Structural optimization of novel 6‐methoxy‐3‐nitropyridin‐2‐amine derivatives as potential fungicidal agents against Botrytis cinerea : structure–activity relationship, bioactivity, and mechanistic insights

Abstract Background Plant pathogenic fungi present a dual threat, leading to significant agricultural yield reductions while concurrently endangering human health. The growing resistance risk from the misuse of fungicides is driving the urgent need for novel agents with new structures and modes of action. Result Based on the promising antifungal potential of the pyridine scaffold, the structural optimization of 6‐methoxy‐3‐nitropyridin‐2‐amine derivatives led to the design and synthesis of 28 novel compounds. Systematic evaluation identified N ‐((2‐chlorothiazol‐5‐yl) methyl) ‐ N ‐ethyl‐6‐methoxy‐3‐nitropyridin‐2‐amine (T10), which exhibited remarkable activity against Botrytis cinerea , with in vitro and in vivo EC 50 values of 0.47 and 7.30 mg/L, respectively, demonstrating performance comparable to the commercial fungicide boscalid. In addition, acute toxicity tests indicate that the oral LD 50 of T10 mice is greater than 2 g/kg. Mechanistic studies via RNA sequencing preliminarily indicate that T10 exerts its antifungal effect by inhibiting the ribosome biogenesis pathway, a mode of action distinct from conventional fungicides. Conclusion The results identified the 6‐methoxy‐ N ‐ethyl‐3‐nitropyridin‐2‐amine scaffold as a valuable novel structural template, offering a fresh perspective for designing next‐generation fungicides with innovative architectures and mechanisms. © 2026 Society of Chemical Industry.