Potassium ethanethioate → (S)-2-(Acetylthio)-4,4-dimethylpentanoic acid

A slurry of potassium thioacetate (750 mg, 6.58 mmol) and acetonitrile (10 ml, molecular sieves dried) was cooled to 0° C. and treated with a solution of (R)-2-bromo-4,4-dimethylpentanoic acid from part (a) in acetonitrile (2 ml) over 5 minutes. The reaction mixture was allowed to warm to room temperature and stirred for 2.5 hours. The slurry was filtered. The filtrate was concentrated in vacuo. The residue was diluted in ether (50 ml), washed with two portions of 5% aqueous sodium thiosulfate (50 ml) and brine (25 ml), dried (magnesium sulfate), and concentrated in vacuo. The pale yellow oil was purified by flash chromatography (Merck silica gel, 12×3 cm., 10% methanol/methylene chloride) affording 575 mg of title product as a pale yellow oil.