Purines. XLII. Synthesis and glycosidic hydrolysis of 7-alkyladenosines leading to an alternative synthesis of 7-alkyladenines.
作者:Tozo FUJII、Tohru SAITO
DOI:10.1248/cpb.38.1886
日期:——
A full account is given of the synthesis and glycosidic hydrolysis of 7-alkyladenosines (4), which established an alternative synthesis of 7-alkyladenines (11). Methylation of N6-methoxyadenosine(5)with MeI in AcNMe2 at 30°C for 8h gave N6-methoxy-7-methyladenosine, which was isolated in the form of the sulfate [7a (X=1/2SO4)] in 55% yield. N6-Methoxy-N6-methyladenosine (9a) was a by-product in this methylation. Demethoxylation of 7a (X=1/2SO4)by catalytic hydrogenolysis using hydrogen and Raney Ni catalyst produced, after replacement of the anion with perchlorate ion, 7-methyladenosine perchlorate [4a (X=ClO4)] in a pure and crystalline form. 7-Ethyladenosine perchlorate [4b (X=ClO4)] was also synthesized from N6-benzyloxyadenosine (6) through a parallel route via N6-benzyloxy-7-ethyladenosine sulfate [8b (X=1/2SO4)]. On treatment with H2O at 98-100°C for 40 min, 4a (X=ClO4) and 4b (X=ClO4) furnished 7-methyladenine (11a) and 7-ethyladenine (11b) in 84% and 55% yields, respectively. Similar hydrolyses of 7a (X=ClO4) and 8b (X=1/2SO4) gave N6-methoxy-7-methyladenine (12a) and N6-benzyloxy-7-ethyladenine (12b), respectively. Catalytic hydrogenolysis of 12b using hydrogen and Raney Ni catalyst afforded 11b in 82% yield. In 0.1 N aqueous HCl at 25°C, 4a (X=ClO4) and 4b (X=ClO4) were found to undergo glycosidic hydrolysis at rates of 2.22×10-3 min-1 (half-life 5.2h) and 1.69×10-3 min-1 (half-life 6.8h), respectively. Comparison of these rate constants with those of the other three NX-methyladenosines (1-3) has revealed that the ease with which depurinylation occurs decreased in going through the series 3-(2)>7-(4a)»N6-(3)≥1-methyladenosine (1). On treatment with 1 N aqueous NaOH at 60°C for 3h, 4a (X=ClO4) was hydrolyzed to give 11a in 44% yield.
本文全面介绍了 7-烷基腺苷的合成和糖苷水解(4),并由此建立了 7-烷基腺苷的另一种合成方法(11)。在 AcNMe2 中用 MeI 在 30°C 下甲基化 N6-甲氧基腺苷(5)8 小时,得到 N6-甲氧基-7-甲基腺苷,并以硫酸盐[7a (X=1/2SO4)] 的形式分离出来,产率为 55%。N6-甲氧基-N6-甲基腺苷(9a)是该甲基化反应的副产物。使用氢气和 Raney Ni 催化剂催化氢解 7a (X=1/2SO4)脱甲氧基,在阴离子被高氯酸盐离子置换后,生成了纯结晶形式的 7-甲基腺苷高氯酸盐[4a (X=ClO4)]。7-乙基腺苷高氯酸盐[4b(X=ClO4)]也是由 N6-苄氧基腺苷(6)通过 N6-苄氧基-7-乙基腺苷硫酸盐[8b(X=1/2SO4)]的平行路线合成的。在 98-100°C 下用 H2O 处理 40 分钟后,4a(X=ClO4)和 4b(X=ClO4)生成了 7-甲基腺嘌呤(11a)和 7-乙基腺嘌呤(11b),产率分别为 84% 和 55%。7a (X=ClO4) 和 8b (X=1/2SO4) 的类似水解分别得到 N6-甲氧基-7-甲基腺嘌呤 (12a) 和 N6-苄氧基-7-乙基腺嘌呤 (12b)。使用氢气和 Raney Ni 催化剂对 12b 进行催化氢解,可得到产率为 82% 的 11b。在 25°C 的 0.1 N HCl 水溶液中,4a(X=ClO4)和 4b(X=ClO4)发生糖苷水解的速率分别为 2.22×10-3 min-1(半衰期 5.2 小时)和 1.69×10-3 min-1(半衰期 6.8 小时)。将这些速率常数与其他三种 NX-甲基腺苷(1-3)的速率常数进行比较后发现,在 3-(2)>7-(4a) "N6-(3)≥1-甲基腺苷(1)系列中,去嘌呤基化发生的难易程度有所降低。在 60°C 下用 1 N NaOH 水溶液处理 3 小时后,4a(X=ClO4)被水解,得到 11a,产率为 44%。