This review summarizes the state of knowledge on the chemical methods of C(5)-modifications of uridine and cytidine derivatives and may serve as a useful tool for synthetic chemists to choose an appropriate reaction protocol. The synthesis of 5-substituted uracil derivatives is gaining an increasing interest because of their possible applications in medicine and pharmacy. Modifications at the C(5) position of pyrimidine nucleosides can enhance their biostability, bioavailability or(and) biological activity. Among the C(5)-modified nucleosides, 5-halopyrimidines exhibit anticancer, antiviral, radio- and photosensitizing properties. Besides 5-halo-substituted derivatives, there are other examples of nucleosides with confirmed biological activity containing a C–C bond at the C(5) position in the pyrimidine ring. In recent decades, scientists have achieved great progress in the field of cross-coupling reactions. Among them, nickel-catalyzed processes provide a broad spectrum of synthetic methods that are based on less toxic and cheaper starting materials. This review summarizes the synthetic approaches based on the coupling or halogenation reactions, which enable 5-substituted pyrimidine nucleosides to be obtained. Moreover, the importance of the systems considered for medicine and pharmacy is briefly discussed.

The bibliography includes 197 references.

这篇综述总结了对尿苷和胞苷衍生物的C（5）-修饰的化学方法的了解，并且可以作为合成化学家选择合适的反应方案的有用工具。由于5-取代的尿嘧啶衍生物可能在医学和药学上的应用，因此它们的合成越来越受到关注。嘧啶核苷C（5）位置的修饰可以增强其生物稳定性，生物利用度或（和）生物活性。在C（5）修饰的核苷中，5-卤代嘧啶具有抗癌，抗病毒，放射和光敏特性。除了5-卤代衍生物以外，还有其他具有确定的生物活性的核苷实例，在嘧啶环的C（5）位置含有CC键。近几十年来，科学家在交叉偶联反应领域取得了巨大进展。在它们之中，镍催化的方法提供了基于低毒性和廉价原料的多种合成方法。这篇综述总结了基于偶联或卤化反应的合成方法，这些方法使得能够获得5-取代的嘧啶核苷。此外，简要讨论了考虑用于医学和药学的系统的重要性。

参考书目包括197个参考文献。