Synthesis of [1, 6‐α, α′‐Diaminosuberic acid]oxytocin (‘Dicarba‐oxytocin’)

Starting from a selectively protected derivative of α,α′‐diaminosuberic acid ( 3 ) the linear protected peptide 11 has been obtained. Cyclisation to 12 followed by removal of the protecting groups by hydrogenolysis afforded the ‘dicarba’ analogue of oxytocin, 1 c , which showed about 5 IU/μmol of uterotonic activity in vitro .