Syntheses and radiofluorination of two derivatives of 5-cyano-indole as selective ligands for the dopamine subtype-4 receptor
作者:Rainer Tietze、Carsten Hocke、Stefan Löber、Harald Hübner、Torsten Kuwert、Peter Gmeiner、Olaf Prante
DOI:10.1002/jlcr.1026
日期:2006.1
Two fluoroethoxy substituted derivatives, namely 2-[4-(2-(2-fluoroethoxy)phenyl)-piperazin-1-ylmethyl]indole-5-carbonitrile (5a) and 2-[4-(4-(2-fluoroethoxy)-phenyl)piperazin-1-ylmethyl]indole-5-carbonitrile (5b) were synthesized as analogs of the selective D4 receptor ligand 2-[4-(4-fluorophenyl)piperazin-1-ylmethyl]indole-5-carbonitrile (FAUC 316). In vitro characterization using CHO-cells expressing different dopamine receptor subtypes gave Ki values of 2.1 (5a) and 9.9 nM (5b) for the dopamine D4 subtype and displayed a 420-fold D4-selectivity over D2 receptors for 5b. The para-fluoroethoxy substituted candidate 5b revealed substantially reduced α1 and serotoninergic binding affinities in comparison to the ortho-fluoroethoxy substituted compound. In order to provide potential positron emission tomography (PET) imaging probes for the dopamine D4 receptor, 18F-labelling conditions using [18F]fluoroethyl tosylate were optimized and led to radiochemical yields of 81 ± 5% ([18F]5a) and 47 ± 4% ([18F]5b) (n = 3, decay-corrected and referred to labelling agent), respectively. Thus, 18F-fluoroethylation favourably at the para position of the phenylpiperazine moiety of the 5-cyano-indole framework proved to be tolerated by D4 receptors and could also be applied to alternative scaffolds in order to develop D4 radioligand candidates for PET with improved D4 receptor affinity and selectivity. Copyright © 2005 John Wiley & Sons, Ltd.
两种氟乙氧基取代的衍生物、合成了 2-[4-(2-(2-氟乙氧基)苯基)-哌嗪-1-基甲基]吲哚-5-甲腈(5a)和 2-[4-(4-(2-氟乙氧基)-苯基)哌嗪-1-基甲基]吲哚-5-甲腈(5b),作为选择性 D4 受体配体 2-[4-(4-氟苯基)哌嗪-1-基甲基]吲哚-5-甲腈(FAUC 316)的类似物。使用表达不同多巴胺受体亚型的 CHO 细胞进行体外表征,发现多巴胺 D4 亚型的 Ki 值分别为 2.1(5a)和 9.9 nM(5b),5b 的 D4 选择性是 D2 受体的 420 倍。与正氟乙氧基取代的化合物相比,对氟乙氧基取代的候选化合物 5b 的 α1 和血清素能结合亲和力大大降低。为了给多巴胺 D4 受体提供潜在的正电子发射断层扫描(PET)成像探针,对使用[18F]氟乙基对甲苯磺酸盐的 18F 标记条件进行了优化,其放射化学产率分别为 81 ± 5%([18F]5a)和 47 ± 4%([18F]5b)(n = 3,衰变校正和参照标记剂)。因此,5-氰基吲哚框架中苯基哌嗪分子对位的 18F 氟乙基化被证明可被 D4 受体耐受,也可应用于替代支架,以开发具有更好的 D4 受体亲和力和选择性的 PET 用 D4 放射性配体候选化合物。Copyright © 2005 John Wiley & Sons, Ltd. All Rights Reserved.