Asymmetric dihydroxylation and hydrogenation approaches to the enantioselective synthesis of R-(+)-α-lipoic acid

The asymmetric synthesis of methyl (S)-6,8-dihydroxyoctanoate (5) and (S)-6,8-dimethylsulfonyloxyoctane-1-carboxylic acid (13), key precursors to R-(+)-α-lipoic acid (6) is described using OsO4-catalyzed asymmetric dihydroxylation and Ru-catalyzed asymmetric hydrogenation, respectively, as the key steps in the reaction sequence. These methods lead to an efficient formal synthesis of R-(+)-α-lipoic acid in 90% ee.