Enantiospecific Total Synthesis of (+)‐3‐epi‐Epohelmin A Using a Nitrogen‐Substituted Donor–Acceptor Cyclopropane

Abstract

The enantiospecific total synthesis of (+)‐3‐epi‐epohelmin was accomplished by rapid construction of the pyrrolizidine core starting from enantiopure l‐pyroglutamic acid. The key reaction included a highly regio‐ and stereoselective intramolecular cyclopropanation reaction, regioselective ring opening of a nitrogen‐substituted donor–acceptor cyclopropane, stereoselective reduction of a ketone, chemoselective organolithium addition to a Weinreb amide, and chemoselective oxidation of an allylic alcohol.