PREPARATION OF POLY(L-SERINE ESTER) - A STRUCTURAL ANALOG OF CONVENTIONAL POLY(L-SERINE)

The preparation of poly(N-acyl-L-serine ester) from derivatives of N-acyl-L-serine was investigated in detail. N-(Benzyloxycarbonyl)-L-serine was selected as a model monomer since the benzyloxycarbonyl group can be readily removed without degradation of the polymer backbone. The direct polyesterification of N- (benzyloxycarbonyl)-L-serine in solution and the melt transesterification of N-(benzyloxycarbonyl)-L-serine methyl ester failed to yield polymers of high molecular weight. Best results were obtained by the ring-opening polymerization of N-(benzyloxycarbonyl)-L-serine β-lactone. This polymerization was accompanied by a chain-transfer reaction. Under optimized conditions, poly[N-(benzyloxycarbonyl)-L-serine ester] with a molecular weight (Mw) of ca. 40 000 (GPC, relative to polystyrene standards) was obtained. Removal of the N-benzyloxycarbonyl group by catalytic transfer hydrogenation yielded for the first time optically pure poly(L-serine ester-HCl), a structural analogue of conventional poly(L-serine). Such serine-derived polyesters may be used as model compounds in structural studies and may find applications as biomaterials. © 1990, American Chemical Society. All rights reserved.