Polypeptides

1,140,873. Cyclic peptide. SANDOZ Ltd. 3 March, 1966 [15 April, 1965], No. 9342/66. Heading C2C. Deamino1 - Phe2 - Arg8 - vasopressin is prepared by oxidation of the linear octapeptide Mpr - Phe - Phe - Glu(NH 2 ) - Asp(NH 2 ) - Cys- Pro - Arg - GlyNH 2 (where Mpr is betamercaptopropionyl) to form the -S-S- bridged ring system. The octapeptide may be prepared by condensing B 3 - Mpr - Phe - Phe- NHNH 2 with R-Glu(NH 2 )-Asp (NH 2 )-lys(B 3 ) - Pro - Arg(Tos) - Gly.NH 2 and removing the blocking groups. Also prepared as starting materials are Bz - Mpr - Phe Phe - OMe and the hydrazide and CbO-Phe-Phe-OMe. Pharmaceutical compositions useful as antiduiretics contain the cyclic peptide of the invention. The compositions may be in a form suitable for oral, parenteral, enteral or intranasal administration.