i n g a methoxyl  group i n t h e a r o m a t i c r i n g was  a c h i e v e d by the use o f  6-methoxytryptamine i n s t e a d o f t r y p t a m i n e  i n the i n t i a l  condensation.  T h i s has l e d t o t h e t o t a l s y n t h e s i s o f t h e s t r u c t u r e proposed f o r  22  NH, HCO  H C 0 E t CH OBz 2  N  2  Q  _  CH OBz 2  l_  (43)  _ OMes M  MeSCLCl 2 N ^  R  l  R  R  \2  2  R  H  vincadine  H  C0 CH  epivincadine  H  H  vincarainoreine  H  C0 CH  vincaminorine  H  H  C0 CH 2  3  C0 CH  H C0 CH  3  vincaminoridine  2  2  2  H  vincadifformine  R H  3 H  minovine  H  Me  3  H CH C0 2  3  3  3  H  2  R  C0 Me 2  F i g u r e 3.  T o t a l s y n t h e s i s o f some Aspidosperma a l k a l o i d s .  3  32  H C H  3  C H  3  C H  3  - 23 -  vincaminoridine.  Ring c l o s u r e provides  a compound which has most o f  the s t r u c t u r a l f e a t u r e s o f v i n d o l i n e . From t h e summary o f t h e e x p e r i m e n t a l that a general  work p r o v i d e d ,  i t i s apparent  s y n t h e t i c approach t o t h e Aspidosperma and Iboga  a l k a l o i d s has been d e v e l o p e d .  However, w i t h r e s p e c t  t o the s y n t h e s i s  o f t h e d i m e r i c systems, a comparison o f t h e s t r u c t u r e s drawn f o r the n a t u r a l dimers and t h e s t r u c t u r e s drawn i n the s y h t h e t i c schemes, i n d i c a t e t h a t a l t h o u g h t h e c o r r e c t g r o s s s t r u c t u r e s have been s y n t h e s i z e d , the s y n t h e t i c m a t e r i a l s l a c k some o f t h e r e q u i r e d f u n c t i o n a l i t y . t h e r e f o r e , n e c e s s a r y t o d e v e l o p a means by which t h e o x i d a t i o n o f t h e s e compounds d i m e r i c systems.  I t was level  c o u l d be a l t e r e d t o t h a t found i n t h e n a t u r a l Once t h i s had been a c c o m p l i s h e d , t h e means t o c o u p l e  t h e f u n c t i o n a l i z e d Iboga and Aspidosperma u n i t s t o form t h e d i m e r i c compounds would have t o be d e v e l o p e d . The s y n t h e s i s o f t h e a p p r o p r i a t e  Aspidosperma u n i t , s p e c i f i c a l l y  v i n d o l i n e , i s a demanding problem and i s c u r r e n t l y b e i n g o t h e r workers i n our l a b o r a t o r y .  s t u d i e d by  T h i s t h e s i s w i l l d e a l w i t h t h e work  conducted towards a c h i e v i n g t h e c o r r e c t o x i d a t i o n l e v e l o f t h e Iboga system and t h e m o d i f i c a t i o n s n e c e s s a r y t o e f f e c t c o u p l i n g w i t h v i n d o l i n e .  DISCUSSION  The  a i m ' o f t h i s work, as o u t l i n e d i n the i n t r o d u c t i o n , i s  the s y n t h e s i s o f a s e r i e s o f compounds analogous 'to the n a t u r a l d i m e r i c Vinca a l k a l o i d s . under two  The  s t u d i e s c a r r i e d out t o t h i s end can be  general headings:  nine-membered r i n g p r e s e n t  classified  1) the a p p r o p r i a t e f u n c t i o n a l i z a t i o n o f t h e i n t h e c l e a v a m i n e - t y p e system so as t o make  a v a i l a b l e u n i t s s i m i l a r t o t h o s e found i n the n a t u r a l a l k a l o i d s and 2), t h e c o u p l i n g o f t h e s e u n i t s w i t h v i n d o l i n e t o g i v e t h e  appropriate  d i m e r i c m o l e c u l e s c l o s e l y r e l a t e d i n s t r u c t u r e t o the a n t i - t u m o r For purposes o f c l a r i t y and  agents.  ease o f p r e s e n t a t i o n , t h e s e two p a r t s o f  t h e work w i l l be d e a l t w i t h s e p a r a t e l y i n t h i s d i s c u s s i o n . Part I The  f o u r d i m e r i c V i n c a a l k a l o i d s which have shown i n t e r e s t i n g  anti-tumor  a c t i v i t y p o s s e s s a c l e a v a m i n e type u n i t which i s f u n c t i o n -  a l i z e d a t the C^ and/or C^ p o s i t i o n s . g r o u p s , e i t h e r h y d r o x y l or e p o x i d e , compound h a v i n g  The  nature of these f u n c t i o n a l  suggest t h a t the  corresponding  a double bond between C^ and C^ would be a v a l u a b l e  i n t e r m e d i a t e i n a g e n e r a l scheme f o r the s y n t h e s i s o f t h e s e f u n c t i o n a l i z e d systems.  A number o f methods c o u l d be u t i l i z e d f o r the i n t r o d u c t i o n  o f the n e c e s s a r y  groups once t h e d o u b l e bond i s p r o p e r l y p l a c e d i n the  c l e a v a m i n e system.  A t the t i m e t h i s s t u d y was  i n i t i a t e d , compounds h a v i n g  the  - 25 -  d e s i r e d degree o f u n s a t u r a t i o n such as 18-carbomethoxycleavamine cleavamine  (60) on  (23) c o u l d o n l y be o b t a i n e d by d e g r a d a t i o n o f t h e n a t u r a l l y 22 37  o c c u r r i n g a l k a l o i d , c a t h a r a n t h i n e (12) .  '  However, t h e s a t u r a t e d  analogues o f t h e s e compounds, t h a t i s , d i h y d r o c l e a v a m i n e ( 2 9 ) , 18carbomethoxydihydrocleavamine  (32) and d i h y d r o c a t h a r a n t h i n e (34) had 27 31  been o b t a i n e d i n a t o t a l l y s y n t h e t i c manner i n our l a b o r a t o r i e s .  '  I t was t h u s o f i n t e r e s t t o d e v e l o p a method by which t h e r e q u i r e d double bond c o u l d be i n t r o d u c e d i n t o t h e s e compounds and t h e r e b y extend the s y n t h e t i c work t o encompass t h e s e members. From a n o t h e r p o i n t o f v i e w i t was a l s o n e c e s s a r y t o t o t a l l y s y n t h e s i z e c a t h a r a n t h i n e ( 1 2 ) . I t became d e s i r a b l e i n o u r s y n t h e t i c s t u d i e s t o have a s u i t a b l e r e l a y m a t e r i a l , one t h a t would o b v i a t e t h e n e c e s s i t y o f making l a r g e amounts o f m a t e r i a l s , n e c e s s a r y f o r f u r t h e r  - 26 -  s t u d i e s , v i a a l e n g t h y s y n t h e t i c sequence. i s o l a t e d from t h e l e a v e s o f C . r o s e u s , was t o our i n t e r e s t and one which was work.  C a t h a r a n t h i n e , a major a l k a l o i d the compound most s u i t a b l e  used e x t e n s i v e l y t h r o u g h o u t t h i s  T h e r e f o r e any s t u d i e s which would a c h i e v e the i n t r o d u c t i o n o f  t h e double bond i n t o the d i h y d r o c a t h a r a n t h i n e system would be h i g h l y desirable. Our  approach t o t h i s problem was  t o attempt |to s y n t h e s i z e  c l e a v a m i n e from one o f the m a t e r i a l s a l r e a d y a v a i l a b l e v i a the synthetic studies. dihydrocleavamine  previous  E a r l i e r i n our l a b o r a t o r y , i t had been shown t h a t c o u l d be c o n v e r t e d t o 1 8 - c a r b o m e t h o x y d i h y d r o c l e a v a m i n e  and the l a t t e r v i a o x i d a t i o n t o an iminium  i n t e r m e d i a t e , would undergo 27  transannular c y c l i z a t i o n to dihydrocatharanthine.  31 '  I t was  clear  t h a t t h i s sequence o f r e a c t i o n s c o u l d be a p p l i e d i n the c o n v e r s i o n c l e a v a m i n e t o c a t h a r a n t h i n e v i a 18-carbomethoxycleavamine.  On  of  this  b a s i s a s y n t h e s i s of cleavamine should a l s o c o n s t i t u t e a s y n t h e s i s of the a l k a l o i d ,  catharanthine.  Catharanthine  can be c o n v e r t e d  by known p r o c e d u r e s .  i n t o a number o f c l e a v a m i n e d e r i v a t i v e s  These compounds as w e l l as the c h e m i s t r y i m p l i e d  i n t h e t r a n s f o r m a t i o n o f c a t h a r a n t h i n e t o them, have been used t h r o u g h o u t this thesis.  I t i s i n s t r u c t i v e f o r t h i s r e a s o n t o summarize b r i e f l y  t h e r e l e v a n t p o r t i o n s o f t h i s work. Dihydrocatharanthine,  l i k e i t s Iboga r e l a t i v e s , i s r e a d i l y decarboxy-  l a t e d under a c i d i c c o n d i t i o n s .  In c o n t r a s t , the d e c a r b o x y l a t i o n o f  c a t h a r a n t h i n e o c c u r s i n poor y i e l d o n l y under f o r c i n g c o n d i t i o n s , ( r e f l u x i n g concentrated hydrochloric acid) .  The  accepted  decarboxylation  - 27 -  mechanism f o r t h e Iboga a l k a l o i d s  '  r e q u i r e s the i n t e r m e d i a c y o f ( 6 1 ) .  (61) 22 36 The h i g h l y s t r a i n e d n a t u r e o f t h i s i n t e r m e d i a t e has been c i t e d  '  to  account f o r t h e f a i l u r e o f t h i s r e a c t i o n under normal r e a c t i o n c o n d i t i o n s . I n i t i a l r e p o r t s o f t h i s work i n d i c a t e t h e i s o l a t i o n o f c l e a v a m i n e 22 w e l l as some d e s c a r b o m e t h o x y c a t h a r a n t h i n e . o f t h i s work by Kutney and coworkers  Subsequent i n v e s t i g a t i o n and 4 - c t - d i h y d r o -  showed t h a t 4-g  c l e a v a m i n e were a l s o p r o d u c t s o f t h i s r e a c t i o n .  These r e s u l t s were  r a t i o n a l i z e d on t h e b a s i s o f t h e mechanism shown i n f i g u r e 4. c l e a v a g e u t i l i z i n g the l o n e p a i r o f e l e c t r o n s on t h e c o n j u g a t e d iminium ion(44).  as  Ring  would r e s u l t i n  H y d r o l y s i s o f the e s t e r f u n c t i o n and  d e c a r b o x y l a t i o n o f t h e f l e x i b l e r i n g opened system g i v e s t h e i n t e r m e d i a t e (46).  R i n g c l o s u r e would r e s u l t i n d e s c a r b o m e t h o x y c a t h a r a n t h i n e  w h i l e a p r o t o t r o p i c s h i f t t o r e s t o r e t h e i n d o l e system  (47)  l e a d s to(48).  D i r e c t 1,2-reduction of the conjugated iminium s a l t leads to  cleavamine  (23) w h i l e 1 , 4 - r e d u c t i o n would produce the enamine (49) which c o u l d be reduced, v i a the iminium s a l t  (50) i n e q u i l i b r i u m w i t h i t , t o y i e l d  t h e e p i m e r i c 4a (51) and 4g (52) d i h y d r o c l e a v a m i n e s .  In t h e absence o f  added r e d u c i n g agents t h e s e r e a c t i o n s s t i l l o c c u r but i n lower y i e l d s . Under t h e s e c o n d i t i o n s , one m e r e l y v i s u a l i z e s an o x i d a t i o n - r e d u c t i o n '  - 28 -  - 29 -  process  i n which the d i h y d r o p y r i d i n i u m  intermediate  a r e d u c i n g agent, i s o x i d i z e d t o the p y r i d i n i u m s a l t 48 t o t h e  (48) i n i t s r o l e as (53) w h i l e  converting  dihydrocleavamines.  (53)  In g l a c i a l  a c e t i c a c i d , d e c a r b o x y l a t i o n i s not observed  dihydrocatharanthine  or catharanthine.  i n t h i s manner i s r e c o v e r e d A mechanistic ring-opened  along w i t h  r a t i o n a l e of this  species  Dihydrocatharanthine  (34) t r e a t e d  i t s C^ epimer c o r o n a r i d i n e ( 3 5 ) .  i n t e r e s t i n g conversion reveals that the  (54) i s i n e q u i l i b r i u m w i t h the p e n t a c y c l i c  compounds v i a i t s enamine tautomer as shown i n f i g u r e 5. Catharanthine  for either  i n g l a c i a l a c e t i c a c i d with  t o produce carbomethoxydihydrocleavamine.  14  22  z i n c dust was r e p o r t e d  A c a r e f u l ' study o f t h i s  r e a c t i o n i n our l a b o r a t o r i e s showed t h a t f o u r e p i m e r i c  compounds 37  ( e p i m e r i c a t C^g and C^) were produced i n t h i s r e a c t i o n .  These  r e s u l t s can be r e a d i l y e x p l a i n e d by a r e a c t i o n scheme ( f i g u r e 6) s i m i l a r t o t h e one o u t l i n e d i n f i g u r e 4.  The i n t e r m e d i a t e  (44) i n s t e a d  of undergoing h y d r o l y s i s and d e c a r b o x y l a t i o n as i n t h e p r e v i o u s proceeds t o r e s t o r e t h e i n d o l e system C.„.  As b e f o r e , 1 , 4 - r e d u c t i o n  scheme,  (56) w i t h r e s u l t a n t epimers a t  f o l l o w e d by t a u t o m e r i z a t i o n e t c . i n  the manner, 56 -»• 59 produces the f o u r carbomethoxydihydrocleavamines  (59) .  - 30 -  (35)  F i g u r e 5.  Acid catalyzed isomerisation of dihydrocatharanthine to c o r o n a r i d i n e  (35) .  (34)  31 -  (44)  M  e  0  C 2  (56)  Me0 C 2  1,2-reduction  (60)  1,4-reduction  Me0 C 2 o  (23)  Me0 C 2  (59)  F i g u r e 6.  Reduction o f catharanthine t o the epimeric  carbomethoxy-  d i h y d r o c l e a v a m i n e s and 183-carbomethoxycleavamine.  37  - 32 On t h e o t h e r hand, 1 , 2 - r e d u c t i o n o f t h e i n t e r m e d i a t e (56) would be e x p e c t e d t o y i e l d carbomethoxycleavamine.  Indeed c a t h a r a n t h i n e on  r e a c t i o n w i t h sodium b o r o h y d r i d e i n h o t g l a c i a l a c e t i c a c i d gave a good 37 y i e l d o f t h e p r e v i o u s l y unknown 18g-carbomethoxycleavamine  (60).  Because t h i s l a t t e r compound can be e a s i l y d e c a r b o x y l a t e d , t h i s p r o c e d u r e t h e r e b y made c l e avamine (23) and d i h y d r o c l e a v a m i n e (29) r e a d i l y available. P r e v i o u s t o t h e work c a r r i e d o u t f o r t h i s t h e s i s , a t t e m p t s had been made by o t h e r workers i n o u r l a b o r a t o r y t o o b t a i n t h e u n s a t u r a t e d c l e a v a m i n e system from one o f t h e t o t a l l y s y n t h e t i c compounds.  Their,  approach made u s e o f t h e a c i d c a t a l y z e d r i n g opening o f d i h y d r o c a t h a r a n t h i n e (34) ( f i g u r e 5 ) .  The r e s u l t i n g i n t e r m e d i a t e i m i n i u m s a l t (62)  w h i c h may be i n e q u i l i b r i u m w i t h (54) was e x p e c t e d t o p r o v i d e a " h a n d l e " f o r subsequent f a c i l e d e h y d r o g e n a t i o n t o an a r o m a t i c system. t e t r a h y d r o p y r i d i n i u m system as shown i n f i g u r e 7.  Thus t h e  (63) would l e a d t o t h e p y r i d i n i u m s a l t (64)  Sodium b o r o h y d r i d e r e d u c t i o n o f such p y r i d i n i u m  s a l t s i s known t o p r o v i d e t h e t e t r a h y d r o p y r i d i n i u m system ( f o r example, 38 65  -»• 66)  and i t i s c l e a r t h a t t h e above c o n v e r s i o n c o u l d l e a d t o  t h e d e s i r e d carbomethoxycleavamine  (60).  (66)  - 33 -  (60)  Figure 7.  Proposed dehydrogenation-reduction  sequence using the ring  opened catharanthine intermediate (54).  Experimentally, t h i s reaction scheme could not be r e a l i z e d . acid catalyzed r i n g opening step could be r e a d i l y achieved; for t h i s reaction was  The  evidence  the presence of coronaridine i n the product mixture  - 34 -  (see f i g u r e 5 ) . step.  The d i f f i c u l t y was encountered i n t h e d e h y d r o g e n a t i o n  Reagents used f o r t h i s purpose were 2 , 3 - d i c h l o r o - 5 , 6 - d i c y a n o -  benzoquinone (DDQ), p a l l a d i u m , m e r c u r i c a c e t a t e and l e a d t e t r a c e t a t e . A b r o a d range o f e x p e r i m e n t a l  c o n d i t i o n s were t r i e d .  Under m i l d  c o n d i t i o n s no r e a c t i o n was o b s e r v e d and d i h y d r o c a t h a r a n t h i n e r e c o v e r e d a l o n g w i t h some c o r o n a r i d i n e .  More f o r c i n g c o n d i t i o n s  sumed s t a r t i n g m a t e r i a l b u t gave no i d e n t i f i a b l e ! p r o d u c t s . 39 40 t i o n o f t h e mechanism f o r t h i s o x i d a t i o n s a l t intermediate  i s incapable  o f being  '  con-  Considera-  ! i n d i c a t e s t h a t the iminium  oxidized f u r t h e r without  u n d e r g o i n g i s o m e r i z a t i o n t o t h e c o r r e s p o n d i n g enamine.  first  Because t h e  a c i d i c c o n d i t i o n s r e q u i r e d f o r r i n g opening may not f a v o u r formation,  was  enamine  a number o f e x p e r i m e n t s were a l s o c a r r i e d out i n which t h e  a c i d i c r e a c t i o n m i x t u r e c o n t a i n i n g t h e r i n g opened s p e c i e s was t a k e n t o d r y n e s s and t h e n o x i d i z e d i n a b a s i c medium. were o b t a i n e d  under t h e s e c o n d i t i o n s .  No f a v o r a b l e r e s u l t s  Attempts t o o b t a i n t h e enamine  o f 4 B - d i h y d r o c l e a v a m i n e (29) and o f 183-carbomethoxydihydrocleavamine (32) by i s o m e r i z a t i o n o f t h e c o r r e s p o n d i n g i m i n i u m s a l t s r e s u l t i n g from m e r c u r i c a c e t a t e o x i d a t i o n u s i n g b a s i c t r e a t m e n t were a l s o Some o f t h e t r a n s a n n u l a r were o b t a i n e d but  unsuccessful.  c y c l i z a t i o n p r o d u c t s (29 -»- 31 and 32 -> 33)  i n each case i n d i c a t i n g t h a t o x i d a t i o n was i n d e e d  i s o l a t i o n o f the appropriate  occurring  enamines ( i f formed) c o u l d not be  achieved. The approach adopted f o r t h i s t h e s i s i n v o l v e d a  fragmentation  r e a c t i o n w h i c h , i f s u c c e s s f u l , would g e n e r a t e t h e nine-membered r i n g system i n h e r e n t general  i n c l e a v a m i n e as w e l l as t h e enamine group.  way, t h i s r e a c t i o n can be r e p r e s e n t e d  as f o l l o w s :  In a  - 35 -  \  N—  C — C — C —  X  *•  N=C  i V-OH ie t c .  K X = h a l o g e n , OTs,  The  +  +  X  x  +  d e s i r e d h e t e r o l y t i c c l e a v a g e between the  3 and y carbon atoms  would be dependent on the ease w i t h w h i c h the -C-X and  C=C  x  bond i s b r o k e n  the s a t i s f a c t i o n o f t h e r e s u l t a n t e l e c t r o n d e f i c i e n c y at the y  c a r b o n atom.  The  latter condition  i s w e l l accommodated by the  basic  n i t r o g e n w h i l e good l e a v i n g groups such as t o s y l a t e would s a t i s f y f i r s t requirement.  A number o f competing r e a c t i o n s a r e p o s s i b l e :  s u b s t i t u t i o n ; 2) 1 , 2 - e l i m i n a t i o n  and  3) i n t e r - o r  f o u n d , however, t h a t when the i n v o l v e d c e n t r e s arrangement as shown i n s t r u c t u r e 67, f r a g m e n t a t i o n t o o c c u r and  1)  intramolecular  q u a t e r n i z a t i o n o f the n i t r o g e n atom (see f o r eq. 74 -> 75).  observed.  the  It is  are i n a t r a n s  i t i s favourable  for  coplanar  the  t h i s i s the predominant mode o f r e a c t i o n  44  (67)  T h i s r e a c t i o n was  o r i g i n a l l y employed i n the a l k a l o i d f i e l d i n the 41  degradation of ajmaline s a r p a g i n e (69) d e r i v e d type s t r u c t u r e  (68).  The  from a j m a l i n e  i s o q u i n u c l i d i n e system o f was  (70) as shown i n f i g u r e  converted to the 8.  the  corynanthe-  - 36 -  (70) F i g u r e 8.  P a r t i a l scheme o f t h e d e g r a d a t i o n o f a j m a l i n e ( 6 8 ) .  T h i s same r e a c t i o n scheme was s u b s e q u e n t l y a p p l i e d by Renner t o 42 t h e Iboga a l k a l o i d s .  V o a c a n g i n o l - O - t o s y l a t e (71a) underwent  f i s s i o n t o y i e l d t h e 5,18-secodiene (72a) which was reduced by sodium b o r o h y d r i d e t o t h e d i h y d r o compound ( 7 3 a ) .  S i m i l a r l y cOnopharyngol-0-  t o s y l a t e (71b) was c o n v e r t e d t o t h e c o r r e s p o n d i n g f r a g m e n t a t i o n p r o d u c t (72b) and i t s d i h y d r o d e r i v a t i v e (73b).  I n c o n t r a s t i b o x y g a i n e (74)  which does n o t have t h e d e s i r e d t r a n s c o p l a n a r arrangement o f t h e 1,3-aminoalcohol  g r o u p i n g f a i l s t o undergo r i n g c l e a v a g e on t o s y l a t i o n  - 37 -  MeO  MeO  CH OTs 2  ( 7 1 a ) , R=H (71b), R=OMe  MeO  ( 7 3 a ) , R=H  ( 7 2 a ) , R=H  (73b), R=OMe  (72b), R=OMe  F i g u r e 9.  Fragmentation o f voacaginol-O-tosylate  (71a) and conopharyngol-  O-tosy.late (71b) .  and g i v e s i n s t e a d the q u a t e r n a r y t o s y l a t e s a l t (75)  43 TsO"  MeO  (74)  (75)  - 38 -  Renner's r e a c t i o n scheme ( f i g u r e 9) seemed p a r t i c u l a r l y r e l e v a n t  I t o our problem.  Catharanthine  c o u l d be c o n v e r t e d  (76) u s i n g known p r o c e d u r e s .  to dihydrocatharanthinol  Fragmentation of the  corresponding  t o s y l a t e (77) s h o u l d t h e n g i v e the 5,18-seco-diene ( 7 8 ) . •  •  the a c i d c a t a l y z e d r i n g opening o f d i h y d r o c a t h a r a n t h i n e i t was  necessary  (figure  5)  t o t r a p the enamine (55) from an e q u i l i b r a t i n g system,  i n t h i s c a s e , the enamine would be t h e r e s u l t o f an fragmentation  Whereas i n  i  reaction.  irreversible  Once t h i s enamine system were a v a i l a b l e , a  number o f methods might then be employed t o e f f e c t a m i g r a t i o n o f t h i s double bond t o t h e d e s i r e d c l e a v a m i n e system.  The  e x o c y c l i c methylene  i n t h i s i n t e r m e d i a t e would a l s o be u s e f u l i n t h a t t h i s f u n c t i o n would provide a "handle" Catharanthine  by which the carbomethoxy group c o u l d be was  r e a d i l y converted  c a t a l y t i c hydrogenation  reintroduced.  to dihydrocatharanthine  u s i n g Adam's c a t a l y s t i n e t h a n o l .  aluminum h y d r i d e r e d u c t i o n o f t h i s p r o d u c t  by  Lithium  gave d i h y d r o c a t h a r a n t h i n o l  22 (76),  the s t a r t i n g m a t e r i a l f o r our sequence.  Treatment o f d i h y d r o -  c a t h a r a n t h i n o l w i t h an excess o f t o s y l c h l o r i d e i n d r y p y r i d i n e gave the d e s i r e d t o s y l a t e .  This m a t e r i a l f a i l e d to c r y s t a l l i z e using 45  normal work up p r o c e d u r e .  E x t r a c t i o n from aqueous medium gave the  crude t o s y l a t e i n a p y r i d i n e s o l u t i o n . i n vacuo at 0°C  step.  i f the above o p e r a t i o n was  red-brown gum  The  p y r i d i n e had t o be removed  s i n c e t h e p r e s e n c e o f t h i s s o l v e n t c o u l d not be t o l e r a t e d  i n the subsequent d i s p l a c e m e n t occurred  the  Rapid decomposition  conducted a t room t e m p e r a t u r e .  thus o b t a i n e d c o u l d be induced  a l i t t l e benzene and  o f the t o s y l a t e  t o c r y s t a l l i z e by  l e t t i n g t h e s o l u t i o n s t a n d a t 0°C  The  adding  overnight.  t o s y l a t e o b t a i n e d as a l i g h t brown c r y s t a l l i n e m a t e r i a l appeared t o  The be  - 39 -  CH,  CH OR 2  (76),  R=H  (77a),R=Tos (77b),R=Mes  (78)  (79)  F i g u r e 10.  Proposed scheme f o r r i n g opening o f c a t h a r a n t h i n e 5,18-seco-diene  s t a b l e a t room t e m p e r a t u r e . failed.  to the  system ( 7 8 ) .  A l l attempts t o r e c r y s t a l l i z e t h i s m a t e r i a l  The i r and uv s p e c t r a o f t h i s crude c r y s t a l l i n e m a t e r i a l were  in accord with the d e s i r e d s t r u c t u r e .  The benzene mother l i q u o r s from  t h e above c r y s t a l l i z a t i o n c o u l d be f r e e z e d r i e d t o g i v e a d d i t i o n a l q u a n t i t i e s o f t h e t o s y l a t e as a brown amorphous powder.  The  tosylate  c o u l d be used i n t h e f o l l o w i n g s t e p , however, as t h e crude gum  provided  40 -  v e r y l i t t l e p y r i d i n e were p r e s e n t . Displacement  \  i  o f t h e t o s y l a t e o c c u r r e d r a p i d l y i n a warm s o l u t i o n l  o f benzene c o n t a i n i n g some t r i e t h y l a m i n e .  The change o f chromophore  from i n d o l e t o a v i n y l - i n d o l e system a l l o w e d t h i s r e a c t i o n t o be c o n v e n i e n t l y m o n i t o r e d by uv s p e c t r o s c o p y .  Optimum r e s u l t s were  o b t a i n e d by k e e p i n g t h e s o l u t i o n a t 70°C f o r two hours under a d r y n i t r o g e n atmosphere. when exposed  The 5,18-seco-diene  t o t h e atmosphere.  was  quite unstable i n solution  The work up p r o c e d u r e c o n s i s t e d o f  c o o l i n g t h e s o l u t i o n under t h e n i t r o g e n atmosphere, f l u s h i n g i t under p o s i t i v e p r e s s u r e t h r o u g h a v e r y s h o r t column o f d e a c t i v a t e d a l u m i n a  and  t h e n s t r i p p i n g o f f t h e s o l v e n t a t room temperature under reduced pressure.  I n t h i s manner, t h e dark brown r e a c t i o n m i x t u r e was  converted  t o a l i g h t y e l l o w s o l u t i o n which c r y s t a l l i z e d r e a d i l y on e v a p o r a t i o n o f solvent.  This material  (mp  s p e c t r o s c o p i c means and was  129-135) was  almost pure as d e t e r m i n e d  o b t a i n e d i n 62% o v e r a l l y i e l d based  by  on  starting dihydrocatharanthinol. Much o f our e a r l i e r work i n t h i s sequence was  f r u s t r a t e d by the  a p p a r e n t l y complex m i x t u r e s o b t a i n e d from t h i s r e a c t i o n as by  tic  evidenced  (both a l u m i n a and s i l i c a ) on t h e crude p r o d u c t as w e l l as a  m u l t i t u d e o f p r o d u c t s o b t a i n e d by column chromatography. i n f a c t t h a t t h e 5,18-seco-diene  I t t u r n e d out  o b t a i n e d c r y s t a l l i n e and pure by the  above p r o c e d u r e a l s o gave an e x t r e m e l y complex m i x t u r e on  tic  (about  e i g h t s p o t s on b o t h a l u m i n a and s i l i c a ) and i t became obvious a t t h i s p o i n t t h a t t h e m a t e r i a l was  very u n s t a b l e to chromatographic  procedures.  An a n a l y t i c a l l y pure sample, o b t a i n e d by s u b l i m a t i o n , mp was  exposed  to a detailed spectroscopic analysis.  136-136.5  High r e s o l u t i o n mass  s p e c t r o m e t r y gave the c o r r e c t m o l e c u l a r f o r m u l a , ^20^24^2' ^  o r  t  ^  ie  compound.  The enamine gave a s t r o n g i r a b s o r p t i o n a t 1657 cm  the s i n g l e enamine p r o t o n o f t h i s system appeared a t s i n g l e t i n t h e nmr spectrum.  4.29  x  and  as a b r o a d  The e x o c y c l i c o l e f i n was apparent as 47  p a r t o f t h e v i n y l - i n d o l e chromophore i n the uv ( A  306),  by t h e  IIT13-X  a b s o r p t i o n s a t 1408 and 880 cm T 4.75  and 4.89  i n t h e nmr.  1  i n the i r ,  and two s i n g l e t s a t  F i n a l l y s p e c t r o s c o p i c comparison w i t h an  a u t h e n t i c sample o f t h e 5,18-seco-diene system d e r i v e d from v o a c a n g i n o l 0-tosylate  ( f i g u r e 8) w h i c h d i f f e r s from our compound o n l y i n t h e  p r e s e n c e o f the C ^ - m e t h o x y l > e s t a b l i s h e d w i t h c e r t a i n t y t h a t our 46 m a t e r i a l p o s s e s s e d the d e s i r e d s t r u c t u r e ( 7 8 ) . R e d u c t i o n o f t h i s compound w i t h sodium b o r o h y d r i d e i n methanol produced t h e e x p e c t e d e x o c y c l i c o l e f i n still  (79).  The nmr o f t h i s m a t e r i a l  showed t h e p r o t o n s a t t r i b u t e d t o t h e e x o c y c l i c o l e f i n i c p r o t o n s  as o b s e r v e d i n t h e s t a r t i n g m a t e r i a l but t h e s i n g l e p r o t o n s i n g l e t a t t r i b u t e d t o the enamine system had d i s a p p e a r e d .  The  spectrum a l s o showed t h e same v i n y l i n d o l e chromophore.  ultraviolet The y i e l d o f  t h e o v e r a l l sequence from d i h y d r o c a t h a r a n t h i n o l t o the e x o c y c l i c  olefin  (79) was optimum (72%) when the i n t e r m e d i a t e s e c o - d i e n e (78) was  not  i s o l a t e d but i m m e d i a t e l y reduced d i r e c t l y i n t h e r e a c t i o n m i x t u r e . The analogous r e a c t i o n sequence u s i n g t h e m e s y l a t e i n s t e a d o f t o s y l a t e was a l s o s t u d i e d .  