A protected cyclic hexapeptide (XVI), cyclo-(diglycyl-ε-benzyloxycarbonyl-l-lysyl)2, was synthesized in three different ways; the cyclization reactions of a protected tripeptide azide, a protected tripeptide active ester, and a protected hexapeptide active ester produced the protected cyclic hexapeptide (XVI) in fairly good yields. The product (XVI) was then converted by hydrogenolysis to the cyclic hexapeptide (XVII), cyclo-(digrycyl-l-lysyl)2. It was found that the cyclic hexapeptide was hydrolyzed slowly by trypsin to a tripeptide diglycyl-lysine, whereas a synthetic hexapeptide, diglycyl-lysyl-diglycyl-lysine, was hydrolyzed very rapidly to the tripeptide.
受保护的环状六肽(XVI),环-(二甘
氨酰-ε-苄氧基羰基-1-赖
氨酰)2,以三种不同的方式合成;受保护的三肽
叠氮化物、受保护的三肽活性酯和受保护的六肽活性酯的环化反应以相当好的收率产生了受保护的环状六肽(XVI)。然后通过氢解将产物(XVI)转化为环状六肽(XVII),环-(二甘
氨酰-1-赖
氨酰) 2 。研究发现,环状六肽被胰
蛋白酶缓慢
水解为三肽二甘
氨酰-赖
氨酸,而合成的六肽二甘
氨酰-赖
氨酰-二甘
氨酰-赖
氨酸则非常快速地
水解为三肽。