Enzymatic transglycosylation – the transfer of the carbohydrate moiety from one heterocyclic base to another – is being actively developed and applied for the synthesis of practically important nucleosides. This reaction is catalyzed by nucleoside phosphorylases (NPs), which are responsible for reversible phosphorolysis of nucleosides to yield the corresponding heterocyclic bases and monosaccharide 1‐phosphates. We found that 7‐methyl‐2′‐deoxyguanosine (7‐Me‐dGuo) is an efficient and novel donor of the 2‐deoxyribose moiety in the enzymatic transglycosylation for the synthesis of purine and pyrimidine 2′‐deoxyribonucleosides in excellent yields. Unlike 7‐methylguanosine, its 2′‐deoxy derivative is dramatically less stable. Fortunately, we have found that 7‐methyl‐2′‐deoxyguanosine hydroiodide may be stored for 24 h in Tris‐HCl buffer (pH 7.5) at room temperature without significant decomposition. In order to optimize the reagent ratio, a series of analytical transglycosylation reactions were conducted at ambient temperature. According to HPLC analysis of the transglycosylation reactions, the product 5‐ethyl‐2′‐deoxyuridine (5‐Et‐dUrd) was obtained in high yield (84–93%) by using a small excess (1.5 and 2.0 equiv.) of 7‐Me‐dGuo over 5‐ethyluracil (5‐Et‐Ura) and 0.5 equiv. of inorganic phosphate. Thymidine is a less effective precursor of α‐d‐2‐deoxyribofuranose 1‐phosphate (dRib‐1p) compared to 7‐Me‐dGuo. We synthesized 2′‐deoxyuridine, 5‐Et‐dUrd, 2′‐deoxyadenosine and 2′‐deoxyinosine on a semi‐preparative scale using the optimized reagent ratio (1.5:1:0.5) in high yields. Unlike other transglycosylation reactions, the synthesis of 2‐chloro‐2′‐deoxyadenosine was performed in a heterogeneous medium because of the poor solubility of the initial 2‐chloro‐6‐aminopurine. Nevertheless, this nucleoside was prepared in good yield. The developed enzymatic procedure for the preparation of 2′‐deoxynucleosides may compete with the known chemical approaches.

中文翻译：

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使用核苷磷酸化酶制备嘌呤和嘧啶2'-脱氧核苷

酶促糖基化反应（碳水化合物部分从一个杂环碱基到另一个杂环碱基的转移）正在积极开发中，并用于合成实际上重要的核苷。该反应由核苷磷酸化酶（NPs）催化，核苷磷酸化酶负责核苷的可逆磷酸分解，以产生相应的杂环碱基和单糖1-磷酸。我们发现7-甲基-2'-脱氧鸟苷（7-Me-dGuo）是酶促糖基化反应中2-脱氧核糖部分的高效且新颖的供体，用于嘌呤和嘧啶2'-脱氧核糖核苷的合成，收率很高。与7-甲基鸟苷不同，其2'-脱氧衍生物的稳定性要差得多。幸运的是，我们发现7-甲基-2'-脱氧鸟苷氢碘酸盐可以在Tris-HCl缓冲液（pH 7）中保存24小时。5）在室温下无明显分解。为了优化试剂比例，在环境温度下进行了一系列分析性转糖基化反应。根据转糖基化反应的HPLC分析，使用少量过量（1.5和2.0当量）的五氯乙烷（1.5和2.0当量）可得到高产率（84-93％）的产物5-乙基-2'-脱氧尿苷（5-Et-dUrd）。 7-MeGuo超过5-乙基尿嘧啶（5-Et-Ura）和0.5当量。无机磷酸盐。胸苷是α-的无效前体 通过使用比5-乙基尿嘧啶少过量（1.5和2.0当量）的7-Me-dGuo，可以高产率（84-93％）获得5-乙基-2'-脱氧尿苷（5-Et-dUrd）产品（5-等-乌拉）和0.5当量。无机磷酸盐。胸苷是α-的无效前体 通过使用比5-乙基尿嘧啶少过量（1.5和2.0当量）的7-Me-dGuo，可以高产率（84-93％）获得5-乙基-2'-脱氧尿苷（5-Et-dUrd）产品（5-等-乌拉）和0.5当量。无机磷酸盐。胸苷是α-的无效前体d -2-脱氧核糖呋喃糖1-磷酸（dRib-1p）与7-Me-dGuo相比。我们使用优化的试剂比例（1.5：1：0.5）以高产率合成了半制备规模的2'-脱氧尿苷，5-Et-dUrd，2'-脱氧腺苷和2'-脱氧肌苷。与其他转糖基化反应不同，由于最初的2-氯-6-氨基嘌呤的溶解性较差，因此在异质介质中进行了2-氯-2'-脱氧腺苷的合成。然而，该核苷以高收率制备。用于制备2'-脱氧核苷的酶促方法可能会与已知的化学方法竞争。