Abstract
A total synthesis of (±)-warburganal has been completed starting from (±)-isodrimenin and other drimane-type compounds. 11, 12-Diacetoxy-drim-8-ene (9), which can be readily obtained from the above starting compounds, was converted to the 7-oxo derivative (7). Treatment of 7 with 30% H2O2 followed by NH2NH2·H2O promoted reductive opening of the resulting keto epoxide group to afford the trialcohol (11). Selective silylation of the allylic primary alcohol in 11 with tert-butyldimethylsilyl chloride followed by protection of the α-glycol with N, N'-carbonyldiimidazole afforded the carbonate (14). Desilylation of 14 and subsequent oxidation of the allyl alcohol moiety afforded 16. Protection of the aldehyde followed by base-induced deprotection of the glycol afforded 18, which was subjected to Moffatt oxidation to give 19. Treatment of 19 with p-TsOH-acetone afforded (±)-warburganal.
