Bioinspired Synthesis of Nortriterpenoid Propindilactone G.

A concise bioinspired synthesis of nortriterpenoid propindilactone G has been accomplished from a readily accessible steroidal lactone. Key transformations include a Breslow remote functionalization, a Suárez remote radical functionalization, a ring expansion enabled by a Wagner-Meerwein rearrangement, a stereoinversion of a tertiary alcohol, and a biomimetic transesterification/oxa-Michael addition cascade. This work also provides experimental evidence of the putative propindilactone G biosynthesis pathway.