Syntheses of the Insect Antifeedant (+/-)-Cinnamodial and the Drimane Sesquiterpenoids (+/-)-Isodrimenin and (+/-)-Fragrolide

Article abstract of DOI:10.1021/jo00203a014

Total syntheses of (+/-)-cinnamodial (5), (+/-)-isodrimenin (24), and (+/-)-fragrolide (29) are described begining from the diene 7.Hydroboration-oxidation of 7 gave the trans-fused alcohol 18, and elimination of mesylate 21, followed by selective reduction at the more accesible ester function, led to γ-lactone 23, which afforded 24 upon hydrogenation.A different route from 18 produced triol 27, which was selectively oxidized at the more exposed primary alcohol to yield γ-lactone 28.The latter, upon oxidation, furnished 29.The synthesis of 5 hinged upon the construction of furan 38 , which was obtained from lactone 26 via 37 or, directly, by oxidation of 27.Oxidation of 38 with lead tetraacetate gave 41, which underwent elimination with DBU to provide 43.Regio- and stereoselective epoxidation of this dienone gave 45 which, upon acidic methanolysis, led to 50.Reduction of this ketone resulted in the 6β alcohol 51, and exposure of this bis acetal to acid released the dialdehyde array of 52.Finally, acetylation of 52 gave 5.