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Remote oxidation of natural products

University of British Columbia

Remote oxidation at the C-5 position of isobornyl acetate (37) by chromium trioxide in glacial acetic acid/acetic anhydride, and the application of this oxidation to monoterpenes having the bicyclo[2.2.1] heptane framework is described. Subsequent conversion of 5- ketoisobornyl acetate (38) to 5-ketocamphene (42) and the relevance of this sequence to the proposed synthesis of the sesquiterpenes, culmorin (95), helminthosporol (99) and helmintho-sporal (97) is discussed. The oxidation of dihydroisocampherenyl acetate (87) at C-5 and subsequent conversion to b-ketodihyriro-p-santalene (90) is also described. The postulate that "certain compounds are susceptible to oxidation at positions remote from functionality" is further tested by the oxidation of fatty acid esters. The formation of a mixture of mono-ketoesters from the oxidation of methyl stearate (72;n=16), methyl docosanoate (72;n=20), methyl myristate (72;n=12), methyl palmitate (72;n=14), and methyl decanoate (72;n=8) by Cr03-Ac20/AcOH, and the procedure used to obtain a quantitative estimation of the relative amounts of isomeric ketoesters present in the product mixtures, is reported. Evidence is given for the validity of the analytical method used to estimate the relative amounts of isomeric ketoesters.

Text

2010-01-21

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http://hdl.handle.net/2429/18885

Chemistry

University of British Columbia

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