Synthesis and immunosuppressive activity of glycine containing linear analogs of cyclolinopeptide A.

We demonstrated that a linear peptide Gly-Ile-Ile-Leu-Val-Pro-Pro-Phe, the analog of a cyclic nonapeptide c-(Leu-Ile-Ile-Leu-Val-Pro-Pro-Phe-Phe) possesses a distinct immunosuppressive activity. We synthesized a series of eight other analogs of the linear peptide. The series consists of the nonapeptides protected on N- and/or C-terminus by acetyl-, succinyl-, and amido- functions and of Gly-Ile-Ile-Leu-Val-Pro-Pro-Phe-Phe elongated on N- and/or C-terminus by additional glycine residues. It was found that the protection of the terminal functional groups of the peptide slightly increases its immunosuppressor potency. At the same time the elongation of the peptide chain on both termini by additional glycine residues evokes a distinct increase of the immunosuppressive activity.