[1 β Mercaptopropionic acid, 2 (3,5 dibromo L tyrosine)] oxytocin, a potent inhibitor of oxytocin

Article abstract of DOI:10.1021/jm00244a023

[1 β Mercaptopropionic acid,2 (3,5 dibromo L tyrosine)]oxytocin was synthesized from a protected polypeptide intermediate that had been prepared by the condensation of S ethylcarbamoyl β mercaptopropionyl 3,5 dibromotyrosine with H Ile Gln Asn Cys(Ec) Pro Leu Gly NH₂, using dicyclohexylcarbodiimide in dimethylformamide. The ethylcarbamoyl (Ec) protecting groups were removed by refluxing NH₃, and the resulting disulfhydryl peptide was oxidatively cyclized to the corresponding disulfide by ICH₂CH₂I. Purification of the analog was effected by partition chromatography and gel filtration. The analog possesses antioxytocic (pA₂ = 7.05) and antiavian vasodepressor (pA₂ = 7.44) activities but has neither agonist nor antagonist activity in the rat pressor assay.