Optical Resolution of Amino Acids by a Polymer Membrane Having Cyclodextrin Moieties

Abstract

In order to separate the optical isomers of amino acids by permeation through a membrane, a polymer membrane having β-cyclodextrin moieties in the side chains was pre pared and the permeation characteristics of amino acids through the polymer membrane were investi-gated. When phenylalanine was permeated through the polymer membrane in water, the permeation rate of _L-isomer was greater than that of _D-isomer. The ratio of the permeation coefficient of _L-isomer to that of D-isomer was 1.4 0. A similar result was obtained in the case of tryptophan and histidine permeation. No difference in the permeation rat e between the optical isomers was observed with the polymer membrane having gluc ose instead of cyclodextrin moieties. It was found that the β-cyclodextrin moiety in teracts with _D-isorner more strongly than with _L-isomer through adsorption experiments of amino acids onto a cross-linked β-cyclodextrin gel. The diffusivity of _D-isomer in the mem brane was thus depressed by the interaction with the cyclodextrin moiety. The polymer membrane having β-cyclodextrin moieties can separate the optical isomers of phenylalanine and the _L/_D molar ratio, of phenylalanine permeated, was 61.7/38.3.