With the increasing evolution of pesticide resistance, pyrimidinamine derivatives are considered promising agricultural compounds because of their outstanding activity and their mode of action which is different from other fungicides. But diflumetorim, the commercial pyrimidinamine fungicide, is not effective in controlling corn rust (Puccinia sorghi). In this study, a series of pyrimidinamine derivatives were designed and synthesized using pyrimidifen as a template according to the bioisosterism. The new compounds showed excellent fungicidal activity. Among these compounds, (S)-5-chloro-6-(difluoromethyl)-2-methyl-N-(1-((5-(trifluoromethyl)pyridin- 2-yl)oxy)propan-2-yl)pyrimidin-4-amine, T33, had the best control effect on corn rust with EC₅₀ values of 0.60 mg/L, versus commercial fungicide tebuconazole (1.65 mg/L). The synthesis, characterization, and activity data of the compounds are presented in the text, and the structure-activity relationships are discussed.

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