Separation of amino-acid enantiomers using micellar-enhanced ultrafiltration

Micellar-enhanced ultrafiltration (MEUF) is investigated as a large-scale technique for separating amino acid enantiomers. Specifically, L-5-cholesterol glutamate, a chiral ligand-exchange cosurfactant, is used together with a nonionic surfactant to form mixed micelles that preferentially bind D-phenylalanine over L-phenylalanine in the presence of copper(II). Operational selectivities as high as 4.2 are obtained. Potentiometric titrations using a water-soluble model compound similar to the chiral cosurfactant indicate that the ternary copper complex with phenylalanine has a stereoselectivity for the D enantiomer which is significantly smaller than that observed in the MEUF system. Thus, the selectivity of the chiral legend's local solvent and structural environment. (c) 1994 John Wiley & Sons, Inc.