Enantiocontrolled Total Synthesis of (-)-Retigeranic Acid A.

The asymmetric total synthesis of (-)-retigeranic acid A has been realized. The key features of the current synthesis include (1) a Pt-catalyzed Conia-ene 5- exo-dig cyclization of enolyne to establish the key quaternary stereochemical center of C-10 (D/E ring), (2) an intramolecular diastereoselective Prins cyclization to construct the trans -hydrindane backbone (A/B ring), and (3) a late-stage intramolecular Fe-mediated hydrogen atom transfer (HAT) Baldwin-disfavored 5- endo - trig radical cyclization to rapidly assemble vicinal quaternary centers and the core structure of (-)-retigeranic acid A (C ring).