Enantioselective liquid-liquid extraction of 3-chloro-phenylglycine enantiomers using (S,S)-DIOP as extractant.

(S,S)-DIOP, a common catalyst used in asymmetric reaction, was adopted as chiral extractant to separate 3-chloro-phenylglycine enantiomers in liquid-liquid extraction. The factors affecting extraction efficiency were studied, including metal precursors, organic solvents, extraction temperature, chiral extractant concentration, and pH of aqueous phase. (S,S)-DIOP-Pd exhibited good ability to recognize 3-chloro-phenylglycine enantiomers, and the operational enantioselectivity (α) is 1.836. The highest performance factor (pf) was obtained under the condition of extraction temperature of 9.1°C, (S,S)-DIOP-Pd concentration of 1.7 mmol/L, and pH of aqueous phase of 7.0. In addition, the possible recognition mechanism of (S,S)-DIOP-Pd towards 3-chloro-phenylglycine enantiomers was discussed.