CHIRAL SEPARATION OF UNMODIFIED ALPHA-HYDROXY ACIDS BY LIGAND-EXCHANGE HPLC USING CHIRAL COPPER(II) COMPLEXES OF (S)-PHENYLALANINAMIDE AS ADDITIVES TO THE ELUENT

Copper(II) complexes of (S)-phenylalaninamide have been successfully u sed for the direct enantiomeric separation of unmodified (R,S)-alpha-h ydroxy acids in reversed phase high-performance liquid chromatography (RP-HPLC). The effect of various parameters (pH, eluent polarity, sele ctor concentration) on enantioselectivity is discussed. Evidence is pr ovided that a mechanism of ligand exchange is actually occurring durin g the chromatographic separation. The method is very convenient and ea sy to use, and the chiral selector is commercially available and can b e recovered at the end of the analysis. A conventional achiral RP-ODS- 2 column is used and no pretreatment of the samples is required. This method allows the accurate determination of the enantiomeric excess of alpha-hydroxy acids in synthetic and biological samples. (C) 1995 Wil ey-Liss, Inc.