Resolution of Optical Isomers as the Mixed Chelate Copper(III) Complexes by Reversed Phase Chromatography

Abstract

Abstract Highly selective separation of D and L amino acids can be effected by reversed phase chromatography of mixed chelate complexes of the analyte acids with equimolar concentrations of Cu(II) and an optically active second amino acid in the mobile phase. The stabilities of the formed diastereomeric ternary complexes will determine the resolution of enantiomers. By this approach, amino acids were resolved as the dansyl and O-phthalaldehyde (OPA) derivatives and imino acids were separated without derivatization. Resolution of D and L dansyl amino acids was accomplished as the mixed complexes of Cu(II) with L-proline, L-arginine, L-histidine and L-histidine methyl ester as the second amino acids. Among the chiral ligands we studied, L-histidine methyl ester is unique in that it possesses both achiral selectivity for the dansyl amino acids and chiral selectivity for the respective D and L enantiomers. With a mobile phase gradient of acetonitrile in a buffer containing Cu(II) L-histidine methyl ester comp...