[1-Desaminopenicillamine, 8-α-hydroxyisocaproic acid] oxytocin. A selective inhibitor in rats of the uterine response to oxytocin

[1-Desaminopenicillamine, 8-α-hydroxyisocaproic acid] oxytocin was synthesized by a 6 + 3 fragment condensation from precursors which had been formed by solution methods. This analog inhibited uterine responses to oxytocin (pA2 7.37, 7.9, 6.17; uterus in vitro without Mg++, in vitro with Mg++, and in vivo, respectively) and showed little or no activity in other bioassays.