Convergent Total Synthesis of (–)-Principinol D, a Rearranged Kaurane Diterpenoid

The total synthesis of principinol D, a rearranged kaurane diterpenoid, is reported. This grayanane natural product was constructed via a convergent fragment coupling approach, wherein the central 7-membered ring was synthesized at a late stage. The bicyclo[3.2.1]octane fragment is accessed by a Ni-catalyzed α-vinylation reaction, followed by a diastereoselective SmI₂-mediated ketone reduction. The convergent strategy reported herein may be an entry point to a wide range of kaurane diterpenoids.