The Enantioresolution of Methylthiohydantoin-Amino Acids on R,S-2-hydroxypropyl Derivatized β-Cyclodextrin Bonded Stationary Phase Using the Water-Based Mobile Phase

The enantioresolution of thirteen methylthiohydantoin-amino acids (MTH-amino acids), which are substrates for producing D-amino acids through enzyme-catalyzed hydrolysis, is described on R, S-2-hydroxypropyl derivatized β-cyclodextrin bonded stationary phase (RSP-β-CD CSP) with a water-based mobile phase. The enantioresolution is relatively sensitive to the structural variation of group which is attached to the carbon at position five on methylthiohydantoin moiety and subsequently turns into side-chain group of corresponding D-amino acid produced after hydrolysis. The inclusion complexation is believed to be the mechanism responsible for the observed enantioresolution that cannot be reproduced either on native β-cyclodextrin CSP under the same chromatographic conditions or on both CSPs using the acetonitrile-based mobile phase. Approaches for enantioimprovement include varying the percentage of organic modifier in the mobile phase and using the buffer-typed mobile phase such as triethylammonium acetate (pH 4.1).