Design, synthesis, and biological evaluation of conformationally restricted rivastigmine analogues
Design, synthesis, and biological evaluation of conformationally restricted rivastigmine analogues
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DOI：
10.1021/jm049782n
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发表时间：
2004-11-18
影响因子：
7.3
通讯作者：
Melchiorre, C
中科院分区：
文献类型：
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作者：
Bolognesi, ML;Bartolini, M;Melchiorre, C
卡巴拉汀 (1) 是一种乙酰胆碱酯酶 (AChE) 抑制剂，于 2000 年被批准用于治疗阿尔茨海默病，其结构中带有氨基甲酸酯部分，能够与酶的活性位点发生共价反应。关于 1 与不同胆碱酯酶相互作用的动力学和结构研究已经发表，为催化机制提供了更深入但非明确的见解。基于这些发现，并结合我们之前对一系列苯并吡喃并[4,3-b]吡咯氨基甲酸酯作为AChE抑制剂的研究，我们通过在不同的三环系统中包含二甲氨基-a-甲基苄基部分，设计了一系列1的构象限制类似物。从蒙特卡罗模拟中获得的1和碳衍生物4的构象之间的叠加支持了三环衍生物可能充当1的刚性类似物的想法。针对人类AChE和BChE进行体外评估的4-9的生物学特征验证了我们的合理设计。带有含硫系统的化合物 5 显示出最高的抑制活性，比 1 强 192 倍。在本研究中，最有效的抑制剂始终是甲基衍生物 3-5，具有纳摩尔范围的效力，而乙基衍生物的效力低 40 倍。对于这一发现的合理解释可能是活性位点中 1 的乙基和 His440 之间的空间位阻效应，正如复合物 AChE/1 的晶体结构已经表明的那样。当考虑 BChE 抑制时，氨基甲酰基 N-烷基链对 AChE 抑制的不利影响不太明显，因为 BChE 的特点是比 AChE 具有更大的酰基结合袋。事实上，氨基甲酸甲酯3-5没有表现出AChE/BChE选择性，而化合物6-9在抑制BChE方面比抑制AChE活性明显更有效。在 100 muM 时，5 被发现仅能抑制 AChE 诱导的聚集 19%，可能是因为它不能与 AChE 的外周阴离子位点强烈相互作用，而 AChE 在酶介导的 A,3 聚集中起着重要作用，但缺乏 BChE 结构。
Rivastigmine (1), an acetylcholinesterase (AChE) inhibitor approved in 2000 for the treatment of Alzheimer disease, bears a carbamate moiety in its structure, which is able to react covalently with the active site of the enzyme. Kinetic and structural studies on the interaction of 1 with different cholinesterases have been published, giving deeper, but not definitive, insights on the catalysis mechanism. On the basis of these findings and in connection with our previous studies on a series of benzopyrano[4,3-b]pyrrole carbamates as AChE inhibitors, we designed a series of conformationally restricted analogues of 1 by including the dimethylamino-a-methylbenzyl moiety in different tricyclic systems. A superimposition between the conformation of 1 and the carbon derivative 4, as obtained from Monte Carlo simulations, supported the idea that the tricyclic derivatives might act as rigid analogues of 1. The biological profile of 4-9, assessed in vitro against human AChE and BChE, validated our rational design. Compound 5, bearing a sulfur-containing system, showed the highest inhibitory activity, being 192-fold more potent than 1. In the present study, the most potent inhibitors were always methyl derivatives 3-5, endowed with a nanomolar range potency, whereas the ethyl ones were 40 times less potent. A reasonable explanation for this finding might be a steric hindrance effect between the ethyl group of 1 and His440 in the active site, as already suggested by the crystal structure of the complex AChE/1. The unfavorable influence of the carbamic N-alkyl chain on AChE inhibition is less striking when considering BChE inhibition, since BChE is characterized by a bigger acyl binding pocket than AChE. In fact, methyl carbamates 3-5 did not show AChE/BChE selectivity, whereas compounds 6-9 were significantly more potent in inhibiting BChE than AChE activity. At 100 muM, 5 was found to inhibit the AChE-induced aggregation only by 19% likely because it is not able to strongly interact with the peripheral anionic site of AChE, which plays an essential role in the A,3 aggregation mediated by the enzyme but is lacking in BChE structure.