Dual-Target Inhibitors─Discovery of Novel Diphenyl-(Thio)ether-Containing Benzoxaborole Derivatives as Potential Antifungal and Herbicidal Agents

LeuRS and PPO are important targets in the development of green pesticides; novel diphenyl-(thio)ether-containing benzoxaborole derivatives were designed and synthesized as novel dual-target enzyme inhibitors; their antifungal activities against six kinds of common plant pathogens in vitro and their herbicidal activities against purslane and barnyard grass were studied. Most of the target compounds showed excellent antifungal activity against six kinds of plant pathogenic fungi in vitro, and this is highlighted by compounds <b>6c</b> and <b>6h</b>, both displayed 100.0% inhibition effects against three kinds of the tested plant pathogenic fungi under the concentrations of 50.0 μg/mL, and the EC₅₀ value of compound <b>6r</b> against <i>Rhizoctonia solani</i> was 0.763 μg/mL, significantly lower than that of boscalid (1.20 μg/mL). In addition, compound <b>6c</b> was also used in negative control experiments, and the results revealed that compound <b>6c</b> had no significant effect on the growth of noninfected plants. Meanwhile, most of the compounds also demonstrated promising herbicidal activity, as compounds <b>6b</b>, <b>6h</b>, <b>6m</b>, and <b>7e</b> showed effective control on purslane and barnyard grass. Beyond that, compound <b>6s</b> demonstrated certain safety against rape. Enzymatic inhibition experiments further confirmed that compound <b>7e</b> exhibited remarkable inhibitory activity against NtPPO. Moreover, the molecular docking results between <b>6c</b> and <b>7g</b> and tLeuRS and <i>Nt</i>PPO further revealed the mechanisms of action for their biological activities. In summary, compounds <b>6b</b>, <b>6c</b>, <b>6h</b>, <b>7e</b>, and <b>7g</b> showed excellent antifungal and herbicidal activities and can be further studied as new antifungal and herbicidal agents in the next step.