Chiral separation of mandelic acid by temperature-induced aqueous two-phase system



BACKGROUND: R-mandelic acid is an important chiral pharmaceutical intermediate, which is commonly obtained by biotransformation. This work has focused on using novel chiral recognition technology, aqueous two-phase extraction, for the chiral separation of mandelic acid.

RESULTS: The copper (II) formed a 2:1 complex with β-CD in an alkaline solution, which was isolated from solution by the addition of ethanol. The complex structure was characterized by IR and UV spectroscopy. The chiral recognition system was established by adding Cu2-β-CD into the triton-114 aqueous two-phase extraction system, which preferentially recognizes the (R)-enantiomer rather than the (S)-enantiomer. Factors affecting the extraction mechanism were analyzed, namely the concentration of Cu2-β-CD and tritonX-114, the types of salts, pH, and temperature. It was found that the concentration of Cu2-β-CD and temperature were the most important influencing factors for chiral separation of mandedlic acid. The experimental results showed that the ee values increased with pH and concentration of trition-114, and the maximum ee was 67.91%. The addition of inorganic salt had a strong influence on ee, which decreased when salt was added into the aqueous two-phase extraction system.

CONCLUSION: A novel chiral recognition technology - aqueous two phase extraction is reported in this paper.The tritonX-114 aqueous two phase system have a good recognition ability for mandelic acid. Copyright © 2012 Society of Chemical Industry