Total synthesis of (−)-ephedradine A: an efficient construction of optically active dihydrobenzofuran-ring via C–H insertion reaction

Abstract

The stereocontrolled total synthesis of (−)-ephedradine A ( 1 ) has been accomplished. Construction of optically active dihydrobenzofuran-ring was performed by a novel asymmetric C–H insertion reaction. After an intramolecular ester–amide exchange reaction and a Sharpless asymmetric aminohydroxylation reaction, construction of the complex macrocyclic ring was performed by Ns-strategy and an intramolecular aza-Wittig reaction.