Synthesis, NMR conformational analysis and pharmacological evaluation of 7,7a,13,14-tetrahydro-6H-cyclobuta[b]pyrimido[1,2-a:3,4-a′]diindole analogues as melatonin receptor ligands
作者:Mohamed I. Attia、Deniz Güclü、Barbara Hertlein、Justin Julius、Paula A. Witt-Enderby、Darius P. Zlotos
DOI:10.1039/b705550a
日期:——
A structure for the self-condensation product of 2-(1H-indol-2-yl)ethyl tosylate2a, previously proposed as 6,7,14,15-tetrahydro-15aH-azocino[1,2-a:6,5-b]diindole3a, was revised based on the 13C-2D-INADEQUATE experiment, and proved to be 7,7a,13,14-tetrahydro-6H-cyclobuta[b]pyrimido[1,2-a:3,4-aâ²]diindole4a. A mechanism for the unexpected formation of this novel hexacyclic heterocycle was proposed and its NMR solution structure was elucidated. Five derivatives of the title ring skeleton 12â16 designed as melatonin receptor ligands were synthesized and their affinities for the human MT1 and MT2 receptors were determined. Both butyramides 13 and 15, as well as the non-methoxy acetamide 12 exhibited micromolar binding affinities for both receptors being slightly MT2 selective. The methoxy acetamide 14 showed the best pharmacological profile exhibiting a five times higher affinity for MT1 (Ki = 49 nM) than for MT2 (Ki = 246 nM) receptor.
2-(1H-吲哚-2-基)乙基对甲苯磺酸酯自缩合产物的结构2a,之前被提议为6,7,14,15-四氢-15aH-偶氮环[1,2-a:6,5-b]二吲哚3a,基于13C-2D-INADEQUATE实验进行了修订,证明其为7,7a,13,14-四氢-6H-环丁[b]嘧啶[1,2-a:3,4-a']二吲哚4a。提出了一种机制来解释这个新颖六元环杂环的意外形成,并阐明了其NMR溶液结构。合成了五种设计为褪黑素受体配体的标题环骨架衍生物12–16,并测定其对人MT1和MT2受体的亲和力。布酸酰胺衍生物13和15,以及非甲氧基乙酰胺12对这两种受体都表现出微摩尔结合亲和力,稍微选择性偏向MT2。甲氧基乙酰胺14则展示了最佳的药理特征,对MT1(Ki = 49 nM)的亲和力比MT2(Ki = 246 nM)高出五倍。