L-tyrosine-based backbone-modified poly(amino acids).

Tyrosine-based pseudo-peptide polymers, first introduced in 1987 by Kohn and Langer, have been identified for potential biomaterial applications. These materials combine the desired polypeptide properties of biocompatibility, biodegradability, non-toxicity, and non-immunogenicity with good processing properties including solubility, thermal stability, and moldability which arise from alternating non-amide bonds along the polymer backbone. This paper focuses on the analysis of two such polymers based on the natural amino acid L-tyrosine. Starting from L-tyrosine and its deaminated analogue, 3-(4-para-hydroxy)-phenylpropionic acid, a diphenolic structure containing an amide linkage, was synthesized following standard procedures of peptide synthesis. This diphenolic structure was then used as a monomer to synthesize a polyiminocarbonate using a cyanogen bromide-initiated reaction and a polycarbonate using a triphosgene-initiated reaction. The polyiminocarbonate has iminocarbonate linkages and the polycarbonate has carbonate linkages alternating with amide linkages in the respective polymer backbone. Analytical studies were performed regarding the feasibility of the reaction procedures, the physical properties of the polymers, and their degradation processes, to gain insight into the potential biomaterial applications of these polymers. These results independently reaffirm the studies published by Kohn et al. working on similar polymeric systems.