The m e s y l a t e o f d i h y d r o c a t h a r a n t h i n o l (77b)  formed r e a d i l y by r e a c t i n g t h e s t a r t i n g m a t e r i a l w i t h m e t h a n e s u l p h o n y l c h l o r i d e i n p y r i d i n e a t 0°C. chromatography  T h i s m a t e r i a l c o u l d be p u r i f i e d by  a l t h o u g h w i t h c o n s i d e r a b l e l o s s and t h u s the b e s t y i e l d s  were o b t a i n e d by the use o f t h e crude m a t e r i a l i n the subsequent displacement r e a c t i o n .  D i s p l a c e m e n t o f t h e m e s y l a t e i n t h i s case  was  - 42  -  c a r r i e d out u s i n g p o t a s s i u m t e r t - b u t o x i d e i n t e r t - b u t a n o l . ii intermediate  The  (78) c o u l d not be i s o l a t e d from t h i s r e a c t i o n m i x t u r e . I  Sodium b o r o h y d r i d e  reduction of t h i s mixture  gave the e x o c y c l i c o l e f i n  i d e n t i c a l t o t h a t from the t o s y l a t e sequence but i n much lower y i e l d s i  (20%). The  above s t u d i e s had now  provided,  i n good y i e l d , an enamine  g r o u p i n g i n the nine-membered r i n g c l e a v a m i n e - t y p e system.  I t was  n e c e s s a r y t o e f f e c t an i s o m e r i z a t i o n o f t h i s double.bond t o  the  C^-C^  now  position. Our  f i r s t approach t o t h i s problem was  t o attempt t o dehydrogenate  t h i s t e t r a h y d r o p y r i d i n e system t o e i t h e r the d i h y d r o p y r i d i n e or the aromatic  pyridinium s a l t .  intermediates  fully  S e l e c t i v e r e d u c t i o n on e i t h e r o f t h e s e  i n a manner p a r a l l e l t o t h a t attempted on t h e a c i d c a t a l y z e d  r i n g opened s p e c i e s d e r i v e d from d i h y d r o c a t h a r a n t h i n e  ( c f . f i g u r e 7)  c o u l d p r o v i d e an e n t r y t o the c l e a v a m i n e system b e a r i n g a  C^-C^  (81)  (83)  (82)  - 43 -  I double bond.  A l t h o u g h a r o m a t i z a t i o n would be t h e d r i v i n g f o r c e t h e r e b y j  f a v o u r i n g the f o r m a t i o n o f the i n t e r m e d i a t e p y r i d i n i u m s a l t  ( 8 2 ) , an  e x a m i n a t i o n o f t h e m o l e c u l a r models o f t h i s i n t e r m e d i a t e showed i t t o be s e v e r e l y s t r a i n e d and i t was  thought t h a t d e h y d r o g e n a t i o n  would  not o c c u r t o t h i s e x t e n t . However, the d i h y d r o p y r i d i n i u m s a l t (81) 3 which r e t a i n s an sp h y b r i d i z e d c a r b o n at t h e b r i d g e d p o s i t i o n i s n o t s t r a i n e d and would be e x p e c t e d t o form. R e d u c t i o n o f such a system 37 had been a c c o m p l i s h e d w i t h sodium b o r o h y d r i d e d e s i r e d d i e n e system  and;would l e a d t o t h e  ( c f . f i g u r e 6, 56 ->• 6 0 ) .  R e a c t i o n of the seco-diene t e m p e r a t u r e l e d t o t h e immediate  (78) w i t h DDQ  i n benzene a t room  f o r m a t i o n o f a dark green p r e c i p i t a t e .  T h i s m a t e r i a l on r e d u c t i o n w i t h sodium b o r o h y d r i d e i n methanol  led to  a number o f p r o d u c t s , a major one b e i n g the e x o c y c l i c o l e f i n ( 7 9 ) . The r e m a i n i n g p r o d u c t s showed i n d o l e a b s o r p t i o n i n the uv s p e c t r a i n s t e a d o f t h e v i n y l - i n d o l e system which was n e c e s s a r y f o r our f u r t h e r studies.  D e h y d r o g e n a t i o n w i t h m e r c u r i c a c e t a t e l e d t o a v e r y complex  mixture of products.  The uv s p e c t r a o f f r a c t i o n s from the  chromato-  graphy o f t h i s m i x t u r e a l s o i n d i c a t e d an i n d o l e chromophore. An e x a m i n a t i o n o f t h e model o f t h e d e s i r e d d i e n e p r o d u c t  (83)  i n d i c a t e d t h a t i t i s more, d i f f i c u l t f o r t h i s s t r u c t u r e t h a n i t i s f o r the o l e f i n  ( 7 9 ) , t o e x i s t i n a c o n f o r m a t i o n which would a l l o w t h e  e x o c y c l i c double bond t o be i n t h e p l a n e o f t h e i n d o l e system and hence i n conjugation with i t .  Thus a l t h o u g h t h e o l e f i n  (79) e x h i b i t s the  c h a r a c t e r i s t i c v i n y l - i n d o l e a b s o r p t i o n , t h e d i e n e which c o u l d c o n c e i v a b have t h e e x o c y c l i c double bond i n a p l a n e o r t h o g o n a l t o t h a t o f the i n d o l e m o i e t y , might i n such a case e x h i b i t a s i m p l e i n d o l e a b s o r p t i o n . The m u l t i t u d e o f p r o d u c t s o b t a i n e d from t h e d e h y d r o g e n a t i o n  reactions  - 44  i |  c o u l d not t h e r e f o r e be i g n o r e d as b e i n g u n d e s i r e d m a t e r i a l s j u s t i  because they e x h i b i t e d an i n d o l e a b s o r p t i o n i n the uv From t h e s e i n i t i a l experiments  spectrum.  i t became c l e a r t h a t i s o l a t i o n o f  t h e d i e n e (83) i n r e a s o n a b l e y i e l d from t h i s d e h y d r o g e n a t i o n - r e d u c t i o n approach might be d i f f i c u l t . simplified  I t was  thought t h a t t h i s t a s k c o u l d be  c o n s i d e r a b l y i f t h i s compound were o b t a i n e d f i r s t v i a a  pathway s t a r t i n g w i t h a model s u b s t a n c e a l r e a d y c o n t a i n i n g t h e d e s i r e d double bond.  I f t h e model sequence c o u l d p r o v i d e t h e d i e n e , i t s  s t a b i l i t y , s p e c t r a l p r o p e r t i e s and p a r t i c u l a r l y p r o c e d u r e s f o r i t s i s o l a t i o n c o u l d be s t u d i e d .  I t would t h e n be an e a s i e r m a t t e r t o  d e t e r m i n e whether t h e d e h y d r o g e n a t i o n - r e d u c t i o n approach was  actually  c a p a b l e o f p r o d u c i n g t h i s compound and i f s o , t h e n t o s e t about o p t i m i z i n g the r e a c t i o n c o n d i t i o n s . The model s u b s t a n c e which appeared a l k a l o i d , catharanthine.  i d e a l f o r t h i s study was  R i n g opening o f c a t h a r a n t h i n o l - O - t o s y l a t e  (85) would g i v e t h e same i n t e r m e d i a t e (81) d e s i r e d i n t h e reaction.  the  dehydrogenation  R e d u c t i o n o f t h i s compound would t h e n g i v e the d i e n e ( 8 3 ) .  - 45 -  | C a t h a r a n t h i n o l (84) o b t a i n e d by l i t h i u m aluminum h y d r i d e r e d u c t i o n  j o f c a t h a r a n t h i n e was t o s y l a t e d i n t h e u s u a l manner. was  T h i s compound  s u b j e c t e d t o c o n d i t i o n s i d e n t i c a l t o t h o s e s u c c e s s f u l l y employed  i n t h e case o f d i h y d r o c a t h a r a n t h i n o l - O - t o s y l a t e .  The p r o d u c t o b t a i n e d j  was n o t i s o l a t e d b u t s u b j e c t e d i m m e d i a t e l y t o sodium b o r o h y d r i d e reduction.  A complex m i x t u r e o f p r o d u c t s was o b t a i n e d .  Attempts t o  i s o l a t e t h e s e m a t e r i a l s by chromatography l e d t o an even worse p r o d u c t m i x t u r e t h a n had been o b s e r v e d i n t h e p r e v i o u s s t u d i e s . I t was now c l e a r t h a t t h i s p r o c e d u r e would p r o v i d e no s i m p l e s o l u t i o n t o o u r problem and we t u r n e d t o an a l t e r n a t i v e method f o r t h e p r e p a r a t i o n o f t h e d e s i r e d d i e n e (83) . Carbomethoxycleavamine  C0 Me  CH 0R  2  (60)  (60) had  2  ( 8 6 ) , R=H (87) , R=Tosyl (88) , R=Acetyl (89) _, R = 3 , 5 - D i n i t r o b e n z o y l  (83)  - 46 -  '  •  i  '  I i  most o f t h e r e q u i r e d s t r u c t u r a l f e a t u r e s and a c o n v e r s i o n o f the c a r b o methoxy f u n c t i o n t o a methylene group would p r o v i d e t h e d i e n e ( 8 3 ) . i carbomethoxy group i n (60) was h y d r i d e t o 18-hydroxymethyl  r e a d i l y reduced by l i t h i u m aluminum  ., c l e a v a m i n e  (86).  Dehydration using a  v a r i e t y o f c o n d i t i o n s gave no e n c o u r a g i n g r e s u l t s .  The  corresponding  t o s y l a t e (87) decomposed r a p i d l y t o g i v e a m i x t u r e o f p r o d u c t s . a c e t a t e (88) was  The  The  c o n s i d e r a b l y more s t a b l e and t r e a t m e n t w i t h s t r o n g  base gave m a i n l y unchanged s t a r t i n g m a t e r i a l .  P y r o l y s i s , however, gave  a p r o d u c t m i x t u r e which on t i c showed a continuum  of spots.  The  3,5-  d i n i t r o b e n z o a t e (89) was p r e p a r e d i n an attempt t o a c h i e v e an i n t e r m e d i a t e between t h e u n s t a b l e t o s y l a t e and s t a b l e a c e t a t e . d e r i v a t i v e w i t h a number o f bases produced  Treatment o f t h i s  a mixture of the unreacted  b e n z o a t e , t h e c o r r e s p o n d i n g a l c o h o l and some v e r y p o l a r m a t e r i a l s which because o f t h e i r p o l a r n a t u r e c o u l d be d i s r e g a r d e d as not b e i n g t h e desired diene.  This c o l l e c t i o n of negative r e s u l t s discouraged  f u r t h e r work i n t h i s d i r e c t i o n and thus an a l t e r n a t e study t o e f f e c t the m i g r a t i o n o f t h e double bond i n the s e c o - d i e n e system  (78)  was  initiated. Enamines a r e s u b j e c t t o e l e c t r o p h i l i c s u b s t i t u t i o n and  addition  r e a c t i o n s ; b o t h t h e n i t r o g e n and B-carbon are c a p a b l e o f r e a c t i n g w i t h 49 electrophiles.  I n our case the B - p o s i t i o n o f t h e enamine i s a t e r t i a r y  c a r b o n and s t e r i c f a c t o r s might i n f a c t f a v o u r a t t a c k at the n i t r o g e n . However, i f r e a c t i o n d i d o c c u r a t t h e t e r t i a r y B - p o s i t i o n , the s u b s t i t u e n t t h u s i n t r o d u c e d s h o u l d be e a s i l y e l i m i n a t e d and t h e r e b y r e i n t r o d u c e a d o u b l e bond i n t o t h e  system.  - 47 -  j . |  The r e a c t i o n o f c h o i c e i n our case was h y d r o b o r a t i o n .  Hydrobora-  t i o n o f enamines has been used i n the conversion^ o f ketones t o a l k e n e s v i a an i n t e r m e d i a t e enamine.  I n our system, h y d r o b o r a t i o n f o l l o w e d by  RCOOH  o x i d a t i o n would be e x p e c t e d t o i n t r o d u c e an h y d r o x y l f u n c t i o n a t the position.  T h i s i s t h e same p o s i t i o n which b e a r s t h e h y d r o x y l i n t h e  n a t u r a l dirners v i n b l a s t i n e  (16) and v i n c r i s t i n e  (19) . The a l c o h o l  o b t a i n e d from t h i s r e a c t i o n would t h e r e f o r e be a v a l u a b l e i n t e r m e d i a t e f o r subsequent d i m e r i z a t i o n r e a c t i o n s . r e a d i l y d e h y d r a t e t o the c o r r e s p o n d i n g shown t h a t velbanamine  Furthermore t e r t i a r y a l c o h o l s olefins.  I t had a l r e a d y been  ( 2 2 ) , t h e monomeric u n i t d e r i v e d from t h e degrada-  t i o n o f v i n b l a s t i n e , d e h y d r a t e d t o g i v e c l e a v a m i n e (23) under a c i d i c 21 conditions. the unsaturated C_-C.  position.  T h i s approach c o u l d t h e r e f o r e a l s o be e x p e c t e d t o y i e l d compound (86) h a v i n g t h e double bond i n the d e s i r e d I t was e x p e c t e d t h a t t h e e x o c y c l i c double bond would  48  a l s o be h y d r a t e d i n t h i s p r o c e s s .  Oxidation o f the primary alcohol  thus formed, f o l l o w e d by e s t e r i f i c a t i o n o f t h e ackd would p r o v i d e a c o n v e n i e n t method f o r i n t r o d u c i n g t h e carbomethoxy f u n c t i o n .  CH 0H 2 o  (78)  (90)  CH 0H 2  (86)  I n t h e c o u r s e o f t h i s work and i n subsequent  hydroboration experi-  ments, i t was found t h a t t h e t e r t i a r y n i t r o g e n i n t h e s e compounds c o u l d complex w i t h t h e d i b o r a n e . t o form amine-borane a d d u c t s . were s t a b l e t o c h r o m a t o g r a p h i c  These adducts  s e p a r a t i o n and c o u l d be i s o l a t e d i n t h i s  manner as c r y s t a l l i n e m a t e r i a l s .  As a c l a s s o f compounds t h e s e amine-  borane complexes a r e e a s i l y i d e n t i f i e d by a medium t o s t r o n g , f a i r l y % b r o a d a b s o r p t i o n bonds i n t h e i r spectrum  i n t h e r e g i o n 2200-2400 cm  -1  u s u a l l y accompanied by a sharp a b s o r p t i o n a t about 2300 cm''' which i s an -  o v e r t o n e o f t h e BH^ asymmetric  d e f o r m a t i o n seen a t about 1150 cm~*.^"  - 49 i  i A convenient  method was  t o the f r e e b a s e s . b o r i n e from one  found t o c o n v e r t  these amine-borane complexes  T h i s p r o c e d u r e s i m p l y i n v o l v e d exchange o f t h e  amine base t o a s t r o n g e r amine base.  Thus, t h e complex  when r e f l u x e d i n t e t r a h y d r o f u r a n i n the p r e s e n c e o f t r i e t h y l a m i n e , p r o v i d e d the f r e e base and  triethylamine-borane.  Some o f the  complexes o b t a i n e d were found t o undergo o n l y p a r t i a l exchange u s i n g t h i s p r o c e d u r e ; an e q u i l i b r i u m m i x t u r e was  obtained.  In t h e s e  complete exchange c o u l d be a c h i e v e d by u s i n g t r i e t h y l a m i n e as  cases, solvent  at r e f l u x i n g temperature. The h y d r o b o r a t i o n  o f the s e c o - d i e n e system (78) i n t e t r a h y d r o f u r a n  u s i n g an excess o f d i b o r a n e , t h e s e was product  led to a mixture  of products.  shown t o be the amine-borane complex o f the major  One  of  decomposition  o b s e r v e d p r e v i o u s l y i n o t h e r r e a c t i o n s o f t h e enamine system.  Three o t h e r m a t e r i a l s o f i n t e r e s t were o b t a i n e d . t h e s e compounds i n d i c a t e d t h a t one was were amine-boranes.  The  i r spectra of  the a l c o h o l and the o t h e r  two  Both o f t h e s e compounds gave on exchange a compound  which was  i d e n t i c a l w i t h the a l c o h o l o b t a i n e d d i r e c t l y from t h e r e a c t i o n  mixture.  The p r e s e n c e o f two amine-boranes which y i e l d on exchange the  same compound i n d i c a t e s t h a t t h e s e compounds a r e most a t the n i t r o g e n atom. i n v e r s i o n and  likely  epimeric  I t . i s w e l l known t h a t amines undergo f a c i l e  i t i s reasonable  t o expect t h a t each o f the i n v e r s i o n  epimers formed by t e r t i a r y amines c o u l d be t r a p p e d by c o m p l e x i n g w i t h the l o n e p a i r o f e l e c t r o n s . The  alcohol obtained  from t h i s h y d r o b o r a t i o n  the i r s p e c t r u m , an a b s o r p t i o n at 3300 cm (v C-0  f o r primary  * (v 0-H)  r e a c t i o n showed i n and a t 1045  cm  ^  a l c o h o l s ) w h i l e the uv gave a t y p i c a l i n d o l e a b s o r p t i o n .  - 50 -  j Nmr  showed a l o s s o f b o t h t h e enamine p r o t o n and t h e two p r o t o n s o f the  e x o c y c l i c methylene.  Two  m u l t i p l e t s o f i n t e r e s t appeared, a one p r o t o n i  q u i n t u p l e t (two o v e r l a p p i n g t r i p l e t , J = 9 and 5 Hz) a t T 5.81 two p r o t o n d o u b l e t ( J = 5 Hz) a t T 6.24.  In a decoupling  and a  experiment,  i r r a d i a t i o n a t t h e f r e q u e n c y o f t h e d o u b l e t , reduced t h e q u i n t u p l e t t o a broad doublet (J = 9 Hz).  These d a t a were i n a c c o r d w i t h t h e h y d r a t i o n  o f t h e e x o c y c l i c o l e f i n which would g i v e an hydroxymethyl on a t e r t i a r y c a r b o n .  grouping  No e v i d e n c e f o r t h e h y d r a t i o n o f the enamine  p a r t o f t h i s m o l e c u l e was  o b t a i n e d a l t h o u g h i t was  nmr,  no l o n g e r p r e s e n t i n the p r o d u c t .  t h a t t h e enamine was  c l e a r from the i r and  The mass spectrum gave t h e f i r s t i n d i c a t i o n t h a t t h i s a l c o h o l not the d e s i r e d d i o l  (90) . The m o l e c u l a r i o n was  seen a t m/e  was  312  i n s t e a d o f t h e e x p e c t e d v a l u e o f 326, and showed a f r a g m e n t a t i o n p a t t e r n i n d i c a t i n g r e d u c t i o n o f t h e enamine r a t h e r t h a n h y d r a t i o n .  A pure  sample o f t h e a l c o h o l o b t a i n e d by s u b l i m a t i o n (mp 146.5-147.5) gave t h e c o r r e c t a n a l y s i s f o r t h e reduced enamine a l c o h o l . To e s t a b l i s h t h e i d e n t i t y o f t h i s compound, t h e o l e f i n hydroborated.  (79)  was  As i n t h e p r e v i o u s c a s e , two amine-borane complexes were  i s o l a t e d a l o n g w i t h the f r e e a l c o h o l . t r i e t h y l a m i n e produced  Exchange o f t h e s e complexes w i t h  t h e same f r e e a l c o h o l .  T h i s a l c o h o l (92)  i d e n t i c a l w i t h t h a t o b t a i n e d from the s e c o - d i e n e as shown by o f s p e c t r a l d a t a , t i c , and m e l t i n g p o i n t s .  was  comparison  C0 Me 2  (32)  R e d u c t i o n o f 188-carbomethoxy-48-dihydrocleavamine l i t h i u m aluminum h y d r i d e gave t h e same a l c o h o l  (92) and  (93) w i t h established  w i t h o u t doubt t h a t the s t r u c t u r e of t h e a l c o h o l o b t a i n e d from b o t h t h e olefin  (79) and s e c o d i e n e (78) by h y d r o b o r a t i o n was  186-hydroxymethyl-  43-dihydrocleavamine. In an attempt t o l i m i t the r e d u c t i o n o f the enamine system, a number o f h y d r o b o r a t i o n e x p e r i m e n t s were r u n u s i n g d e c r e a s i n g amounts of diborane.  I n the above h y d r o b o r a t i o n o f t h e s e c o d i e n e system a t e n -  f o l d excess o f d i b o r a n e had been employed.  When t h i s excess d e c r e a s e d  t o 0.5 moles based on m o n o - a l k y l b o r a n e s b e i n g formed r a t h e r t h a n d i or t r i - a l k y l b o r a n e s , the o l e f i n  (79) and i t s amine-borane  were  i s o l a t e d from t h e r e a c t i o n m i x t u r e i n a d d i t i o n t o t h e p r o d u c t s n o t e d  -• 52 before. before  R e d u c t i o n o f t h e enamine system, t h e r e f o r e , was o c c u r r i n g hydroboration  o f t h e e x o c y c l i c d o u b l e bond.  d i b o r a n e was f u r t h e r d e c r e a s e d , c a r b o n y l obtained  When t h e excess o f  c o n t a i n i n g p r o d u c t s were  i n d i c a t i n g h y d o l y s i s o f u n r e a c t e d enamine presumably i n t h e  work up.  ' '  These r e s u l t s show t h a t t h e d e s i r e d h y d r a t i o n o f t h i s enamine system c o u l d n o t be a c h i e v e d by h y d r o b o r a t i o n r o u t e had t o be d e v i s e d .  and t h u s an a l t e r n a t e  A number o f r e a g e n t s have been used t o  52 oxygenate enamines.  The r e a c t i o n g e n e r a l l y g i v e s a g-oxygenated  iminium s a l t intermediate  which n o r m a l l y  t h e a-oxygenated c a r b o n y l  system.  p e r m i s s i b l e and t h e i n t e r m e d i a t e  i s then hydrolyzed  t o give  I n o u r case h y d r o l y s i s was n o t imminium s a l t would have t o be  r e d u c e d t o g i v e t h e g-oxygenated amine.  Oxidation  o f an i n d o l e m o i e t y , however, g e n e r a l l y p r e s e n t s  i n the presence  a problem because 53  the i n d o l e group i s i t s e l f r a p i d l y o x i d i z e d under m i l d The  use o f t h e c o n v e n t i o n a l  conditions.  r e a g e n t s f o r enamine o x i d a t i o n s , such as  p e r a c i d s , was t h e r e f o r e n o t s u i t a b l e . Our  c h o i c e o f r e a g e n t f o r t h i s r e a c t i o n was osmium t e t r o x i d e .  A l t h o u g h t h e r e have been no p r e v i o u s  reports o f t h i s reagent having  been used f o r t h e h y d r o x y l a t i o n o f enamines, examples o f i t s use i n o t h e r systems i n d i c a t e d t h a t i t would p r o b a b l y s e r v e w e l l i n c a r r y i n g out t h e r e q u i r e d t r a n s f o r m a t i o n .  F o r example, g - a l l y l i n d o l e had been  oxidized t o 3,3'-indolylpropan-1,2-diol 54 t e t r o x i d e a t low t e m p e r a t u r e . system was u n a f f e c t e d Use  i n h i g h y i e l d u s i n g osmium  Under t h e s e c o n d i t i o n s , t h e i n d o l e  and r e a c t i o n was s p e c i f i c t o t h e d o u b l e bond.  o f t h i s r e a c t i o n was made s u b s e q u e n t l y by v a n Tamelen i n h i s  - 53 i  i yohimbine  s y n t h e s e s t o a c h i e v e h y d r o x y 1 a t i o n o f t h e c y c l i c e n o l (94)  to the d i o l  ( 9 5 ) . I n b o t h o f t h e above i n s t a n c e s , t h e double bond  which i s o x i d i z e d i s a c t i v a t e d t o e l e c t r o p h i l i c a t t a c k . The enamine double bond would a l s o be e x p e c t e d t o undergo f a c i l e a t t a c k and i t seemed r e a s o n a b l e t h a t h y d r o x y l a t i o n s h o u l d o c c u r under t h e s e conditions. The r e a c t i o n scheme e n v i s a g e d f o r t h e c o n v e r s i o n o f t h e s e c o d i e n e (78) t o c l e a v a m i n e and/or velbanamine tetrol  i s p r e s e n t e d i n f i g u r e 11.  The  (96) r e s u l t i n g from t h e o s m y l a t i o n o f 78 would be e x p e c t e d t o  undergo s e l e c t i v e r e d u c t i o n t o t h e t r i o l  (97) and t h e l a t t e r , v i a  p e r i o d a t e c l e a v a g e and r e d u c t i o n s h o u l d p r o v i d e t h e d i o l ( 9 9 ) . H y d r o g e n o l y s i s o f t h e " b e n z y l i c " a l c o h o l i n t h i s compound would t h e n g i v e (100) which s h o u l d be e i t h e r velbanamine  (22) o r i t s epimer.  D e h y d r a t i o n o f t h i s compound would g i v e c l e a v a m i n e ( 2 3 ) . The o s m y l a t i o n r e a c t i o n was c a r r i e d out a t d r y - i c e - a c e t o n e temperature u s i n g e x a c t l y two e q u i v a l e n t s o f osmium t e t r o x i d e i n a t e t r a h y d r o f u r a n - p y r i d i n e s o l v e n t system.  The major p r o d u c t o b t a i n e d  i n 35-40% y i e l d gave s p e c t r a l i n d i c a t i o n s o f b e i n g t h e c o r r e c t  tetrol.  - 54 -  CH  OH  (98) (97)  (23)  gure 11.  S y n t h e s i s o f c l e a v a m i n e (23) from the s e c o d i e n e osmium t e t r o x i d e  oxidation.  (83)  - 55 The uv spectrum showed a t y p i c a l i n d o l e a b s o r p t i o n w h i l e the i r spectrum c o n f i r m e d t h e p r e s e n c e  o f an a l c o h o l w i t h t h r e e b r o a d  bands i n the r e g i o n , 3300-3500 cm *.  overlapping  No m o l e c u l a r i o n c o u l d be seen  i n t h e mass spectrum, ( f i g u r e 12) t h e h i g h e s t peak a p p e a r i n g a t 342  (M-18).:  m/e  High r e s o l u t i o n mass measurement e s t a b l i s h e d the  f o r m u l a ^20^26^2^3'  c o r r e s  P  o n (  i i n g not u n e x p e c t e d l y ,  from t h e m o l e c u l a r f o r m u l a ^20^28^2^4' ( f i g u r e 14) was  ^  particularly instructive.  e  n m r  s  P  t o a l o s s o f water  e c 1 : r u m  A one-proton  °f t h i s compound s i n g l e t at T  5.42  58 was  i n the expected p o s i t i o n f o r a carbinol-amine proton.  somewhat broadened s i n g l e t a t x 6.36,  i n t e g r a t i n g f o r two p r o t o n s  w h i c h showed a d r a m a t i c s h a r p e n i n g on d e u t e r i u m a s s i g n e d t o t h e hydroxymethyl  A  function.  and  exchange, c o u l d be  Deuterium exchange r e s u l t e d  i n t h e l o s s o f a t l e a s t t h r e e p r o t o n s , o t h e r than the i n d o l e N-H, shown by comparison o f t h e i n t e g r a l b e f o r e and a f t e r exchange.  as Two  o f t h e s e h y d r o x y l p r o t o n s appeared as s u r p r i s i n g l y sharp s i n g l e t s a t x 6.58  and x 7.51  and t h i s r e s u l t i n d i c a t e s t h a t t h e s e p r o t o n s  are  p r o b a b l y e x p e r i e n c i n g s t r o n g i n t r a m o l e c u l a r hydrogen bonding.  The  r e l a t i v e l y n o n - p o l a r n a t u r e o f t h i s compound as shown on t i c and column chromatography u n d o u b t e d l y I t was  expected  a l s o r e f l e c t s t h i s same phenomenon.  t h a t the c a r b i n o l - a m i n e h y d r o x y l f u n c t i o n would  r e a d i l y undergo h y d r o g e n o l y s i s w i t h a m e t a l h y d r i d e r e d u c i n g The  complex n o r m a l l y o b t a i n e d from t h e r e a c t i o n o f an  alcoholic  f u n c t i o n and t h e h y d r i d e would e l i m i n a t e r e a d i l y t o form an s a l t intermediate.  T h i s i n t e r m e d i a t e i n the p r e s e n c e  agent.  iminium  of a d d i t i o n a l  m e t a l h y d r i d e would r a p i d l y form t h e s a t u r a t e d amine. The  t e t r o l was,  t h e r e f o r e , t r e a t e d a t room temperature  w i t h sodium  RELATIVE  INTENSITY  RELATIVE INTENSITY  - 9S "  - 58 -  i i  |  b o r o h y d r i d e i n methanol.  The r e s u l t a n t compound formed i n e s s e n t i a l l y  q u a n t i t a t i v e y i e l d had a l l t h e p r o p e r t i e s e x p e c t e d f o r the t r i o l The mass spectrum  ( f i g u r e 13) gave a p a r e n t i o n a t m/e  344 and h i g h  r e s o l u t i o n o f t h i s peak e s t a b l i s h e d the f o r m u l a , 2 0 2 8 2 ° 3 ' C  H  N  o f t h e i m p o r t a n t f e a t u r e s o f t h i s spectrum i s the fragment m/e  154.  (97).  0 n e  i o n at  By a n a l o g y w i t h t h e mass s p e c t r a l work done on v e l b a n a m i n e ,  t h i s i o n can be c o n s i d e r e d t o r e s u l t from t h e f r a g m e n t a t i o n shown i n s t r u c t u r e 101.*  4  I t t h e r e f o r e p r e s e n t e d good e v i d e n c e f o r t h e p r e s e n c e  CH 0H 2  (101)  o f an hydroxy1 f u n c t i o n i n the p i p e r i d i n e p o r t i o n o f the compound. The i r spectrum showed t h r e e b r o a d o v e r l a p p i n g a b s o r p t i o n s i n the N-H,  0-H  stretching region.  Comparison  o f the nmr  ( f i g u r e 15) o f  t h i s compound w i t h t h a t . o f the t e t r o l showed t h e l o s s o f the s i n g l e t a t t r i b u t e d t o t h e c a r b i n o l amine p r o t o n . t h e h y d r o x y m e t h y l f u n c t i o n was  The t w o - p r o t o n s i n g l e t o f  s t i l l p r e s e n t , a p p e a r i n g now  at T  6.22.  Deuterium exchange i n d i c a t e d a l o s s o f t h r e e p r o t o n s o t h e r t h a n the i n d o l e N-H;  o n l y one o f t h e s e h y d r o x y l p r o t o n s can be seen as a  b r o a d s i n g l e t a t x 0.29.  Loss o f t h e o t h e r two p r o t o n s i s shown by  t h e i n t e g r a t i o n a f t e r d e u t e r i u m exchange  - 60 I  | F u r t h e r h y d r o g e n o l y s i s o f the t r i o l  c o u l d be a c h i e v e d when i t i  was  t r e a t e d w i t h l i t h i u m aluminum h y d r i d e i n r e f l u x i n g t e t r a h y d r o f u r a n .  Under t h e s e c o n d i t i o n s , t h e " b e n z y l i c " h y d r o x y l a t C^g lost.  (see 102)  was  A l t h o u g h t h i s r e a c t i o n was not on the main s y n t h e t i c pathway,  the p r o d u c t i o n of t h i s d i o l  (102) was u s e f u l because i t s nmr  spectrum  p r o v e d c o n c l u s i v e l y the o s m y l a t i o n o f t h e e x o c y c l i c o l e f i n p o r t i o n of  the s t a r t i n g secodiene.  The nmr  spectrum o f 102 p o s s e s s e d  (97)  q u i n t u p l e t a t T 5.90  (102)  ( J = 5 Hz) and a d o u b l e t a t T 6.28  v i r t u a l l y i d e n t i c a l t o the m u l t i p l e t s observed f o r cleavamine 16). of  the t r i o l  ( J = 5 Hz),  18g-hydroxymethyl-  (86) and 1 8 3 - h y d r o x y m e t h y l d i h y d r o c l e a v a m i n e  I t was  a  (92)  (figure  thus c e r t a i n t h a t the compound o b t a i n e d from r e d u c t i o n 97 was  F o r t h e purpose  r e p r e s e n t e d by  102.  