Tranberg C Elisabet, Zickgraf Andrea, Giunta Brian N, Luetjens Henning, Figler Heidi, Murphree Lauren J, Falke Ruediger, Fleischer Holger, Linden Joel, Scammells Peter J, Olsson Ray A
Centre for Chiral and Molecular Technologies, Deakin University, Geelong, Victoria 3217, Australia.
J Med Chem. 2002 Jan 17;45(2):382-9. doi: 10.1021/jm010081p.
2-Amino-3-benzoylthiophenes are allosteric enhancers (AE) of agonist activity at the A(1) adenosine receptor. The present report describes syntheses and assays of the AE activity at the human A(1)AR (hA(1)AR) of a panel of compounds consisting of nine 2-amino-3-aroylthiophenes (3a-i), eight 2-amino-3-benzoyl-4,5-dimethylthiophenes (12a-h), three 3-aroyl-2-carboxy-4,5-dimethylthiophenes (15a-c), 10 2-amino-3-benzoyl-5,6-dihydro-4H-cyclopenta[b]thiophenes (17a-j), 14 2-amino-3-benzoyl-4,5,6,7-tetrahydrobenzo[b]thiophenes (18a-n), and 15 2-amino-3-benzoyl-5,6,7,8-tetrahydro-4H-cyclohepta[b]thiophenes (19a-o). An in vitro assay employing the A(1)AR agonist [(125)I]ABA and membranes from CHO-K1 cells stably expressing the hA(1)AR measured, as an index of AE activity, the ability of a candidate AE to stabilize the agonist-A(1)AR-G protein ternary complex. Compounds 3a-i had little or no AE activity, and compounds 12a-h had only modest activity, evidence that AE activity depended absolutely on the presence of at least a methyl group at C-4 and C-5. Compounds 17a-c lacked AE activity, suggesting the 2-amino group is essential. Polymethylene bridges linked thiophene C-4 and C-5 of compounds 17a-j, 18a-n, and 19a-o. AE activity increased with the size of the -(CH(2))(n)()- bridge, n = 3 < n = 4 < n = 5. The 3-carbethoxy substituents of 17a, 18a, and 19a did not support AE activity, but a 3-aroyl group did. Bulky (or hydrophobic) substituents at the meta and para positions of the 3-benzoyl group and also 3-naphthoyl groups greatly enhanced activity. Thus, the hA(1)AR contains an allosteric binding site able to accommodate 3-aroyl substituents that are bulky and/or hydrophobic but not necessarily planar. A second region in the allosteric binding site interacts constructively with alkyl substituents at thiophene C-4 and/or C-5.
2-氨基-3-苯甲酰基噻吩是A(1)腺苷受体激动剂活性的变构增强剂（AE）。本报告描述了一组化合物在人A(1)AR（hA(1)AR）上的AE活性的合成及测定，该组化合物包括九个2-氨基-3-芳甲酰基噻吩（3a-i）、八个2-氨基-3-苯甲酰基-4,5-二甲基噻吩（12a-h）、三个3-芳甲酰基-2-羧基-4,5-二甲基噻吩（15a-c）、十个2-氨基-3-苯甲酰基-5,6-二氢-4H-环戊并[b]噻吩（17a-j）、十四个2-氨基-3-苯甲酰基-4,5,6,7-四氢苯并[b]噻吩（18a-n）以及十五个2-氨基-3-苯甲酰基-5,6,7,8-四氢-4H-环庚并[b]噻吩（19a-o）。采用A(1)AR激动剂[(125)I]ABA以及稳定表达hA(1)AR的CHO-K1细胞膜进行的体外测定，将候选AE稳定激动剂-A(1)AR-G蛋白三元复合物的能力作为AE活性指标进行测量。化合物3a-i几乎没有或没有AE活性，化合物12a-h只有适度活性，这证明AE活性绝对依赖于C-4和C-5处至少存在一个甲基。化合物17a-c缺乏AE活性，表明2-氨基基团是必不可少的。聚亚甲基桥连接了化合物17a-j、18a-n和19a-o的噻吩C-4和C-5。AE活性随着-(CH(2))(n)-桥的大小增加而增强，n = 3 < n = 4 < n = 5。17a、18a和19a的3-乙氧羰基取代基不支持AE活性，但3-芳甲酰基取代基支持。3-苯甲酰基间位和对位的庞大（或疏水）取代基以及3-萘甲酰基取代基极大地增强了活性。因此，hA(1)AR含有一个变构结合位点，能够容纳庞大且/或疏水但不一定是平面的3-芳甲酰基取代基。变构结合位点中的第二个区域与噻吩C-4和/或C-5处的烷基取代基发生协同相互作用。
