Novel heterocyclic amide derivatives containing a diphenylmethyl moiety: systematic optimizations, synthesis, antifungal activity and action mechanism

BACKGROUND The development of fungicides with low cross resistance, high efficacy and low resistance plays a central role in protecting crops, reducing yield losses, improving quality and maintaining global food security. Based on this important role, after a systematic optimization strategy, novel heterocyclic amide derivatives bearing diphenylmethyl fragment were screened, synthesized and verified with the spectrographic and x‐ray diffraction analysis. RESULTS In this study, the aforementioned optimization obtained compound B19 that was measured for antifungal activity against Rhizoctonia solani (median effective concentration, EC 50 = 1.11 μg mL −1 ). Meanwhile, the anti‐ R. solani protective effect (79.34%) of compound B19 was evaluated in vivo at 100 μg mL −1 , which is comparable to that of the control agent fluxapyroxad (80.67%). Thence, morphological observations revealed that compound B19 induced mycelium disruption and shrinking, mitochondrial number reduction and apoptosis acceleration, consistent with the results of the mitochondrial membrane potential and cell membrane permeability. Further investigations found that the potential target enzyme of compound B19 was SDH, which exerted fluorescence quenching dynamic curves similar to that of the commercialized SDHI fluxapyroxad. Additionally, research by molecular docking and MD simulations demonstrated that compound B19 had a similar binding mode acting on the surrounding residues in the SDH active pocket to that offluxapyroxad. CONCLUSION The above results demonstrated that heterocyclic amide derivatives containing a diphenylmethyl moiety are promising scaffolds for targeting SDH of fungi and provide valuable antifungal leads with the potential to develop new SDH inhibitors.