Synthesis, Antibacterial Activity, and Action Mechanism of Novel Sulfonamides Containing Oxyacetal and Pyrimidine

Bacterial leaf blight (BLB) and bacterial leaf streak (BLS) are two serious bacterial diseases caused by Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), respectively. However, the control of these diseases by conventional pesticides remains challenging due to development of resistances. We aimed to address this pending problem and developed a series of novel pyrimidine sulfonamide derivatives. Structurally, title compounds bear a unique oxyacetal group, which has a proven immune-activating effect. Compound E35 designed based on the 3D-QSAR model was demonstrated as the optimal in vitro activity against Xoo and Xoc, with EC₅₀ values of 26.7 and 30.8 mg/L, respectively, which were higher than the positive controls bismerthiazol (29.9 and 32.7 mg/L) and thiodiazole copper (30.5 and 36.4 mg/L). On the prevention level, the biological activity test showed compound E35 had superior protective activity (43.7%) on BLS to thiodiazole copper (32.1%). The defense enzymes and proteomics results suggested that compound E35 could be a versatile candidate as it improved plant's resistance to disease.