Purines. LXXV. Dimroth Rearrangement, Hydrolytic Deamination, and Pyrimidine-Ring Breakdown of 7-Alkylated 1-Alkoxyadenines: N(1)-C(2) versus N(1)-C(6) Bond Fission.
作者:Taisuke ITAYA、Nobuaki ITO、Tae KANAI、Tozo FUJII
DOI:10.1248/cpb.45.832
日期:——
On treatment with boiling H2O for 5-6h, 1-alkoxy-7-alkyladenines (13) underwent hydrolytic cleavage at the N(1)-C(2) and the N(1)-C(6) bonds to produce the imidazole-5-carboxamidines (14) in 53-60% yields and the imidazole-5-carboxamides (18) in 5-7% yields, respectively. The Dimroth rearrangement of 13 to N6-alkoxy-7-alkyladenine (15) was found to proceed through 14 more slowly than that of the 9-alkyl analogues 1 at pH 7 and above, being accompanied by hydrolysis to give the deformylated product (16) and by deamination through 18 leading to 7-alkylhypoxanthine (12), 1-alkoxy-7-alkylhypoxanthine (19), and 1-alkyl-4-aminoimidazole-5-carboxamide (20). Interestingly, the N(1)-C(6) bond fission product 17a was obtained from 13a by treatment with 0.01N aqueous NaOH at 4°C for 35d, but in only 2% yield, or more efficiently (in 56% yield) by pyrolysis at 150°C for 1h. On the other hand, 13 underwent acid hydrolysis faster than 1, providing the deformylated product 16 in 85-96% yields on treatment with 1-2N aqueous HCl at room temperature for 2-5h. 4-amino-N'-methoxy-1-methyl-5-carboxamidine (16a) was alternatively obtained in 59% yield by treatment of 1-methoxy-7-methyladenine (13a) with boiling 2N aqueous NaOH for 10min. Efficient preparations of the rearranged products 15 (80-86%) were accomplished by treating 13 with boiling 0.1N aqueous NaOH for 20-30min.
用沸腾的 H2O 处理 5-6 小时后,1-烷氧基-7-烷基腺嘌呤 (13) 在 N(1)-C(2) 键和 N(1)-C(6) 键处发生水解裂解,生成咪唑-5-甲酰胺 (14),收率为 53-60%,咪唑-5-甲酰胺 (18) 的收率为 5-7%。与 9-烷基类似物 1 相比,在 pH 值为 7 及以上的条件下,13 到 N6-烷氧基-7-烷基腺嘌呤(15)的 Dimroth 重排通过 14 的速度更慢,伴随着水解得到变形产物(16),以及通过 18 的脱氨得到 7-烷基次黄嘌呤(12)、1-烷氧基-7-烷基次黄嘌呤(19)和 1-烷基-4-氨基咪唑-5-甲酰胺(20)。有趣的是,用 0.01N 的 NaOH 水溶液在 4°C 下处理 35d 后,可从 13a 中得到 N(1)-C(6) 键裂变产物 17a,但收率仅为 2%;在 150°C 下热解 1 小时后,收率更高(56%)。另一方面,13 的酸水解速度比 1 快,在室温下用 1-2N HCl 水溶液处理 2-5 小时后,可得到产率为 85-96% 的变形产物 16。另外,用沸腾的 2N NaOH 水溶液处理 1-甲氧基-7-甲基腺嘌呤(13a)10 分钟,可得到 4-氨基-N'-甲氧基-1-甲基-5-甲脒 (16a),收率为 59%。用沸腾的 0.1N NaOH 水溶液处理 13 20-30 分钟,可有效制备重排产物 15(80-86%)。