1.2.4- Triazolo purin-7 -ones

Since specificity of the nucleoside phosphorylases varies, enzymes that catalyze the formation of the nucleosides of the so-called fraudulent purine bases, 6-mercaptopurine (purine-6(lH)-thione) and 8-aza-guanine (5-amino-t -triazolo[ 4,5-d]pyrimidin-7(6if)-one), have been found, and gram quantities of 8-azaguanosine have been isolated. ... 

Their preparations copied those of their [ ]-analogues. The first method started from 2-hydrazinopurines 287 and suitable ortho esters yielding [l,2,4]triazolo-[4,3- ]purin-9-ones 288 (R2 = Aik, Aryl). Substitution of ortho esters by carbon disulfide led to 7-mercapto-derivative 288 (R2 = SH). The 7-aryl-derivatives were better accessible by the second method—the oxidative cyclization of 2-arylidenehydrazino)-derivatives 289, such as heating with diethyl azodicarboxylate, or oxidation with aerial oxygen (85CPB3113) (Scheme 82). 

New alkylated theophyllines have been synthesized by chemical modification of diphylline <01JCR(S)129>. A series of aryl-1,2,3,6-tetrahydropyridino-purine 63, -3/7-1,23-triazolo [43-r/]pyrimidine 64, -purin-8-one 65 and -7H-pyrrolo[2,3-r/]pyrimidine 66... 

C9H9N5O, 1H-4,6-Dimethylimidazo[1,2-a]purine-9 one, 41B, 341 C9H9N7O3, 1,5-Diamino-1H-1,2,4-triazolo[1,5-c]quinazolinium nitrate, 45B, 292... 

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