Solid-phase synthesis and biological activity of the parallel dimer of deamino-oxytocin.

The parallel dimer of deamino-oxytocin has been synthesized by a novel solid-phase route. Successive orthogonal deprotection and oxidation reactions, carried out while the peptide remained anchored to a polymeric support, resulted in the formation of two disulfide bridges and conversion, with minimal side reactions, of the linear monomeric precursor to the dimer. The purified dimer showed approximately 0.1% to 2% of the biological activities of the monomer, as well as prolonged action. The time course of response to the deamino-oxytocin dimer differed from that of the monomer (and of oxytocin), and is probably due to slow formation of monomer under the conditions of biological testing.