Synthesis of a cross‐linked polypentapeptide of tropoelastin

The synthesis of a cross‐linked polypentapeptide (an insoluble product) by means of a cross‐linking reaction between a lysine‐containing (1%) polypentapeptide and a glutamic acid‐containing (2%) polypentapeptide is described, following description of the synthesis and polymerization of the corresponding pentapeptide p ‐nitrophenyl esters. The pentapeptide p ‐nitrophenylesters—H‐Val 1 ‐Pro 2 ‐Gly 3 ‐Val 4 ‐Gly 5 ‐ONp, H‐Val 1 ‐Pro 2 ‐Gly 3 ‐Lys 4 (ε‐Z)‐Gly 5 ‐ONp, and H‐Val 1 ‐Pro 2 ‐Gly 3 ‐Glu 4 ‐Gly 5 ‐ONp—prior to polymerizing and the polypentapeptides prior to cross‐linking were analyzed by proton and carbon‐13 magnetic resonance. The cross‐linking reaction was achieved in the coacervate state by intermolecular primary amide bond formation. The coupling reagent was a water‐soluble carbodiimide (1‐cyclohexyl‐3‐(2‐ N ‐methylmorpholinoethyl)‐carbodiimide‐ p ‐toluenesulfonate).