Water → (2R)-chloro-3-phenylpropionic acid

Thionyl chloride (0.18 ml, 2.4 mmol) was added dropwise to a solution of 200 mg (1.2 mmol) of (2S)-2-hydroxy-3-phenylpropionic acid (optical purity 100% ee (S)) in 2 ml of dimethoxyethane at room temperature, and the mixture was stirred for 15 hours. To that reaction mixture was added 0.01 ml (0.12 mmol) of pyridine, and the mixture was stirred at 60° C. for 4 hours. Water (10 ml) was added to the reaction mixture and, after 30 minutes of stirring, the mixture was extracted with 50 ml of ethyl acetate. The organic phase was washed with 10 ml of a saturated aqueous solution of sodium chloride and dried over sodium sulfate. The solvent was distilled off under reduced pressure to give 135 mg (yield 61%) of the desired (2R)-2-chloro-3-phenylpropionic acid. The optical purity of the product as determined by the same method as in Example 12 was 97.6% ee (R) (rate of configurational inversion 97.6%).