[Preparation of leucine-methyl glutamate-glutamic acid copolymers]

The method for preparing leucine-methyl glutamate-glutamic acid copolymer was studied. In the first place benzyl glutamate and methyl glutamate were synthesized respectively. Then N-carboxy anhydrides (NCA) of leucine, benzyl glutamate or methyl glutamate were prepared in a closed container by phosgene-toluene solution method. After copolymerization the copolymers were debenzylated and demethylated by anhydrous hydrogen bromide. The free carboxyl group mole content in side chains of the copolymer was controlled by various standing periods following bubbling HBr. Analysis of infrared spectrogram and ultraviolet asorbance of copolymers indicated that this procedure resulted in the loss of almost all benzyl groups and some methyl groups.