o f c o m p l e t i n g t h e c l e a v a m i n e and  functionalized  c l e a v a m i n e s y n t h e s e s i t was n e c e s s a r y t o remove t h e C^g-hydroxymethyl f u n c t i o n and reduce t h i s C  1 Q  p o s i t i o n to i t s saturated state.  f i r s t s t e p i n t h i s p r o c e s s was g l y c o l p o r t i o n o f the t r i o l . consumed) was  The  the p e r i o d a t e c l e a v a g e o f the v i c i n a l The b e s t y i e l d ,  o b t a i n e d when t h i s r e a c t i o n was  (about 60% based on c a r r i e d out i n an  triol  - 61  -  Chemical s h i f t C. - - p r o t o n A  methylene protons, B  1 8  188-hydroxymethylcleavamine  5.74  183-hydroxymethyl48-dihydrocleavamine diol  6.32  5.84  (102)  i n x of  6.27  5.90  6.28  i  B  A  F i g u r e 16.  Partial  nmr spectrum i l l u s t r a t i n g t h e p e r t i n e n t  p a t t e r n s c o r r e s p o n d i n g t o the 18B-hydroxymethyl  a c e t o n e - w a t e r s o l u t i o n a t 0°C.  signal function.  The s p e c t r a l d a t a o f the p r o d u c t  i n e x c e l l e n t agreement w i t h t h a t e x p e c t e d f o r t h e k e t o l  (98).  m o l e c u l e has one r e m a i n i n g h y d r o x y l f u n c t i o n and t h i s f e a t u r e e v i d e n t i n t h e i r spectrum by a b r o a d 0-H 3100  This was  s t r e t c h i n g absorption at  cm * and i n the nmr by a b r o a d o n e - p r o t o n s i n g l e t a t x 7.82  disappeared  o n  d e u t e r i u m exchange.  was^  which  The extended c o n j u g a t i o n produced  by t h e C^g c a r b o n y l f u n c t i o n a f f e c t s the a r o m a t i c a b s o r p t i o n i n t h e uv and t h e c a r b o n y l a b s o r p t i o n i n the i r r e g i o n s . acylindole absorption  5 6  (x  M e 0 H  IT13.X  ( l o g E ) : 317  A typical  (4.25), and 238  2(4.16)) i s  62 o b s e r v e d in the uv and the c a r b o n y l s t r e t c h i n g a b s o r p t i o n i n i s o b s e r v e d a t 1615 cm  -1  which i s a l s o normal f o r t h i s  the i r  system.  57  F u r t h e r s t r o n g e v i d e n c e f o r t h i s s t r u c t u r e came from t h e mass spectrum ( f i g u r e 17).  High  resolution  on the p a r e n t i o n gave a  m o l e c u l a r c o m p o s i t i o n c o r r e s p o n d i n g t o t h e f o r m u l a o f the k e t o l . E x a m i n a t i o n o f t h e spectrum ( f i g u r e 17) showed a prominent i o n a t m/e  154.  A f r a g m e n t a t i o n analogous t o the one shown f o r t h e  t r i o l , namely f i s s i o n a and a this ion.  fragment  1  i n 103 would be e x p e c t e d t o p r o v i d e  Loss o f a 14 mass u n i t s  ( p r o b a b l y CH^)  from t h i s i o n would  (103)  r e s u l t i n t h e peak a t m/e  140.  The o t h e r h a l f o f t h e m o l e c u l e r e s u l t i n g  from t h e f i s s i o n a, a', c o u l d p r o v i d e t h e i o n a t m/e  157.  The  alternate  f r a g m e n t a t i o n s shown as b, a' c o u l d account f o r fragments a t m/e and 144, w h i l e f i s s i o n a, c would produce the i o n o b s e r v e d a t m/e Reduction of the k e t o l t o the d i o l  143 130.  (99) c o u l d be r e a d i l y a c h i e v e d  by t h e a c t i o n o f sodium b o r o h y d r i d e i n methanol a t room t e m p e r a t u r e . T h i s r e d u c t i v e p r o c e s s r e g e n e r a t e d the i n d o l e system and t h i s apparent from t h e uv spectrum.  Once a g a i n t h e mass spectrum  was (figure  18)  supported the c o r r e c t s t r u c t u r e .  m/e  154 and a h i g h r e s o l u t i o n mass measurement on the s t r o n g p a r e n t peak  The main fragment i o n appeared a t  RELATIVE INTENSITY  RELATIVE INTENSITY  - £9 "  - 64 -  | gave t h e m o l e c u l a r c o m p o s i t i o n  corresponding  t o the formula f o r the  diol.  | On t h e b a s i s o f t h e nmr spectrum ( f i g u r e 1 9 ) , t h e s t e r e o c h e m i s t r y  at C , 1C  one o f t h e t h r e e asymmetric c e n t r e s i n t h i s m o l e c u l e ,  j  16  assigned.  c o u l d be  I n t h e c o u r s e o f e a r l i e r s t u d i e s i n our l a b o r a t o r y on t h e 37  a c i d c a t a l y z e d r i n g opening o f c a t h a r a n t h i n e 59 of dihydrocatharanthine  and i n t h e t o t a l  synthes  alluded to e a r l i e r , a s e r i e s of dihydro-  c l e a v a m i n e d e r i v a t i v e s p o s s e s s i n g a v a r i e t y o f s u b s t i t u e n t s (carbomethoxyl,  methoxyl,  h y d r o x y l and n i t r i l e ) a t C^g had been o b t a i n e d .  I t was found t h a t t h e s e compounds c o u l d be c l a s s e d i n t o two groups, those w i t h the C - p r o t o n a b s o r b i n g i n t h e r e g i o n x 4.5-5.0, and its 1 0  those absorbing  in  of these chemical  t h e r e g i o n x 6.0-6.2.  These compounds by v i r t u e  s h i f t s , c o u l d be a s s i g n e d t o t h e 1 8 g - s u b s t i t u t e d o r  1 8 a - s u b s t i t u t e d s e r i e s r e s p e c t i v e l y . The r e a s o n f o r t h i s  dramatic  dependence o f t h e c h e m i c a l s h i f t o f t h i s p r o t o n t o i t s s t e r e o c h e m i s t r y can be a p p r e c i a t e d by c o n s i d e r i n g t h e c o n f o r m a t i o n a l s t r u c t u r e s which 37 60 a r e p o s s i b l e i n t h e s e two s e r i e s . ' I n t h e 1 8 3 - s u b s t i t u t e d compounds  (104)  (105)  !  - 66 -  (104) the C,g-proton i s i n c l o s e p r o x i m i t y t o the b a s i c n i t r o g e n atom o f t h e p i p e r i d i n e m o i e t y and i t would be e x p e c t e d t o absorb a t l o w e r i' f r e q u e n c y . ] Such a s i t u a t i o n does not p r e v a i l f o r the 1 8 a - s u b s t i t u t e d compounds (105) and a more normal resonance f r e q u e n c y would be a n t i c i p a t e d f o r the C - p r o t o n . 1 D  The c h e m i c a l s h i f t o b s e r v e d f o r the C , - p r o t o n i n the d i o l  (99)  0  1o  i s T 4.28.  T h i s i s c l e a r l y i n the r e g i o n f o r t h e 1 8 8 - s u b s t i t u t e d com-  pounds a l t h o u g h i n t h i s case i t i s s h i f t e d t o s l i g h t l y lower f i e l d t h a n i n the above mentioned compounds. e f f e c t must be a t t r i b u t e d t o t h e  T h i s enhanced  deshielding  a l c o h o l s u b s t i t u e n t s which can  be e x p e c t e d t o a f f e c t t h e c o n f o r m a t i o n o f the p i p e r i d i n e r i n g and hence, a l t e r t h e s p a t i a l r e l a t i o n between the n i t r o g e n and C^g-proton. T h i s same e f f e c t can be seen by a comparison o f t h e C^g-proton c h e m i c a l s h i f t f o r 18B-carbomethoxy-48-dihydrocleavamine and  188-carbomethoxy-  4 6 - d i h y d r o c l e a v a m i n e i n which t h e e t h y l group would a f f e c t t h e c o n f o r m a t i o n depending on i t s o r i e n t a t i o n r e l a t i v e t o the n i t r o g e n atom. T  The 4a-compound absorbs a t T 4.53 w h i l e t h e 48 absorbs a t  4.98. H y d r o g e n o l y s i s o f the d i o l  (99) t o t h e monohydroxy d e r i v a t i v e  (100)  c o u l d be a c h i e v e d u s i n g t h e c o n d i t i o n s p r e s c r i b e d by Dolby and c o w o r k e r s . <  These workers found t h a t 2 - i n d o l e c a r b i n o l d e r i v a t i v e s were hydrogeno l y z e d u s i n g l i t h i u m aluminum h y d r i d e i n e t h e r s o l v e n t s .  When  e t h y l e t h e r o r t e t r a h y d r o f u r a n was used as s o l v e n t , a m i x t u r e o f t h e a l c o h o l and t h e h y d r o g e n o l y z e d m a t e r i a l was u s u a l l y o b t a i n e d .  The  p r o p o r t i o n o f h y d r o g e n o l y z e d m a t e r i a l c o u l d be r a i s e d by c a r r y i n g out the r e a c t i o n i n r e f l u x i n g N-methylmorpholine o r i n d i o x a n e .  Thus, •  - 67 -  1 - h y d r o x y t e t r a h y d r o c a r b a z o l e was  c o n v e r t e d almost q u a n t i t a t i v e l y t o  tetrahydrocarbazole u s i n g b o i l i n g dioxane.  N-methyl-l-hydroxytetra-  h y d r o c a r b a z d l e , however, gave o n l y 21% o f t h e h y d r o g e n o l y z e d p r o d u c t . T h i s i n h i b i t i o n o f hydrogep.olysis by m e t h y l a t i o n o f the i n d o l e n i t r o g e n was observed i n a s e r i e s o f compounds and suggested t h a t the r e a c t i o n i n v o l v e d an e l i m i n a t i o n - a d d i t i o n sequence i n v o l v i n g an i m i n e i n t e r mediate such as (106).  Such a mechanism i s not p o s s i b l e when t h e  (106)  i n d o l e n i t r o g e n i s m e t h y l a t e d and i t was  s u g g e s t e d t h a t under d r a s t i c  c o n d i t i o n s some s i m p l e n u c l e o p h i l i c d i s p l a c e m e n t t a k e s p l a c e t o . g i v e t h e low y i e l d o f t h e h y d r o g e n o l y z e d p r o d u c t o b s e r v e d . I n our i n s t a n c e , t h e d e s i r e d d e r i v a t i v e  (100) c o u l d be o b t a i n e d  from t h e d i o l i n 44% y i e l d u s i n g l i t h i u m aluminum h y d r i d e i n r e f l u x i n g N-methylmorpholine.  The nmr  spectrum o f t h e _ p r o d u c t ( f i g u r e 20) shows  t h a t t h e peak a s s i g n e d t o the C^g-proton i n the d i o l has moved c o n s i d e r a b l y u p f i e l d t o x 6.56 T h i s u p f i e l d s h i f t was function. x 8.77  and now  appears as a complex m u l t i p l e t .  e x p e c t e d on l o s s o f t h e geminal h y d r o x y l  The r e m a i n i n g 0-H  g i v e s a broad, one-proton s i n g l e t at  which d i s a p p e a r s on d e u t e r i u m exchange.  High r e s o l u t i o n mass'  - 69 a n a l y s i s o f the p a r e n t i o n i n t h e mass spectrum e s t a b l i s h e d a m o l e c u l a r c o m p o s i t i o n c o n s i s t e n t w i t h the f o r m u l a f o r the mono-ol.  This  compound had t o be e i t h e r velbanamine ( 2 2 ) , the monomeric d e g r a d a t i o n p r o d u c t o f v i n b l a s t i n e and v i n c r i s t i n e o r the e p i m e r i c a l c o h o l . T h i n l a y e r c h r o m a t o g r a p h i c comparison o f our compound w i t h an a u t h e n t i c sample o f velbanamine o b t a i n e d by the e s t a b l i s h e d p r o c e d u r e from 21 vinblastine,  showed t h a t t h e s e compounds were hot the same.  The  j  mass spectrum o f our compound which has been named i s o v e l b a n a m i n e ( f i g u r e 21) was, however, v i r t u a l l y s u p e r i m p o s a b l e w i t h the spectrum o b t a i n e d f o r velbanamine r u n under the same c o n d i t i o n s and agrees 62 a l s o v e r y w e l l w i t h t h e p u b l i s h e d mass spectrum f o r v e l b a n a m i n e . T h i s r e s u l t p r o v i d e d s t r o n g e v i d e n c e f o r t h e f a c t t h a t t h e s e compounds were e p i m e r i c and t h i s s i t u a t i o n was p r o v e d by t h e n e x t s e r i e s o f reactions. I t was known t h a t velbanamine undergoes some d e h y d r a t i o n t o g i v e 2 c l e a v a m i n e (23) under t h e a c i d i c c o n d i t i o n used t o c l e a v e v i n b l a s t i n e . Because t h e h y d r o x y l group e l i m i n a t e d i s t h a t o f a t e r t i a r y an  alcohol,  t y p e e l i m i n a t i o n which need not have a p a r t i c u l a r s t e r e o c h e m i c a l  r e q u i r e m e n t , would be e x p e c t e d .  Therefore isovelbanamine should  dehydrate under the same . c o n d i t i o n s as v e l b a n a m i n e . Treatment o f i s o v e l b a n a m i n e w i t h c o n c e n t r a t e d s u l p h u r i c a c i d a t 0°C  f o r 2 hours gave a p p r o x i m a t e l y a 30% y i e l d o f c l e a v a m i n e as  i d e n t i f i e d by a comparison w i t h an a u t h e n t i c sample.  A p a r t from  e s t a b l i s h i n g t h e s t r u c t u r e o f 100, t h i s r e a c t i o n p r o v i d e d a t o t a l s y n t h e s i s o f c l e a v a m i n e s i n c e the s t a r t i n g m a t e r i a l f o r t h i s  sequence  d i h y d r o c a t h a r a n t h i n e , had a l r e a d y been s y n t h e s i z e d i n our l a b o r a t o r y .  100 154  8 OH  B 601 z  LU h-  -  u>  4CH 298  u •if l*  I »illll  ..tltl .In  1  T—"i m/e  H.hll I M  1  Ii  I  r  150  100  llii. r  uliii  -i  iih  .  ••  1  i  r  •  i |  Ji  il  IM  r  1  T  1  250  200  1 — i  --a o  r  300  F i g u r e 21. Mass spectrum o f i s o v e l b a n a m i n e (100). 100' 154  80H >-  6CH  to  2 Ul 40H LU  > 5  298  2CH  LU  'iillll I illlli |  1  m/  1 e  III lllilll i ihi li ill illl 11 llil llllll|i 1  1  T — r  10Q 100  -i  Ii  llii  r  ]  150 15U  200  1  1  1  l 1  1  1  I  250  F i g u r e 22. Mass spectrum o f 3 a - h y d r o x y - 4 B - d i h y d r o c l e a v a m i n e .  i  1  1  300  r  i  i  i  - 71 I t was now o f i n t e r e s t t o e x t e n d t h i s sequence f u r t h e r t o t h e synthesis of catharanthine  since the transannular  r e a c t i o n discussed p r e v i o u s l y should cleavamine t o t h i s a l k a l o i d .  cyclization  allow conversion  o f a carbomethoxy-  The p r o b l e m o f i n t r o d u c i n g a C^g  carbomethoxy f u n c t i o n i n t o t h e c l e a v a m i n e m o l e c u l e was now a t hand. The f i r s t p a r t o f t h e r e q u i s i t e r e a c t i o n sequence (23 — 1 0 9 , f i g u r e 23) i s a s p e c i a l case o f a g e n e r a l by t h e i n d o l e system.  t y p e o f r e a c t i o n undergone  T h i s was f i r s t r e c o g n i z e d  by T a y l o r  who  p r o p o s e d t h e scheme shown i n f i g u r e 24 t o e x p l a i n a number o f t r a n s 63 formations  present i n the l i t e r a t u r e .  E l e c t r o p h i l i c attack at the  r e a c t i v e B - p o s i t i o n o f t h e i n d o l e system produces t h e i n d o l e n i n e s (111a) and (111b) which a r e i n e q u i l i b r i u m w i t h each o t h e r .  The  i n d o l e n i n e (111b) i s a c t i v a t e d towards n u c l e o p h i l i c a t t a c k a t t h e carbon a d j a c e n t t o t h e a - p o s i t i o n o f t h e o r i g i n a l i n d o l e system and such a r e a c t i o n leads t o t h e f u n c t i o n a l i z a t i o n a t t h i s c a r b o n . Buchi's 33 c o n v e r s i o n o f i b o g a i n e (112) t o v o a c a n g i n e (113), p r e s e n t e d an a n a l o g y t o t h e t r a n s f o r m a t i o n d e s i r e d i n o u r sequence. 59 The s t u d i e s i n o u r l a b o r a t o r y however, t h a t t h e n i t r i l e  on d i h y d r o c l e a v a m i n e i n d i c a t e d ,  i n t r o d u c t i o n at the 18-position using the  c h l o r o i n d o l e n i n e d i r e c t l y was a v e r y p o o r y i e l d i n g p r o c e s s . s u b s t a n t i a l improvement was a c h i e v e d by f i r s t  A  converting the  c h l o r o i n d o l e n i n e o f 4 B - d i h y d r o c l e a v a m i n e (41) t o i t s q u a t e r n a r y ammonium s a l t obtained  (115) and t h e n t r e a t i n g t h i s s a l t w i t h  the n i t r i l e  ( 4 2 ) . The f o r m a t i o n  cyanide-to  o f t h i s s a l t , was r e a d i l y  a c h i e v e d by t h e r e a c t i o n o f t h e c h l o r o i n d o l e n i n e w i t h a c e t a t e  ion i n  g l a c i a l a c e t i c a c i d , g i v i n g t h e 1 8 - a c e t o x y d i h y d r o c l e a v a m i n e (114) as  (111a) F i g u r e 24.  (111b)  T a y l o r ' s r e a c t i o n scheme f o r f u n c t i o n a l i z a t i o n indolenine  intermediates.  using  - 73 -  an i n t e r m e d i a t e .  T h i s compound under t h e c o n d i t i o n s o f t h e r e a c t i o n ,  undergoes i n t r a m o l e c u l a r d i s p l a c e m e n t o f t h e a c e t o x y f u n c t i o n resulting i n quaternization.  Thus t h e u n s t a b l e  chloroindolenine  (41)  OAc (114)  (115)  was  - 74 -  c o n v e r t e d t o a much more s t a b l e compound, t h e s a l t  (115) .  Nucleophilic  a t t a c k on t h i s s a l t a t t h e 1 8 - p o s i t i o n by t h e c y a n i d e c o u l d be a c h i e v e d and produced t h e d e s i r e d  nitrile.  Because o f t h e e x p e r i e n c e a v a i l a b l e from t h e work i n t h e d i h y d r o c l e a v a m i n e s e r i e s , i t was a r e l a t i v e l y s i m p l e m a t t e r t o c o n v e r t c l e a v amine t o 183-cyanocleavamine.  The o x i d a t i o n w i t h t e r t - b u t y l  was c a r r i e d out a t -15°C t o form t h e c h l o r o i n d o l e n i n e  hypochlorite  (107).  The  c h l o r o i n d o l e n i n e s a r e i n g e n e r a l r e a c t i v e i n t e r m e d i a t e s and no attempt was made t o i s o l a t e t h i s m a t e r i a l .  I n s t e a d , i t was t r e a t e d i m m e d i a t e l y  w i t h f u s e d sodium a c e t a t e i n a s o l u t i o n o f g l a c i a l a c e t i c a c i d and a c e t i c a n h y d r i d e t o form t h e q u a t e r n a r y ammonium s a l t  (108).  Rigorous  p r e c a u t i o n s were t a k e n t o p r e v e n t t h e p r e s e n c e o f water i n t h e system d u r i n g t h e p r e p a r a t i o n o f t h e s a l t and t h e subsequent duction.  intro-  The v e r y p o l a r n a t u r e of t h e q u a t e r n a r y ammonium s a l t made  it difficult to  nitrile  t o work w i t h t h i s m a t e r i a l and i t was found c o n v e n i e n t  i m m e d i a t e l y t r e a t t h e s a l t w i t h a l a r g e excess o f p o t a s s i u m  cyanide i n r e f l u x i n g dimethylformamide.  The d e s i r e d  18g-cyanocleav-  amine (109) was o b t a i n e d i n 30% y i e l d based on s t a r t i n g  cleavamine.  T h i s compound e x h i b i t e d t h e e x p e c t e d s p e c t r a l p r o p e r t i e s , i n p a r t i c u l a r , the c h a r a c t e r i s t i c n i t r i l e at  2240 cm  s t r e t c h i n g bond was o b s e r v e d i n t h e i r r e g i o n  High r e s o l u t i o n mass s p e c t r o m e t r y e s t a b l i s h e d t h e  c o r r e c t m o l e c u l a r c o m p o s i t i o n f o r t h e s t r o n g p a r e n t peak o b s e r v e d . nmr spectrum o f t h i s compound of  ( f i g u r e 2 5 ) , showed a o n e - p r o t o n d o u b l e t  d o u b l e t s a t T.4.48 ( J = 2 and 10 H z ) .  This multiplet  very c l o s e l y t o one o b s e r v e d i n t h e spectrum o f cleavamine  The  corresponded  18g-cyano-4g-dihydro-  (T 4.55, J = 2 and 10 Hz) and was a s s i g n e d t o t h e C - p r o ' t o n . 1R  - 76 -  On t h e b a s i s o f t h e chemical  shift  o f t h i s m u l t i p l e t , the s t e r e o c h e m i s t r y  i o f t h e Cjg s u b s t i t u e n t c o u l d be a s s i g n e d The  as h a v i n g  the 8-configuration.  major d i f f e r e n c e observed between t h i s spectrum and the one observed  f o r the dihydro  analogue c o u l d be e x p l a i n e d by the a d d i t i o n a l double i  bond i n the m o l e c u l e .  A broad one-proton doublet  observed f o r t h e v i n y l p r o t o n  a t T 4.74 was  and t h e t h r e e p r o t o n methyl t r i p l e t a t  x 8.96 was s l i g h t l y d e s h i e l d e d r e l a t i v e  t o i t s normal p o s i t i o n (x 9.1-  9.3) observed i n t h e s a t u r a t e d analogues p o s s e s s i n g  the cleavamine  skeleton. The drastic  h y d r o l y s i s o f the n i t r i l e conditions  c o u l d be a c h i e v e d  (20% p o t a s s i u m h y d r o x i d e  150°C f o r n i n e h o u r s ) .  o n l y under  fairly  i n diethylene g l y c o l at  E s t e r i f i c a t i o n o f the a c i d w i t h  diazomethane  gave t h e d e s i r e d 188-carbomethoxycleavamine (60) i n about 50% y i e l d based on s t a r t i n g  nitrile.  The product  was i d e n t i f i e d by comparison  w i t h an a u t h e n t i c sample o f 188-carbomethoxycleavamine. m a t e r i a l had t h e same m e l t i n g p o i n t , i d e n t i c a l  The s y n t h e t i c  t i c p r o p e r t i e s and  gave an i r spectrum which was superimposable w i t h t h a t o f the authentic The  sample. transannular  catharanthine  cyclization  o f 188-carbomethoxycleavamine t o 64  had a l r e a d y been accomplished i n our l a b o r a t o r y  and  thus the t o t a l s y n t h e s i s o f 188-carbomethoxycleavamine a l s o completed the t o t a l s y n t h e s i s o f t h e a l k a l o i d , Our  catharanthine (12).  f i r s t main o b j e c t i v e , t h e t o t a l s y n t h e s i s o f c a t h a r a n t h i n e and  cleavamine had t h e r e f o r e been a c h i e v e d .  Hence a l l f u r t h e r s t u d i e s i n  t h i s s e r i e s which used compounds d e r i v e d from c a t h a r a n t h i n e  as s t a r t i n g  - 77  -  j m a t e r i a l s , c o u l d be t i o n was  considered  t o t a l l y synthetic.  the i n t r o d u c t i o n o f the a p p r o p r i a t e  and  Our  functionalities  p o s i t i o n s o f the c l e a v a m i n e systems.  As  explained  t h e s e compounds were i m p o r t a n t t o us as i n t e r m e d i a t e s d i m e r i z a t i o n work. already The  The  r e a c t i o n sequence which was  and  These compounds would be v a l u a b l e  The and  earlier,  function.  i n the  natural  i n our d i m e r i z a t i o n work  of dimeric m a t e r i a l s  epimeric  u l t i m a t e l y a l l o w the e v a l u a t i o n o f the i m p o r t a n c e o f  stereochemistry  the  at t h i s c e n t r e , a s e s t a b l i s h e d i n i s o v e l b a n a m i n e  s i n c e t h e y would l e a d t o the s y n t h e s i s at  at  f o r subsequent  hydroxyl  (100), d i f f e r s from t h a t a t the c o r r e s p o n d i n g c e n t r e dimers.  considera-  o u t l i n e d above  gave us a s e r i e s o f compounds h a v i n g the  stereochemistry  next  at t h i s c e n t r e  to b i o l o g i c a l  the  activity.  s y n t h e s e s o f the i s o m e r i c a l c o h o l s , t h a t i s , velbanamine  t h o s e h a v i n g the h y d r o x y l  l e a s t amount o f d i f f i c u l t y was the h y d r o x y l  f u n c t i o n a t C^,  were now  desired.  cleavamine (23).  I t has  Our  approach t o t h i s was  t h i s became  simply  to hydroborate  been w e l l e s t a b l i s h e d t h a t h y d r o b o r a t i o n  sterically sensitive process^ would be o b t a i n e d  The  a n t i c i p a t e d w i t h the i n t r o d u c t i o n o f  f u n c t i o n a t the s e c o n d a r y c a r b o n atom and  our f i r s t c o n s i d e r a t i o n .  (22)  exclusively.  and  i t was  I t was  is a  e x p e c t e d the s e c o n d a r y a l c o h o l  d i f f i c u l t t o p r e d i c t whether  a m o n o - a l k y l o r d i - a l k y l b o r a n e would form i n t h i s r e a c t i o n o r whether c o m p l e x i n g w i t h the b a s i c n i t r o g e n would compete w i t h a t t a c k a t d o u b l e bond.  The  q u a n t i t y o f d i b o r a n e needed i n our  ments c o u l d n o t , t h e r e f o r e , be  c a l c u l a t e d and was  initial  gauged by  the  experithe  d i s a p p e a r a n c e o f the s t a r t i n g m a t e r i a l , c l e a v a m i n e , as seen by t i c . An  experiment c o n d u c t e d i n such a manner l e d t o the i s o l a t i o n o f a  - 78 iI  I  c r y s t a l l i n e m a t e r i a l i n about 80% y i e l d . be an amine-borane which on treatment  T h i s m a t e r i a l t u r n e d out  with triethylamine i n tetrahydro-  f u r a n gave back the s t a r t i n g c l e a v a m i n e .  T h i s amine-borane was  thus  s i m p l y the c l e a v a m i n e N-borane adduct (116) and no h y d r o b o r a t i o n the double bond had been  to  of  achieved.  (23)  (116)  (117)  OH  An i n t e r e s t i n g experiment was  c a r r i e d out w i t h t h i s amine-borane.  c  I t had been r e p o r t e d t h a t the amine-borane/of s i m p l e amines a r e u s e f u l as h y d r o b o r a t i n g  agents.  An e q u i l i b r i u m i s s e t up between the  6 5  amine-borane and f r e e amine a t h i g h t e m p e r a t u r e s and the b o r i n e thus R  3  N : B H  3  3RCH=CH  R  2  +  3  N  1/2 ( B H )  +  1  /2(BH ) 3  »-  2  (RCH  CH ) B  l i b e r a t e d i s a v a i l a b l e f o r the normal h y d r o b o r a t i o n c a s e , we had i t was  reaction.  i n f a c t a s o u r c e o f b o r i n e b u i l t i n t o our m o l e c u l e  In our and  a n t i c i p a t e d t h a t at e l e v a t e d t e m p e r a t u r e , an i n t r a o r i n t e r m o l e c u l a r  t r a n s f e r o f b o r i n e from the n i t r o g e n t o the double bond would t a k e p l a c e .  - 79 -  The  experiment  was  conducted  i n d i g l y m e a t r e f l u x i n g temperature  and  •i was  f o l l o w e d by t h e o x i d a t i v e work up n o r m a l l y employed i n t h e  hydroboration procedure. m a t e r i a l , cleavamine,  The main p r o d u c t s o b t a i n e d were s t a r t i n g  and d i h y d r o c l e a v a m i n e  (29).  Two  m i n o r , more  p o l a r p r o d u c t s were a l s o o b t a i n e d i n i n s u f f i c i e n t q u a n t i t y f o r characterization. (117) was  In subsequent work, however, t h e secondary  obtained.  alcohol  A comparison o f t h e s e minor p r o d u c t s w i t h t h i s  a l c o h o l showed i n f a c t t h a t one o f t h e s e had the same t i c p r o p e r t i e s and i r spectrum.  The o t h e r p r o d u c t had v e r y s i m i l a r t i c p r o p e r t i e s ,  b e i n g v e r y s l i g h t l y l e s s p o l a r and gave a somewhat s i m i l a r i r spectrum.  This m a t e r i a l i s p o s s i b l y the epimeric a l c o h o l .  f u r t h e r work was encountered.  No  done i n t h i s d i r e c t i o n because o f t h e p o o r y i e l d s  I n s t e a d we turned, back t o the normal h y d r o b o r a t i o n  process. The  i s o l a t i o n o f the c l e a v a m i n e  b o r a t i o n experiment was  i n d i c a t e d t h a t an i n s u f f i c i e n t amount o f  used i n t h e r e a c t i o n .  When a l a r g e excess o f d i b o r a n e  u t i l i z e d , t h e d e s i r e d secondary The  N-borane i n t h e p r e v i o u s  a l c o h o l was  o b t a i n e d i n 77%  hydrodiborane  was yield.  s p e c t r a l d a t a f o r t h i s compound were i n complete agreement w i t h t h e  s t r u c t u r e o f the a l c o h o l (117) and s u b l i m a t i o n o f t h e compound p r o v i d e d an a n a l y t i c a l sample.  A comparison o f t h e mass spectrum o f t h i s  compound ( f i g u r e 22) w i t h t h a t o f velbanamine and ( f i g u r e 21) showed, as e x p e c t e d , a v e r y them.  The nmr  isovelbanamine  c l o s e resemblance between  spectrum showed two p r o t o n s i n t h e r e g i o n x 6.4.  o f these c o u l d be a s s i g n e d t o the C - p r o t o n , 1 Q  p o s i t i o n i n cleavamine-type  One  s i n c e t h i s i s i t s normal  compounds b e a r i n g no s u b s t i t u e n t a t  C . 1R  - 80 The  o t h e r p r o t o n w i t h t h i s c h e m i c a l s h i f t c o u l d be a s s i g n e d t o t h e  C^-proton which i s geminal  t o the h y d r o x y l f u n c t i o n .  The nmr  spectrum  o f the a c e t a t e o f t h i s a l c o h o l ( f i g u r e 26) showed a s i n g l e p r o t o n a complex m u l t i p l e t a t T 6.4, a t lower f i e l d , x 4.90, The  (C, -proton) Q  and now  as a d o u b l e t o f d o u b l e t s  showed t h e C_-proton ( J = 6 and 10 Hz.).  s t e r e o c h e m i s t r y o f t h i s a l c o h o l (117) a t the two  c e n t r e s c o u l d be a s s i g n e d by a c o m b i n a t i o n evidence.  