Enantiomerically Pure Epoxychromans via Asymmetric Catalysis.

Abstract A practical and highly effective process for the asymmetric epoxidation of several 2,2-dimethylchromene derivatives is reported. Catalysis by Mn(salen) complex 4 in all cases affords epoxychromans with >90% ee, and this method has been applied to the synthesis of two recently developed antihypertensive agents in enantiomerically pure form.