The First Total Synthesis of (-)-Mitragynine, an Analgesic Indole Alkaloid in Mitragyna speciosa.

Starting from an optically pure alcohol, (R)-(3), which was prepared by enzymatic hydrolysis of the racemic acetate (2) or enantioselective reduction of the ketone derivative (4), the chiral total synthesis of mitragynine (1), a major corynanthe-type indole alkaloid having an analgesic effect in Mitragyna speciosa, was accomplished.