The h y d r o b o r a t i o n p r o c e s s  h y d r a t i o n o f a double bond.  asymmetric  o f c h e m i c a l and  nmr  i s known t o r e s u l t i n the c i s  That i s , t h e h y d r o x y l f u n c t i o n and  p r o t o n a r e i n t r o d u c e d a t a d j a c e n t carbons i n a c i s r e l a t i o n s h i p each o t h e r and t h i s i s e x p l a i n e d m e c h a n i s t i c a l l y by t h e o f a c y c l i c t r a n s i t i o n state. ''' 5  as  the toward  intermediacy  From t h i s i n f o r m a t i o n , t h e  r e l a t i v e s t e r e o c h e m i s t r y between C„ and C. i s e s t a b l i s h e d . 3 4 1  An e x a m i n a t i o n  o f a model o f cleavamine  shows c l e a r l y t h a t  because o f t h e s t e r i c e f f e c t o f the b r i d g e a t C_,  approach i s v e r y  much f a v o u r e d from the s i d e o f t h e p i p e r i d i n e r i n g o p p o s i t e bridge.  T h i s i s i n d e e d g e n e r a l l y observed  cleavamine  system.  Hydrogenation  this  i n o t h e r r e a c t i o n s o f the  of cleavamine  therefore gives  - 82  e x c l u s i v e l y 48-dihydrocleavamine  -  ( 2 9 ) . The o s y m l a t i o n r e a c t i o n on the  enamine (83); r e p o r t e d e a r l i e r i n t h i s work was  also  stereoselective,  i  r e s u l t i n g i r i the eventual formation of isovelbanamine s t e r e o c h e m i s t r y at  (100).  The  o f i s o v e l b a n a m i n e which has t h e e t h y l group i n a  g - o r i e n t a t i o n shows t h a t a t t a c k i n t h i s case i s a l s o f a v o u r e d from the s i d e o p p o s i t e the b r i d g e . use o f t h i s s t e r i c approach ethylmagnesium  bromide,  Buchi's s y n t h e s i s of v e l b a n a m i n e  control.  makes  6 6  Thus t r e a t m e n t o f (150) w i t h  f o l l o w e d by l i t h i u m aluminum h y d r i d e r e d u c t i o n  (150)  gave velbanamine  (22).  On t h e b a s i s o f t h e s e r e s u l t s i t would be e x p e c t e d t h a t the h y d r o b o r a t i o n o f the c l e a v a m i n e double bond would f o l l o w t h e same s t e r i c c o u r s e and l e a d t o the 3 a - h y d r o x y - 4 8 - d i h y d r o c l e a v a m i n e . s u g g e s t i o n was  s u p p o r t e d by nmr  evidence.  The C^-proton  This  i n the  a c e t a t e o f t h i s m o l e c u l e i s o b s e r v e d as a d o u b l e t o f d o u b l e t s J = 6 and 10 Hz.  I f a t t a c k i s from the s i d e o p p o s i t e t h e b r i d g e , t h e  r e s u l t i n g compound would have t h e e t h y l and h y d r o x y l groups i n a t r a n s - d i a x i a l r e l a t i o n s h i p assuming t h e c h a i r c o n f o r m a t i o n f o r the piperidine ring.  Because o f t h e c o n f o r m a t i o n a l m o b i l i t y i n t h e  c l e a v a m i n e r i n g system i t i s d i f f i c u l t t o be e n t i r e l y d e f i n i t i v e about  - 83 -  the conformational s t r u c t u r e . mode o f a t t a c k . bridge at  We c a n , however, r u l e out the a l t e r n a t e  A t t a c k o f t h e double bond from t h e same s i d e as the  would l e a d t o a compound which has b o t h the e t h y l  and  h y d r o x y l groups i n t h e e q u a t o r i a l p o s i t i o n i n t h e c h a i r c o n f o r m a t i o n . T h i s s i t u a t i o n r e p r e s e n t s t h e most s t a b l e c o n f o r m a t i o n p o s s i b l e . t h i s c a s e , t h e d i h e d r a l a n g l e s are w e l l d e f i n e d b e i n g 180° between t h e C^-C^  and ^2~^i  protons r e s p e c t i v e l y .  and  In  60°  From t h e K a r p l u s  67 relation,  t h e s e a n g l e s s h o u l d l e a d t o c o u p l i n g c o n s t a n t s o f about  16 and 2 Hz.  T h i s c l e a r l y does not agree w i t h t h e observed v a l u e s o f  10 and 6 Hz and t h e r e f o r e e x c l u d e s t h i s c o u r s e o f a t t a c k . on the b a s i s o f models, c h e m i c a l precedence (117) can be a s s i g n e d as  and nmr  Therefore,  data, the a l c o h o l  3a-hydroxy-43-dihydrocleavamine.  I t i s o f i n t e r e s t t o compare t h i s compound w i t h t h e monomeric u n i t d e r i v e d from l e u r o s i d i n e ( 1 8 ) .  Cleavage o f t h i s dimer l e a d s t o  t h e i s o l a t i o n o f a secondary a l c o h o l , v i n r o s a m i n e , which was the s t r u c t u r e of 3a-hydroxy-4a-dihydrocleavamine.^  A  assigned  comparison  o f our d a t a w i t h the p h y s i c a l c o n s t a n t s r e p o r t e d f o r v i n r o s a m i n e  and  v i n r o s a m i n e a c e t a t e shows d e f i n i t e l y t h a t t h e s e compounds are d i f f e r e n t . I t i s r e p o r t e d t h a t v i n r o s a m i n e e x h i b i t s a mass spectrum major fragment i o n (M  +  i n which  i o n c o r r e s p o n d s t o a l o s s o f water from the m o l e c u l a r  - 1 8 ) , and t h a t the r e s t  o f t h e spectrum c o r r e s p o n d s t o t h a t  n o r m a l l y found f o r c l e a v a m i n e t y p e compounds. t h e f a c t t h a t i t was  Our a l c o h o l , d e s p i t e  e p i m e r i c t o t h i s m a t e r i a l a t o n l y one  position  (C^) behaved e n t i r e l y d i f f e r e n t l y and gave a spectrum which c l o s e l y t o t h a t o f velbanamine unexpected  the  and i s o v e l b a n a m i n e .  This  corresponded  perhaps  d i f f e r e n c e between the mass s p e c t r a o f t h e s e two  secondary  -••  - 84 -  a l c o h o l s can.be e a s i l y e x p l a i n e d by a c o n s i d e r a t i o n o f t h e i r s t r u c t u r e s . Vinrosamine i n  the c h a i r c o n f o r m a t i o n , has the e t h y l group i n an  e q u a t o r i a l p o s i t i o n and the diaxial relationship.  h y d r o x y l and  hydrogen i n a t r a n s -  T h i s s p a t i a l arrangement between the  hydroxyl  and a d j a c e n t hydrogen i s v e r y f a v o r a b l e f o r e l i m i n a t i o n and the dehydration to :  unexpected.  c l e a v a m i n e as observed  facile  i n the mass spectrum i s not  In our a l c o h o l (118), t h e r e are no hydrogen atoms which  a r e t r a n s t o the h y d r o x y l group and thus o n l y a c i s e l i m i n a t i o n i s possible. (118)  The major fragment i o n i n the mass spectrum o f the a l c o h o l  i s m/e  154  i n d i c a t i n g that fragmentation  adjacent to the i n d o l e aromatic and the i o n observed o f the  corresponds  a t carbon c e n t e r s  system i s f a v o u r e d  [cf structure  (101)]  t o the h y d r o x y l a t e d p i p e r i d i n e p o r t i o n  molecule.  Having achieved  the f u n c t i o n a l i z a t i o n a t b o t h  and  we  t u r n e d our a t t e n t i o n t o the f o r m a t i o n o f the e p i m e r i c systems.  now The  compounds s y n t h e s i z e d so f a r d i f f e r e d i n s t e r e o c h e m i s t r y a t the asymmetric c e n t r e s  and/or C^,  from the n a t u r a l dimers and i t was  from the monomeric u n i t s d e r i v e d d e s i r a b l e t o have a v a i l a b l e as  s y n t h e t i c m a t e r i a l s , the compounds h a v i n g the same s t e r e o c h e m i s t r y these centers. (22).  Of p a r t i c u l a r i n t e r e s t was  at  the s y n t h e s i s o f velbanamine  I t w i l l become c l e a r i n the second p a r t o f the d i s c u s s i o n t h a t  the sequence a l r e a d y outlining the t o t a l s y n t h e s i s o f i s o v e l b a n a m i n e important  i n the s y n t h e s i s o f d i m e r i c systems.  e p i m e r i z a t i o n a t the  was  A means o f a l l o w i n g  p o s i t i o n o f i n t e r m e d i a t e s u t i l i z e d i n the  p r e s e n t sequence would g i v e us the s y n t h e t i c c a p a b i l i t y o f s y n t h e s i z i n g v i n b l a s t i n e or i s o v i n b l a s t i n e epimeric at only C . R  T h i s achievement  - 85 would p r o v i d e t h e f i r s t r e a l o p p o r t u n i t y t o e v a l u a t e the of  t h i s and o t h e r asymmetric  importance  centers i n imparting anti-tumor  activity  l'  in this  series.  The e p i m e r i z a t i o n o f t h e t e r t i a r y C ^ - h y d r o x y l f u n c t i o n a n t i c i p a t e d t o be a complex p r o c e s s .  From our e x p e r i e n c e w i t h t h e  d e h y d r a t i o n o f i s o v e l b a n a m i n e t o c l e a v a m i n e , which was  r e a d i l y achieved  under a c i d i c c o n d i t i o n s , i t seemed l i k e l y t h a t any approach i n v o l v e d the i n t e r m e d i a t e carbonium  was  which  i o n would s u f f e r t h e u n d e s i r e d l o s s  of  a proton to give o l e f i n i c products.  to  S^2  We thus t u r n e d our a t t e n t i o n  t y p e r e a c t i o n s even though a t e r t i a r y c e n t e r i s not n o r m a l l y  prone t o such s i t u a t i o n s .  Our f i r s t experiment  i n v o l v e d the use  of  c o n c e n t r a t e d sodium h y d r o x i d e i n a w a t e r - d i m e t h y l s u l p h o x i d e s o l u t i o n . Dimethyl s u l p h o x i d e was used because i t i s known t o g r e a t l y enhance t h e a c t i v i t y o f a n i o n s and thus i s an e x c e l l e n t s o l v e n t f o r n u c l e o p h i l i c 69 displacement r e a c t i o n s .  The d r i v i n g f o r c e f o r the r e a c t i o n would  be t h e a t t a i n m e n t o f a more s t a b l e i s o m e r ; i s o v e l b a n a m i n e has  the  e t h y l s u b s t i t u e n t i n an a x i a l p o s i t i o n when t h e p i p e r i d i n e r i n g i s i n a c h a i r c o n f o r m a t i o n , whereas velbanamine  has the e t h y l group i n an  e q u a t o r i a l p o s i t i o n and a l s o t h e h y d r o x y l f u n c t i o n i n the  8-axial  p o s i t i o n i s f a v o r a b l y o r i e n t e d f o r hydrogen b o n d i n g w i t h t h e nitrogen.  tertiary  However, t h e experiment under a v a r i e t y o f c o n d i t i o n s ,  t o produce any velbanamine  as e v i d e n c e d by  failed  tic.  The f o l l o w i n g approach was based on a known p r o c e d u r e f o r t h e 70 c l e a v a g e o f s t e r o i d a l m e t h y l e t h e r s u s i n g boron In  trifluoride-etherate.  t h e s e i n s t a n c e s t h e combined r e a c t i o n o f B F ^ - e t h e r a t e and  acetic  a n h y d r i d e i n e t h e r c o n v e r t e d secondary methyl e t h e r s t o the c o r r e s p o n d i n g  - 86 -  acetates.  The p r o d u c t was r e p o r t e d t o sometimes c o n s i s t o f a m i x t u r e  of epimeric materials.  I t was  f e l t t h a t t h i s r e a c t i o n sequence s h o u l d  i  be a p p l i c a b l e t o our Treatment  system.  o f i s o v e l b a n a m i n e under the p r e s c r i b e d c o n d i t i o n s l e d t o  t h e d i s a p p e a r a n c e o f s t a r t i n g m a t e r i a l as e v i d e n c e d by t i c and major product r e s u l t e d .  Treatment  one  of t h i s product with l i t h i u m  aluminum h y d r i d e gave, however, i s o v e l b a n a m i n e as a major p r o d u c t no velbanamine.  Thus i s o v e l b a n a m i n e a c e t a t e was  formed  and  indicating  a t t a c k by t h e a c y l i u m i o n a t t h e h y d r o x y l oxygen r a t h e r t h a n d i s p l a c e ment o f t h e h y d r o x y l by the a c e t a t e a n i o n . These e x p e r i m e n t s c o n f i r m e d our i n i t i a l s u s p i c i o n s t h a t  steric  f a c t o r s were p r o h i b i t i v e t o the r e q u i r e d n u c l e o p h i l i c a t t a c k a t t h i s center.  We were thus f o r c e d t o examine the a l t e r n a t e approach,  i s , r e a c t i o n c o n d i t i o n s which would be e x p e c t e d t o g e n e r a t e  that  carbonium  i o n i n t e r m e d i a t e s . Under the c o n d i t i o n s f o r t h e c o n v e r s i o n o f i s o v e l banamine t o c l e a v a m i n e t h e carbonium systems.  ( c o n c e n t r a t e d s u l p h u r i c a c i d a t 0°C  i o n r a p i d l y loses a proton t o p r o v i d e the o l e f i n i c  We r e q u i r e d i n t h i s case n o n - d e h y d r a t i n g c o n d i t i o n s  t h a t t h e r e a c t i o n a t t h e carbonium attack. 0°C  f o r 2 hours),  such  i o n would i n s t e a d be n u c l e o p h i l i c  We thus t r e a t e d i s o v e l b a n a m i n e w i t h d i l u t e aqueous a c i d a t  up t o t h r e e days and found under t h e s e c o n d i t i o n s , t h e compound  underwent no change.  A l s o a t room t e m p e r a t u r e no change was  observed.  However, r e f l u x i n g t h i s same s o l u t i o n , gave a f t e r f o u r h o u r s , the f i r s t i n d i c a t i o n on t i c o f the p r e s e n c e o f some velbanamine. p r o p o r t i o n o f velbanamine was  The  seemed t o i n c r e a s e w i t h time and the r e a c t i o n  a l l o w e d t o c o n t i n u e f o r two days.  Work up a f t e r t h i s time gave  -87'-  b o t h v e l b a n a m i n e and had  s t a r t i n g isovelbanamine.  The  velbanamine  t h e same m e l t i n g p o i n t , i d e n t i c a l t i c p r o p e r t i e s and  superimposable  i  i r s p e c t r u m ^ w i t h t h a t o f an a u t h e n t i c sample o f v e l b a n a m i n e . The  71  e x t e n s i o n o f our sequence t o the t o t a l s y n t h e s i s o f velbanamine  s a t i s f i e d one  o f our main s y n t h e t i c o b j e c t i v e s w i t h r e s p e c t t o  s y n t h e s i s o f t h e n a t u r a l d i m e r i c V i n c a a l k a l o i d s and r e l a t e d d i m e r i c analogues. u n i t was  obtained  Now  1) t h e c o m p l e t i o n  their closely  that s y n t h e s i s of the i n d o l e  i n hand, two problems s t i l l  remain t o be s o l v e d .  o f the d i h y d r o i n d o l e  the  (velbanamine)  These a r e  ( v i n d o l i n e ) u n i t and,  2)  c o u p l i n g o f t h e s e systems t o p r o v i d e the d i m e r i c a l k a l o i d s .  the  W h i l e the  v i n d o l i n e s y n t h e s i s i s under s t u d y by s e v e r a l o t h e r workers i n group, the i n v e s t i g a t i o n s c o n c e r n i n g  the  the d i m e r i z a t i o n r e a c t i o n form  Part I I of t h i s t h e s i s .  Part I I The  d i m e r i c V i n c a a l k a l o i d s c o n t a i n a l i n k a g e between the  p o s i t i o n o f v i n d o l i n e or i t s r e l a t i v e s and C^  R  o f the nine-membered  r i n g system c h a r a c t e r i s t i c o f the c l e a v a m i n e f a m i l y .  A l t h o u g h i t would  be s a t i s f y i n g t o complete the t o t a l s y n t h e s i s o f the n a t u r a l s e r i e s , i t was  o f utmost i m p o r t a n c e t o d e v e l o p , i f p o s s i b l e , a v e r s a t i l e  g e n e r a l c o u p l i n g r e a c t i o n which would p r o v i d e a new analogues f o r b i o l o g i c a l e v a l u a t i o n . the r e l a t i o n s h i p between c h e m i c a l can be Our  In t h i s way  s t r u c t u r e and  and  f a m i l y of s y n t h e t i c  information  anti-tumor  concerning  activity,  obtained. approach t o t h i s work was  p r e v i o u s l y had  considerable  t o employ a r e a c t i o n w i t h which  experience  we  and which seemed a t t r a c t i v e f o r  - 88  t h i s purpose.  I t was  pointed  -  out e a r l i e r t h a t i n d o l e systems can  be  c o n v e r t e d by o x i d a t i v e p r o c e d u r e s t o i n d o l e n i n e s which are r e a c t i v e to n u c l e o p h i l i c attack at centers  a d j a c e n t t o the a - p o s i t i o n o f  o r i g i n a l i n d o l e system (see f i g u r e 23). chloroindolenines  served  Thus the f o r m a t i o n  as an i n t e r m e d i a t e  of  the the  s t e p f o r the i n t r o d u c t i o n  o f n u c l e o p h i l i c s u b s t i t u e n t s at the 18 p o s i t i o n o f the Iboga systems (for  example see f i g u r e 22).  V i n d o l i n e on the o t h e r hand i s a c t i v a t e d  toward e l e c t r o p h i l i c s u b s t i t u t i o n .  The  aromatic p o r t i o n of  this  m o l e c u l e i s a m e t a - m e t h o x y - a n i l i n e system which because o f the combined "electron donating" a t b o t h the 15 and p o s i t i o n should  e f f e c t o f the methoxy and  a n i l i n o functions i s activated  17 p o s i t i o n s toward e l e c t r o p h i l i c a t t a c k .  a r e a c t i o n between the c h l o r o i n d o l e n i n e  Thus i t was  predicted  and  that  o f the c l e a v a m i n e t y p e system  and v i n d o l i n e , would r e s u l t i n a d i m e r i z a t i o n i n v o l v i n g the  The  15  i n f a c t be more r e a c t i v e t h a n the 17 p o s i t i o n when  s t e r i c f a c t o r s are t a k e n i n t o c o n s i d e r a t i o n .  c e n t r e s , C^g,  The  correct  C^.  numbering system t h a t w i l l be used i n r e f e r r i n g t o the dirners,  w i l l be t h a t o f the c o r r e s p o n d i n g monomeric u n i t s , t h a t i s , A s p i d o sperma a l k a l o i d numbering f o r the d i h y d r o i n d o l e numbering f o r the velbanamine m o i e t y .  unit while  Iboga  To d i s t i n g u i s h the numbering  systems, the numbers o f the "Iboga h a l f " w i l l be p r i m e d (see Our  i n i t i a l experiment was  118).  conducted u s i n g the l e a s t f u n c t i o n a l i z e d  o f t h e c l e a v a m i n e systems, 4 8 - d i h y d r o c l e a v a m i n e (29) i n the hope t h a t the p o s s i b i l i t y o f s i d e r e a c t i o n s would be m i n i m i z e d . c h l o r o i n d o l e n i n e o f t h i s compound had intermediate  i n the c o n v e r s i o n  Also,  a l r e a d y been s y n t h e s i z e d  the as  an  o f 4 8 - d i h y d r o c l e a v a m i n e t o 188-carbo-  - 89 -  methoxy-46-dihydrocleavamine (32).  The r a t h e r u n s t a b l e c h l o r i n d o l e n i n e i n t e r m e d i a t e  ( 4 1 ) , formed  from t - b u t y l h y p o c h l o r i t e o x i d a t i o n o f 29, was r e a c t e d w i t h v i n d o l i n e i n an anhydrous m e t h a n o l i c  1% h y d r o c h l o r i c a c i d s o l u t i o n .  The  r e a c t i o n seemed complete a f t e r two hours a t r e f l u x t e m p e r a t u r e . major p r o d u c t  The  o f t h i s r e a c t i o n e x h i b i t e d a l l the p r o p e r t i e s expected  f o r t h e dimer (118).  The uv spectrum appeared as a s i m p l e  superimposition  o f t h e i n d o l e and i n d o l i n e a b s o r p t i o n and t h i s agreed q u a l i t a t i v e l y w i t h t h e spectrum o b t a i n e d f o r v i n b l a s t i n e . The mass spectrum 27)  shows a number o f fragment i o n s c o r r e s p o n d i n g  p a t t e r n e x h i b i t e d by d i h y d r o c l e a v a m i n e a b s o r p t i o n s a t m/e  (figure  t o the fragmentation  and v i n d o l i n e .  The prominent .  124, 138 and l e s s i n t e n s e ones a t 143, 144, 156, and  - 91 i  ^ 22 282 are v e r y c h a r a c t e r i s t i c o f d i h y d r o c l e a v a m i n e .  j  s t r o n g a b s o r p t i o n s a t m/e  Similarly  the  121, 122, 135, and 149 w i t h l e s s i n t e n s e i  ones a t 174 and 188 d e f i n e t h e v i n d o l i n e p o r t i o n o f the m o l e c u l e .  72  High r e s o l u t i o n mass d e t e r m i n a t i o n o f the p a r e n t i o n e s t a b l i s h e d a i  m o l e c u l a r f o r m u l a i n agreement w i t h t h e s t r u c t u r e o f t h e d e s i r e d compound. From t h e e v i d e n c e p r e s e n t e d so f a r , t h e r e was no doubt t h a t we had a d i m e r i c system composed o f a c l e a v a m i n e and a v i n d o l i n e p o r t i o n . S t r o n g e v i d e n c e i n f a v o r o f the dimer as w e l l as t h e p r o o f f o r the c o r r e c t j u n c t i o n between the two u n i t s came from t h e nmr I n many r e s p e c t s , t h e nmr  spectrum o f t h e dimer  spectrum.  ( f i g u r e 28),  appeared  t o be a c o m b i n a t i o n o f t h e s p e c t r a o f t h e i n d i v i d u a l monomeric u n i t s ( f i g u r e 29,30) but a few i m p o r t a n t changes were observed.  The  aromatic  p r o t o n s o f v i n d o l i n e appear as t h r e e d i s c r e t e m u l t i p l e t s i n t h e r e g i o n T 6-7;  normal  c o u p l i n g , o r t h o and meta w i t h no p a r a c o u p l i n g  i s observed.  In the dimer, the s i g n a l c o r r e s p o n d i n g t o t h e  i s absent as e x p e c t e d and t h e  and  p r o t o n s now  s i n g l e t s because o f the s m a l l p a r a c o u p l i n g . e s t a b l i s h e d t o be a t t h e  appear as  The j u n c t i o n  p o s i t i o n of v i n d o l i n e .  proton  i s therefore  The C^g,  proton  i s o b s e r v e d as t h e b r o a d d o u b l e t c h a r a c t e r i s t i c f o r 1 8 - s u b s t i t u t e d cleavamines.  As d i s c u s s e d p r e v i o u s l y , the c h e m i c a l s h i f t o f t h i s  p r o t o n has been used i n the s i m p l e s u b s t i t u t e d cleavamine systems t o a s s i g n the s t e r e o c h e m i s t r y at t h i s p o s i t i o n .  However, i t was  unlikely  t h a t t h e d i m e r i c system, because o f t h e v a s t l y i n c r e a s e d s t e r i c b u l k o f t h e s u b s t i t u e n t , t h e v i n d o l i n e m o i e t y , would f i t i n t o t h i s g e n e r a l scheme and no s t e r e o c h e m i c a l assignment  f o r t h i s j u n c t i o n c o u l d be made a t  Figure 28.  Nmr of dimer 118.  - 95 -  this point. The  One  I |  further observation  c o u l d be made from t h i s spectrum. i f o r the carbomethoxy land methoxy s u b s t i t u e n t s  two m e t h y l a b s o r p t i o n s  i have t h e same c h e m i c a l can be seen t h a t one  shift in vindoline.  However, i n the dimer i t  of these methyls i s s h i f t e d to higher  field.  j It i s probable that t h i s s i g n a l represents because i t i s a d j a c e n t the i n d o l e a r o m a t i c  the methoxyl m e t h y l w h i c h ,  t o the j u n c t i o n , i s now put i n c l o s e p r o x i m i t y  system and  i s thereby  a f f e c t e d by the magnetic  f i e l d a s s o c i a t e d w i t h t h i s system.  :  To e s t a b l i s h beyond a doubt t h a t t h i s compound was dimer (118) product,  indeed  the  and not f o r example a dimer composed o f a rearrangement  a sample o f the m a t e r i a l was  compound under a c i d i c r e d u c i n g which were s e p a r a t e d  and  cleaved.  Treatment o f  c o n d i t i o n s gave a m i x t u r e  i d e n t i f i e d as  v i n d o l i n e , d e s a c e t y l v i n d o l i n e and  of products  s t a r t i n g dimer.  These i s o l a t e d This  experiment i n c o n j u n c t i o n w i t h the s p e c t r a l d a t a , p r e s e n t e d r i g o r o u s p r o o f o f the s t r u c t u r e o f the dimer n e x t experiment was  dirners o f known s t r u c t u r e .  a  (118).  d e s i g n e d t o t e s t the a p p l i c a b i l i t y  t h i s approach t o the s y n t h e s i s o f d i m e r i c m a t e r i a l s h a v i n g methoxy f u n c t i o n at C^g,.  this  48-dihydrocleavamine,  p r o d u c t s a c c o u n t e d f o r 75% o f the s t a r t i n g m a t e r i a l .  Our  to  This f u n c t i o n i s present  a  of  carbo-  i n a l l the n a t u r a l  I t seemed p r e f e r a b l e t o c o u p l e the  18-  c a r b o m e t h o x y c l e a v a m i n e - t y p e system w i t h v i n d o l i n e r a t h e r t h a n t o t r y and  i n t r o d u c e the carbomethoxy group a t a l a t e r s t a g e .  experiment we w h i c h was Reaction  For  this  t h e r e f o r e s t a r t e d w i t h 18 8-carbomethoxycleavamine  converted  t o the c h l o r o i n d o l e n i n e  (120)  i n the u s u a l  (32) fashion.  o f t h i s c h l o r o i n d o l e n i n e w i t h v i n d o l i n e gave one major p r o d u c t  - 96 which e x h i b i t e d t h e s p e c t r a l p r o p e r t i e s e x p e c t e d f o r t h e dimer (119). As b e f o r e , t h e uv spectrum showed the p r e s e n c e o f b o t h chromophores and t h e mass; spectrum ( f i g u r e 31) gave s t r o n g e v i d e n c e f o r t h e p r e s e n c e o f b o t h t h e i n d o l e and d i h y d r o i n d o l e u n i t s .  High r e s o l u t i o n mass  measurement on t h e p a r e n t i o n e s t a b l i s h e d t h e m o l e c u l a r f o r m u l a expected f o r the product. 32) showed many o f  The nmr spectrum o f t h i s compound  (figure  t h e f e a t u r e s o f t h e spectrum f o r t h e p r e v i o u s  dimer but w i t h a few i m p o r t a n t changes.  The C^  RI  p r o t o n seen a t T  5.6  f o r dimer (118) was m i s s i n g i n t h i s spectrum and i t was n o t e d t h a t the s i n g l e t a t t r i b u t e d t o the carbomethoxy m e t h y l was e n l a r g e d and i n t e g r a t e d f o r two m e t h y l groups.  A comparison o f the c h e m i c a l s h i f t s f o r the  v i n d o l i n e a r o m a t i c p r o t o n s showed i n t h i s spectrum a s h i e l d i n g f o r t h e C j ^ p r o t o n and a d e s h i e l d i n g e f f e c t f o r the t o t h a t o b s e r v e d i n the descarbomethoxy  dimer (118).  effect  proton r e l a t i v e These s h i f t s  could  be a t t r i b u t e d t o e i t h e r o f two f a c t o r s o r a c o m b i n a t i o n o f them; 1) a d i f f e r e n c e i n the s p a t i a l arrangement o f t h e two h a l v e s o f t h e dimer caused by the e x t r a C^  RI  s u b s t i t u e n t which c o u l d p l a c e t h e s e  p r o t o n s i n a d i f f e r e n t p r o x i m i t y t o t h e magnetic f i e l d a s s o c i a t e d w i t h t h e i n d o l e a r o m a t i c system, 2) an a d d i t i o n a l a n i s o t r o p i c caused by t h e i n t r o d u c t i o n o f the c a r b o n y l s u b s t i t u e n t a t  effect C^ . RI  As w i t h t h e p r e v i o u s dimer, t h i s compound was s u b j e c t e d t o cleaving conditions.  The p r o d u c t s i s o l a t e d were i d e n t i f i e d by t i c  and s p e c t r a l comparison w i t h a u t h e n t i c m a t e r i a l s and were found t o be: 18a-carbomethoxydihydrocleavamine, v i n d o l i n e and d e s a c e t y l v i n d o l i n e . (120) was  proved.  18g-carbomethoxydihydrocleavamine, Thus the s t r u c t u r e o f t h e dimer  Figure 32.  Nmr spectrum of dimer (119).  - 99  i  i In the mass spectrum o f b o t h o f t h e s e d i m e r i c compounds, the i molecular  i o n was  the spectrum.  not the h i g h e s t m o l e c u l a r weight peak observed  Instead, M  +  +14  and M  +  +28  peaks' were p r e s e n t  in  although  i n each o f the s p e c t r a o b t a i n e d , t h e y were e x t r e m e l y weak.  These  i  s p u r i o u s peaks had been p r e v i o u s l y r e p o r t e d i n the mass spectrum o f v i n b l a s t i n e ^ and v o a c a m i n e ^ and have been a t t r i b u t e d t o an 6  m o l e c u l a r m e t h y l t r a n s f e r from a carbomethoxy group o f one t o the n i t r o g e n atom o f a n o t h e r , elimination.  This process  inter-  molecule  f o l l o w e d by a t h e r m a l Hofmann-  can be r e p e a t e d  t w i c e s i n c e two  basic  n i t r o g e n atoms a r e a v a i l a b l e f o r r e a c t i o n and thus l e a d s t o the M and M  +  +28  i o n s observed.  the hydrazide  When v i n b l a s t i n e was  (121) o b t a i n e d p o s s e s s e d  +  +14  treated with hydrazine,  no carbomethoxy f u n c t i o n s and  i n d e e d , d i d not show t h e s e s p u r i o u s peaks i n i t s mass spectrum.  Because i t was important  a n t i c i p a t e d t h a t mass s p e c t r o s c o p y would p l a y an  r o l e i n the s t r u c t u r a l p r o o f o f the s y n t h e t i c d i m e r i c  compounds, a p a r a l l e l s e r i e s o f d i m e r i z a t i o n e x p e r i m e n t s were c a r r i e d out by o t h e r workers i n our l a b o r a t o r y u s i n g v i n d o l i n e h y d r a z i d e i n s t e a d o f v i n d o l i n e as r e p o r t e d i n t h i s work. 146-dihydrocleavamine  The  d i m e r i z a t i o n of  w i t h v i n d o l i n e h y d r a z i d e gave dimer  (122)  - 100  I  i  1 possessing  no carbomethoxy f u n c t i o n .  