Purines. XLVII. Dimroth rearrangement versus hydrolytic deamination of 1-ethyladenine.
作者:Tozo FUJII、Tohru SAITO、Hiromi HISATA、Koji SHINBO
DOI:10.1248/cpb.38.3326
日期:——
The Dimroth rearrangement of 1-ethyladenine (6) to give N6-ethyladenine (11)(91% yield) was accompanied with unusual hydrolytic deaminations to produce hypoxanthine (8)(2%) and 1-ethylhypoxanthine (14)(2%), when carried out in 0.2N aqueous NaOH at 100°C for 7h. Probable pathways leading to these by-products are discussed on the basis of the results of alkaline hydrolysis of 5-amino-N'-ethylimidazole-4-carboxamidine dihydrochloride (5), which yielded both 5-aminoimidazoli-4-carboxamide (9) and 5-amino-N-ethylimidazole-4-carboxamide (12). For structural identification, 14 was alternatively synthesized from inosine (17) through 1-ethylinosine (16), and 12 was synthesized from 16 through 5-amino-N-ethyl-1-β-D-ribofuranosylimidazole-4-carboxamide (15). Comparison of the reaction rates in the Dimroth rearrangements of 6·HClO4 and 1-ethyl-9-methyladenine perchlorate [1·HClO4 (R1=Et; R2=Me)] in H2O at pH 6.92 and 8.70 (ionic strength 1.0) at 70°C has revealed that nonsubstitution at the 9-position decreases the rearrangement rate by a factor of 4-30 under these conditions.
1-乙基腺苷(6)的迪莫罗斯重排生成N6-乙基腺苷(11)(91%的产率)过程中,伴随着不寻常的水解脱胺反应,产生了次黄嘌呤(8)(2%)和1-乙基次黄嘌呤(14)(2%)。该反应在0.2N氢氧化钠水溶液中于100°C进行7小时。基于5-氨基-N'-乙基咪唑-4-羧酰胺二盐酸盐(5)的碱性水解结果,讨论了导致这些副产物的可能反应途径,该反应生成了5-氨基咪唑-4-羧酰胺(9)和5-氨基-N-乙基咪唑-4-羧酰胺(12)。为了进行结构鉴定,14也通过肌苷(17)合成,经过1-乙基肌苷(16)合成,12则是通过16进一步合成的,反应中间体为5-氨基-N-乙基-1-β-D-核糖苷咪唑-4-羧酰胺(15)。在pH 6.92和8.70(离子强度1.0)下,于70°C比较了6·HClO4和1-乙基-9-甲基腺苷过氯酸盐[1·HClO4(R1=Et; R2=Me)]的迪莫罗斯重排反应速率,结果表明,在这些条件下,9位上不发生取代反应会使重排速率降低4到30倍。