Toward the Development of a General Chiral Auxiliary. Enantioselective Alkylation and a New Catalytic Asymmetric Addition of Silyloxyfurans: Application to a Total Synthesis of (−)-Rasfonin

An enantioselective total synthesis of the apoptosis-inducing natural product, (-)-rasfonin, is described. Camphor lactam-mediated asymmetric alkylation reactions enabled the installation of three stereogenic centers with >95:5 diastereoselectivity. A modified Corey-Peterson olefination was employed in the construction of the (E,E)-diene system. A highly diastereoselective, asymmetric vinylogous Mukaiyama aldol addition was conducted using a chiral cationic oxazaborolidine catalyst. The pyranone core of the natural product was prepared via a DBU-promoted rearrangement of a furanol to its corresponding pyranol with concomitant [1,4]-silyl transfer.