A convergent liquid-phase synthesis of salmon calcitonin

Salmon calcitonin (sCT) was prepared in good yield and high purity by the c ondensation of N-alpha-Boc-cyclic decapeptide, Boc-C(1)SNLSTC(7)VLG-OH (1,7 -disulfide), with protected docosapeptide (Psc)LSQE(OPse)LHK(Psc)LQTYPRTNTG SGTP-NH2.3TFA, followed by deprotection of Boc with trifluoroacetic acid an d Psc/Pse with piperidine. The 2-(phenylsulfonyl)ethoxycarbonyl (Psc) and 2 -(phenylsulfonyl)ethyl (Pse) protecting groups were recently developed. The two peptides were built up by stepwise and fragment condensation using app ropriate N-alpha-Boc-amino acids and subsequent deprotection in solution. T he synthetic sCT exhibited hypocalcemic potency of more than 4000 IU/mg in rats.