AbstractRecently, it was reported that the alkynyl modification of nucleobases mitigates the toxicity of antisense oligonucleotides (ASO) while maintaining the efficacy. However, the general effect of alkynyl modifications on the duplex‐forming ability of oligonucleotides (ONs) is unclear. In this study, post‐synthetic nucleobase modification by Sonogashira coupling in aqueous medium was carried out to efficiently evaluate the physiological properties of various ONs with alkynyl‐modified nucleobases. Although several undesired reactions, including nucleobase cyclization, were observed, various types of alkynyl‐modified ONs were successfully obtained via Sonogashira coupling of ONs containing iodinated nucleobases. Evaluation of the stability of the duplex formed by the synthesized alkynyl‐modified ONs showed that the alkynyl modification of pyrimidine was less tolerated than that of purine, although both the modifications occurred in the major groove of the duplex. These results can be attributed to the bond angle of the alkyne on the pyrimidine and the close proximity of the alkynyl substituents to the phosphodiester backbone. The synthetic method developed in this study may contribute to the screening of the optimal chemical modification of ASO because various alkynyl‐modified ONs that are effective in reducing the toxicity of ASO can be easily synthesized by this method.
摘要最近有报道称,核碱基的炔基修饰可减轻反义寡核苷酸(ASO)的毒性,同时保持其有效性。然而,炔基修饰对寡核苷酸(ONs)双链形成能力的一般影响尚不清楚。本研究通过在
水性介质中进行Sonogashira偶联来对核碱基进行合成后修饰,以有效评估炔基修饰核碱基的各种寡核苷酸的生理特性。虽然观察到了一些不希望发生的反应,包括核碱基环化,但通过含有
碘化核碱基的ON的Sonogashira偶联,成功获得了各种类型的炔基修饰ON。对合成的炔基修饰 ON 所形成的双链体的稳定性进行的评估表明,
嘧啶的炔基修饰耐受性比
嘌呤的炔基修饰耐受性差,尽管这两种修饰都发生在双链体的主沟中。这些结果可归因于
嘧啶上的炔基的键角以及炔基取代基与
磷酸二酯骨架的接近程度。本研究中开发的合成方法可能有助于筛选 ASO 的最佳
化学修饰,因为用这种方法可以很容易地合成各种有效降低 ASO 毒性的炔基修饰 ON。