Synthesis of the macrocyclic core of iriomoteolide 3a.

The asymmetric synthesis of the fully functionalized macrocyclic core of iriomoteolide 3a, a cytotoxic 15-membered macrolide, is disclosed. The key steps involve Sharpless asymmetric dihydroxylation, Sharpless asymmetric epoxidation, olefin cross-metathesis, Yamaguchi esterification, and a ring-closing metathesis reaction for macrocyclization.