合成路线1

The enantiomerically pure sulfoxide was prepared by a different route, starting from the alkylation of hydroxyquinolinone (A) with (S)-glycidyl tosylate (IV) to give the chiral epoxide (V). Ring opening with mercaptoimidazole (I) afforded the enantiomerically rich (R)-mercapto alcohol (VI), which after recrystallization from EtOH provided the pure (R)-isomer. Oxidation with m-chloroperbenzoic acid yielded a diastereomeric mixture of hydroxy sulfoxides (VII). After separation by column chromatography, the required (S)-sulfoxide was converted to mesylate (VIII), and finally reduced with lithium triethylborohydride to afford the target (S)-compound.