Preparation and characterization of pseudopoly(trans-4-hydroxy-L-proline ester)

The preparation and characterization of polyesters derived from hydroxyproline were investigated. Two new polymers of poly(trans-4-hydroxy-N-benzyloxycarbonyl-L-proline) [poly(N-Z-Hpr-OH)] and poly(trans-4-hydroxy-N-benzyloxycarbonyl-L-proline ester) [poly(N-Z-Hpr-OMe)], with easily removable pendant N-benzyloxycarbonyl group, were prepared. Weight-average molecular weight (M_w) of about 254000 and 33000 were obtained via esterification or transesterification, using stannous octoate as a catalyst, at 140 °C under vacuum (20 mmHg) for 16 h. Removal of the N-benzyloxycarbonyl group by catalytic transfer hydrogenation yielded pseudopoly(trans-4-hydroxy-L-proline, ester) [poly(Hpr-OMe·HCl)].