An Efficient Stereoselective Synthesis of Penaresidin A from (E)-2-Protected Amino-3,4-unsaturated Sulfoxide

An efficient, modular, asymmetric synthesis of penaresidin A is disclosed. A beta-protected amino-gamma,delta-unsaturated sulfoxide was prepared by stereoselective addition of the lithio anion of (R)-methyl p-tolyl sulfoxide to an unsaturated sulfinylimine. The pendant sulfoxide group was used as an intramolecular nucleophile to functionalize an alkene regio- and stereoselectively to furnish a bromohydrin, which was employed as the key intermediate in the preparation of the azetidine subunit of penaresidin A. The stereogenic centers of the side chain were introduced by a regioselective opening of an epoxide. Julia-Kocienski olefination was used to couple the azetidine and side chain subunits. The methodology disclosed herein is also useful for the synthesis of ribo- and arabino-phytosphingosines and compounds possessing the amino alcohol moiety.