Synthesis and properties of [2-[3,5-3H2]-tyrosine,4-glutamic acid]deamino-1-carba-oxytocin

The title compound (specific activity 11.1-32.7 Ci (0.41-1.22 TBq)/mmol) was prepared by iodination and subsequent catalytic replacement of iodine by tritium. The analogue which was unstable in the form of a lyophilizate was purified by reversed phase liquid chromatography. Using the N,N'-dicyclohexylcarbodiimide method, the pure analogue was converted into N-hydroxybenzotriazolyl ester, an irreversible oxytocin inhibitor. However, attempts to label specifically the uterotonic receptor, present in the enriched rat myometrium fraction, were hithero unsuccessful