Structure–Activity Studies of N-Heterocyclic Benzoyl Arylamine Derivatives Led to a Highly Fungicidal Candidate against Gaeumannomyces graminis var. tritici and Four Fusarium Wheat Pathogens

Wheat root diseases can seriously reduce yields and quality of wheat. 1,2,4-Triazole benzoyl arylamine derivatives previously showed good activities against some wheat root fungal pathogens. To further systematically disclose the structure-activity relationship, a series of benzoyl arylamines were designed and prepared. Their structures were characterized and fungicidal activities against Gaeumannomyces graminis var. tritici and Fusarium graminearum were evaluated. The results indicated that the structure of the N-heterocyclic group and the substituted group and their position on the benzamide scaffold had an important influence on the activities, as predicted. Finally, compound 18f was found to show excellent activities against G. graminis var. tritici, F. graminearum, Fusarium culmorum, Fusarium pseudograminearum, and Fusarium moniliforme with half-maximum effective concentrations of 0.002, 0.093, 0.011, 0.881, and 0.287 μg/mL, respectively. These results proposed that compound 18f deserved serious consideration as a novel fungicide candidate for the control of wheat root diseases.