An Efficient Formal Synthesis of (−)-Balanol by Using Ruthenium-Catalyzed Asymmetric Hydrogenation

An efficient formal synthesis of (−)-balanol is reported. The ten-step sequence leading to a key precursor 4 features a highly stereoselective synthesis of the functionalized hexahydroazepine core through dynamic kinetic resolution of a racemic α-amido β-keto ester using a ruthenium(II)-catalyzed hydrogenation reaction.