Effect of Nitrogen Atom Substitution in A₃ Adenosine Receptor Binding: <i>N</i>‑(4,6-Diarylpyridin-2-yl)acetamides as Potent and Selective Antagonists

We report the first family of 2-acetamidopyridines as potent and selective A3 adenosine receptor (AR) antagonists. The computer-assisted design was focused on the bioisosteric replacement of the N1 atom by a CH group in a previous series of diarylpyrimidines. Some of the generated 2-acetamidopyridines elicit an antagonistic effect with excellent affinity (Ki < 10 nM) and outstanding selectivity profiles, providing an alternative and simpler chemical scaffold to the parent series of diarylpyrimidines. In addition, using molecular dynamics and free energy perturbation simulations, we elucidate the effect of the second nitrogen of the parent diarylpyrimidines, which is revealed as a stabilizer of a water network in the binding site. The discovery of 2,6-diaryl-2-acetamidopyridines represents a step forward in the search of chemically simple, potent, and selective antagonists for the hA3AR, and exemplifies the benefits of a joint theoretical–experimental approach to identify novel hA3AR antagonists through succinct and efficient synthetic methodologies.本研究首次报道了一类作为强效选择性A3腺苷受体（A3 adenosine receptor, AR）拮抗剂的2-乙酰氨基吡啶化合物家族。本次计算机辅助设计的核心策略为，在既往报道的二芳基嘧啶类化合物系列中，以CH基团对N1原子实施生物等排置换。部分合成得到的2-乙酰氨基吡啶类化合物展现出优异的拮抗活性，其亲和性极佳（抑制常数Ki < 10 nM）且选择性表现突出，相较于母核二芳基嘧啶类系列，提供了一种更为简洁的备选化学骨架。此外，本研究通过分子动力学与自由能微扰模拟，阐明了母核二芳基嘧啶类化合物中第二个氮原子的作用：该氮原子可作为结合位点内水网络的稳定剂。2,6-二芳基-2-乙酰氨基吡啶的发现，为人A3腺苷受体（hA3AR）强效、选择性且化学结构简洁的拮抗剂开发迈出了重要一步，同时也印证了理论与实验联合研究策略的优势——该策略可通过简洁高效的合成方法快速发掘新型hA3AR拮抗剂。