expected,  the h i g h e s t m/e  supported  the view t h a t we  I t s mass spectrum had  v a l u e as the m o l e c u l a r had  i n f a c t observed  i o n and  as  thus  t h i s same  transmethyla-  t i o n phenomenon i n the s p e c t r a o f our o t h e r dimers and were i n not  t a k i n g the h i g h e s t m/e  v a l u e as our m o l e c u l a r  ion.  justified Two  other  d i m e r i z a t i o n s were c a r r i e d out, both o f these used the c h l o r o i n d o l e n i n e o f 18g-carbomethoxy-43-dihydrocleavamine coupled  to v i n d o l i n e hydrazide  o t h e r case  i t was  (120).  to g i v e the dimer  coupled with d i h y d r o v i n d o l i n e .  In one (123) The  case and  i t was  i n the  details  of  76  these  three dimerizations, reported i n f u l l  completely  elsewhere,  c o n s i s t e n t w i t h the r e s u l t s p r e s e n t e d  i n t h i s work.  were  f o r the d i m e r i z a t i o n s  I t s h o u l d a l s o be p o i n t e d out, t h a t the s y n t h e s i s o f  the dimer o f 4g-dihydrochleavamine w i t h v i n d o l i n e h y d r a z i d e the c h l o r o i n d o l e n i n e approach has another  a l s o been r e p o r t e d r e c e n t l y by  group o f w o r k e r s . ^  One  f u r t h e r p o i n t which has been i g n o r e d so f a r , i s the s t e r e o -  chemistry  at the C^ , 8  end  o f the j u n c t i o n i n the dimers  u s i n g the c h l o r o i n d o l e n i n e as i n t e r m e d i a t e . e s t a b l i s h the s t e r e o c h e m i s t r y (119)  using  synthesized  In an endeavour to  at t h i s p o i n t , we  chose to compare dimer  w i t h v i n b l a s t i n e i n which the s t e r e o c h e m i s t r y has been e s t a b l i s h e d  by X-ray a n a l y s i s .  Ignoring stereochemical  from v i n b l a s t i n e i n o n l y one a t C^,.  dimer  (119)  expected  w i t h the s t e r e o c h e m i s t r y  differs  feature, a lack of a hydroxyl f u n c t i o n  T h i s p o i n t o f d i f f e r e n c e i s f a r removed from the C-^g,  and would not be  An  detail,  position  t o i n f l u e n c e the s p e c t r a l p r o p e r t i e s a s s o c i a t e d at t h i s j u n c t i o n .  i n s p e c t i o n o f the models o f the dimers, i n d i c a t e d t h a t a  - 101  -  I j difference i n stereochemistry  at C ,  profoundly  1D  influenced  the  1 o  o v e r a l l shape o f the m o l e c u l e . i n d o l e and  The  s p a t i a l arrangement between the  i n d o l i n e chromophores would be a l t e r e d i f a d i f f e r e n c e  i n stereochemistry  e x i s t e d between t h e s e compounds and a l t h o u g h  these  two  chromophoric systems are not i n c o n j u g a t i o n w i t h each o t h e r , i t  was  thought t h a t such a change i n s p a t i a l arrangement when t h e s e  groups are i n c l o s e p r o x i m i t y , would be r e f l e c t e d by a d i f f e r e n c e i n the uv s p e c t r a o f t h e s e compounds.  A comparison o f t h e i r uv  spectra,  f i g u r e 33, i n d i c a t e s a c o n s i d e r a b l e d i f f e r e n c e i n e x t i n c t i o n c o e f f i c i e n t and a s m a l l s h i f t i n the a b s o r p t i o n maxima. recorded  u s i n g methanol as s o l v e n t and  These s p e c t r a were  i t i s p o s s i b l e t h a t the d i f f e r e n c e  i n s o l v a t i o n which u n d o u b t e d l y e x i s t s and  i s caused by  the  h y d r o x y l , can account f o r the d i f f e r e n c e i n e x t i n c t i o n c o e f i c i e n t s . s h i f t i n the a b s o r p t i o n bands, a l t h o u g h  they are small could  i n d i c a t i v e o f a change i n s t e r e o c h e m i s t r y .  The  be  A comparison o f the  nmr  s p e c t r a o f t h e s e compounds, however, showed pronounced changes which c o u l d not be e x p l a i n e d by the p r e s e n c e or absence o f the f u n c t i o n at C^,.  The major d i f f e r e n c e s o b s e r v e d between the spectrum  o f v i n b l a s t i n e ( f i g u r e 34) and t h a t o f dimer (119) l i s t e d i n Table I I . on the a r o m a t i c considerable  hydroxyl  ( f i g u r e 32)  are  I t can be seen from t h i s t a b l e t h a t the s u b s t i t u e n t s  p o r t i o n o f the v i n d o l i n e h a l f c£ t h e dimer show a  change i n c h e m i c a l  shift.  These p r o t o n s are v e r y n e a r  the j u n c t i o n between the h a l v e s o f the dimer and the changes i n chemical  s h i f t no doubt r e f l e c t s a s u b s t a n t i a l change i n t h e i r environment.  These d a t a suggest t h e r e f o r e t h a t the s t e r e o c h e m i s t r y i n the s y n t h e t i c dimer (119)  a t C^g,  from t h a t o f the n a t u r a l s e r i e s .  differs  - 102 -  Figure 34.  Nmr  spectrum of vinblastine  (16).  - 104 Table I I .  The major d i f f e r e n c e s o b s e r v e d between t h e nmr s p e c t r a o f v i n b l a s t i n e and dimer (119)  Chemical vinblastine  Shift dimer (119)  H  3.42  3 .05  H  3.94  4 .05  OCH  6.43  6.16 9.34  }  9.12 9.09  C.'CH CH 4 2 — 0  Experimentally,  o n l y one isomer has been o b t a i n e d  dimerization reactions.  from each o f t h e  S i n c e t h e same r e a c t i o n i s i n v o l v e d f o r t h e  s y n t h e s i s o f each d i m e r , i t i s r e a s o n a b l e  t o assume t h a t t h e s e dirners  a l l p o s s e s s t h e same s t e r e o c h e m i s t r y ,  and, on t h e b a s i s o f t h e above  comparison, that t h i s stereochemistry  d i f f e r s from t h a t o f t h e n a t u r a l  series.  •  I t i s d i f f i c u l t t o e x p l a i n m e c h a n i s t i c a l l y the of t h i s reaction. intermediates  The s t e r e o c h e m i s t r y  of the c h l o r o i n d o l e n i n e  have not been e s t a b l i s h e d .  From t i c and s p e c t r a l  i t i s seen t h a t t h e y a r e s i n g l e m a t e r i a l s r a t h e r t h a n mixtures.  An i n s p e c t i o n o f m o l e c u l a r  stereoselectivity  data,  epimeric  models show t h a t t h e a l i c y c l i c  p o r t i o n o f t h e m o l e c u l e e f f e c t i v e l y b l o c k s one s i d e o f t h e i n d o l e system from a t t a c k and f o r t h i s r e a s o n t h e s e compounds must be indolenines.  Reaction  g-chloro-  o f t h i s compound w i t h a n u c l e o p h i l e can o c c u r i n  - 105  two ways:  1) a c o n c e r t e d  -  d i s p l a c e m e n t o f c h l o r i d e by the  nucleophile  i n an S^2'-type r e a c t i o n , o r 2) i n i t i a l l o s s o f c h l o r i d e w i t h subsequent n u c l e o p h i l i c a t t a c k on the i n t e r m e d i a t e  formed.  In t h e f i r s t c a s e , a t t a c k by the n u c l e o p h i l e i s on the indolenine.  For s t e r i c and  chloro-  e l e c t r o n i c r e a s o n s , the d i r e c t i o n o f  a t t a c k w i l l be from the same s i d e of the m o l e c u l e as the c h l o r i n e . The  chloroindolenine  intermediate  i s , however, c a p a b l e o f e x i s t i n g  i n b o t h the i s o m e r i c forms, i n d i c a t e d by s t r u c t u r e s and t h e s e may  be i n e q u i l i b r i u m .  f a c t t h a t a) the c h l o r o i n d o l e n i n e s (125)  may  (124)  T h i s s i t u a t i o n may  (126)  (125)  r e s u l t from the  as shown by s t r u c t u r e s  be i n e q u i l i b r i u m w i t h t h e s t r u c t u r e (126),  and  (124)  allowing  and  - 106 c o n f o r m a t i o n a l l y v e r y m o b i l e , p a r t i c u l a r l y when i n v e r s i o n o f t h e n i t r o g e n i s allowed.  On t h i s b a s i s b o t h double-bond isomers  c o u l d e x i s t w i t h no u n f a v o u r a b l e  interactions.  (124) and (125)  Thus a l t h o u g h a t t a c k  by t h e n u c l e o p h i l e may o c c u r from one d i r e c t i o n , b o t h epimers c o u l d i n f a c t be formed. The  second r e a c t i o n mode may i n v o l v e an i n i t i a l  loss of chloride  i n a r a t e d e t e r m i n i n g s t e p t o form t h e i n t e r m e d i a t e (127).  This  l a t t e r s p e c i e s may e x i s t i n t a u t o m e r i c e q u i l i b r i u m w i t h 128 w h i c h upon r e a c t i o n w i t h a n u c l e o p h i l e would be e x p e c t e d  t o y i e l d a mixture o f  isomers.  (127)  A l t h o u g h we had expected  (128)  a m i x t u r e o f isomers  from t h i s  reaction,  t h e e x p e r i m e n t a l f i n d i n g s were t h a t o n l y one epimer was formed.  From  t h e d a t a p r e s e n t e d p r e v i o u s l y t h i s dimer appeared t o p o s s e s s t h e i n c o r r e c t s t e r e o c h e m i s t r y a t C, '.  I t was d e s i r a b l e , however, t o  o b t a i n dirners w i t h t h e s t e r e o c h e m i s t r y as found i n t h e n a t u r a l , systems because i t c o u l d be seen from m o l e c u l a r models t h a t a change o f s t e r e o c h e m i s t r y a t t h i s C^g' p o s i t i o n made a s u b s t a n t i a l d i f f e r e n c e t o t h e o v e r a l l shape o f t h e m o l e c u l e .  S i n c e m o l e c u l a r shape o f t e n  p l a y s an i m p o r t a n t r o l e i n d e t e r m i n i n g t h e b i o l o g i c a l a c t i v i t y , an  - 107 u n n a t u r a l s t e r e o c h e m i s t r y a t t h i s c e n t r e may  r e v e a l a dramatic  a l t e r a t i o n i n the d e s i r e d a n t i - t u m o r a c t i o n o f t h e s e m o l e c u l e s .  We  t h e r e f o r e t u r n e d t o an a l t e r n a t e approach f o r the c o u p l i n g o f the monomeric u n i t s . The  second d i m e r i z a t i o n approach was based on a method  developed  74 by B u c h i f o r the s y n t h e s i s o f voacamine (129).  He found t h a t  t h i s compound c o u l d be s y n t h e s i z e d by s i m p l y h e a t i n g v o b a s i n o l and v o a c a n g i n o l acid.  (130)  (131) t o g e t h e r i n a s o l u t i o n o f m e t h a n o l i c h y d r o c h l o r i c  T h i s method was  s u b s e q u e n t l y used by Harley-Mason t o condense  (129)  - 108 1 8 - h y d r o x y d i h y d r o c l e a v a m i n e (132) w i t h v i n d o l i n e t o g i v e the dimer  (133).  The b r i e f r e p o r t on t h i s work makes no mention o f t h e s t e r e o c h e m i c a l aspects of t h i s r e a c t i o n .  The mechanism o f t h i s r e a c t i o n would be e x p e c t e d t o i n v o l v e a protonation of the C  1 0  a l c o h o l f u n c t i o n t o form an i n t e r m e d i a t e oxonium  i o n w h i c h upon l o s s o f water would y i e l d t h e carbonium i o n (137). A g a i n as i n t h e mechanism i n v o l v i n g t h e i n t e r m e d i a t e  127 and 128, t h e  (137) f o r m a t i o n o f b o t h epimers a t t h e C. ' p o s i t i o n would be  expected.  - 109 In o u r i n i t i a l  i n v e s t i g a t i o n s o f t h i s r e a c t i o n , t h e sequence  outlined i n Part I of t h i s discussion developed.  ( f i g u r e s 10 and 11) had n o t been  The r e a c t i o n sequence proposed a t t h a t t i m e i n v o l v e d  t h e s y n t h e s i s o f t h e e x o c y c l i c o l e f i n (79) from 18-hydroxymethyl-4gdihydrocleavamine (92). (135).  O s m y l a t i o n o f t h i s o l e f i n would g i v e t h e d i o l  T h i s m a t e r i a l c o u l d be used f o r d i m e r i z a t i o n and t h e p r o d u c t  would c o n t a i n t h e h y d r o x y m e t h y l f u n c t i o n a t t h e |C^ ' p o s i t i o n . R  f u n c t i o n would p r o v i d e  a convenient handle f o r the eventual  production  CH 0R 2  (92) R=H  (79)  (138) R=C0Ph  (132)  dimer (C  '-CH.OH) lo  dimer (133)  dimer  2.  (C '-C0 Me) lg  2  This  - 110 of* the C  '-carbomethoxy group t o g i v e a dimer e i t h e r i d e n t i c a l t o  dimer (119) o r i t s C^g'  epimer.  An a l t e r n a t e and perhaps more s i m p l e  r o u t e f o r a comparison o f t h e s t e r e o c h e m i s t r y o f t h i s d i m e r i z a t i o n w i t h the c h l o r o i n d o l e n i n e approach would be the s y n t h e s i s o f dimer v i a the a c y l i n d o l e (136). o b t a i n e d fromthe d i o l  The  l a t t e r i n t e r m e d i a t e c o u l d be  (133) readily  (135) by p e r i o d a t e c l e a v a g e .  I n o r d e r t o e v a l u a t e t h i s sequence 183-hydroxymethyl-4B-dihydrocleavamine  ( 9 2 ) , r e a d i l y a v a i l a b l e from c a t h a r a n t h i n e by r i n g  t o 183-carbomethoxycleavamine (see f i g u r e 6 ) , f o l l o w e d by and l i t h i u m aluminum h y d r i d e r e d u c t i o n , was material.  The  opening  catalytic  c o n s i d e r e d as a s t a r t i n g  approach e q u i v a l e n t t o d e h y d r a t i o n i n v o l v e d s i m p l y the  c o n v e r s i o n o f the a l c o h o l t o a good l e a v i n g group and then e l i m i n a t i o n e i t h e r by use o f heat o r base. was  Our f i r s t attempt a t t h i s sequence  the p r e p a r a t i o n o f the 3 , 5 - d i n i t r o b e n z o a t e .  c a r r i e d out a t room temperature aqueous base work up chloride.  One  The r e a c t i o n was  i n p y r i d i n e and was  f o l l o w e d by a weak  t o remove the excess 3 , 5 - d i n i t r o b e n z o y l  p r o d u c t o t h e r t h a n s t a r t i n g m a t e r i a l was  obtained  and  t h i s m a t e r i a l gave s p e c t r a l e v i d e n c e i n d i c a t i n g c l e a r l y t h a t i t was not the 3 , 5 - d i n i t r o b e n z o a t e ,  C h a r a c t e r i z a t i o n of t h i s m a t e r i a l  showed i t t o be i n s t e a d , the e l i m i n a t i o n p r o d u c t , o l e f i n  (76),  o b t a i n e d i n 40% y i e l d based on s t a r t i n g m a t e r i a l consumed. m a t e r i a l was  shown t o be i d e n t i c a l t o the o l e f i n o b t a i n e d  by t h e r e a c t i o n sequence a l r e a d y d i s c u s s e d (see f i g u r e I t was  thought  This subsequently  10).  t h a t the y i e l d o f o l e f i n c o u l d be i n c r e a s e d by  the p r e p a r a t i o n o f a d e r i v a t i v e which was  s t a b l e enough t o be  isolated  - Ill  -  and would undergo e l i m i n a t i o n under c o n t r o l l e d c o n d i t i o n s r a t h e r t h a n d u r i n g t h e work-up. T h i s m a t e r i a l was  For t h i s r e a s o n , the b e n z o a t e (138)  s t a b l e and  c o u l d be p u r i f i e d .  was  Treatment o f  prepared. this  compound w i t h base consumed the b e n z o a t e but f a i l e d t o g i v e the P y r o l y s i s under h i g h vacuum y i e l d e d b e n z o i c a c i d but the contained  none o f the d e s i r e d o l e f i n .  r e s u l t s were o b t a i n e d .  I t was  a s i m i l a r set  became a v a i l a b l e i n b e t t e r t h a n 70% y i e l d from osmylation,  which was  sequence c o u l d not be a c h i e v e d .  the  olefin  dihydrocatharanthinol.  the n e x t r e a c t i o n i n our p r o p o s e d A v a r i e t y o f c o n d i t i o n s were a t t e m p t e d  i n c l u d i n g t h o s e found t o be s u c c e s s f u l f o r the s e c o d i e n e ( f i g u r e 11).  of  a t t h i s t i m e , t h a t the sequence  o f r e a c t i o n s o u t l i n e d i n f i g u r e 10 were d e v e l o p e d and  The  residue  A p a r a l l e l s e r i e s of experiments  were c a r r i e d out on the a c e t a t e o f the a l c o h o l and negative  olefin.  In a l l c a s e s , e x t r e m e l y c o m p l i c a t e d  (78)  mixtures of products  resulted. The  subsequent o s m y l a t i o n  ( f i g u r e 11)  o f the s e c o d i e n e and  l e d t o the s y n t h e s i s o f two  compounds p a r t i c u l a r l y w e l l  s u i t e d t o t h i s d i m e r i z a t i o n approach, the t r i o l  (97)  ensuing r e a c t i o n s  (97) and the d i o l  (99)  (99).  - 112 -  C o u p l i n g o f t h e s e compounds w i t h v i n d o l i n e would g i v e d i m e r i c m a t e r i a l s h a v i n g t h e h y d r o x y l f u n c t i o n a t C^' as i s found i n the n a t u r a l dirners, a l t h o u g h i t was known from the work p r e v i o u s l y d i s c u s s e d , t h a t t h e stereochemistry series.  a t t h i s c e n t e r was e p i m e r i c t o t h a t i n the n a t u r a l  The t r i o l d i m e r i z a t i o n s h o u l d g i v e a dimer w i t h an hydroxy-  m e t h y l group a t the C  ' p o s i t i o n and the c o n v e r s i o n o f t h i s f u n c t i o n j  to  the e s t e r would g i v e a dimer p o s s e s s i n g  a l l the f u n c t i o n a l i t y o f  v i n b l a s t i n e and d i f f e r i n g o n l y i n t h e s t e r e o c h e m i s t r y  a t the C^' and  perhaps a t t h e C^g' p o s i t i o n s . The c o u p l i n g o f the t r i o l be a c h i e v e d .  (97) w i t h v i n d o l i n e c o u l d , however, n o t  The r e a c t i o n l e d t o a t o t a l r e c o v e r y o f v i n d o l i n e and  l o s s o f a l l the t r i o l .  The p r o d u c t s o b t a i n e d showed a t y p i c a l  indole  a b s o r p t i o n i n t h e i r uv spectrum and showed a c a r b o n y l s t r e t c h i n g bond i n the i r .  That the t r i o l  s h o u l d decompose under  acidic  c o n d i t i o n s t o g i v e c a r b o n y l c o n t a i n i n g compounds i s not e n t i r e l y unexpected.  The t e r t i a r y a l c o h o l a t C^g c o u l d be v i s u a l i z e d t o undergo  a l o s s o f w a t e r t o an i n t e r m e d i a t e such as (139) which would be s u s c e p t i b l e t o n u c l e o p h i l i c a t t a c k by v i n d o l i n e .  CH OH  CHOH  2  (139)  An a l t e r n a t i v e mode  (140)  CHO  (141)  - 113 -  o f d e h y d r a t i o n which does n o t i n v o l v e t h e l o s s o f a r o r a a t i c i t y as e n t a i l e d by s t r u c t u r e (139), g i v e s i n s t e a d t h e c o n j u g a t e d  enol  (140).  Simple t a u t o m e r i z a t i o n o f t h i s i n t e r m e d i a t e l e a d s t o an e p i m e r i c m i x t u r e o f aldehydes The  (141).  coupling o f the d i o l  (99) w i t h v i n d o l i n e was a c h i e v e d under  r e f l u x i n g c o n d i t i o n s i n an anhydrous m e t h a n o l i c h y d r o c h l o r i c a c i d (1%) solution.  The major p r o d u c t , o b t a i n e d i n 45% y i e l d , gave s p e c t r a l  d a t a c o n s i s t e n t w i t h t h e s t r u c t u r e o f t h e dimer (142).  The d i m e r i c  n a t u r e was e v i d e n t from t h e s u p e r i m p o s i t i o n o f t h e i n d o l e and t h e i n d o l i n e chromophores i n t h e uv spectrum.  High r e s o l u t i o n mass a n a l y s i s on t h e  m o l e c u l a r i o n i n t h e mass spectrum gave a m o l e c u l a r c o m p o s i t i o n i n p e r f e c t agreement w i t h t h a t e x p e c t e d  f o r t h e dimer.  A comparison o f t h e  nmr o f t h i s compound ( f i g u r e 35) w i t h t h a t o f dimer (118) ( f i g u r e 28) p r e p a r e d by t h e c h l o r o i n d o l e n i n e approach c o n f i r m s t h e s i m i l a r i t y o f  (142)  Figure 35.  Nmr spectrum of dimer (142).  - 115 t h e s e two compounds. d i f f e r only i n  With r e s p e c t t o f u n c t i o n a l i t y , t h e s e compounds  t h a t t h e dimer (142) p o s s e s s e s  T h i s l e a d s t o minor d i f f e r e n c e s i n t h e nmr higher f i e l d  (> T 6.5).  correspond very  a h y d r o x y l at  C^ . 1  spectrum p a r t i c u l a r l y a t  A t lower f i e l d , however, t h e s e s p e c t r a  c l o s e l y t o each o t h e r .  T h i s a r e a o f t h e spectrum  c o n t a i n s t h e p r o t o n s a s s o c i a t e d w i t h b o t h a r o m a t i c systems and,  as  p o i n t e d out b e f o r e , s h o u l d be most a f f e c t e d by changes i n s t e r e o -  I chemistry at C  '.  The  f a c t t h a t these s p e c t r a j a r e n e a r l y i d e n t i c a l  j  18  i n t h i s r e g i o n p r o v i d e s s t r o n g e v i d e n c e f o r the same s t e r 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 n both these dimers.  Cleavage o f t h i s dimer under  t h e u s u a l a c i d i c r e d u c i n g c o n d i t i o n s gave a m i x t u r e o f v i n d o l i n e , d e s a c e t y l v i n d o l i n e , isovelbanamine, d e r i v a t i v e o f t h e dimer.  unchanged dimer and t h e d e s a c e t y l  This evidence  i n a d d i t i o n t o the s p e c t r a l  d a t a , e s t a b l i s h e d w i t h c e r t a i n t y t h e s t r u c t u r e o f t h e dimer One  o t h e r d i m e r i c m a t e r i a l was  this dimerization reaction. i t was  (142).  o b t a i n e d i n v e r y minor amounts from  An nmr  o f t h i s compound r e v e a l e d t h a t  t h e d e s a c e t y l analogue o f t h e dimer (142).  This m a t e r i a l  p r o b a b l y r e s u l t e d from h y d r o l y s i s d u r i n g t h e work up. I t appears from t h e e v i d e n c e p r e s e n t e d so f a r , t h a t t h i s d i m e r i z a t i o n approach has t h e same l i m i t a t i o n s as t h e d i m e r i z a t i o n v i a t h e c h l o r o i n d o l e n i n e s , t h a t i s , o n l y one o f t h e two p o s s i b l e isomers C^g'  i s formed and t h i s s t e r e o c h e m i s t r y i s p r o b a b l y not t h e one  i n the n a t u r a l . s y s t e m s .  The p r o o f f o r t h i s statement  at found  i s not c o n c l u s i v e  because i t i s based on comparisons o f s p e c t r a l d a t a f o r d i s s i m i l a r compounds.  To e s t a b l i s h t h i s w i t h c e r t a i n t y we r e t u r n e d t o t h e problem  o f s y n t h e s i z i n g e i t h e r o f t h e dimers (118) o r (119), which were  -  116  -  a v a i l a b l e from the c h l o r o i n d o l e n i n e approach by t h i s second c o u p l i n g procedure. For the s y n t h e s i s o f the s i m p l e s t o f t h e s e , dimer (118) i t s epimer, we were r e q u i r e d t o s y n t h e s i z e amine (132).  or  18-hydroxy-4B-dihydrocleav-  T h i s compound had been o b t a i n e d  i n e a r l i e r work i n our  l a b o r a t o r y from s t u d i e s i n v o l v e d w i t h the i n t r o d u c t i o n o f c y a n i d e the C  lo  1 Q  p o s i t i o n i n the c h l o r o i n d o l e n i n e o f  As d e s c r i b e d e a r l i e r , i t was  48-dihydrocleavamine. j  advantageous t o c o n v e r t t h i s c h l o r o -  i n d o l e n i n e (41) t o the q u a t e r n a r y  ammonium s a l t  (115).  s a l t r e s u l t e d from an i n t r a m o l e c u l a r d i s p l a c e m e n t f u n c t i o n at C  1 0  i n the i n t e r m e d i a t e a c e t a t e  dihydrocleavamine  (114)  at  c o u l d be o b t a i n e d  The  o f the  (114).  The  quaternary  acetoxy 18-acetoxy-4B-  impure i n low y i e l d  attempts to p u r i f y i t l e d to decomposition  but  and o n l y 18-hydroxy-48-  dihydrocleavamine  c o u l d be i d e n t i f i e d from the p r o d u c t s  obtained.  T h i s m a t e r i a l was  o b t a i n e d from the c h l o r o i n d o l e n i n e i n o n l y  2-3%  y i e l d which i s not good enough f o r p r e p a r a t i v e s y n t h e t i c work. a l t e r n a t e but v e r y s i m i l a r p r o c e d u r e was  An  a v a i l a b l e from p u b l i s h e d work  33 i n the i b o g a i n e s e r i e s .  T h i s sequence i n v o l v e d t h e i n t r o d u c t i o n o f  an 18-methoxyl s u b s t i t u t u e n t by t r e a t m e n t  o f the c h l o r o i n d o l e n i n e  w i t h methanol and a c i d and t h e n t o c l e a v e t h i s m e t h y l e t h e r t o g i v e the 18-hydroxy compound. We  chose t o s u b j e c t the c h l o r o i n d o l e n i n e o f 4 8 - d i h y d r o c l e a v a m i n e  (41) t o a s o l u t i o n o f aqueous a c e t i c a c i d .  E i t h e r o f two  p o s s i b l e i n t h i s system would l e a d t o the d e s i r e d p r o d u c t . a t t a c k by a c e t a t e a t the C^g  p o s i t i o n would g i v e t h e  processes Initial  18-acetoxy.  compound (114) which i n t h i s r e a c t i o n medium would r a p i d l y h y d r o l y z e  to  - 117 -  the 18-hydroxy analogue (132), o r t h e 18-hydroxy compound c o u l d be formed d i r e c t l y by n u c l e o p h i l i c a t t a c k o f water a t t h e C^g The  r e a c t i o n was a l l o w e d  t o p r o c e e d a t room t e m p e r a t u r e f o r 24 h o u r s .  A f t e r t h i s time one major p r o d u c t was p r e s e n t starting  position.  c h l o r o i n d o l e n i n e . The p r o d u c t ,  a l o n g w i t h some o f t h e  obtained  i n 38% y i e l d based  on s t a r t i n g m a t e r i a l consumed, had t h e same m e l t i n g p o i n t ,  identical  t i c p r o p e r t i e s and gave an i r s u p e r i m p o s a b l e w i t h t h a t o f an a u t h e n t i c sample o f 1 8 B - h y d r o x y - 4 3 - d i h y d r o c l e a v a m i n e . The achieved solution.  d i m e r i z a t i o n o f t h i s compound w i t h v i n d o l i n e was i n refluxing  readily  anhydrous m e t h a n o l i c 1% h y d r o c h l o r i c a c i d  The p r o d u c t o f t h i s r e a c t i o n , i s o l a t e d  i n 65% y i e l d had  i d e n t i c a l t i c p r o p e r t i e s and gave s u p e r i m p o s a b l e i r and nmr s p e c t r a compared t o t h e dimer (118) which was p r e p a r e d u s i n g t h e c h l o r o i n d o l e n i n e - d i m e r i z a t i o n approach. obtained  The o n l y o t h e r d i m e r i c  material  from t h i s r e a c t i o n was a s m a l l amount o f t h e d e s a c e t y l  d e r i v a t i v e o f dimer (118) p r e s e n t A repeat  i n about 5% y i e l d .  o f t h i s r e a c t i o n a t a much lower t e m p e r a t u r e , 24 hours  a t -5°C, l e d t o a p r o d u c t m i x t u r e c o n t a i n i n g much o f t h e s t a r t i n g m a t e r i a l s , some dimer (118) and one o t h e r p r o d u c t . chromophore o b t a i n e d  The s i m p l e  indole  f o r t h i s p r o d u c t i n t h e uv spectrum e x c l u d e d t h e  p o s s i b i l i t y o f t h i s m a t e r i a l b e i n g a dimer. spectrum was n o t o b t a i n e d ,  A l t h o u g h a good nmr  t h e spectrum resembled v e r y c l o s e l y  that  o f 18B-methoxy-4B-dihydrocleavamine and s u g g e s t e d r e a c t i o n o f t h e chloroindolenine with the solvent. These e x p e r i m e n t s t h e r e f o r e , c o n f i r m e d t h a t t h i s  dimerization  - 118  f o l l o w e d the same s t e r e o c h e m i c a l ization.  c o u r s e as the c h l o r o i n d o l e n i n e dimer-  S i n c e i t seemed u n l i k e l y  stereochemistry was  -  c o u l d be o b t a i n e d  a t t h i s t i m e t h a t the  d i r e c t l y i n the c o u p l i n g p r o c e s s ,  i n i t i a t e d t o a l t e r the s t e r e o c h e m i s t r y  formed.  Our  opposite work  o f the dimer once i t was  approach t o t h i s would be t o s t a r t w i t h a dimer  u n s u b s t i t u t e d at the C^g'  position,  t h i s compound t o a t e r t - b u t y l  such as dimer (118)  and t o  h y p o c h l o r i t e o x i d a t i o n i n order  subject to  I convert  i t t o the c h l o r o i n d o l e n i n e .  N u c l e o p h i l i c a t t a c k by  would t h e n form the 18'-cyano dimer (143).  f o l l o w s the same s t e r i c c o u r s e as was i n i t i a l formation  cyanide  I f a t t a c k by t h i s  nucleophile  the case w i t h v i n d o l i n e i n the  o f the dimer (118), t h e n the o v e r a l l r e s u l t would be  an i n v e r s i o n o f s t e r e o c h e m i s t r y  at the C^g'  position.  Conversion of  t h e n i t r i l e t o the carbomethoxy f u n c t i o n would t h e n l e a d t o  an  - 119 18-carbomethoxy dimer (144) h a v i n g t h e o p p o s i t e s t e r e o c h e m i s t r y a t C  ' t o t h a t o f dimer  (119).  