Synthesis of new polyamides from natural monomers: L-malic acid and L-lysine

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 triflouroacetic 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.