Synthesis and Some Biological Properties and ll-Deamino=4=valine=oxytocin* of 4-Valine-oxytocin

4-Valine-oxytocin and 1-deamino-4-valine-oxytocin, analogues of the posterior pituitary hormone containing a valine residue in place of the glutamine residue in position 4, have been synthesized by the p-nitrophenyl ester method of peptide synthesis and tested for pharmacological activity. The 4-valine-oxytocin possesses 140 units per mg of oxytocic activity and 240 units per mg of avian vasodepressor activity. The 1-deamino-4-valine-oxytocin, in which the free amino group on the half-cystine residue in position 1 of C-valineoxytocin is replaced by hydrogen, is a highly potent compound, possessing approximately 350 units of oxytocic activity and 800 units of avian vasodepressor activity per mg.