lo  Our  e x p e r i e n c e w i t h t h e f o r m a t i o n o f 18-cyanocleavamine and  18-cyanodihydrocleavamine  by t h e r e a c t i o n o f t h e c o r r e s p o n d i n g c h l o r o -  i n d o l e n i n e s w i t h cyanide, suggested s e r i e s would be d i f f i c u l t  that t h i s conversion i n the dimeric  t o achieve.  To f a c i l i t a t e  the i d e n t i f i c a t i o n  o f t h e 18-cyano dimer ( 1 4 3 ) , i t was d e c i d e d t o |also s y n t h e s i z e a cyano dimer by t h e c o u p l i n g o f 1 8 - c y a n o - 4 g - d i h y d r o c l e a v a m i n e (42) with vindoline.  The dimer thus o b t a i n e d s h o u l d i n f a c t be t h e epimer  o f t h e cyano dimer (143) r e s u l t i n g from t h e i n v e r s i o n scheme, and would p r o v i d e a f u r t h e r c o m p a r i s o n o f two dimers d i f f e r i n g o n l y i n s t e r e o chemistry at C  '. 1o  The s y n t h e s i s o f 1 8 g - c y a n o - 4 B - d i h y d r o c l e a v a m i n e (42) was 59 developed  e a r l i e r i n our l a b o r a t o r y  Thus 4 g - d i h y d r o c l e a v a m i n e  was c o n v e r t e d t o i t s c h l o r o i n d o l e n i n e (41)  and t h i s compound on t r e a t m e n t gave t h e q u a t e r n a r y  salt  and has a l r e a d y been d i s c u s s e d .  (115).  w i t h sodium a c e t a t e i n a c e t i c  acid  Treatment o f t h e s a l t w i t h c y a n i d e i n  r e f l u x i n g d i m e t h y l formamide p r o v i d e d  18g-cyano-4g-dihydrocleavamine.  T h i s compound was t h e n t r e a t e d w i t h t e r t - b u t y l h y p o c h l o r i t e a t -15°C t o produce t h e c h l o r o i n d o l e n i n e (145).  T h i s m a t e r i a l was found t o be  u n s t a b l e and was t h e r e f o r e t r e a t e d i m m e d i a t e l y  w i t h v i n d o l i n e under  t h e u s u a l d i m e r i z i n g c o n d i t i o n s ( r e f l u x i n g i n anhydrous 1% h y d r o c h l o r i c a c i d s o l u t i o n ) t o g i v e the cyano dimer  methanolic  (146).  The s p e c t r a l d a t a f o r t h i s compound p r o v i d e d ample p r o o f f o r t h e s t r u c t u r e (145).  Once a g a i n t h e d i m e r i c n a t u r e o f t h e m a t e r i a l was  e v i d e n t from b o t h t h e uv and mass s p e c t r a w h i l e a weak a b s o r p t i o n i n  - 120 i  t h e i r a t 2250 cm  -1  e s t a b l i s h e d the presence  • I  of the n i t r i l e ;  H i g h r e s o l u t i o n mass measurement p r o v i d e d a m o l e c u l a r a g r e e i n g w i t h t h e m o l e c u l a r f o r m u l a f o r t h i s compound. spectrum  function.  composition The  nmr  ( f i g u r e 36) can be seen on t h e b a s i s o f our p r e v i o u s  experience  !  t o be t y p i c a l f o r t h i s c l a s s o f dirners.  One u n u s u a l f e a t u r e was  (146) observed  i n t h i s spectrum  and t h a t i s t h e c h e m i c a l s h i f t o f the  C,.14  r  proton s i g n a l . C.  In the case o f t h e dirners b e a r i n g no s u b s t i t u e n t a t  ' ( c f f i g u r e s 28 and 34) t h i s s i g n a l i s observed a t x 3.3.  dimer h a v i n g a carbomethoxy f u n c t i o n a t C  r 1 Q  shows t h i s p r o t o n t o  be d e s h i e l d e d r e l a t i v e t o t h i s and i s o b s e r v e d a t x 3.05. cyano dimer ( 1 4 6 ) , however, t h e same p r o t o n i s now and i s o b s e r v e d a t x 3.79.  The  In t h i s  strongly shielded  T h i s i s not s u r p r i s i n g s i n c e t h i s  proton  and n i t r i l e f u n c t i o n a r e q u i t e c l o s e t o each o t h e r i n one o f the p o s s i b l e rotomers  two  and a r e a r r a n g e d s p a t i a l l y such t h a t t h e axes o f  t h e i r bonds a r e p a r a l l e l .  S i n c e t h e s h i e l d i n g cone of t h e n i t r i l e  group  i s perpendicular  -  t o the a x i s o f the C=N  put d i r e c t l y i n t o t h i s The  122  bond, the p r o t o n a t  field.  approach t o t h e cyano dimer (143)  chloroindolenine  (118)  othei*- workers i n our  is  u s i n g the r e a c t i o n o f  the  with cyanide i s c u r r e n t l y being i n v e s t i g a t e d  laboratory.  I f t h i s r e a c t i o n can be  developed,  t h e n the d i m e r i z a t i o n approaches u s i n g e i t h e r the c h l o r o i n d o l e n i n e s the C j - a l c o h o l s w i l l 8  stereoisomeric  s e r v e as a g e n e r a l  or  s y n t h e t i c scheme f o r b o t h  s e r i e s of dimers.  \ As y e t , no s y n t h e t i c m a t e r i a l s the f u n c t i o n a l i t y o f one has been s y n t h e s i z e d , schemes p r o v i d e  by  are a v a i l a b l e which p o s s e s s a l l  o f the n a t u r a l d i m e r s .  the q u e s t i o n  the s t e r e o c h e m i s t r y  U n t i l such a compound  o f whether o r not t h e s e s y n t h e t i c at C  ' corresponding to  the  lo  n a t u r a l s y s t e m s , w i l l not be p r o p e r l y s e t t l e d . T h i s i s a v e r y i m p o r t a n t p o i n t and d i r e c t i o n are being i n i t i a t e d . now  further studies i n this  For example, the work o f t h i s t h e s i s  p r o v i d e s t h e means o f s y n t h e s i z i n g v i n b l a s t i n e or t h e  isomer a t C^g'.  stereo-  0° the b a s i s o f the s u c c e s s f u l i s o m e r i z a t i o n  i s o v e l b a n a m i n e t o v e l b a n a m i n e and attempts to dimerize  the t r i o l  the r e s u l t s obtained  of  from the  ( 9 7 ) , i t i s a n t i c i p a t e d t h a t the  w i l l be c o n v e r t e d t o the compound (147)  on a c i d t r e a t m e n t .  triol  - 123 -  T h i s compound now b e a r s stereochemistry.  the hydroxyl f u n c t i o n at  O x i d a t i o n o f t h e 18-formyl  with the correct  s u b s t i t u e n t f o l l o w e d by  e s t e r i f i c a t i o n then g i v e s 18-carbomethoxyvelbanamine  (148).  D i m e r i z a t i o n w i l l produce e i t h e r v i n b l a s t i n e o r i t s C - e p i m e r and 1 0  lo  e i t h e r r e s u l t w i l l determine w i t h c e r t a i n t y the stereochemical of the d i m e r i z a t i o n r e a c t i o n .  course  I f the epimeric m a t e r i a l i s obtained  the e f f e c t o f t h i s s t e r e o c h e m i c a l d i f f e r e n c e on t h e b i o l o g i c a l a c t i v i t y can then be c l e a r l y a s c e r t a i n e d .  Once b o t h t h e s e p o i n t s  have been s e t t l e d , t h e n a s y s t e m a t i c s t u d y o f t h e e f f e c t s o f f u r t h e r s t r u c t u r a l m o d i f i c a t i o n o f t h e dirners on b i o l o g i c a l a c t i v i t y can b e i n g .  r  ;  EXPERIMENTAL  M e l t i n g p o i n t s were d e t e r m i n e d on a K o f l e r b l o c k and a r e u n c o r r e c t e d . The u l t r a v i o l e t s p e c t r a (uv) were r e c o r d e d on a Cary 11 meter u s i n g methanol as s o l v e n t unless o t h e r w i s e  spectrophoto-  specified.  Infrared  s p e c t r a ( i r ) were r e c o r d e d on a P e r k i n - E l m e r Model 21 and Model 137 spectrometers.  N u c l e a r magnetic resonance (nmr) s p e c t r a were  r e c o r d e d i n d e u t e r i o c h l o r o f o r m a t 100 Hz on a V a r i a n HA-100  instrument  and the c h e m i c a l s h i f t s a r e g i v e n i n the T i e r s x s c a l e w i t h r e f e r e n c e t o t e t r a m e t h y l s i l a n e as t h e i n t e r n a l s t a n d a r d .  Mass s p e c t r a were  r e c o r d e d on an A t l a s CH-4 o r an AE-MS-9 mass s p e c t r o m e t e r .  Analyses  were c a r r i e d out by Mr. P. Borda o f t h e m i c r o a n a l y t i c a l l a b o r a t o r y , the U n i v e r s i t y o f B r i t i s h Columbia.  Woelm n e u t r a l a l u m i n a and S i l i c a  G e l G ( a c c . t o S t a h l ) c o n t a i n i n g 1% by weight o f G e n e r a l  Electric  R e t i n a p-1 Type 188-2-7 e l e c t r o n i c phosphor were used f o r a n a l y t i c a l t h i n - l a y e r chromatography ( t i c ) .  C h r o m a t o p l a t e s were developed  1:1 c a r b o n t e t r a c h l o r i d e - a n t i m o n y p e n t a c h l o r i d e s o l u t i o n . alumina  using  Woelm n e u t r a l  ( a c t i v i t y I I I ) was used f o r column chromatography ( u n l e s s o t h e r -  wise i n d i c a t e d ) .  22 Dihydrocatharanthine Catharanthine  (34)  h y d r o c h l o r i d e (20 g) was suspended i n w a t e r (400 c c ) ,  the m i x t u r e c o o l e d t o 0°C and then b a s i f i e d w i t h i c e - c o l d  ammonia.  - 125  The  r e s u l t i n g suspension  was  -  t h e n e x t r a c t e d w i t h e t h e r , the  organic  l a y e r d r i e d w i t h anhydrous sodium s u l p h a t e and the s o l v e n t removed t o g i v e the f r e e base as a w h i t e foam. 95% e t h a n o l mixture  (1000  c c ) , Adam's c a t a l y s t (800 mg)  was  dissolved i n  added and  the  s t i r r e d under hydrogen at room t e m p e r a t u r e f o r 4 days.  c a t a l y s t was white  T h i s m a t e r i a l was  The  f i l t e r e d o f f and the f i l t r a t e t a k e n t o d r y n e s s t o g i v e a  foam o f s u b s t a n t i a l l y p u r e d i h y d r o c a t h a r a n t h i n e  dihydrocatharanthine  was  Pure  o b t a i n e d by chromatography u s i n g a l u m i n a  (Woelm n e u t r a l , a c t i v i t y I , 600 i n benzene (14.5  (17 g ) .  g, 8 0 % ) .  g) and e l u t i n g w i t h 5% d i e t h y l  ether  C r y s t a l l i z a t i o n from methanol gave p l a t e s 22  mp  68-73° w i t h r e c r y s t a l l i z a t i o n and subsequent mp  i ) 63-65°, i i ) 150°  145-147° ( l i t . mp  decomp.) 22  Dihydrocatharanthinol  (76)  L i t h i u m aluminum h y d r i d e catharanthine  (11.4  (5.4 g) was  g) i n d r y t e t r a h y d r o f u r a n  mixture r e f l u x e d f o r 5 hours. (35 cc) was  added t o a s o l u t i o n o f d i h y d r o -  I t was  (500 cc) and the  t h e n c o o l e d i n i c e and  added d r o p w i s e w i t h s t i r r i n g .  The  resulting  water  grey s u s p e n s i o n  was  h e a t e d under r e f l u x f o r 1/2 h o u r and the r e s u l t i n g w h i t e p r e c i p i t a t e filtered off. foam (11.0  The  f i l t r a t e was  g) which was  taken to dryness to give a  chromatographed on a l u m i n a (320 g ) .  d i h y d r o c a t h a r a n t h i n o l was  eluted with chloroform  (10.3 g ) .  c r y s t a l l i z e d from c h l o r o f o r m - l i g h t p e t r o l e u m e t h e r 143°  (7.34  g)  (lit.  2 2  mp  132°).  white Pure This m a t e r i a l  as rhombs mp  142-  - 126 D i h y d r o c a t h a r a n t h i n o l O - p - t o l u e n e s u l f o n a t e (77a) Dihydrocatharanthinol  (1.58 g) was d i s s o l v e d  (30 c c ) and ; p - t o l u e n e s u l f o n y l  chloride  i n dry pyridine  (4.7 g) was added t o t h i s s o l u t i o n .  The  r e a c t i o n was a l l o w e d t o p r o c e e d f o r 10 h o u r s a t room t e m p e r a t u r e .  The  r e a c t i o n m i x t u r e was t h e n c o o l e d t o 0°C, i c e - c o l d methylene  chloride  (50 c c ) was added and t h i s s o l u t i o n was washed w i t h 3%  sodium b i c a r b o n a t e s o l u t i o n at a l l times.  (3 x 50 c c ) , k e e p i n g t h e s o l u t i o n a t 0°C  The methylene c h l o r i d e - p y r i d i n e  s o l u t i o n was t h e n  t a k e n t o d r y n e s s u s i n g f i r s t waterpump p r e s s u r e and f i n a l l y h i g h vacuum.  A g a i n t h e s o l u t i o n had t o be kept below 0°C t h r o u g h o u t t h i s  procedure.  The r e s u l t i n g r e d gum s t i l l  was d i s s o l v e d  containing  traces  of pyridine,  i n d r y benzene (5 c c ) and l e f t t o c r y s t a l l i z e  i n the r e f r i g e r a t o r .  overnight  The crude t o s y l a t e was f i l t e r e d o f f t o g i v e  1.64 g o f l i g h t brown c r y s t a l l i n e m a t e r i a l . The mother l i q u o r s were t a k e n up i n benzene (10 c c ) and f r e e z e - d r i e d o f s u b s t a n t i a l l y pure t o s y l a t e as a r e d d i s h  t o g i v e a f u r t h e r 0.65 g amorphous powder.  Attempts t o r e c r y s t a l l i z e the c r y s t a l l i n e m a t e r i a l  f a i l e d and g e n e r a l l y  l e d t o l e s s p u r e t o s y l a t e because o f d e c o m p o s i t i o n i n s o l u t i o n . KBr c r y s t a l l i n e material (v SCO '•as 2  and 1173 c m  gave t h e f o l l o w i n g d a t a : - 1  v m  a  x  The  -1 1355 cm  (v S C L ) ; X 292, 285, 276 (sh) . s 2' max ' ' J  J  5,18-Seco-diene (78) Dihydrocatharanthinol o-tosylate dissolved  (400 mgs; 0.86 mmole) was  i n a s o l u t i o n o f d r y benzene (15 c c ) and t r i e t h y l a m i n e  1.73 mmole).  T h i s s o l u t i o n was s t i r r e d under a n i t r o g e n  (0.24 m l ;  atmosphere  f o r 2 h o u r s a t 70°C t o e f f e c t t h e d i s p l a c e m e n t . The s o l u t i o n was t h e n  - 127  -  c o o l e d t o room t e m p e r a t u r e and was ( b a s i c Woelm:, I I I , pressure. column.  f l u s h e d r a p i d l y through  alumina  10 g s e t up as a 1 i n c h h i g h column) u s i n g p o s i t i v e  A f u r t h e r p o r t i o n o f benzene (100 cc) was  used t o wash the  ;  The: combined s o l u t i o n s on removal o f s o l v e n t under r e d u c e d  p r e s s u r e and a t room t e m p e r a t u r e gave a l i g h t y e l l o w gum  which  c r y s t a l l i z e d on s t a n d i n g t o g i v e v i r t u a l l y p u r e p r o d u c t  (155 mg,  mp  129-135°C).  T h i s m a t e r i a l c o u l d be r e c r y s t a l l i z e d from c o l d benzene  mp  S u b l i m a t i o n gave an a n a l y t i c a l l y pure sample mp  130-132.  136.5.  v  KRr  max  1  3445 cm  enamine), 1408,  880  ( i n d o l e N-H ^  s t r e t c h ) , 1657  ( e x o c y c l i c methylene);  A  1  cm  306,  235  (v  136C=C,  ( s h ) , 340  in 3.x (sh) ( l o g e 4.16, IH,  N-H),  340 r e s p e c t i v e l y ) ;  2.5-3.0 ( d i f f u s e , 4H,  R N-CH=CR ), 4.75 3  4.34,  2  9.05  ( t r i p l e t , 3H,  168,  135,  122,  a r o m a t i c ) , 4.29  ( s i n g l e t , IH, R C=CH_ ) , 4.89  121,  2  2  -CH CH_ ); mass spectrum: 2  3  T 2.05  (broad  singlet,  (broad s i n g l e t ,  IH,  ( s i n g l e t , IH, R C=CH ), 2  main p e a k s , m/e  2  292,  185,  M.W.  292.194  107.  Anal. Calcd. f o r C 0 2 2 4 N  H  :  2  Found:  NMR:  C, 82.26; H, 8.27;  C, 82.19; H, 8.22;  N, 9.72;  M.W.  N, 9.59;  292.191 ( h i g h r e s o l u t i o n  mass s p e c t r o m e t r y ) .  1 8 - M e t h y l e n e - 4 B - d i h y d r o c l e a v a m i n e ( 7 9 ) ; c o n c e r t e d sequence from dihydrocatharanthinol O-tosylate  (77a)  Dihydrocatharanthinol O-p-toluenesulfonate  (400 mg,  0.86  mmole) was  d i s s o l v e d i n a s o l u t i o n o f d r y benzene (15 cc) and t r i e t h y l a m i n e (0.24  c c , 1.73  mmole).  T h i s s o l u t i o n was  s t i r r e d under a n i t r o g e n  f o r 2 hours a t 70°C t o e f f e c t the d i s p l a c e m e n t .  S o l v e n t was  removed,  under reduced p r e s s u r e and the brown r e s i d u e d i s s o l v e d i n methanol.  - 128 -  Sodium b o r o h y d r i d e (200 mg) was added i m m e d i a t e l y and t h e r e a c t i o n m i x t u r e s t i r r e d f o r 0.5 hours a f t e r w h i c h , t h e e f f e r v e s c e n c e had ceased.  T h i s s o l u t i o n was s t r i p p e d o f s o l v e n t and t h e r e s i d u e was  p a r t i t i o n e d between d i c h l o r o m e t h a n e The  (100 cc) and water  (100 c c ) .  aqueous, l a y e r was e x t r a c t e d w i t h a d d i t i o n a l d i c h l o r o m e t h a n e  (2 x  50 cc) and t h e combined o r g a n i c e x t r a c t was d r i e d o v e r anhydrous s u l f a t e and t h e s o l v e n t was removed t o g i v e a y e l l o w gum. m a t e r i a l was chromatographed  on a l u m i n a (100 g ) .  the d e s i r e d 1 8 - m e t h y l e n e - 4 8 - d i h y d r o c l e a v a m i n e from methanol-water 3.92,  mp 90-94°C.  A  m  a  x  sodium  This  Benzene e l u t i o n gave  (182 mg); c r y s t a l l i z e d  306, 315 ( s h ) , 218 ( l o g e 3.97,  4.16, r e s p e c t i v e l y ) ; NMR: T 1.90 (broad s i n g l e t , IH, N-H), 2.5-  3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 4.79 and 4.93 (two s i n g l e t s , IH each,  C^CFLp, 9.13 ( t r i p l e t , 3H, -Q^-CH^) ; Mass spectrum:  main p e a k s ,  m/e 294, 292, 207, 139, 124. A n a l . C a l c d . f o r C -N_H.,: 0  ZU  M.W.  294.209.  Found: M.W.  294.209.  Z ZD  D i h y d r o c a t h a r a n t h i n o l O-methanesulfonate (77b) D i h y d r o c a t h a r a n t h i n o l (1.0 g) was d i s s o l v e d i n d r y p y r i d i n e (10 c c ) and t o t h i s s o l u t i o n c o o l e d t o -5°C was added f r e s h l y methanesulfonyl c h l o r i d e  (6 c c ) .  s t i r r e d a t 0°C f o r 20 h o u r s .  distilled  The r e s u l t i n g r e d s o l u t i o n was  I c e - c o l d c h l o r o f o r m (100 cc) was t h e n  added t o t h e r e a c t i o n m i x t u r e and t h e r e s u l t i n g s o l u t i o n e x t r a c t e d w i t h water  (3 x 50 c c ) .  The c o l d c h l o r o f o r m s o l u t i o n was d r i e d o v e r  anhydrous  sodium s u l f a t e and c o n c e n t r a t e d under reduced p r e s s u r e t o a  red  R a p i d p e r c o l a t i o n o f t h i s m a t e r i a l u s i n g d i c h l o r o m e t h a n e as  gum.  e l u e n t , t h r o u g h a l u m i n a ( I V , 30 g) removed most o f t h e v e r y p o l a r  - 129 I  material  and gave t h e crude m e t h a n e s u l f o n a t e e s t e r as a y e l l o w o i l .  Chromatography on a l u m i n a ( I V , n e u t r a l , 60 g) y i e l d e d impurities  (15 mg) i n t h e benzene f r a c t i o n s f o l l o w e d  dihydrocatharanthinol  O-methanesulfonate  non-polar by t h e d e s i r e d  as a y e l l o w u n s t a b l e foam.  X 276, 283, 292. The m e t h a n e s u l f o n a t e was u n s t a b l e and was used max immediately' i n t h e subsequent e l i m i n a t i o n  18-Methylene-4g-dihydrocleavamine  reaction.  ( 7 9 ) ; from  dihydrocatharanthinol-  O-methanesulfonate (77b) A s o l u t i o n o f potassium tert-butoxide  was p r e p a r e d by d i s s o l v i n g  c l e a n p o t a s s i u m (1.2 g) i n r e f l u x i n g t e r t - b u t a n o l d i s t i l l e d from sodium). mg) was d i s s o l v e d under a n i t r o g e n  (50 c c , f r e s h l y  D i h y d r o c a t h a r a n t h i n o l - O - m e t h a n e s u l f o n a t e (350  i n t h i s s o l u t i o n and t h e r e s u l t i n g s o l u t i o n  refluxed  atmosphere f o r 50 min. The uv o f t h i s s o l u t i o n showed  a maximum a t 304 my w i t h no i n d o l e a b s o r p t i o n e v i d e n t . was made j u s t a c i d i c w i t h g l a c i a l a c e t i c a c i d sodium b o r o h y d r i d e (600 mg) was added.  This  solution  (2 c c ) and an excess o f  T h i s s o l u t i o n was r e f l u x e d  f o r 3 hours.  S o l v e n t was removed under reduced p r e s s u r e , t h e r e s i d u e  was d i s s o l v e d  i n c o l d water  (100 c c ) and t h i s m i x t u r e was  w i t h d i c h l o r o m e t h a n e (3 x 50 c c ) .  extracted  The combined o r g a n i c e x t r a c t s  were  d r i e d o v e r anhydrous p o t a s s i u m c a r b o n a t e and c o n c e n t r a t e d t o g i v e a y e l l o w gum (170 mg) which was chromatographed 6 g) u s i n g benzene as e l u e n t . exocyclic olefin  The e a r l y f r a c t i o n s gave t h e pure  (79) as a c o l o u r l e s s  glass  had i d e n t i c a l t i c and s p e c t r a l p r o p e r t i e s o b t a i n e d from t h e r e d u c t i o n  on a l u m i n a ( I V , n e u t r a l ,  (29 mg).  This  to the e x o c y c l i c  o f 5,18-seco-diene ( 7 8 ) .  material olefin  - 130 18-Methylene-4g-dihydrocleavamine  ( 7 9 ) ; c o n c e r t e d sequence  from  d i h y d r o c a t h a r a n t h i n o l v i a methanesulfonate e s t e r Dihydrbcatharanthinol  (1 g) i n anhydrous  pyridine  (9 c c )  t r e a t e d a t -r5°C w i t h m e t h a n e s u l f o n y l c h l o r i d e  (3 cc) .  The  r e d s o l u t i o n was k e p t a t 0°C f o r 3 h o u r s .  resulting  The m i x t u r e was poured  i c e - c o l d d i c h l o r o m e t h a n e (75 cc) and e x t r a c t e d w i t h water The o r g a n i c phase was  was  into  (2 x 50 c c ) .  concentrated to a red c r y s t a l l i n e paste.  This  m a t e r i a l was p e r c o l a t e d r a p i d l y t h r o u g h a l u m i n a ( I V , n e u t r a l , 30 g) u s i n g d i c h l o r o m e t h a n e and the s o l u t i o n on removal o f s o l v e n t gave a y e l l o w gum.  T h i s was  d i s s o l v e d i n a s o l u t i o n of potassium t e r t -  butoxide i n tert-butanol r e f l u x e d f o r 20 min.  ( 3 . 5 g o f p o t a s s i u m i n 200 cc d r y b u t a n o l ) and  S o l v e n t was removed under r e d u c e d p r e s s u r e and  the r e s i d u e p a r t i t i o n e d between e t h e r and w a t e r . was  d r i e d o v e r anhydrous  i n g y e l l o w o i l was  The e t h e r e x t r a c t  sodium s u l f a t e and c o n c e n t r a t e d .  The  result-  t h e n d i s s o l v e d i n i s o p r o p a n o l (70 c c ) and a c e t i c  (1 cc) and e x c e s s sodium b o r o h y d r i d e (2 g) was  added.  acid  When the e f f e r v e s -  cence had s u b s i d e d , s o l v e n t was removed, the r e s i d u e p a r t i t i o n e d between e t h e r and w a t e r and the o r g a n i c l a y e r , a f t e r d r y i n g , c o n c e n t r a t e d t o a y e l l o w gum. The  T h i s m a t e r i a l was  chromatographed  on a l u m i n a (50 g ) .  e a r l y benzene f r a c t i o n s gave pure e x o c y c l i c o l e f i n  ( 7 6 ) (180  mg)  i d e n t i c a l on t i c and nmr w i t h the m a t e r i a l o b t a i n e d from the r e d u c t i o n of 5,18-seco-diene ( 7 8 ) .  18g-Hydroxymethylcleavamine  (86)  18g-Carbomethoxycleavamine  (100 mg)  was  d i s s o l v e d i n dry  t e t r a h y d r o f u r a n and l i t h i u m aluminum h y d r i d e (50 mg)  was  added.  This  - 131 m i x t u r e was r e f l u x e d f o r 2 hours under n i t r o g e n .  The r e a c t i o n  p r o d u c t was c o o l e d i n an i c e - b a t h and s a t u r a t e d sodium s u l f a t e was added d r o p w i s e .  (10 c c )  Water (50 c c ) was t h e n added and t h e m i x t u r e  e x t r a c t e d w i t h d i c h l o r o m e t h a n e (4 x 25 c c ) .  The combined  organic  e x t r a c t s were d r i e d o v e r anhydrous sodium s u l f a t e and t h e s o l v e n t was removed. 3450 cm"  (v 0-H),  1  CHC1 v 3: max  The a l c o h o l o b t a i n e d gave t h e f o l l o w i n g d a t a ; 1030 cm"  1  (v C-0); NMR: T 1.50 (broad s i n g l e t , I H ,  N-H),  2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 4.66 ( p o o r l y d e f i n e d m u l t i p l e t ,  IH,  C=CH-), 5.74 ( q u i n t u p l e t , I H , C - p r o t o n ) , 6.32 ( d o u b l e t , 2H, 1 Q  —  lo  CH-CH_ 0H), 8.98 ( t r i p l e t , 2  3H, -CH CH_ ). 2  3  Mass spectrum:  main p e a k s ,  m/e 310, 187, 136, 135, 124.  186-Hydroxymethylcleavamine  a c e t a t e (88)  186-Hydroxymethylcleavamine of  a c e t i c anhydride i n p y r i d i n e  (92 mg) was d i s s o l v e d i n a s o l u t i o n (10% v/v) and t h e r e s u l t i n g  s t i r r e d a t room t e m p e r a t u r e f o r 1 day under a n i t r o g e n  solution  atmosphere.  The r e a c t i o n m i x t u r e was c o o l e d t o 0°C and was t h e n poured onto i c e ( c r u s h e d % 30 g ) .  On s t i r r i n g ,  m i x t u r e (83 mg) mp 123-127°C;  t h e a c e t a t e c r y s t a l l i z e d from t h e  KRr  v ^ :  1705 cm  1  (v C=0),  -1 1260 cm  (v C-0); NMR:T 1.87 (broad s i n g l e t , I H , N-H), 2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 4.75 (broad s i n g l e t , I H ,  C=CH-), 5.5 (broad t r i p l e t , I H ,  C - H ) , 5.70 and 5.98 (two d o u b l e t o f d o u b l e t s , 2H, 1 0  lo  ( s i n g l e t , 3H, -OAc), 8.96 ( t r i p l e t ,  3H, -CH^H^) .  p e a k s , m/e 352, 293, 229, 136, 135, 124, 122.  CH-CHJDAc), 7.98 —2.  Mass spectrum:  main  - 132 j  18grHydroxymethylcleavamine  3 , 5 - d i n i t r o b e n z o a t e (89)  183-Hydrpxymethylcleavamine pyridine  (25 c c ) .  (470 mg)  T h i s s o l u t i o n was  b e n z o y l c h l o r i d e was  added  c o o l e d t o 0°C and  3,5-dinitro-  s t i r r e d f o r 1 hour a t 0°C and was  poured onto c r u s h e d i c e (^ 300 g ) . filtered  d i s s o l v e d i n dry  i n p o r t i o n s over a 10 minute i n t e r v a l .  r e s u l t i n g r e d s o l u t i o n was  which was  was  On s t i r r i n g  then  a precipitate  o f f t o g i v e the crude p r o d u c t (714 mg).  The  formed  Chromato-  graphy on alumina (200 g) gave the pure 3 , 5 - d i n i t r o b e n z o a t e (89) (406 mg)  w i t h benzene e l u t i o n .  The m a t e r i a l c r y s t a l l i z e d  as b r i g h t orange n e e d l e s ; mp  155-157°C;  3400 c m  (v C=0),  (v  s  1.03  (  -1  N0 ),  v  N-H),  1280  2  cm  -1  1710  cm  -1  (v C-0); NMR:  2H,  IHcLX  1545  9.09  T  :  (quintriplet,  IH, C^g-H), 5.41  CH-CH 0R), 8.99 2  (triplet,  (300 mg)  f o r m i n g , i t was solution  228;  -NO.), 1340  KBr IH3.X  :  cm"  1  IH, benzoate p - p r o t o n  (broad s i n g l e t ,  (broad d o u b l e t , IH,  IH,  N-H),  C=CH-),  (two d o u b l e t o f d o u b l e t s ,  2  3  (92) from the h y d r o b o r a t i o n o f  (78), was  and was  p r e p a r e d from d i h y d r o c a t h a r a n t h i n o l  used as the crude r e a c t i o n p r o d u c t .  On  immediately d i s s o l v e d i n a d i b o r a n e - t e t r a h y d r o f u r a n  ( d i b o r a n e produced from sodium b o r o h y d r i d e (200 mg)  boron t r i f l u o r i d e - e t h e r a t e tetrahydrofuran  v  (78)  The 5,18-seco-diene 0-tosylate  ( v  285,  -CH CH_ ).  18g-Hydromethyl-4g-dihydrocleavamine the 5,18-seco-diene  1  (triplet,  and 5.63  3H,  293,  cm"  ( d o u b l e t , 2H, benzoate o - p r o t o n s ) , 2.10  2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 4.70 5.16  \  from methanol  (1 cc) i n diglyme  (25 c c ) ) . T h i s s o l u t i o n was  room temperature.  and  (25 cc) and b u b l e d i n t o s t i r r e d f o r 1 hour a t  2 M aqueous p o t a s s i u m h y d r o x i d e s o l u t i o n was  added  - 133 u n t i l the e f f e r v e s c e n c e had ceased and t h e n hydrogen p e r o x i d e (0.5 c c , 30%)  was added.  The s o l u t i o n was  s t i r r e d f o r 10 min.'and was  then  p a r t i t i o n e d between d i c h l o r o m e t h a n e (100 cc) and water (100 c c ) . F u r t h e r e x t r a c t i o n w i t h d i c h l o r o m e t h a n e (2 x 50 cc) and removal o f s o l v e n t from t h e combined o r g a n i c e x t r a c t s gave the crude p r o d u c t as a y e l l o w gum.  T h i s m a t e r i a l was  chromatographed  on a l u m i n a (20 g ) .  E l u t i o n w i t h benzene-20% e t h y l a c e t a t e gave t h e l e s s p o l a r t i o n p r o d u c t s i n the f i r s t t h r e e f r a c t i o n s .  decomposi-  The f o l l o w i n g t e n  f r a c t i o n s c o n t a i n e d a m i x t u r e o f t h e a l c o h o l and the amine boranes of the a l c o h o l .  These f r a c t i o n s combined (85 mg) was d i s s o l v e d i n  a s o l u t i o n o f t e t r a h y d r o f u r a n (25 c c ) and t r i e t h y l a m i n e r e f l u x e d under n i t r o g e n f o r 2 h o u r s .  The s o l v e n t was removed under  r e d u c e d p r e s s u r e and the crude p r o d u c t chromatographed (III,  10 g ) .  Benzene-20% e t h y l a c e t a t e e l u t i o n gave  4B-dihydrocleavaraine Sublimed sample mp e 3.76,  3.84,  3.72,  (47 mg)  4.44,  X  1  (v 0-H),  respectively);  1045 cm"  (v C-0); NMR:  1  2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 5.84 ( d o u b l e t , 2H, main peak, m/e  CH-CH_ 0H), 9.16  v  :  C, 77.17; H, 8.88;  N,  3510 cm  (  v  N-N),  3.x  T 1.54  (broad s i n g l e t , IH,  (quintuplet, 2  312, 207, 138, 124. o  methanol-water.  