The a',,!? elimination of the carbanion derived from [a-2H2] benzyl isolongifolyl thioether and [a-2H2] benzyl camphyl thioether gives the chiral [~-~ H] benzyl mercaptan, the S isomer with 38 f 6% ee and the R isomer with 49 f 7% ee. The chirality of the [a-2H] benzyl mercaptan was determined by optical rotation of [a-2H] benzyl methyl thioether and thiosulfone. The enantiomeric excess was evaluated from 'H NMR measurement of ethyl ( ...