Synthesis of poly‐O‐tert‐butyl‐ L ‐serine and poly‐ L ‐serine

The synthesis of polymers containing O‐tert‐butyl‐L‐serine, O‐tert‐butyl‐DL‐serine, L‐serine, and DL‐serine is reported. The N‐benzyloxycarbonyl‐(L or DL)‐serine benzyl ester was used to synthesize the corresponding N‐benzyloxycarbonyl‐O‐tert‐butyl‐(Lor DL)‐serine benzyl ester. Catalytic hydrogenation of this material gave O‐tert‐butyl‐(Lor DL)‐serine. The reaction of O‐tert‐butyl‐(Lor DL)‐serine with phosgene produced the corresponding N‐carboxyanhydrides. The kinetics of polymerization of N‐carboxyanhydrides were investigated to facilitate, the preparation of block copolymers. The O‐tert‐butyl blocking group was removed from polymers by treatment with HCl and HBr in benzene. Both high molecular weight (water‐insoluble) and low molecular weight (water‐soluble) homopolymers have been prepared, as well as water‐soluble block copolymers of the type (DL‐serine)x (L‐serine)y, (DL‐serine)z.