Ligand-exchange chromatography of racemates, 9. Ligand-exchange chromatography of amino acid enantiomers on asymmetric sorbents with polydentate sulfur containing groupings

The paper describes the syntheses of four asymmetric sorbents, which contain S-(2-aminoethyl)-L -cysteine ( 1a ), S-(carboxymethyl)-L -cysteine ( 1c ), S,S′-(ethylene)-bis(L -cysteine) ( 2a ), and N,N′-(ethylene)-bis(D-methionine) ( 3a ) groupings as the chiral fixed ligands in a cross-linked polystyrene matrix. The sorbents were used for ligand-exchange chromatography of amino acid enantiomers in the presence of Cu(II) and Ni(II) ions. Enantioselective effects in the formation of mixed-ligand complexes consisting of a fixed ligand, a metal ion, and an amino acid enantiomer were determined. The highest values of enantioselectivity reaching 1 300 to 1 890J/mol were found in mixed-ligand complexes containing histidine or β-phenyl-α-alanine.