Enantioseparation of α-amino acids and dipeptides by ligand-exchange capillary electrophoresis of various l-4-hydroxyproline derivatives

The principle of ligand exchange has been applied to the enantioseparation of underivatized aromatic and aliphatic amino acids as well as dipeptides. Two non commercially available N-alkyl- l -4-hydroxyproline derivatives were compared to underivatized l -4-hydroxyproline for their ability to resolve α-amino acids and dipeptides. N-(2-hydroxyoctyl)- l -4-hydroxyproline and N-(2-hydroxypropyl)- l -4-hydroxyproline were used as their copper(II) complexes as chiral selectors. With these selectors, several aliphatic amino acids and dipeptides, in addition to aromatic amino acids, were resolved. The pH optimum was found to be 4.3 for amino acids and 6.0 for dipeptides.