Designing novel candidates as potential antibacterial scaffolds has become crucial due to the lack of new antibiotics entering the market and the persistent rise in multidrug resistance. Here, we describe a new class of potent antibacterial agents based on a 5-aryl-N²,N⁴-dibutylpyrimidine-2,4-diamine scaffold. Structural optimization focused on the 5-aryl moiety and the bioisosteric replacement of the side chain linker atom. Screening of the synthesized compounds focused on a panel of bacterial strains, including gram-positive Staphylococcus aureus strains (Newman MSSA, methicillin- and vancomycin-resistant), and the gram-negative Escherichia coli (ΔAcrB strain). Several compounds showed broad-spectrum antibacterial activity with compound 12, bearing a 4-chlorophenyl substituent, being the most potent among this series of compounds. This frontrunner compound revealed a minimum inhibitory concentration (MIC) value of 1 µg/mL against the S. aureus strain (Mu50 methicillin-resistant S. aureus/vancomycin-intermediate S. aureus) and an MIC of 2 µg/mL against other tested strains. The most potent derivatives were further tested against a wider panel of bacteria and evaluated for their cytotoxicity, revealing further potent activities toward Streptococcus pneumoniae, Enterococcus faecium, and Enterococcus faecalis. To explore the mode of action, compound 12 was tested in a macromolecule inhibition assay. The obtained data were supported by the safety profile of compound 12, which possessed an IC₅₀ of 12.3 µg/mL against HepG2 cells. The current results hold good potential for a new class of extended-spectrum antibacterial agents.

中文翻译：

---

2,4-二取代-5-芳基嘧啶衍生物抗菌剂的开发与评价

由于缺乏新的抗生素进入市场以及多重耐药性的持续上升，设计新的候选药物作为潜在的抗菌支架变得至关重要。在这里，我们描述了一类基于 5-芳基-N ² , N ^{4 -}二丁基嘧啶-2,4-二胺支架的新型有效抗菌剂。结构优化集中在 5-芳基部分和侧链连接原子的生物电子等排取代上。合成化合物的筛选集中在一组细菌菌株上，包括革兰氏阳性金黄色葡萄球菌菌株（纽曼 MSSA，耐甲氧西林和万古霉素）和革兰氏阴性大肠杆菌（ΔAcrB 菌株）。几种化合物显示出广谱抗菌活性，其中带有 4-氯苯基取代基的化合物12是该系列化合物中最有效的。该领先化合物对金黄色葡萄球菌菌株（Mu50 甲氧西林耐药金黄色葡萄球菌/万古霉素中效金黄色葡萄球菌）的最低抑菌浓度 (MIC) 值为 1 µg/mL ，对其他测试菌株的 MIC 为 2 µg/mL菌株。最有效的衍生物进一步针对更广泛的细菌进行了测试，并评估了其细胞毒性，揭示了对肺炎链球菌、屎肠球菌和粪肠球菌的进一步有效活性。为了探索作用方式，化合物12在大分子抑制测定中进行了测试。所获得的数据得到了化合物12的安全性的支持，该化合物对 HepG2 细胞的IC ₅₀为 12.3 µg/mL。目前的结果对于新型广谱抗菌剂具有良好的潜力。