Protecting Group-Free Total Synthesis of (−)-Boscartin H

Abstract

Herein, we report the first protecting group-free total synthesis of (−)-boscartin H, which features a 5-12-5-fused tricyclic structure. The key steps, which include a diastereoselective THF-ring-forming/aldol reaction sequence and ring-closing metathesis, afforded high stereoselectivity with (−)-boscartin H obtained in 3.6% overall yield using a 11-step long linear sequence. In addition, X-ray crystallography clearly confirmed the stereochemistry of boscartin H.