ENANTIOSELECTIVE PERMEATION THROUGH MA-[3-(PENTAMETHYLDISILOXANYL)PROPYL]-L-GLUTAMATE) MEMBRANES

Poly(L-glutamic acid ester) with 3-(pentamethyldisiloxanyl) propyl gro ups was prepared from poly(gamma-methyl-L-glutamate) (PMLG) by ester e xchange reaction. This polymer had an alpha-helical structure in the m embrane prepared from 1,2-dichloroethane solution. The membrane formin g ability of the polymer was better than that of PMLG. Optical resolut ion of (+/-)-tryptophan was achieved by pressure driven permeation thr ough the membrane. The enantioselectivity was 16% enantiomeric excess (%ee) and the permeation rate was high (10(-6) g m/m2 h). This enantio selective permeation continued for more than 160 h. With an increase i n the disiloxane side chain content, the permeation rate could be incr eased while maintaining the selectivity. Since the enantioselectivity for adsorption favoured the (+)-isomer and that for permeation favoure d the (-)-isomer, enantioselective permeation was caused by suppressio n of the (+)-isomer permeation. It was suggested that the permeation o f dilute aqueous tryptophan solution occurred mainly in the region of highly mobile disiloxane side chains, which had no asymmetric centers, by measurements and analysis of the pervaporation of dilute aqueous e thanol solution. Therefore it was believed that this siloxane region w as small enough for the asymmetric centers in the main chain to recogn ize enantioselectively the permeating solute.