Abstract
Gly8‐oxytocin and Ala8‐oxytocin have been synthesized according to the 3+6 scheme, and But8‐oxytocin to the full recurring scheme, active esters having been used almost throughout for the formation of peptide bonds. The comparison of their biological activities with those of oxytocin, Val8‐oxytocin and Ile8‐oxytocin, shows that omission of the aliphatic side chain of the amino‐acid in position 8 strongly depresses the activities. Nevertheless an ethyl group (But8‐oxytocin) and even a methyl group (Ala8‐oxytocin) are sufficient to confer to the, molecule a high degree of activity.