Synthesis and Biological Evaluation of Benzimidazole Phenylhydrazone Derivatives as Antifungal Agents against Phytopathogenic Fungi

A series of benzimidazole phenylhydrazone derivatives (6a–6ai) were synthesized and characterized by1H-NMR, ESI-MS, and elemental analysis. The structure of6bwas further confirmed by single crystal X-ray diffraction as (E)-configuration. All the compounds were screened for antifungal activity againstRhizoctonia solaniandMagnaporthe oryzaeemploying a mycelium growth rate method. Compound6fexhibited significant inhibitory activity againstR. solaniandM. oryzaewith the EC50values of 1.20 and 1.85 μg/mL, respectively. In vivo testing demonstrated that6fcould effectively control the development of rice sheath blight (RSB) and rice blast (RB) caused by the above two phytopathogens. This work indicated that the compound6fwith a benzimidazole phenylhydrazone scaffold could be considered as a leading structure for the development of novel fungicides.Keywords:benzimidazole;phenylhydrazone;antifungal activity