Linear octapeptides were prepared by stepwise synthesis in solution. Cyclization by the method of active esters yielded analogues of deamino-1-carba-oxytocin with valine, leucine or isoleucine in position 4 instead of the glutamine residue. The basic pharmacological activities of the analogues were determined; their natriuretic action was lower than that of oxytocin.
[8-Arginine]deamino-1-carba-vasopressin and its 7-glycine derivative were prepared by condensation of the amino-terminal, cyclic part of the molecule with carboxy-terminal tripeptide amides. Replacement of proline by glycine in the position 7 results in a substantial decrease in the vasopressin-like activities, the oxytocin-like activities remaining unchanged.