Thirty diketopiperazines were synthesized as analogs of cyclo (-Tyr-Arg-). The analgesic activities of these analogs were evaluated after intracerebral administration in mice. In the cyclo (-X-Arg-) series of analogs, cyclo [-Tyr (Et)-Arg-] showed the most potent activity. In the cyclo (-Tyr-Y-) series of analogs, the activity decreased in the order Y=homoarginine, p-guanidinophenylalanine, 2-amino-4-guanidinobutyric acid, Lys, Orn, His, α, γ-diaminobutyric acid and Pro. Among the analogs synthesized, cyclo-[-Tyr (Et)-Har-], which was designed on the basis of the above results, exhibited remarkably potent analgesic activity, being 17 times more potent than cyclo (-Tyr-Arg-) and nearly as potent as morphine on a molar basis. The structure-activity relation of cyclo(-Tyr-Arg-) is discussed in the light of these results.
合成了30种双
吡咯并
哌嗪类环(-Tyr-Arg-)类似物,并评价了它们对小鼠脑室内给药后的镇痛活性。在环(-X-Arg-)系列类似物中,环[-Tyr(Et)-Arg-]显示出最强的活性。在环(-Tyr-Y-)系列类似物中,活性按Y=
高精氨酸、对
胍苯丙
氨酸、2-
氨基-4-
胍基
丁酸、赖
氨酸、
鸟氨酸、组
氨酸、α,γ-二
氨基
丁酸和脯
氨酸的顺序递减。在合成的类似物中,环-[-Tyr(Et)-Har-]基于上述结果设计,表现出极其强大的镇痛活性,比环(-Tyr-Arg-)强17倍,按摩尔计算几乎与
吗啡一样有效。根据这些结果,讨论了环(-Tyr-Arg-)的构效关系。