IH, C - H ) , l g  ( t r i p l e t , 3H, -CH CH_ ) .  2  A n a l . C a l c d . f o r C_„H_ N„0: Found:  18g-hydroxymethyl-  293, 285, 2 7 5 ( s h ) , 221 ( l o g  in  3300 cm"  u s i n g alumina  which c r y s t a l l i z e d from  146.5-147.5°C;  (1 c c ) and  3  6.27  Mass spectrum:  ~ C, 76.91; H, 8.98;  8.79.  NH),  N, 8.98;  0,  5.13.  - 134 -  183-Hydromethyl-43-dihydrocleavamine 1700  cm  N-H),  -1  (v C=0),  1265  cm  -1  a c e t a t e mp  (v C-0); NMR:  156-160°C, v  T 1.92  KBr max  (broad s i n g l e t ,  2.5-310 ( d i f f u s e , 4H, a r o m a t i c ) , 5.4-6.0 ( d i f f u s e , 3H,  C - H ) , 7.97 lg  ( s i n g l e t , 3H, OAc), 9.13  (triplet,  18g-Hydroxymethyl-43-dihydrocleavamine  3H,  IH,  -CH^OAc,  -CH CH_ ). 2  3  (92), from h y d r o b o r a t i o n o f  18-methylene-4g-dihydrocleavamine Dihydrocatharanthinol  (200 mg)  was  converted to  18-methylene-43-  dihydrocleavamine  (79) u s i n g the p r o c e d u r e a l r e a d y o u t l i n e d .  crude p r o d u c t was  d i s s o l v e d i n anhydrous  the s o l u t i o n was 2.0 M) was was  c o o l e d t o 0°C.  tetrahydrofuran  (3.0 c c ,  The r e a c t i o n m i x t u r e  then a l l o w e d t o come t o room temperature and s t i r r e d  f o r an  The excess d i b o r a n e and s o l v e n t were removed  u s i n g water-pump p r e s s u r e .  The r e s i d u e was  taken up in  (50 c c ) , aqueous sodium h y d r o x i d e (10 dp, 3M) was hydrogen p e r o x i d e (0.10 c c , 30%) f o r 15 min.  (25 cc) and  Diborane i n t e t r a h y d r o f u r a n  added dropwise over a 1 hour p e r i o d .  a d d i t i o n a l 0.5 hour.  The  tetrahydrofuran  added f o l l o w e d by  and the r e s u l t i n g s o l u t i o n  stirred  The r e a c t i o n m i x t u r e was p a r t i t i o n e d between water  and d i c h l o r o m e t h a n e (100 c c ) .  (150 c c  Further e x t r a c t i o n with dichloromethane  (2 x 50 cc) and removal o f s o l v e n t from the combined gave the crude p r o d u c t as a y e l l o w gum.  organic  T h i s m a t e r i a l was  graphed on alumina (70 g) u s i n g e t h y l a c e t a t e as e l u t i n g  extracts  chromato-  solvent.  The main p r o d u c t s were; the d e s i r e d 183-hydroxymethyl-43-dihydrocleavamine  (92) (22 mg),  i d e n t i c a l w i t h the m a t e r i a l o b t a i n e d from  h y d r o b o r a t i o n o f 5,18-seco-diene; amine-borane, tic,  ethylacetate elution)  (61 mg)  A,  (R^ 0.7,  alumina  and a second amine-borane,  B,  -  (R  f  135  -  0.6, 14 mg). Amine-borane A was d i s s o l v e d i n anhydrous t e t r a h y d r o f u r a n (10 c c )  c o n t a i n i n g t r i e t h y l a m i n e (0.1 c c ) and t h e s o l u t i o n r e f l u x e d f o r 2 hours under n i t r o g e n .  Pure  183-hydroxymethyl-48-dihydrocleavamine  was o b t a i n e d on t a k i n g t h e r e a c t i o n s o l u t i o n t o d r y n e s s and c r y s t a l l i z i n g t h e r e s i d u e from methano1-water. Amine-borane B, was d i s s o l v e d i n anhydrous t e t r a h y d r o f u r a n (2 c c ) containing triethylamine  (0.05 c c ) and t h e s o l u t i o n was r e f l u x e d f o r  2 hours under n i t r o g e n .  A m i x t u r e o f s t a r t i n g amine-borane  t h e a l c o h o l was o b t a i n e d .  B and  S e p a r a t i o n by p r e p a r a t i v e t i c gave pure  188-hydroxymethy1-48-dihydrocleavamine.  18g-Hydroxymethyl-43-dihydrocleavamine  (92) from r e d u c t i o n o f 188-  c a r b o m e t h o x y - 4 8 - d i h y d r o c l e a v a m i n e (52) 188-Carbomethoxy-48-dihydrocleavamine  (100 mg) was added t o a  s o l u t i o n o f l i t h i u m aluminum h y d r i d e (70 mg) i n t e t r a h y d r o f u r a n (15 c c ) and t h e r e a c t i o n m i x t u r e was r e f l u x e d f o r 2 h o u r s .  The  m i x t u r e was c o o l e d i n an i c e b a t h and s a t u r a t e d aqueous sodium sulfate solution  (0.5 c c ) was added d r o p w i s e .  Water (100 c c ) was  t h e n added and t h i s m i x t u r e was e x t r a c t e d w i t h d i c h l o r o m e t h a n e (5 x 25 c c ) . The combined  e x t r a c t was d r i e d o v e r anhydrous sodium s u l f a t e and t h e  s o l v e n t was removed under r e d u c e d p r e s s u r e . gum c o u l d be c r y s t a l l i z e d from methanol-water  The s l i g h t l y y e l l o w (64 mg, mp  140-144).  S u b l i m a t i o n gave a w h i t e c r y s t a l l i n e sample mp 146.5-147.5°C i d e n t i c a l t o t h e m a t e r i a l o b t a i n e d from t h e h y d r o b o r a t i o n o f b o t h and  18-methylene-48-dihydrocleavamine.  5,18-seco-diene  - 136 -  Tetrol  (96)  Pure 5,;18-seco-diene  (78) (300 mg)  was d i s s o l v e d i n a s o l u t i o n  o f anhydrous  t e t r a h y d r o f u r a n (18 c c ) and dry p y r i d i n e (1.8 c c ) .  r e a c t i o n was  c a r r i e d out i n a long-necked f l a s k and t h i s f l a s k  t a i n i n g the s o l u t i o n was  The con-  immersed i n a d r y i c e - a c e t o n e b a t h such t h a t  3 o r 4 i n c h e s o f t h e neck o f the f l a s k was o f osmium t e t r o x i d e (522 mg)  i n anhydrous  a l s o immersed.  A solution  t e t r a h y d r a f u r a n (5 c c )  was  t h e n added d r o p w i s e o v e r a 1 hour p e r i o d and i n such a manner t h a t i t r a n down t h e c o o l e d neck o f t h e f l a s k . t h e osmic a c i d s o l u t i o n was  I n t h i s way  i t was  assured that  c o o l e d t o the b a t h t e m p e r a t u r e when i t  reached the r e a c t i o n mixture.  Care was  t a k e n t o keep t h e system  closed  t o t h e atmosphere w h i l e a d d i n g t h e osmic a c i d s o l u t i o n t o p r e v e n t c o n d e n s a t i o n o f water i n t o the r e a c t i o n s o l u t i o n . m i x t u r e was  The  s t i r r e d f o r an a d d i t i o n a l 6 hours and was  come t o room t e m p e r a t u r e o v e r a 1/2 hour p e r i o d .  reaction then allowed t o  I t was  t h e n poured  i n t o a s o l u t i o n o f e t h a n o l - d i c h l o r o m e t h a n e (1:1, 50 c c ) and  hydrogen  s u l f i d e was b u b b l e d t h r o u g h t h i s s o l u t i o n w i t h r a p i d s t i r r i n g f o r 10 min.  T h i s m i x t u r e was  f i l t e r e d t h r o u g h c e l i t e and t h e b l a c k r e s i d u e  was washed w i t h an a d d i t i o n a l amount o f e t h a n o l - d i c h l o r o m e t h a n e ( 1 : 1 , 100 c c ) .  The r e s i d u e was  t h e n suspended  s t i r r e d f o r about 15 h o u r s . before.  desired t e t r o l (187 mg). 123°C;  T h i s m i x t u r e was  The combined f i l t r a t e was  on a l u m i n a (50 g ) .  A  i n t r i e t h y l a m i n e (20 c c ) and f i l t e r e d and washed as  t a k e n t o d r y n e s s and  D i c h l o r o m e t h a n e - 1 % methanol  chromatographed  s o l u t i o n e l u t e d the  which c r y s t a l l i z e d on t a k i n g t h e e l u e n t t o d r y n e s s  T h i s m a t e r i a l r e c r y s t a l l i z e d from methanol-water; 293, 285, 275, 228  ( l o g e 3.85,  3.89,  3.82,  mp  4.52,  120-  - 137 -  respectively); r  NH);  X " : max nu;J  /  3360 cm" , 3510 c m " ( s h ) , 3350 cm"  01  1  1  (v OH and  1  NMR: T 1.84 (broad s i n g l e t , IH, N-H), 2.4-3.0 ( d i f f u s e , 4H,  a r o m a t i c ) , 5.42 (broad s i n g l e t , IH, :; N-CHOH), 6.36 (broad  singlet,  sharpened on D 0 exchange, 2H, -CH_ 0H), 8.96 ( t r i p l e t , 3H, -CH CH_ ). 2  2  Mass spectrum: Anal:  2  main p e a k s , m/e 342, 311, 143, 9 1 , no p a r e n t  for M  +  - H 0(18).  Calcd. f o r C 0 2°3 26 N  2  H  ion.  342.194.  :  2  342.192 ( h i g h r e s o l u t i o n mass  3  Found:  spectrometry).  T r i o l (97) The  tetrol  (96) (330 mg) was d i s s o l v e d i n methanol (50 c c ) and  sodium b o r o h y d r i d e  (200 mg) was added.  t e m p e r a t u r e f o r 1 hour.  The s o l u t i o n was s t i r r e d a t room  The s o l v e n t was removed and t h e r e s i d u e was  p a r t i t i o n e d between d i c h l o r o m e t h a n e (100 c c ) and water (100 c c ) .  The  aqueous phase was e x t r a c t e d w i t h an a d d i t i o n a l q u a n t i t y o f d i c h l o r o methane (2 x 50 c c ) and t h e combined e x t r a c t s a f t e r d r y i n g o v e r anhydrous sodium s u l f a t e , was s t r i p p e d o f s o l v e n t .  The r e s i d u e  c r y s t a l l i z e d on t r i t u r a t i o n w i t h methanol t o g i v e pure t r i o l (97) (325 mg).  T h i s m a t e r i a l c o u l d be r e c r y s t a l l i z e d from methanol-water;  mp 230-235 (decomp.); 3.87,  X  :  293, 285, 2 7 7 ( s h ) ,  4.53, r e s p e c t i v e l y ) ; X ^ ' max n u  '  r  0 1  1J  :  227, ( l o g e 3.87, 3.91,  3540, 3430 and 3200 cm" '  1  (v  0-H  and N-H); NMR: T 0.29 (broad s i n g l e t , l o s t on d e u t e r i u m exchange, IH, 0-H),  1.48 (broad s i n g l e t , I H , N-H), 2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) ,  6.22 ( s i n g l e t , 2H, -CH_ 0H), 9.10 ( t r i p l e t , 3H, -CH CH_ ) . 2  main p e a k s , m/e  2  n  r e s o l u t i o n mass  Mass spectrum:  344, 326, 154, 95, 92, 91.  A n a l . C a l c d . f o r C„ H„ N.0_: — -  3  o  zU z o z J  spectrometry).  344.206.  Found:  344.210 ( h i g h •  .  - 138  i  Ketol  j  (98) The t r i o l  (97) (150 mg)  d i s s o l u t i o n , water  was d i s s o l v e d i n acetone  (5 cc) was  added.  (15 cc), and  T h i s s o l u t i o n was  after  c o o l e d i n an  i c e - w a t e r b a t h and t o i t was  added d r o p w i s e an aqueous s o l u t i o n o f  p e r i o d a t e (90 mg  The s o l u t i o n was  at  0°C.  i n 10 c c ) .  The r e a c t i o n s o l u t i o n was  to  g i v e a y e l l o w gum.  (3 x 50 c c ) .  (98) (75 mg).  T h i s m a t e r i a l was  ( l o g e. 4.25,  3100  (v 0-H),  N-H),  1  (15 mg).  The k e t o l c o u l d be  4.16,  1615 c m  respectively); (v C=0);  -1  NMR:  2.4-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 7.82  d e u t e r i u m exchange, IH, 0-H), main p e a k s , m/e  on a l u m i n a  e l u t i o n brought down t h e d e s i r e d  t o g i v e y e l l o w p l a t e s ; mp  317, 238, cm"  chromatographed  Further e l u t i o n using dichloromethane-2%  gave some o f t h e s t a r t i n g t r i o l from methanol-water  The combined e x t r a c t s  sodium s u l f a t e and t h e n s t r i p p e d o f s o l v e n t  (20 g ) ; d i c h l o r o m e t h a n e - 1 % methanol ketol  hours  t h e n poured i n t o i c e - w a t e r (70 c c )  and e x t r a c t e d w i t h d i c h l o r o m e t h a n e were d r i e d o v e r anhydrous  s t i r r e d f o r 1.5  9.03  C  H 1 9  4 2 2 0  2  N  :  methanol crystallized  105-109 ( d e c ) ; X™j  o 1  x 0.73  :  ^  3430 cm"  1  : m a x  (v  (broad s i n g l e t ,  (broad s i n g l e t , l o s t  ( t r i p l e t , 3H, - C ^ C H O .  312, 154, 144, 143,  Anal. Calcd. f o r  sodium  N-H), IH,  on  Mass spectrum:  140.  312.184.  Found:  312.183 ( h i g h  r e s o l u t i o n mass s p e c t r o m e t r y ) .  Diol  (99) The k e t o l  (98) (93 mg)  was d i s s o l v e d i n methanol  s o l u t i o n c o o l e d i n an i c e - b a t h . added; t h e r e a c t i o n m i x t u r e was was  then s t i r r e d f o r two h o u r s .  (20 c c ) and the  Sodium b o r o h y d r i d e (100 mg)  was  a l l o w e d t o come t o room t e m p e r a t u r e The s o l u t i o n was  taken to dryness  and and  - 139  -  p a r t i t i o n e d between d i c h l o r o m e t h a n e aqueous phase was  (50 c c ) and water  (50 c c ) .  f u r t h e r e x t r a c t e d w i t h d i c h l o r o m e t h a n e and t h e n t h e  combined o r g a n i c e x t r a c t s , a f t e r d r y i n g o v e r anhydrous was  taken to dryness.  294, 286, 2 7 9 ( s h ) , 227 3  2  5  -1  0  a n d  sodium  3  (99) (86 mg) mp  ( l o g e 3.83, 3  6  Q  (broad s i n g l e t , IH, N-H),  c m  *l(  s h v  )  J  3.86, (  v  ^  195-200°C ( d e c ) ; X  3.82,  o-H  respectively); '  J  NMR:  x  1.62  2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 4.28  (doublet  ( t r i p l e t , 3H, -CH_CH_). Z  lo  main peaks, m/e  :  in 3.x  4.50,  and v N-H);  o f d o u b l e t s , J=2,10 Hz, IH, C._-H), 9.08 spectrum:  sulfate,  The p r o d u c t c r y s t a l l i z e d r e a d i l y from d i c h l o r o -  methane t o g i v e t h e pure d i o l  nujol max  The  314, 173, 154, 144, 142, 140, 130,  A n a l . C a l c d . f o r C H-,0-N_:- 314.199. i y zo z z in  Found:  Mass  —o  124.  314.199 ( h i g h  r e s o l u t i o n mass s p e c t r o m e t r y ) .  Isovelbanamine The d i o l  (100) (99) (100 mg)  was d i s s o l v e d i n anhydrous  (20 c c ) , l i t h i u m aluminum h y d r i d e (100 mg) m i x t u r e was  r e f l u x e d f o r 10 h o u r s .  was  N-methylmorpholine  added and the r e s u l t i n g  A f t e r t h i s t i m e , i t was  cooled  i n an i c e - b a t h and a s a t u r a t e d aqueous sodium s u l f a t e s o l u t i o n was  added d r o p w i s e .  Water (60 cc) was  was  t h e n e x t r a c t e d w i t h e t h y l a c e t a t e (5 x 20 c c ) .  added t o t h i s m i x t u r e and The  Dichloromethane  V  max°  1 ;  3  2  5  0  c m _ 1  s i n g l e t , IH, N-H),  ^  ( l o g e 3.88,  °~ ^' H  3  5  0  0  on  e l u t i o n gave i s o v e l b a n a m i n e (100)  c r y s t a l l i z e d from t h i s s o l v e n t (42 mg), mp 293, 286, 2 7 6 ( s h ) , 229  this  combined  e x t r a c t s were t a k e n t o d r y n e s s and t h e r e s i d u e chromatographed a l u m i n a (10 g ) .  (0.5 cc)  c m _ 1  3.90, ^  v  N  "  190-194°; ^ 3.82,  H ) ;  N M R :  4.54, T  m a x  which  °.  respectively);  2 - 2 6  2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 6.56  (  b r o a d  (complex  multiplet,  - 140 i 1H, C - H ) , 8.77 lo 1 0  0-H),  9.13  298,  154.  (broad s i n g l e t , d i s a p p e a r s on d e u t e r i u m exchange,  (triplet,  3H, -CH C H ) .  A n a l . C a l c d . f o r C H_,0N_: i y zo z in  Mass spectrum:  298.205.  main p e a k s ,  Found:  IH,  m/e  298.205 ( h i g h  r e s o l u t i o n mass s p e c t r o m e t r y ) .  Cleavamine  (23); dehydration of isovelbanamine  Concentrated s u l f u r i c a c i d  (100)  (0.5 c c , 36 N) was c o o l e d i n an i c e -  w a t e r b a t h and t o t h i s c o l d a c i d was  added i s o v e l b a n a m i n e (100)(10  The compound d i s s o l v e d s l o w l y and t h e r e s u l t i n g s o l u t i o n was under a d r y n i t r o g e n atmosphere f o r 2 h o u r s .  stirred  T h i s s o l u t i o n was  then  added d r o p w i s e t o an i c e - c o l d ammonium h y d r o x i d e s o l u t i o n (10 c c , and t h e r e s u l t i n g s u s p e n s i o n was 5 cc). the  mg).  2N)  e x t r a c t e d w i t h d i c h l o r o m e t h a n e (3 x  The combined e x t r a c t s were f l u s h e d t h r o u g h a l u m i n a (1 g) and  e l u t e d m a t e r i a l c o n c e n t r a t e d t o g i v e a p a l e y e l l o w gum  T h i s m a t e r i a l was chromatographed  (9 mg).  on a l u m i n a (1 g) e l u t i n g w i t h benzene  t o g i v e t h e d e s i r e d c l e a v a m i n e c o n t a m i n a t e d w i t h some s l i g h t l y more polar material. ether-benzene methanol  Rechromatography  on a l u m i n a (1 g) e l u t i n g w i t h p e t r o l e u m  (1:1) gave pure c l e a v a m i n e which c r y s t a l l i z e d  (2.6 mg), mp  113-117°C ( L i t  2 2  '  3 6  mp  117-119°).  from  This material  had t i c p r o p e r t i e s i d e n t i c a l t o an a u t h e n t i c sample o f c l e a v a m i n e and the  i r spectrum  ( n u j o l ) was  superimposable t o that of the a u t h e n t i c  sample.  18g-Cyanocleavamine  (109)  A s o l u t i o n o f c l e a v a m i n e (250 mg)  i n d i c h l o r o m e t h a n e (30 c c ) and  - 141  t r i e t h y l a m i n e (0.15 cc) was was  -  c o o l e d i n an i c e - a c e t o n e ,bath and t o i t  added d r o p w i s e a s o l u t i o n o f t e r t - b u t y l h y p o c h l o r i t e i n carbon l'  tetrachloride  (48 cc o f 0.38  r e a c t i o n s o l u t i o n was  M), over the p e r i o d o f 1 h o u r .  then t a k e n t o dryness  i n a s o l u t i o n o f f u s e d sodium a c e t a t e (22.5 cc) and a c e t i c a n h y d r i d e  and the r e s i d u e d i s s o l v e d  (250 mg)  (2.5 c c ) .  This  i n glacial acetic  T h i s s o l u t i o n was  stirred  at room t e m p e r a t u r e f o r 1 hour and t h e n f o r 2 hours a t 60°C. s o l v e n t was  a s h o r t column o f a l u m i n a  (20 g as a 1" column).  e l u t e d m a t e r i a l on removal o f s o l v e n t gave the crude  ammonium s a l t as a p a l e y e l l o w foam.  3 hours under h i g h vacuum a t about 70°C.  mg)  d r i e d i n a s i m i l a r manner was  formamide (15 cc) was reaction flask.  hours.  The  dried  cyanide  d i s t i l l e d from over b a r i u m o x i d e i n t o  (250  dimethylthe  r e f l u x e d under a n i t r o g e n  s o l v e n t was  p r e s s u r e and the r e s i d u e o b t a i n e d was 15 g ) .  Potassium  added t o t h i s r e s i d u e and  T h i s r e a c t i o n m i x t u r e was  atmosphere f o r 1 3/4  quaternary  T h i s crude m a t e r i a l was  for  (III,  The  removed under vacuum and the r e s i d u e d i s s o l v e d i n e t h a n o l  and f l u s h e d through The  acid  removed under r e d u c e d  chromatographed u s i n g  Benzene e l u t i o n gave t h e d e s i r e d p r o d u c t ,  alumina  18g-cyano-  c l e a v a m i n e (109), which c r y s t a l l i z e d r e a d i l y from methanol-water (81.3 mp  87-90°;  A  :  respectively); IH, N-H),  305,  n U  ^  Q l  284,  :  277,  2240 cm  225, 1  ( l o g e 3.89,  (v C=N);  NMR:  2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 4.48  J = 2 Hz and CH=C  v  293,  10 Hz,  ) , 8.96  136,  124.  IH, C - p r o t o n ) ,  (triplet,  1 0  3H,  4.74  -CH^C^).  3.96,  T 1.60  3.93,  (broad  mg);  4.57, singlet,  (doublet of doublets,  (poorly defined doublet, Mass spectrum:  IH,  main p e a k s ,  m/e  - 142 -  A n a l . C a l c d . f o r C^H^y r e s o l u t i o n inass  305.189.  305.187 ( h i g h  spectrometry).  j  *  18g-Carbomethoxycleavamine 18g-Cyanocleavamine glycol  Found:  ( 6 0 ) , from 18g-cyanocleavamine (109) (109) (81 mg) was d i s s o l v e d i n d i e t h y l e n e  (2.5 c c ) and p o t a s s i u m h y d r o x i d e (0.5 g) was added.  m i x t u r e was k e p t a t 150° f o r 9 h o u r s .  This  The s o l u t i o n was t h e n c o o l e d  i n an i c e - b a t h , made s l i g h t l y a c i d i c w i t h a s o l u t i o n o f methanol saturated with hydrochloric acid.  A l a r g e e x c e s s o f diazomethane  i n d i e t h y l e t h e r was added and t h e r e a c t i o n m i x t u r e was s t i r r e d v i g o r o u s l y f o r 0.5 h o u r .  The s o l u t i o n was a l l o w e d t o come t o room  t e m p e r a t u r e and t h e excess diazomethane was blown o f f u s i n g of nitrogen.  a stream  Water (150 c c ) was t h e n added and t h e s o l u t i o n was  e x t r a c t e d w i t h d i e t h y l e t h e r (4 x 50 c c ) . The combined e x t r a c t s were washed w i t h water (2 x 25 c c ) , d r i e d o v e r anhydrous sodium s u l f a t e and t a k e n t o d r y n e s s .  The r e s i d u e was chromatographed on a l u m i n a  (10 g) and p u r e 18g-carbomethoxycleavamine e l u t i o n w i t h p e t r o l e u m ether-benzene ( 1 : 1 ) .  (45 mg) was o b t a i n e d on This m a t e r i a l  crystallize  from m e t h a n o l , mp 122-126°C ( L i t . mp 122-123°C); i t had i d e n t i c a l p r o p e r t i e s compared w i t h an a u t h e n t i c sample o f 18g-carbomethoxycleavamine on t i c , and gave a s u p e r i m p o s a b l e i n f r a r e d spectrum.  Cleavamine N-borane (116) Cleavamine (50 mg) was d i s s o l v e d i n anhydrous t e t r a h y d r o f u r a n (5 and  t h e s o l u t i o n c o o l e d t o 0°C.  D i b o r a n e produced e x t e r n a l l y (by .  the r e a c t i o n o f a s o l u t i o n o f sodium b o r o h y d r i d e (17 mg) i n anhydrous  -  diglyme  143'  (5 c c ) w i t h a s o l u t i o n o f b o r o n t r i f l u o r i d e - e t h e r a t e  i n anhydrous'diglyme  (0.07 c c )  (2 c c ) ) was p a s s e d i n t o t h e r e a c t i o n s o l u t i o n  o v e r t h e p e r i o d o f 1 hour.  The r e a c t i o n m i x t u r e was a l l o w e d t o come  t o room t e m p e r a t u r e and s t i r r e d f o r an a d d i t i o n a l 1/2 hour. t h e n p a r t i t i o n e d between d i c h l o r o m e t h a n e  (50 c c ) and water  I t was (50 c c ) ;  t h e aqueous phase was e x t r a c t e d w i t h a d d i t i o n a l d i c h l o r o m e t h a n e c c ) and t h e combined o r g a n i c e x t r a c t s t a k e n t o d r y n e s s . c r y s t a l l i z e d r e a d i l y from benzene (43 mg).  A  (2 x 25  The p r o d u c t  : 293, 285, 2 7 5 ( s h ) ;  nicLX  v  C H C 1  max  cm  1  3450 c m  - 1  ( s h a r p , v N-H), 2375 cm"  1  r  (v B-H), 1170 cm"  1  w i t h 2260  o v e r t o n e (6 B-H). The amine-borane (25 mg) was d i s s o l v e d i n anhydrous t e t r a h y d r o -  f u r a n (1.0 c c ) , t r i e t h y l a m i n e  (0.2 c c ) was added and t h i s  was r e f l u x e d f o r 2 hours under a n i t r o g e n atmosphere. m i x t u r e was p a r t i t i o n e d between d i c h l o r o m e t h a n e  The r e a c t i o n  (20 c c ) and water  (20 c c ) and t h e o r g a n i c phase was t a k e n t o d r y n e s s . on a l u m i n a ( I I I , 10 g) gave on e l u t i o n w i t h p e t r o l e u m (1:1) pure c l e a v a m i n e  solution  Chromatography ether-benzene  (14 mg), i d e n t i f i e d by t i c and i r .  H y d r o b o r a t i o n o f c l e a v a m i n e u s i n g c l e a v a m i n e N-borane (116) - Cleavamine N-borane (40 mg) was d i s s o l v e d i n anhydrous  diglyme  (2 c c ) and t h i s s o l u t i o n was r e f l u x e d under a n i t r o g e n atmosphere f o r 1.5 h o u r .  The r e a c t i o n s o l u t i o n was t h e n a l l o w e d t o come t o room  t e m p e r a t u r e , aqueous p o t a s s i u m h y d r o x i d e s o l u t i o n (1 dp, 2 M) was added f o l l o w e d by hydrogen  p e r o x i d e (60 y l ,  s o l u t i o n was s t i r r e d f o r 15 min. between e t h e r (20 c c ) and water  30%) and t h e r e s u l t i n g  The r e a c t i o n m i x t u r e was p a r t i t i o n e d  (20 c c ) , and t h e o r g a n i c phase t a k e n  - 144 to dryness.  The p r o d u c t m i x t u r e was  preparative t i c .  The  s e p a r a t e d i n t o i t s components by  i n i t i a l s e p a r a t i o n on a l u m i n a w i t h benzene-20%  e t h y l a c e t a t e e l u t i o n gave t h e n o n - p o l a r m a t e r i a l s polar materials, A with R B was  f  0.2  (2.0 mg)  i d e n t i c a l i n t i c and i r w i t h  (18 mg)  andB w i t h R  f  0.15  and  two more  (2.5  mg).  3a-hydroxy-4g-dihydrocleavamine  o b t a i n e d by h y d r o b o r a t i o n i n subsequent work and A on the b a s i s o f s i m i l a r t i c and i r i s p r o b a b l y the e p i m e r i c a l c o h o l . p r e p a r a t i v e t i c system  A second  ( a l u m i n a , benzene e l u t i o n ) was used t o s e p a r a t e 1  the less p o l a r m a t e r i a l s .  Cleavamine  (8 mg)  and 4 g - d i h y d r o c l e a v a m i n e  (5.5 mg) were o b t a i n e d and were i d e n t i f i e d by t i c and nmr with authentic  comparison  samples.  3q-Hydroxy-4g-dihydrocleavamine  (117); h y d r o b o r a t i o n of cleavamine  To a s o l u t i o n o f c l e a v a m i n e (23) (450 mg) f u r a n c o o l e d i n an i c e - b a t h , was  in  anhydrous  (23)  tetrahydro-  added t o 10 molar e x c e s s o f d i b o r a n e  (8 cc o f 2 M d i b o r a n e i n t e t r a h y d r o f u r a n ) d r o p w i s e o v e r a 1 hour period.  The r e a c t i o n s o l u t i o n was  t h e n a l l o w e d t o come t o room  t e m p e r a t u r e and s t i r r e d f o r an a d d i t i o n a l 0.5 hour.  The s o l v e n t and  e x c e s s d i b o r a n e were removed under water-pump p r e s s u r e t o g i v e a s l i g h t l y y e l l o w gum.  T h i s r e s i d u e was d i s s o l v e d i n t e t r a h y d r o f u r a n (50 c c )  and aqueous sodium h y d r o x i d e (0.5 c c , 3 M) was added f o l l o w e d by hydrogen p e r o x i d e s o l u t i o n  (0.7 m l , 3 0 % ) .  T h i s s o l u t i o n was  f o r 15 min. a t room t e m p e r a t u r e and r e a c t i o n was  t h e n quenched by  p a r t i t i o n i n g i t between d i c h l o r o m e t h a n e (100 cc) and w a t e r The aqueous phase was  stirred  (100 c c ) .  f u r t h e r e x t r a c t e d w i t h d i c h l o r o m e t h a n e (2 x 50 cc)  and t h e combined e x t r a c t s were t a k e n t o d r y n e s s t o g i v e the crude  - 145 -  amine-borane (634 mg).  T h i s m a t e r i a l was d i s s o l v e d  i n tetrahydrofuran  (50 c c ) , t r i e t h y l a m i n e (0.7 c c ) was added and t h e s o l u t i o n was r e f l u x e d under a n i t r o g e n atmosphere f o r 2 h o u r s .  The s o l v e n t was  removed and t h e r e s i d u e was chromatographed on a l u m i n a (200 g ) .  Elution  w i t h d i c h l o r o m e t h a n e gave t h e d e s i r e d 3 a - h y d r o x y - 4 B - d i h y d r o c l e a v a m i n e which c r y s t a l l i z e d on c o n c e n t r a t i o n o f t h e e l u e n t ; mp 131-139°C, (342 mg).  T h i s m a t e r i a l c o u l d be s u b l i m e d  mp 140-156°C; X  :  4.54, r e s p e c t i v e l y ) ;  to give an!analytical  293, 286, 2 7 7 ( s h ) , v  C H C 1  3:  3440 c m  sample;  229 ( l o g e 3.87, 3.90, 3.85, - 1  (v N-H), 3250 cm"  1  (v 0-H);  IH3-X  NMR: 6.4  x 2.14 (broad s i n g l e t , IH, N-H), 2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , (complex m u l t i p l e t , 2H,  disappears  298.205.  and C - H ) , 8.5 (broad, IH, l g  on d e u t e r i u m exchange, 0-H), 9.10  Mass spectrum: . Anal.  C^-OH  main p e a k s , m/e  Calcd. f o r C Found:  r e s o l u t i o n mass  H 1 9  2  N 6  2  ( t r i p l e t , 3H, -C^-CH ) .  298, 154, 144, 143. 0 :  C, 76.51; H, 8.72; N, 9.40;  C, 76.35; H, 8.57; N, 9.25; M.W.,  M.W.  298.203 ( h i g h  spectrometry).  3a-Acetoxy-4g-dihydrocleavamine 3ct-Acetoxy-4B-dihydrocleavamine dihydrocleavamine  was o b t a i n e d from 3a-hydroxy-4B-  by a normal a c e t i c a n h y d r i d e - p y r i d i n e  acetylation.  The compound c r y s t a l l i z e d from m e t h a n o l - a c e t o n e , mp 212-215°C; 1720 cm"  1  (v C=0), 3370 cm"  1  (v N-H); NMR:  v  max°^  x 2.08 (broad s i n g l e t , IH,  N-H), 2.5-3.0 ( d i f f u s e , 4H, a r o m a t i c ) , 4.90 ( d o u b l e t o f d o u b l e t s , J = 6, 10 Hz, IH,  C ^ O A c ) , 6.4  ( t r i p l e t , 3H, -CH CH.j) . 2  196,  144, 143, 138, 136.  (complex m u l t i p l e t , IH, C - H ) , 9.17  Mass spectrum:  l g  main p e a k s , m/e 340, 280,  :  - 146 j  A n a l . C a l c d . f o r C_.H. N_0 • o  — —  z l  Zo  z  340.215.  z  Found:  340.213 ( h i g h  ,  r e s o l u t i o n mass s p e c t r o m e t r y ) .  '  .  I  i  -  Velbanamine (22) Isovelbanamine  (100) (65 mg) was d i s s o l v e d i n an aqueous s u l f u r i c  a c i d s o l u t i o n (10 c c , 10% v/v) and t h i s s o l u t i o n was r e f l u x e d a n i t r o g e n atmosphere f o r 2 days.  under  The s o l u t i o n was t h e n c o o l e d t o  0°C and added d r o p w i s e t o an i c e - c o l d aqueous ammonium h y d o x i d e s o l u t i o n (20 c c , 5 N ) .  The r e s u l t i n g s u s p e n s i o n was e x t r a c t e d u s i n g  d i c h l o r o m e t h a n e (3 x 25 c c ) and the combined o r g a n i c e x t r a c t was t a k e n to dryness.  The r e s i d u e was chromatographed  D i c h l o r o m e t h a n e e l u t i o n gave velbanamine  on a l u m i n a (20 g ) .  (7.9 mg) i n f r a c t i o n 4 and  5 (15 c c f r a c t i o n s ) and isovelbanamine (21 mg) i n f r a c t i o n s 7 t o 10. The velbanamine  c r y s t a l l i z e d from methanol-water, mp 144-146° ( a u t h e n t i c  71 velbanamine 143-146°).  , mp 117-134°, r e c r y s t a l l i z e d from methanol-water, The s y n t h e t i c velbanamine  and had an i r spectrum  mp  exhibited identical t i c properties  (nujol) superimposable t o that o f the authentic  sample. 183-Carbomethoxycleavamine  (60)  To a 1 l i t r e , t h r e e - n e c k e d round b o t t o m e d ' f l a s k , ' f i t t e d w i t h a r e f l u x condenser and m e c h a n i c a l s t i r r e r , was added g l a c i a l a c i d (300 c c ) .  acetic  The a c i d was h e a t e d t o 100°C and t h e n c a t h a r a n t h i n e  h y d r o c h l o r i d e (11.0 g) w i t h a f u r t h e r p o r t i o n o f a c e t i c a c i d was added w i t h r a p i d s t i r r i n g . b o r o h y d r i d e was added; 42  (100 c c )  Immediately a p o r t i o n o f sodium  g were added o v e r about a 1 hour p e r i o d a t  -  147  -  a r a t e which m a i n t a i n e d t h e t e m p e r a t u r e a t 90-105°C, t a k i n g t o keep t h e r a t e o f hydrogen e v o l u t i o n under c o n t r o l .  caution  A f t e r the a d d i t i o n  r  was complete, t h e r e a c t i o n m i x t u r e was c o o l e d i n an i c e - b a t h and t h e r e s u l t i n g v i s c o u s mass was poured i n t o aqueous ammonium h y d r o x i d e s o l u t i o n (500 c c , 9 N ) .  The r e s u l t i n g s u s p e n s i o n was e x t r a c t e d  with  d i c h l o r o m e t h a n e (3 x 400 c c ) and t h e combined o r g a n i c e x t r a c t e d a f t e r d r y i n g o v e r anhydrous  sodium s u l f a t e , was t a k e n t o d r y n e s s t o g i v e a  w h i t e foam (10.85 g ) . C r y s t a l l i s a t i o n from methanol gave pure 1883 carbomethoxycleavamine,  f i r s t crop 4.4 g, mp 121-123°C ( a u t h e n t i c sample  mp 122-123°C). 183-Carbomethoxy-48-dihydrocleavamine 188-Carbomethoxycleavamine  (32)  (4.4 g) was h y d r o g e n a t e d a t room  t e m p e r a t u r e and a t m o s p h e r i c p r e s s u r e o v e r Adam's c a t a l y s t (350 mg) in ethylacetate  (50 c c ) .  Hydrogen u p t a k e ceased a f t e r 2 h o u r s .  c a t a l y s t was f i l t e r e d o f f and t h e foam.  The  s o l v e n t removed t o g i v e a w h i t e  T h i s m a t e r i a l c r y s t a l l i z e d from methanol t o g i v e pure 4837  d i h y d r o c l e a v a m i n e , f i r s t crop 4.1 g, mp 143-145°C ( a u t h e n t i c sample mp 146-148°C). 4 g - D i h y d r o c l e a v a m i n e (29) A s o l u t i o n o f 18B-carbomethoxy-4g-dihydrocleavamine  (3.0 g) i n  aqueous h y d r o c h l o r i c a c i d (190 c c , 5 N) was h e a t e d t o 90°C under a n i t r o g e n atmosphere and t h e t e m p e r a t u r e was m a i n t a i n e d f o r 7 h o u r s . The s o l u t i o n was c o o l e d i n an i c e - w a t e r b a t h and made j u s t b a s i c by  - 148 t h e a d d i t i o n ;of ammonium h y d r o x i d e (15 N).  The s u s p e n s i o n  was  e x t r a c t e d w i t h d i c h l o r o m e t h a n e (3 x 125 c c ) , the o r g a n i c e x t r a c t s d r i e d f o v e r anhydrous sodium s u l f a t e and t h e s o l v e n t removed. The r e s i d u e c r y s t a l l i z e d from methanol  to give 48-dihydrocleavamine  (2.4 g,  37 mp  134-138°); ( a u t h e n t i c sample  mp  136-138°C).  C h l o r o i n d o l e n i n e of 48-dihydrocleavamine  (41)  A s o l u t i o n of t e r t - b u t y l h y p o c h l o r i t e i n carbon t e t r a c h l o r i d e (7.1 c c , 0.050 M) was 48-dihydrocleavamine triethylamine  added o v e r a 0.5 hour p e r i o d t o a s o l u t i o n o f (100 mg)  i n dichloromethane  (0.07 cc) which was  A f t e r t h e a d d i t i o n was  c o o l e d i n an i c e - a c e t o n e b a t h .  c o m p l e t e , t h e s o l u t i o n was  a d d i t i o n a l 15 min. a t the b a t h t e m p e r a t u r e . s o l u t i o n was  (13.3 c c ) and  The  s t i r r e d f o r an orange-coloured  t h e n d i l u t e d w i t h an e q u a l volume o f benzene and  p e r c o l a t e d t h r o u g h a column o f a l u m i n a (1.5 g ) .  S o l v e n t was  rapidly removed  under reduced p r e s s u r e , the l a s t t r a c e s under h i g h vacuum, t o p r o v i d e X S O O C13.T1e  the  c h l o r o i n d o l e n i n e as  260, 303  ( l o g e 4.31,  a p a l e y e l l o w o i l (101  3.55,  3.42  (Bohlman b a n d s ) , 1600 and 1560 c m ( d i f f u s e , 4H, a r o m a t i c ) , 8.79 3H, -CH CH_ ); 2  3  Mass spectrum:  mg);  respectively);  v  ^ max  3:  2776 cm  227, -1  NMR:  T 2.5-3.0  ( q u a r t e t , 2H, -CH_ CH ), 9.14  (triplet,  -1  ( i n d o l e n i n e C=N);  '  m a x  CHf" 1  2  main p e a k s , m7e  Anal. Calcd. f o r C ^ H ^ N ^ l :  316.171.  3  316, 281, 138, Found:  124.  316.172 ( h i g h  r e s o l u t i o n mass s p e c t r o m e t r y ) .  Dimer ( 1 1 8 ) , from c h l o r o i n d o l e n i n e o f 4 8 - d i h y d r o c l e a v a m i n e vindoline  (41) p l u s  (11)  The c h l o r o i n d o l e n i n e o f 4 8 - d i h y d r o c l e a v a m i n e  (557 mg)  and v i n d o l i n e  - 149 ! 1  | (523  mg) were d i s s o l v e d i n anhydrous m e t h a n o l i c 1.5% h y d r o c h l o r i c  I acid solution.  T h i s s o l u t i o n was r e f l u x e d f o r '2.5 hours under a d r y  n i t r o g e n atmosphere. (87  c c ) and t h e r e s u l t i n g s o l u t i o n was made j u s t b a s i c w i t h p o t a s s i u m  carbonate. the  The r e a c t i o n m i x t u r e was d i l u t e d w i t h w a t e r  E x t r a c t i o n w i t h d i c h l o r o m e t h a n e (5 x 50 c c ) and r e m o v a l o f  s o l v e n t a f t e r d r y i n g t h e e x t r a c t s o v e r anydrous sodium s u l f a t e  gave t h e crude dimer as a y e l l o w g l a s s - l i k e m a t e r i a l  (1.006 g ) .  Chromatography on a l u m i n a (100 g) gave t h e p u r e dimer (118) on e l u t i o n w i t h b e n z e n e - e t h y l e t h e r (1:1) as a c o l o u r l e s s g l a s s C r y s t a l l i s a t i o n from methanol gave a sample, mp 205-206°; 3430 cm"  (v N-H), 1733 c m  1  C=C f o r v i n d o l i n e ) ;  -1  3 : m  a  x  (v  1  X : 214, 257, 287, 293, 3 1 0 ( s h ) , ( l o g e 4.63, ni 3.x T 0.38  (broad s i n g l e t , IH,  (broad s i n g l e t , IH, i n d o l e N-H), 2.5-3.0 ( d i f f u s e ,  i n d o l e a r o m a t i c ) , 3.32 IH,  v  (v C=0 f o r -OAc, -CO Me), 1630 cm"  4.18, 4.06, 4.07, 3.88 r e s p e c t i v e l y ) ; NMR: 0-H), 2.13  (656 mg). CHC1  ( s i n g l e t , IH, i n d o l i n e , C ^ - H ) , 3.92  i n d o l i n e C ^ - H ) , 4.16  (broad d o u b l e t o f d o u b l e t s , IH,  I /  4H, (singlet,  C =C_HR), I  D  4.66 ( s i n g l e t , IH, C.HOAc), 4.76 (broad d o u b l e t , IH, C_=C HR), 5.57 (broad d o u b l e t , IH, c ' -H), 6.14 ( s i n g l e t , 3H, C.,-0CH,), 6.28 ( s i n g l e t , 0 lo lo —o A  3H, -C0CH ), 6.36 3  ( s i n g l e t , IH, C ~ H ) , 7.35  ( s i n g l e t , 3H, OAc), 9.17 C CH CH_ ). 5  2  2  (triplet,  Mass s p e c t r u m :  3  main p e a k s , m/e  +  v  c  J  735.412.  3  3H, C^CH CH ) , 9.93  107, 121, 122, 135, 138, 149. A n a l . C a l c d . f o r C..H_-0,N.: 736.420. 44 56 6 4 f o r M + IH, (C,.H__0,N,); 737.428. Found: 44 57 6 A (C„ .H„ O,N.); 44 55 6 4  ( s i n g l e t , 3H, N-CH ),  Found: 735.408.  (triplet,  7.97 3H,  58, 60, 74, 91, 92, 106, Found: 737.425.  736.420.  Calcd.  Calcd. f o r M  +  - IH  - 150 Cleavage o f dimer (118) The  dimer (118)  anhydrous m e t h a n o l i c  as t h e h y d r o c h l o r i d e  (30 mg) was d i s s o l v e d i n  7% h y d r o c h l o r i c a c i d s o l u t i o n (5 c c ) .  To t h i s  s o l u t i o n was added t i n (50 mg) and stannous c h l o r i d e (50 mg) and t h e r e a c t i o n m i x t u r e was r e f l u x e d f o r 2 hours under a n i t r o g e n atmosphere. A f t e r t h i s t i m e , a c e t y l c h l o r i d e (1 c c ) and an a d d i t i o n a l amount o f tin  (50 mg) was added and t h e m i x t u r e r e f l u x e d f o r a n o t h e r 1 hour.  T h i s s o l u t i o n was t h e n made b a s i c w i t h ammonium h y d r o x i d e s o l u t i o n and e x t r a c t e d w i t h d i c h l o r o m e t h a n e (2 x 25 c c ) . product  The crude r e a c t i o n  o b t a i n e d on t a k i n g t h e o r g a n i c e x t r a c t t o d r y n e s s was s e p a r a t e d  i n t o i t s components u s i n g p r e p a r a t i v e a l u m i n a t i c e l u t i n g w i t h acetate-chloroform  (1:1).  The p r o d u c t s  i s o l a t e d were  ethyl-  48-dihydrocleav-  amine (5.9 mg), v i n d o l i n e (2.-3 mg), s t a r t i n g dimer (3.4 mg) and desacetylvindoline  (10.2 mg).  Each o f t h e s e m a t e r i a l s were i d e n t i f i e d  by t i c and i r comparison w i t h samples o f a u t h e n t i c m a t e r i a l .  C h l o r o i n d o l e n i n e o f 18g-carbomethoxy-4B-dihydrocleavamine (120) To a s o l u t i o n o f 186-carboamethoxy-46-dihydrocleavamine (400 mg) i n d i c h l o r o m e t h a n e (40 c c ) and t r i e t h y l a m i n e (0.2 c c ) c o o l e d i n an i c e - w a t e r b a t h , was added a s o l u t i o n o f t e r t - b u t y l h y p o c h l o r i t e i n . c a r b o n t e t r a c h l o r i d e (25 c c , 0.05 M) o v e r a p e r i o d o f 45 min. s o l u t i o n was washed w i t h i c e - w a t e r  The  (2 x 30 c c ) , d r i e d o v e r anhydrous  sodium s u l f a t e and t h e s o l v e n t was removed under r e d u c e d p r e s s u r e t o d 10 X 3-Tl 6  g i v e t h e c h l o r o i n d o l e n i n e as an amorphous s o l i d 292,  (440 mg); ^  275, 227 ( l o g e 3.44, 3.44, 4.30 r e s p e c t i v e l y ) ; v  C H C 1  m a x  3:  : 2775 cm"'  IH3-X  (Bohlmann b o n d s ) , 1727 cm  1  (v C=0),  1612 and 1575 cm  1  (indolenine v  -  C=N);  NMR:  -  151  T 2.40-2.98 (4H, a r o m a t i c ) , 5.53  ( s i n g l e t , 3H', -COOCH_ ), 9.14  ( t r i p l e t , 3H,  3  main p e a k s , m/e  376,  374,  138,  Dimer  -CH CH_ ). 2  6.41  Mass spectrum:  3  374.176.  Found:  374.174, ( h i g h  spectrometry).  (119) The  (400 mg) 1.5%  g  124.  Anal. Calcd. f o r C ^ ^ N ^ C l : r e s o l u t i o n mass  ( d o u b l e t , IH, C - H ) ,  c h l o r o i n d o l e n i n e o f 183-carbomethoxy-43-dihydrocleavamine and v i n d o l i n e (336 mg)  were d i s s o l v e d i n anhydrous  methanolic  h y d r o c h l o r i c a c i d s o l u t i o n and the r e s u l t i n g s o l u t i o n was  under a n i t r o g e n atmosphere f o r 3 h o u r s . under r e d u c e d p r e s s u r e  The  and the r e s i d u e was  s o l v e n t was  refluxed  removed  p a r t i t i o n e d between  d i c h l o r o m e t h a n e (100 cc) and aqueous p o t a s s i u m b i c a r b o n a t e s o l u t i o n (100 c c , 1%).  The  aqueous phase was  e x t r a c t e d w i t h a f u r t h e r amount  o f d i c h l o r o m e t h a n e (2 x 30 cc) and the combined e x t r a c t s were d r i e d o v e r anhydrous sodium s u l f a t e . yellow g l a s s - l i k e residue  The  s o l v e n t was  (823 mg).  T h i s m a t e r i a l was  on a l u m i n a (100 g ) ; b e n z e n e - d i e t h y l e t h e r d e s i r e d dimer as a c o l o u r l e s s g l a s s . gave a sample, mp ( l o g e 4.48, (v N-H),  1730  3.93, cm  -1  s i n g l e t , IH, OH),  221-225°C; 3.92,  3.92,  (v C=0), 1.00  i n d o l e a r o m a t i c ) , 3.05  X  C r y s t a l l i z a t i o n from methanol 217,  3.78  265,  287,  respectively);  cm"  (v C=C);  1  NMR:  ( s i n g l e t , IH, C ^ - H ) , 4.04  ( d o u b l e t o f d o u b l e t s , IH,  4.72  (broad d o u b l e t , IH,  C = C H R ) , 4.67 6  y  C = C H ) , 6.16 ?  two-COOMe), 6.36  6  chromatographed  (1:1) e l u t i o n gave the  (broad s i n g l e t , IH, N-H),  4.12  ( s i n g l e t , 6H,  :  1630  removed t o g i v e a  296, v  C H C 1  313(sh) 3:  T 0.49  3430  cm  -1  (broad  2.5-3.0 ( d i f f u s e ,  4H,  ( s i n g l e t , IH, C ^ - H ) , ( s i n g l e t , IH, C ~H),.  ( s i n g l e t , 3H,  4  -OMe),  ( s i n g l e t , IH, C -H), 7.40  6.29  (singlet,  3H,  - 152 -  N-Me), 7.96 ( s i n g l e t , 3H, -OAc), 9.09 ( t r i p l e t , 3H, C -CH CH_ ), 9.34 4  ( t r i p l e t , 3Hi C CH CH ) . Mass spectrum:  2  3  main peaks, m/e 58, 74, 9 1 ,  106, 107, 121, 122, 135, 138. Anal. Calcd. f o r M  794.425.  Found: 794.419.  Calcd. f o r M  +  + H, C.JL^OoN,,: ' 46 59 8 4  795.433.  Found:  795.428.  Calcd. f o r M  +  796.441.  Found:  796.437.  Calcd. f o r M  +  +2H, C.^H^O-N.: 46 60 8 4 -IH, C,,H_,0 N • ' 46 57 8 4  793.417.  Found:  793.410.  Calcd. f o r M  +  792.409.  Found:  792.403  ( h i g h r e s o l u t i o n mass  o  -2H, C . - H 0 N • ' 46 56 8 4 C£  o  spectrometry).  Cleavage o f dimer (119) The dimer (119) as t h e h y d r o c h l o r i d e  (50 mg) was d i s s o l v e d i n  anhydrous m e t h a n o l i c 7% h y d r o c h l o r i c a c i d s o l u t i o n (5 c c ) , (100 mg) and stannous c h l o r i d e (100 mg) were added. r e f l u x e d f o r 1 hour under a n i t r o g e n atmosphere, u s i n g ammonium h y d r o x i d e s o l u t i o n .  and t i n  T h i s m i x t u r e was  and was t h e n b a s i f i e d  To t h i s s u s p e n s i o n was added  d i c h l o r o m e t h a n e (50 c c ) and water (30 c c ) and t h e e m u l s i o n formed on s h a k i n g was f i l t e r e d  under r e d u c e d p r e s s u r e .  The aqueous phase  was e x t r a c t e d w i t h a f u r t h e r amount o f d i c h l o r o m e t h a n e and combined o r g a n i c e x t r a c t s were d r i e d o v e r anhydrous sodium s u l f a t e and t a k e n t o dryness.  The crude p r o d u c t (53 mg) was s e p a r a t e d i n t o i t s components  by p r e p a r a t i v e a l u m i n a t i c u s i n g e t h y l a c e t a t e - c h l o r o f o r m eluting solvent.  (1:1) as  The p r o d u c t s o b t a i n e d were v i n d o l i n e (12.6 mg),  d e s a c e t y l v i n d o l i n e (3.2 mg), 18a-carbomethoxydihydrocleavamine and 18g-carbomethoxydihydrocleavamine  (8.0 mg).  (8.1 mg)  The i d e n t i t y o f t h e s e  p r o d u c t s was e s t a b l i s h e d by a comparison w i t h a u t h e n t i c m a t e r i a l s on  - 153 -  t i c ; s u p e r i m p o s a b l e i r s p e c t r a were o b t a i n e d f o r a l l except 18a-carbomethoxy-48-dihydrocleavamine.  The i d e n t i t y o f t h i s compound was  e s t a b l i s h e d !by nmr comparison w i t h an a u t h e n t i c  1 8 - M e t h y l e n e - 4 g - d i h y d r o c l e a v a m i n e (79) from dihydrocleavamine  sample.  18g-hydroxymethyl-4g-  (92)  To a s o l u t i o n o f 1 8 g - h y d r o x y m e t h y l - 4 g - d i h y d r o c l e a v a m i n e (200  mg)  i n d r y p y r i d i n e (20 cc) was added f r e s h l y p r e p a r e d 3 , 5 - d i n i t r o b e n z o y l chloride  (110 mg).  The r e s u l t i n g r e d s o l u t i o n was s t i r r e d  t e m p e r a t u r e f o r 2 days.  a t room  D i c h l o r o m e t h a n e (100 c c ) was t h e n added t o t h e  r e a c t i o n m i x t u r e and t h i s s o l u t i o n was t h e n washed b r i e f l y w i t h aqueous sodium c a r b o n a t e s o l u t i o n (100 c c , 3 % ) , f o l l o w e d by water (100 c c ) . The o r g a n i c phase was d r i e d o v e r anhydrous o f s o l v e n t t o g i v e a r e d gum.  Chromatography  18-methylene-4g-dihydrocleavamine solvent.  E l u t i o n w i t h benzene-10%  on a l u m i n a (30 g) gave  (43 mg) w i t h benzene as e l u t i n g d i e t h y l e t h e r gave s t a r t i n g  h y d r o x y m e t h y l - 4 g - d i h y d r o c l e a v a m i n e (86 mg). c l e a v a m i n e was  sodium s u l f a t e and s t r i p p e d  The  18g-  18-methylene-4g-dihydro-  i d e n t i c a l i n a l l r e s p e c t s w i t h a sample o b t a i n e d  the fragmentation  reaction of dihydrocatharanthinol-O-tosylate.  18-Hydroxymethyl-4g-dihydrocleavamine benzoate 18-Hydromethyl-4g-dihydrocleavamine  (138)  (200 mg) was d i s s o l v e d i n  t r i e t h y l a m i n e (15 c c ) and b e n z o y l c h l o r i d e (0.11 c c ) was added. s o l u t i o n was  from  s t i r r e d a t room t e m p e r a t u r e f o r 12 h o u r s .  This  After this  t i m e , t h e t r i e t h y l a m i n e was removed under r e d u c e d p r e s s u r e and t h e r e s i d u e was d i s s o l v e d i n d i c h l o r o m e t h a n e (50 c c ) .  T h i s s o l u t i o n was  - 154 washed w i t h aqueous sodium b i c a r b o n a t e  (50 c c , 3%) f o l l o w e d by w a t e r  (50 c c ) and t h e o r g a n i c phase was t h e n d r i e d o v e r anhydrous sodium s u l f a t e and s t r i p p e d o f s o l v e n t .  The r e s i d u e was chromatographed on  a l u m i n a (20 g) u s i n g p e t r o l e u m e t h e r - b e n z e n e (1:1) as e l u a n t t o g i v e 1 8 3 - h y d r o m e t h y l - 4 8 - d i h y d r o c l e a v a m i n e b e n z o a t e (184 mg);  X  : 227,  nicLX _ 1  pupI  283,  293, 3 0 5 ( s h ) ,  315 ( s h ) , 3 3 5 ( s h ) ;  v 3: m 3.x  1720 cm  (v  O O ) ; NMR:  T 1.32 (broad s i n g l e t , IH, N-H), 1.7-3.0 (complex, 9H, i n d o l e and b e n z o a t e a r o m a t i c ) , 5.35 (broad s i n g l e t , 2H, -CH_ 0C0R), 5.55 ( m u l t i p l e t , IH, c -H).; 2  l g  Dimer (142) The  diol  (99) (193 mg) and v i n d o l i n e (226 mg) were d i s s o l v e d i n  an anhydrous m e t h a n o l i c  h y d r o c h l o r i c a c i d s o l u t i o n (18 c c , 1%) and  t h i s s o l u t i o n was r e f l u x e d under a n i t r o g e n atmosphere f o r 4 h o u r s . The  r e a c t i o n was t h e n poured i n t o i c e - c o l d aqueous ammonium  hydroxide  (20 c c , 2N) and t h e r e s u l t i n g s u s p e n s i o n was e x t r a c t e d w i t h d i c h l o r o methane (3 x 30 c c ) .  The combined o r g a n i c e x t r a c t s were t a k e n t o d r y n e s s  and t h e r e s i d u e was chromatographed on a l u m i n a (100 g ) .  The dimer  (142)(197 mg) was e l u t e d w i t h d i c h l o r o m e t h a n e - 1 % m e t h a n o l .  Further  e l u t i o n w i t h t h i s s o l v e n t gave some d e s a c e t y l dimer (12 mg).  The  dimer (142) c r y s t a l l i z e d from d i e t h y l - e t h e r ; mp 205-215 ( d e c ) ; 213,  ^  : m a x  257, 286, 293, 312(sh) ( l o g c 4.61, 4.10, 3.95, 3.97, 3.82 r e s p e c t -  ively);  v™^  0 1  :  3400 cm"  1  (v N-H, 0-H), 1740 cm"  1  (v C=0); NMR: T 0.47  max (broad s i n g l e t , IH, 0-H), 2.24 (broad s i n g l e t , I H , N-H), 2.5-3.1 ( d i f f u s e , 4H, i n d o l e a r o m a t i c ) , 3.30 ( s i n g l e t , I H , C ~ H ) , 3.97 1 4  ( s i n g l e t , IH, 0,.,-H), 4.18 ( d o u b l e t o f d o u b l e t s , I/ ( s i n g l e t , IH, C - H ) , 4.7 (broad d o u b l e t ,  IH,  C,.=C,HR), 4.68 6 /—  IH, C =C HR), 5.56  (broad  - 155 doublet,  IH, C j - H ) , g  6.19  -  ( s i n g l e t , 3H,  -C0 Me), 6.36  ( s i n g l e t , IH, C ~ H ) , 7.39  ( s i n g l e t , 3H,  OAc),  2  CgCH^CH^). 88,  101,  9.24  ( t r i p l e t , 3H,  Mass spectrum:  128,  154,  165,  C l e a v a g e o f dimer  50,  7.99  (triplet,  51, 57, 69,  77,  3H, 78,  204. 752.415.  Found:  752.414 ( h i g h • 6  (142) (50 mg)  was  d i s s o l v e d i n an anhydrous m e t h a n o l i c  h y d r o c h l o r i c a c i d s o l u t i o n (5 c c , 6%) were added.  atmosphere f o r 3 h o u r s .  and  t i n (50 mg)  T h i s m i x t u r e was  A f t e r t h i s t i m e i t was  a d d i t i o n o f ammonium h y d r o x i d e s o l u t i o n and methane (3 x 15 c c ) .  The  e x t r a c t s t o d r y n e s s was  residue obtained  and  stannous  r e f l u x e d under a b a s i f i e d by  nitrogen  the  extracted with dichloroon t a k i n g the  organic  chromatographed on a l u m i n a (5 g ) .  d i c h l o r o m e t h a n e gave f i r s t v i n d o l i n e (4.0 mg), amine (3.9 mg).  3H,  spectroscopy).  dimer (142)  c h l o r i d e (50 mg)  N-Me),  C^-CJ^CH ) , 9.49  main p e a k s , m/e  £  r e s o l u t i o n mass  (singlet,  ( s i n g l e t , 3H,  2  A n a l . C a l c d . f o r C..H_ 0_N„: 44 56 7 4  The  -OMe), 6.27  Elution with  f o l l o w e d by  isovelban-  Changing t o the d i c h l o r o m e t h a n e - 1 % methanol as  e l u e n t , gave d e s a c e t y l v i n d o l i n e d e s a c e t y l dimer (8.3 mg).  The  (3.6 mg),  s t a r t i n g dimer (18.0  mg)  and  methanol f l u s h gave a m i x t u r e o f  u n i d e n t i f i e d p o l a r p r o d u c t s (6.3 mg). i d e n t i f i e d by comparison on t i c and  188-Hydroxy-4g-dihydrocleavamine 4 8 - D i h y d r o c l e a v a m i n e (88 mg)  The  above m a t e r i a l s were  i r with authentic  samples.  (132) was  c o n v e r t e d t o the  c h l o r o i n d o l e n i n e as p r e v i o u s l y d e s c r i b e d .  corresponding  T h i s m a t e r i a l was  -  dissolved  - 156 -  in glacial acetic acid was added.  (2 c c ) and a f t e r d i s s o l u t i o n , water (1 c c )  T h i s s o l u t i o n was s t i r r e d a t room t e m p e r a t u r e f o r 24 h o u r s .  A f t e r t h i s t i m e i t was poured i n t o aqueous ammonium h y d r o x i d e s o l u t i o n (10 c c , 5 N) and t h e r e s u l t i n g s u s p e n s i o n was e x t r a c t e d methane (3 x 10 c c ) .  The combined  r e s i d u e was chromatographed  with  dichloro-  e x t r a c t was t a k e n t o d r y n e s s and t h e  on a l u m i n a (20 g ) . D i c h l o r o m e t h a n e e l u t i o n . i  gave f i r s t some s t a r t i n g c h l o r o i n d o l e n i n e gave t h e d e s i r e d material  (20 mg) and f u r t h e r  18g-hydroxy-4g-dihydrocleavamine  (27 mg).  c r y s t a l l i z e d from methanol-water, mp 203-205°C.  w i t h an a u t h e n t i c  elution  This Comparison  sample, mp 202-205°, showed i d e n t i c a l t i c p r o p e r t i e s  and s u p e r i m p o s a b l e i r s p e c t r a . Dimer ( 1 1 8 ) , from 1 8 g - h y d r o x y - 4 g - d i h y d r o c l e a v a m i n e 18g-Hydroxy-4g-dihydrocleavamine (157 mg) were d i s s o l v e d solution  f o r 4 hours.  i n an anhydrous m e t h a n o l i c h y d r o c h l o r i c  r e s u l t i n g s u s p e n s i o n was e x t r a c t e d  acid  nitrogen  The r e a c t i o n m i x t u r e was t h e n poured  i c e - c o l d aqueous ammonium h y d r o x i d e s o l u t i o n  The combined  vindoline  (132) (106 mg) and v i n d o l i n e  ( 1 % , 10 c c ) and t h e s o l u t i o n was r e f l u x e d under a  atmosphere  into  (10 c c , 5 N) and t h e  w i t h d i c h l o r o m e t h a n e (3 x 30 c c ) .  o r g a n i c e x t r a c t was t a k e n t o d r y n e s s and t h e r e s i d u e  was chromatographed vindoline  (132) p l u s  on a l u m i n a (100 g ) . D i c h l o r o m e t h a n e e l u t i o n gave  (10 mg) i n t h e e a r l y f r a c t i o n and f u r t h e r e l u t i o n gave t h e  dimer (118) (173 mg). desacetylvindoline  D i c h l o r o m e t h a n e - 1 % methanol e l u t i o n gave  (3 mg) which was f o l l o w e d  by d e s a c e t y l  dimer (15 mg).  The major d i m e r i c p r o d u c t , dimer (118), had i d e n t i c a l t i c p r o p e r t i e s - a n d gave t h e same nmr spectrum as t h a t o b t a i n e d f o r t h e p r o d u c t from  - 157 -  the  d i m e r i s a t i o n o f the c h l o r o i n d o l e n i n e o f 4 8 - d i h y d r o c l e a v a m i n e  (41)  with vindoline.  18g-Cyano-48-dihydrocleavamine 48-Dihydrocleavamine  (42)  (1.00 g) was  converted t o the corresponding  c h l o r o i n d o l e n i n e by t h e p r o c e d u r e a l r e a d y d e s c r i b e d .  This material  I  was d i s s o l v e d i n a s o l u t i o n o f f u s e d sodium a c e t a t e (10 g) i n g l a c i a l acetic acid  (80 c c ) and a c e t i c a n h y d r i d e (20 c c ) .  warmed t o 60°C f o r 2 h o u r s .  This solution  was  The s o l v e n t was removed under reduced  p r e s s u r e ; h i g h vacuum was used f o r t h e l a s t t r a c e s .  The r e s i d u e was  f l u s h e d t h r o u g h a s h o r t column o f a l u m i n a (20 g as a 2" column) u s i n g ethanol.  T h i s s o l v e n t was removed and t h e r e s i d u e was d r i e d under  h i g h vacuum.  P o t a s s i u m c y a n i d e (500 mg)  was added and i n t o t h e  r e a c t i o n v e s s e l was d i s t i l l e d d i m e t h y l f o r m a m i d e from o v e r b a r i u m o x i d e . T h i s m i x t u r e was r e f l u x e d f o r 1 2/3 hour.  The s o l v e n t was  removed  under reduced p r e s s u r e and t h e d i c h l o r o m e t h a n e s o l u b l e m a t e r i a l chromatographed  on a l u m i n a (200 g ) .  188-cyano-48-dihydrocleavamine from m e t h a n o l , mp  Benzene e l u t i o n gave t h e d e s i r e d  (42) (224 mg).  This material  crystallized  150-152° and showed i d e n t i c a l t i c p r o p e r t i e s  s u p e r i m p o s a b l e i r and nmr s p e c t r a s compared w i t h an a u t h e n t i c mp  was  and sample,  150-152°.  Dimer ( 1 4 6 ) , from  18B-cyano-48-dihydrocleavamine  188-Cyano-48-dihydrocleavamine  (147 mg)  was d i s s o l v e d i n a  s o l u t i o n o f d i c h l o r o m e t h a n e (17 c c ) and t r i e t h y l a m i n e (0.079 c c ) and t h i s s o l u t i o n was  cooled to ice-acetone bath temperature.  A solution  - 158  -  o f t e r t - b u t y l h y p o c h l o r i t e i n carbon t e t r a c h l o r i d e (12 c c , 0.042 M) was  added d r o p w i s e t o the c o o l e d s o l u t i o n , o v e r a 0.5  The  s o l v e n t was  removed under r e d u c e d p r e s s u r e  benzene (20 c c ) was  and an a l i q u o t o f  added t o the r e s i d u e and d i s t i l l e d o f f i n o r d e r  a z e o t r o p e o f f any water which might be p r e s e n t . i n d o l e n i n e was  hour p e r i o d .  added v i n d o l i n e (217 mg)  To t h i s crude c h l o r o -  and t h i s m i x t u r e  was  dissolved  i n an anhydrous m e t h a n o l i c h y d r o c h l o r i c a c i d s o l u t i o n (15 c c , The  s o l u t i o n was  to  1%).  r e f l u x e d under a n i t r o g e n atmosphere f o r 2 h o u r s .  A f t e r t h i s t i m e , the s o l v e n t was  removed, the r e s i d u e was  w a t e r (50 cc) and made s l i g h t l y b a s i c .  T h i s m i x t u r e was  t a k e n up i n extracted  w i t h d i c h l o r o m e t h a n e (3 x 30 cc) and the combined e x t r a c t s t a k e n t o dryness.  The  r e s i d u e was  chromatographed on a l u m i n a (100 g ) .  e t h y l a c e t a t e e l u t i o n gave unconsumed v i n d o l i n e (119 mg) 10% e t h y l a c e t a t e e l u t i o n gave the dimer (146) c r y s t a l l i z e d from d i e t h y l - e t h e r , mp 294,  312(sh) ( l o g e 4.68,  ^nujol.  3  3  2  0  -l  c m  b r o a d , IH, 0-H),  ( v  N  _ ^ H  1.90  a r o m a t i c ) , 3.79  2  77,  3  H  1 7 4 Q  4.01,  c m  -l ^  IH, N-H),  6  ?  6  c = 0  124,  '  215,  )  m  R  :  t  Q  ( v e r y  4  main p e a k s , m/e  spectrometry).  y  ( s i n g l e t , IH, C - H ) ,  ( s i n g l e t , 3H,  135,  285,  indole 4.20  i y  4  128,  265,  ( s i n g l e t , IH, C - H ) ,  -OCH^, 6.29  4.80 (singlet,  ( s i n g l e t , 3H, N-CH ), 2  3  (triplet,  50, 51, 55, 57, 67,  3H, 69,  138. 761.415.  7.99  3  ( t r i p l e t , 3H, C -CH CH_ ), 9.45  Calcd. f o r C ^ H ^ O ^ :  r e s o l u t i o n mass  - .  2  Mass spectrum: 122,  m a x  This m a t e r i a l  3.78, r e s p e c t i v e l y ) ;  ( s i n g l e t , IH, C ~ H ) , 7.35  -OAc), 9.11  *  and benzene-  2.5-3.0 ( d i f f u s e , 4H,  IH, C = C H R ) , 4.70 ?  78, 79, 107, Anal.  _ ^  IH, C = C H R ) , 6.12 6.36  3  Cg-CH CH_ ).  4.02,  1 4  -C0 CH_ ),  ( s i n g l e t , 3H,  204-224°C;  ( s i n g l e t , IH, C - H ) , 3.94  (broad d o u b l e t , 2  Q  (broad,  (doublet of doublets,  3H,  4.19,  (22 mg).  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