Stereoselective total synthesis of (±)-tochuinyl acetate and (±)-dihydrotochuinyl acetates

Abstract

Details of the first total synthesis of the marine natural product dihydrotochuinyl acetate is described. Cyclopentenone annulation of p-methylacetophenone via a Claisen rearrangement-Wacker oxidation based sequence generated the cyclopentenone 3, a known precursor for the sesquiterpenes cuparene, laurene, α-cuparenone and β-cuparenones. Conversion of the ketone moiety into a carboxylate followed by stereoselective alkylation and reduction transformed the cyclopentenone 3 into the primary alcohol 19. Birch reduction of the alcohol 19 followed by acetylation furnished (±)-dihydrotochuinyl acetate, whereas direct acetylation of 19 furnished (±)-tochuinyl acetate.