Synthesis and Pharmacological Characterization of Novel Analogues of the Nicotinic Acetylcholine Receptor Agonist (±)-UB-165
作者:Christopher G. V. Sharples、Gunter Karig、Graham L. Simpson、James A. Spencer、Emma Wright、Neil S. Millar、Susan Wonnacott、Timothy Gallagher
DOI:10.1021/jm020814l
日期:2002.7.1
(+/-)-UB-165 (1) is a potent neuronal nicotinic acetylcholine receptor (nAChR) ligand, which displays functional selectivity between nAChR subtypes. Using UB-165 as a lead structure, two classes of racemic ligands were synthesized and assessed in binding assays for three major nAChR subtypes (alpha4beta2*, alpha3beta4, and alpha7). The first class of compounds comprises the three pyridine isomers 4-6, corresponding to the 3-, 2-, and 4-substituted pyridine isomers, respectively. Deschloro UB-165 (4) displayed a 2-3-fold decrease in affinity at alpha4beta2* and alpha3beta4 nAChR subtypes,. as compared with (+/-)-UB- 165, while at the alpha7 subtype a 31-fold increase in affinity was observed. At each of the nAChR subtypes, high affinity binding was dependent on the presence of a 3-substituted pyridine, and the other isomers, 5 and 6, resulted in marked decreases in binding affinities. The second class of compounds is based on replacing the pyridyl unit of 1 with a diazine moiety, giving pyridazine (7), pyrimidine (8), and pyrazine (9), which retain the "3-pyridyl" substructure. Modest reductions in binding affinity were observed for all of the diazine ligands at all nAChR subtypes, with the exception of 7, which retained potency comparable to that of 4 in binding to alpha7 nAChR. In functional assays at the alpha3beta4 nAChR, all analogues 4-9 were less potent, as compared with 1, and the rank order of functional potencies correlated with that of binding potencies. Computational studies indicate that the 3-substituted pyridine 4 and 2-substituted pyridine 5, as well as the diazine analogues 7-9, all conform to a distance-based pharmacophore model recently proposed for the alpha4beta2* receptor. However, the nicotinic potencies of these ligands vary considerably and because 5 lacks appreciable nicotinic activity, it is clear that further refinements of this model are necessary in order to describe adequately the structural and electronic demands associated with this nAChR subtype. This rational series of compounds based on UB-165 presents a systematic approach to defining subtype specific pharmacophores.
(±)-UB-165 (1) 是一种高效的神经元烟碱型乙酰胆碱受体 (nAChR) 配体,它在不同的 nAChR 亚型之间表现出功能选择性。以 UB-165 为先导结构,合成了两类外消旋配体,并在三种主要的 nAChR 亚型(α4β2\*、α3β4 和 α7)的结合实验中进行了评估。第一类化合物由三种吡啶异构体(4-6)组成,分别对应于 3-、2-和 4-取代的吡啶异构体。去氯 UB-165 (4) 与 (+/-)-UB-165 相比,在 α4β2\* 和 α3β4 nAChR 亚型上的亲和力降低了 2-3 倍,而在 α7 亚型上观察到亲和力提高了 31 倍。在每种 nAChR 亚型中,高亲和力的结合依赖于 3-取代的吡啶的存在,而其他异构体(5 和 6)导致结合亲和力显著降低。第二类化合物基于将 1 中的吡啶基团替换为二嗪基团,得到吡啶二氮杂环(7)、嘧啶(8)和吡嗪(9),这些化合物保留了“3-吡啶基”亚结构。所有二嗪配体在所有 nAChR 亚型上的结合亲和力略有下降,但 7 在结合 α7 nAChR 时保留了与 4 相当的效力。在 α3β4 nAChR 的功能实验中,所有衍生物(4-9)的效力均低于 1,且功能活性的顺序与结合活性的顺序相吻合。计算研究表明,3-取代的吡啶 4 和 2-取代的吡啶 5,以及二嗪衍生物 7-9,都符合针对 α4β2\* 受体近期提出的基于距离的药效团模型。然而,这些配体的烟碱型活性差异显著,并且由于 5 缺乏明显的烟碱活性,显然需要进一步完善该模型以充分描述与这种 nAChR 亚型相关的结构和电子需求。基于 UB-165 的这一合理设计化合物系列提供了一种系统方法来定义亚型特异性药效团。