Synthesis and structure of polyisopeptides

Abstract

Polyisopeptides are non-peptidic polymers formed by α,ω-polycondensation of tri- or multi-functional α-amino acids. They are expected to possess physical and mechanical properties of synthetic polyamides (or polyesters) and to be biodegradable. In the present paper, the methods of polyisopeptide synthesis are reviewed. Many of them are specific to a given α-amino acid (and sometimes its derivatives, too). We discuss here about two methods giving satisfactory results. One is the polymerization of L-aspartic β-lactam α-esters, in which the structure of a resulting polymer varies according to the solvent used. A new interpretation on the basis of the nature of catalyst anion species (free ion, ion pair) is presented. The other subject is the active ester polycondensation method applied to the amino- and carboxyl- protected L-cystine polyisopeptide and its selective deprotection successively until total deprotection to free amino- and free carboxylic groups. The final polymer is the first poly-L-cystine ever reported in the literature.