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The synthesis of new polyamides from two natural compounds L‐malic acid and L‐lysine was carried out via the active ester polycondensation method (pentafluorophenyl ester). The hydroxyl and carboxylic side groups were orthogonally protected as tert‐butyl ether and benzyl ester, respectively. High molecular masses (reaching 25 000 g/mol) were obtained at 60°C in tetrahydrofuran for fully protected polyamide. This polymer was soluble in chloroform. Total regeneration of hydroxyl groups was carried out in trifluoroacetic acid. Regeneration of the carboxylic group by hydrogenolysis led to a polyamide, soluble in Tris buffer solution (pH = 7.4). The polyamides bearing free hydroxyl and carboxyl groups were water‐soluble.

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Polyisopeptides are non-peptidic polymers formed by ampolycondensation of tri-or multi-functional a-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 a-amino acid (and sometimes its derivatives, too). We discuss here about two methods giving satisfactory results. One is the polymerization of L-aspartic p-lactam a-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 de]ii.oIeclioti siiccessively until totiil deliroteclioii to free aiiiiiio-ulld free carboxylic groups. The final polymer is the first poly-L-cystine ever reported in the literature.