LIQUID PHASE SYNTHESIS METHOD FOR OXYTOCIN USING POLYPEPTIDES

A liquid phase synthesis method for oxytocin having mild reaction conditions. The method synthesizes three oxytocin fragments: a fragment 1: Boc-Cys(Acm)-Tyr(tBu)-OH, a fragment 2: H-Ile-Gln(Trt)-Asn(Trt)-Cys(Acm)-Pro-OMe, and a fragment 3: H-Leu-Gly-NH 2. After the fragments are assembled and synthesized into a full-protected oxytocin amino acid sequence, Acm is removed by using iodine, and at meantime, cyclization is performed to form a disulfide bond to obtain a protected cyclic oxytocin; the remaining protecting groups are removed by using trifluoroacetic acid to obtain a oxytocin crude product; and after recrystallization is performed by using ethyl acetate, purification is performed by reverse phase chromatography to obtain a high-purity (the purity of the crude product reaches 95%) and high-titer oxytocin product (588 IU/mg). The method is used in combination with a Boc polypeptide synthesis method and an Fmoc polypeptide synthesis method; all the reactions are performed under mild conditions; the inve