Enantioselective total synthesis and absolute configuration of the alleged structure of crassinervic acid

An enantioselective synthesis of the structure reported for the natural antifungal compound, (-)-crassinervic acid (1), has been achieved starting from geraniol and p-hydroxybenzoic acid. The key chirality-inducing step is a Sharpless asymmetric epoxidation of an allylic alcohol, on the basis of which the S configuration can be assigned to the (-) natural enantiomer. The discrepancies between the spectroscopic data for synthetic and natural crassinervic acid cast some doubts on the structure assigned to the natural compound. A possible revised structure is discussed.