Synthesis of four vasopressin analogues which do not contain the glycinamine residue in position 9 and have a basic non-coded amino acid in position 8 is described. All the analogues exhibit very low endocrine activities and are effective in the passive avoidance test.
Protected peptides were prepared by fragment condensation according to the scheme 6 + 3 or 9 + 3, which, after the removal of the protecting groups by sodium in liquid ammonia and oxidative cyclization, afforded [7-glycine,8-ornithine]vasopressin, [7-glycine,8-ornithine]deaminovasopressin, and Nα-glycyl-glycyl-glycyl[7-glycine,8-ornithine]vasopressin. All the analogues had very low intrinsic vasopressin-like activities; the analogue with hormonogen nature had a depressor effect and inhibited the pressor action of lysine-vasopressin.