Purines. XXXIV. 3-Methyladenosine and 3-methyl-2'-deoxyadenosine. Their synthesis, glycosidic hydrolysis, and ring fission.
作者:Tozo FUJII、Tohru SAITO、Tsuyoshi NAKASAKA
DOI:10.1248/cpb.37.2601
日期:——
The first syntheses of 3-methyladenosine (3a) and 3-methyl-2'-deoxyadenosine (3b), both in the form of the p-toluenesulfonate salt, have been achieved through two parallel 6-step routes starting from adenosine (5a) and 2'-deoxyadenosine (5b), which are based on the "fission and reclosure" technology for modification of the adenine ring. These 3-methyladenine nucleosides (3a, b·TsOH) were very unstable under not only acidic but also alkaline conditions. At pH 1 and 25°C, 3a·TsOH (half-life 17 min) underwent glycosidic hydrolysis (depurinylation) some thousand times faster than did adenosine (5a) itself. At pH 3.34 and 25°C, the 2-deoxyribosyl analogue 3b·TsOH (half-life 2.7 min) was depurinylated 370 times more rapidly than the ribosyl analogue 3a·TsOH (half-life 1010 min). The glycosidic bond of the imidazole 2-deoxyriboside 11b, an intermediate for the present synthesis of 3b·TsOH, was also hydrolyzed easily at pH 1 and room temperature. In H2O at pH 8.32 and 25°C, 3a·TsOH readily underwent ring opening in the pyrimidine moiety and came to equilibrium with the (N-methylformamido)imidazole derivative 10a, which was further deformylated under more alkaline conditions. The ring opening was ca. 30 times as fast as that of 1-methyladenosine (17). In H2O at pH 8.98 and 25°C, the 2-deoxyribosyl analogue 3b·TsOH underwent not only similar ring opening but also glycosidic hydrolysis competitively. The possible factors responsible for the high reactivity of 3a·TsOH are discussed on the basis of its X-ray crystal structure.
以腺苷(5a)和 2'-脱氧腺苷(5b)为起点,通过两条平行的 6 步路线,首次合成了对甲苯磺酸盐形式的 3-甲基腺苷(3a)和 3-甲基-2'-脱氧腺苷(3b),它们都是基于 "裂变和再封闭 "技术来修饰腺嘌呤环的。这些 3-甲基腺嘌呤核苷(3a、b-TsOH)在酸性和碱性条件下都非常不稳定。在 pH 值为 1 和 25°C 的条件下,3a-TsOH(半衰期为 17 分钟)发生糖苷水解(去嘌呤化)的速度比腺苷(5a)本身快数千倍。在 pH 值为 3.34 和 25°C 的条件下,2-脱氧核糖基类似物 3b-TsOH(半衰期为 2.7 分钟)的去嘌呤化速度是核糖基类似物 3a-TsOH(半衰期为 1010 分钟)的 370 倍。本次合成 3b-TsOH 的中间体咪唑 2-脱氧核苷 11b 的糖苷键在 pH 值为 1 和室温条件下也很容易水解。在 pH 值为 8.32、温度为 25°C 的 H2O 中,3a-TsOH 很容易在嘧啶分子中发生开环反应,并与(N-甲基甲酰氨基)咪唑衍生物 10a 达到平衡,后者在碱性更强的条件下进一步发生变形。开环速度约为 1-甲基腺苷(17)的 30 倍。在 pH 值为 8.98、温度为 25°C 的 H2O 中,2-脱氧核糖基类似物 3b-TsOH 不仅发生了类似的开环反应,而且还发生了糖苷水解竞争反应。本文以 3a-TsOH 的 X 射线晶体结构为基础,讨论了导致其高活性的可能因素。