Abstract: An insoluble cross-linked polypentapeptide is totally synthesized by preparing two modified linear polypentapeptides patterned on the polypentapeptide from the pentapeptide (Val.sub.1 -Pro.sub.2 -Gly.sub.3 -Val.sub.4 -Gly.sub.5) one of the repeating peptide sequences contained in tropoelastin, the precursor protein of the core of the elastic fiber of the vascular wall, and by cross-linking the modified polypentapeptides. One of the intermediate polypentapeptides is modified by replacing a portion of at least one of the amino acid residues with the residue of an amino acid having more than one amino function and the other is modified by replacing a portion of at least one of the amino acid residues with the residue of an amino acid having more than one carboxyl function, to provide free amino groups on the one intermediate and free carboxyl groups on the other for interreaction in the presence of a suitable cross-linking agent.