作者:Zhoupeng Zhang、L. M. V. Tillekeratne、Richard A. Hudson
DOI:10.1055/s-1996-4226
日期:1996.3
Three isomeric analogues 2-4 of the redox-active coenzyme 4,5-dihydro-4,5-dioxo-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylic acid (1, PQQ, methoxatin) were synthesized from methoxynitroanilines 8, 9 and 10a, respectively. Reaction of the diazonium salts of each of the starting compounds with ethyl α-methylacetoacetate gave the corresponding substituted phenylhydrazones of ethyl pyruvate. These intermediates underwent acid-catalyzed Fischer indolization and gave the esters 13, 17 and 25, respectively. Reduction to the corresponding aminoindoles with hydrogen over Pd/C, followed by Doebner-von Miller quinoline synthesis with dimethyl trans-2-ketoglutaconate, oxidation of the intermediate methoxy compound to the o-quinone, and hydrolysis of triester products gave 2, 3, and 4, respectively. These isomers will serve as authentic examples to define their possible formation in nature and will also serve as isosteric probes to define the binding of PQQ at active sites in PQQ-requiring quinoproteins.
三种氧化还原活性辅酶4,5-二氢-4,5-二氧-1H-吡咯并[2,3-f]喹啉-2,7,9-三羧酸(1,PQQ,甲氧嘧啶)的异构类似物2-4,分别从甲氧基硝基苯胺8、9和10a合成得到。各起始化合物的重氮盐与乙基α-甲基乙酰乙酸酯反应,得到相应的乙基丙酮酸取代苯脒。这些中间体在酸性催化下发生Fischer吲哚化反应,分别生成酯13、17和25。通过氢气在Pd/C上的还原得到相应的氨基吲哚,随后与二甲基反式2-氧戊二酸酯进行Doebner-von Miller喹啉合成,将中间甲氧基化合物氧化为邻醌,并水解三酯产物,分别得到2、3和4。这些异构体将作为天然形成可能性的真实例证,并作为等构探针来定义PQQ在需要PQQ的醌蛋白活性位点的结合。