158.A Synthetic Route to The Core Structure of (−)-Retigeranic Acid A

Xiao Wang, Dian Li, Junlin Zhang, Jianxian Gong, Junkai Fu,* and Zhen Yang*

Org. Lett. 2021, 23,(13), 5092–5097

Retigeranic acid A is a uniquely structured pentacyclic sesterterpene bearing eight stereogenic centers. We report a concise route to the core structure of (−)-retigeranic acid A. The stereochemistry of its six chiral centers and three quaternary carbon centers was well-controlled. This route features two intramolecular Pauson–Khand reactions (IMPKRs): the first forged the D and E rings to deliver the triquinane subunit, and the second constructed the A and B rings and diastereoselectively installed the quaternary C6a center.