Papain, α-chymotrypsin, thermolysin and elastase were utilized in the synthesis of peptide bonds of the protected oxytocin nonapeptide, except the S-benzylcysteine-proline bond. Amino groups were protected with benzyloxycarbonyl or tert-butyloxycarbonyl groups, carboxy groups as ethyl ester, phenylhydrazides or amides. The cysteine sulfhydryl group was blocked with the benzyl group whereas the tyrosine hydroxyl was unprotected. Most of the fragments were synthesized in satisfactory yields using an equimolar ratio of both reaction components and minimal (experimentally determined) amount of the given enzyme.
木瓜酶、α-胰蛋白酶、热溶菌素和弹性蛋白酶被用于合成受保护的催产素非肽九肽的肽键,除了S-苄基半胱氨酸-脯氨酸键。氨基团被苄氧羰基或叔丁氧羰基团保护,羧基被乙酯、苯肼或酰胺保护。半胱氨酸巯基被苄基团阻断,而酪氨酸羟基未被保护。大多数片段在使用等摩尔比的反应组分和最小(经实验确定的)给定酶量的情况下以令人满意的产率合成。