Complexation of amino acids as their sodium and potassium salts by optically active diaza crown ethers has been investigated in transport across bulk liquid membranes containing the carriers and in extraction experiments. The observed enantioselectivity was achieved by (noncovalent) steric and repulsive interactions between the side arm of the crown ether and functional group(s) of the amino acids. The highest enantioselectivity was observed in the case of tryptophan.
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