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Abstract：
Selenium-modified nucleosides are powerful tools to study the structure and function of nucleic acids and their protein interactions. The widespread application of 2-selenopyrimidine nucleosides is currently limited by low yields in established synthetic routes. Herein, we describe the optimization of the synthesis of 2-Se-uridine and 2-Se-thymidine derivatives by thermostable nucleoside phosphorylases in transglycosylation reactions using natural uridine or thymidine as sugar donors. Reactions were performed at 60 or 80 °C and at pH 9 under hypoxic conditions to improve the solubility and stability of the 2-Se-nucleobases in aqueous media. To optimize the conversion, the reaction equilibria in analytical transglycosylation reactions were studied. The equilibrium constants of phosphorolysis of the 2-Se-pyrimidines were between 5 and 10, and therefore differ by an order of magnitude from the equilibrium constants of any other known case. Hence, the thermodynamic properties of the target nucleosides are inherently unfavorable, and this complicates their synthesis significantly. A tenfold excess of sugar donor was needed to achieve 40-48 % conversion to the target nucleoside. Scale-up of the optimized conditions provided four Se-containing nucleosides in 6-40 % isolated yield, which compares favorably to established chemical routes.
摘要：
硒修饰核苷是研究核酸的结构和功能及其蛋白质相互作用的有力工具。2-硒代嘧啶核苷的广泛应用目前受到已建立的合成路线的低产率的限制。在这里，我们描述了使用天然尿苷或胸苷作为糖供体在转糖基化反应中通过热稳定核苷磷酸化酶合成2-Se-尿苷和2-Se-胸苷衍生物的优化。在低氧条件下在60或80°C和pH9下进行反应，以改善2-Se-核碱基在水性介质中的溶解度和稳定性。要优化转换，研究了分析性转糖基反应中的反应平衡。2-Se-嘧啶的磷酸化平衡常数在5至10之间，因此与任何其他已知情况的平衡常数相差一个数量级。因此，目标核苷的热力学性质本质上是不利的，这使得它们的合成显著复杂化。需要十倍过量的糖供体来实现向靶核苷的40-48%转化。优化条件的放大以6-40％的分离产率提供了四个含Se的核苷，与既定的化学路线相比，这是有利的。
