Synthesis and Some Pharmacological Activities of [2-L-Valine]-oxytocin and [2-L-Leucine]-oxytocin

[2-Valine]-oxytocin and [2-leucine]-oxytocin have been synthesized from the requisite protected nonapeptide intermediates, which were prepared by the stepwise p-nitrophenyl ester method. The analogs were isolated by partition chromatography and gel filtration on Sephadex and then tested for a number of pharmacological activities. [2-Valine]-oxytocin possesses approximately 7 units/mg of avian vasodepressor, 2 units/mg of oxytocic, 15 units/mg of milk-ejecting, 0.05 unit/mg of pressor, and less than 0.01 unit/mg of antidiuretic activities. [2-Leucine]-oxytocin has approximately 3 units/mg of avian vasodepressor, less than 0.5 unit/mg of oxytocic, about 7 units/mg of milk-ejecting, 0.05 unit/mg of pressor, and negligible antidiuretic activities. Both of these analogs are much less active than [2-isoleucine]-oxytocin.