Convergent Approaches to Saudin Intermediates

Different convergent approaches to the highly oxygenated sesquiterpene natural product saudin (1), has been investigated. Our strategy has included a Michael addition and aldol condensation reaction as key steps. During the synthetic development, we have found serious steric hindrance when an α-Me-substituted alkyl vinyl ketone was used. Such steric hindrance has been overcome by synthesizing the vinyl ketone 16 through an anionic fragmentation, which was carefully studied. Finally, the intermediate 18 has been synthesized in a one-pot reaction from the vinyl ketone 16 and has been cyclized to obtain the promising tricyclic intermediate 20.