Design, Synthesis, and Biological Evaluation of Pyrazol-5-yl-Phenylacetamide Derivatives as Potential Fungicidal Agents.

Fungal infestation in crops can greatly reduce both yield and quality. To discover new fungicides, pyrazol-5-yl-phenylacetamide derivatives were synthesized by elongating the carbon chain of the lead compound pyrazol-5-yl-benzamides. These derivatives were assessed for their effectiveness against fungi. Compound C-13 displayed significant antifungal activity against Sclerotinia sclerotiorum, with an EC50 value of 2.51 mg/L. Additionally, compound C-16 showed effective antifungal properties against Valsa mali, with an EC50 value of 3.14 mg/L. Particularly noteworthy is the superior antifungal efficacy of compound C-42 against Gaeumannomyces graminis, with an EC50 value of 1.81 mg/L, significantly outperforming Fluxapyroxad (EC50 = 21.01 mg/L). Molecular docking and SDH enzymatic inhibition assay results provided insights into the potential mechanism of action of compound C-42. This study supports the development of pyrazol-5-yl-phenylacetamides as promising fungicides, particularly against G. graminis.