DNal(6),DAla(10)]GnRH (21, K(i) = 0.17 nM), which inhibited ovulation significantly at doses equal to or lower than 25 microgram/rat. These results were particularly unexpected in view of the critical role(s) originally ascribed to the side chains of residues 1 and 3.(1) Other closely related analogues, such as those where the [DAsp(1)(betaAla), DOrn(3)] cycle of 21 was changed to [DOrn(1)(betaAla), DAsp(3)]
仔细分析cyclo(4-10)[Ac-Delta(3)Pro(1),DFpa(2),DTrp(3),Asp(4),DNal(6),Dpr(10)的NMR结构GnRH,dicyclo(4-10 / 5-8)[Ac-DNal(1),DCpa(2),DTrp(3),Asp(4),Glu(5),
DArg(6),Lys(8), Dpr(10)] GnRH和dicyclo(4-10 / 5,5'-8)[Ac-DNal(1),DCpa(2),DPal(3),Asp(4),Glu(5)(Gly) ),
DArg(6),Dbu(8),Dpr(10)] GnRH表明,在N末端三肽中,II型可能会围绕残基1和2发生β旋转,而DTrp(可能会围绕γ旋转) 3)/ DPal(3)。这表明通过引入cyclo(1-3)支架来约束N端的可能性。环尺寸和组成的优化导致发现了cyclo(1-3)[Ac-
DAsp(1),DCpa