Design, Synthesis, and Biological Profiles of Novel 1,3,4-Oxadiazole-2-carbohydrazides with Molecular Diversity.

To unceasingly expand the molecular diversity of 1,3,4-oxadiazole-2-carbohydrazides, herein, small fragments (including -CH-, -OCH-, and -SCH-) were incorporated into the target compounds to screen out the potential succinate dehydrogenase inhibitors (SDHIs). The bioassay results showed that the antifungal effects (expressed by EC) against , , , and could reach 1.29 (), 0.63 (), 1.50 (), and 2.09 () μg/mL, respectively, which were slightly lower than those of carbendazim (EC were 0.69, 0.13, 0.55, and 0.80 μg/mL, respectively). Especially, compound was extremely bioactive against () with an EC value of 0.45 μg/mL. This outcome was better than that of fluopyram (3.76 μg/mL) and was similar to prochloraz (0.47 μg/mL). trials against the corn scab (infected by ) showed that compound had control activity of 86.8% at 200 μg/mL, which was better than that of boscalid (79.6%). Further investigations found that compound could inhibit the enzymatic activity of SDH in the strain with an IC value of 3.67 μM, indicating that potential SDHIs might be developed. Additionally, the other biological activities of these molecules were screened simultaneously. The anti-oomycete activity toward afforded a minimal EC value of 3.22 μg/mL (); compound could strongly suppress the growth of bacterial strains pv. and pv. with EC values of 3.79 and 11.4 μg/mL, respectively; and compound displayed some insecticidal activity toward . Given their multipurpose features, these frameworks could be actively studied as potential pesticide leads.