Synthesis of (Rc,Ss)-1,1,1-Trifluoro-3-(p-tolylsulfinyl)-2-propanol by an Asymmetric Reduction with a Yeast, Yamadazyma farinosa, as a Key-step

(Rc,Ss)-1,1,1-trifluoro-3-(p-tolylsulfinyl)-2-propanol (>99% e.e.), an important reagent for the asymmetric protonation of substituted enolates, was prepared (70%) from (S)-methyl p-tolyl sulfoxide. The stereoselectivity of the Yamdazyma farinosacatalyzed reduction of carbonyl groups, the key step for the introduction of an asymmetric carbon, was greatly affected by the stereochemistry of the asymmetric sulfur atom. The reduction of (S)-1,1,1-trifluoro-3-(p-tolylsulfinyl)-2-propanone proceeded smoothly and in a quite stereoselective manner to give the desired compound, while a 76 : 24 mixture of (Rc,Rs)- and (Sc,Rs)-isomers was obtained from the substrate with the opposite (R)-configuration.