Development of Biomimetic Synthesis of Propindilactone G

The Summary of main observation and conclusion The natural product propindilactone G is a complexSchisandranortriterpenoid with a unique 5/5/7/6/5 pentacyclic framework. This full paper describes the development of concise biomimetic synthesis of propindilactone G from a known steroid lactone. The key C19-OH intermediate was synthesizedviaBreslow and Suarez radical remote C-H functionalizations. Wagner-Meerwein rearrangement was subsequently utilized for the expansion of the B ring. To invert the configuration of the C10 tertiary alcohol, an intramolecular peroxide cyclization catalyzed by BF3 center dot Et2O was devised. The 5/5 fused lactone system was then assembled in a biomimetic transesterification/oxa-Michael addition sequence. Our work should provide experimental support for the proposed biosynthetic pathway and facilitate investigation of the biological activities of propindilactone G.