Synthèse de la Phé²‐oxytocine

Abstract

Abstract The synthesis of Phe 2 ‐oxytocin, an analogue of oxytocin without the phenolic hydroxyl, and some of its biological properties are described. N‐CBO‐S‐benzyl‐ L ‐cysteinyl‐ L ‐phenylalanine methyl ester is prepared from N‐CBO‐S‐benzyl‐ L ‐cysteine and L ‐phenylalanine methyl ester, using dicyclohexyl‐carbodiimide as a condensing agent. After saponification and condensation with L ‐isoleucine methyl ester by the same method, N‐CBO‐S‐benzyl‐ L ‐cysteinyl‐ L ‐phenylalanyl‐ L ‐isoleucine methyl ester is obtained and converted to the azide via the hydrazide. Condensation with L ‐glutaminyl‐ L ‐asparaginyl‐S‐benzyl‐ L ‐cysteinyl‐ L ‐prolyl‐ L ‐leucyl‐glycinamide gives the nonapeptide, N‐CBO‐S‐benzyl‐ L ‐cysteinyl‐ L ‐phenylalanyl‐ L ‐isoleucyl‐ L ‐glutaminyl‐ L ‐asparaginyl‐S‐benzyl‐ L ‐cysteinyl‐ L ‐prolyl‐ L ‐leucyl‐glycinamide. Cleavage of the protecting groups with sodium in liquid ammonia and oxidation of the resulting sulfhydryl nonapeptide affords the desired cyclic nonapeptide amide, which has been assayed for several typical oxytocic activities before and after extensive purification by counter‐current distribution. The presence of the phenolic hydroxyl group is found to be favourable but not essential for the appearence of the characteristic oxytocic activities.