Design, Synthesis, and 3D-QASR of Oxazoline Derivatives Containing an S–S Moiety as Potential Acaricide

To mitigate the detrimental effects of agricultural pest mites on crop yield, an active substructure splicing strategy was employed to modify etoxazole by introducing an S-S moiety. The target products were obtained efficiently via a bilateral disulfurating reagent (DSMO), which was developed by our group. The leaf dip method was used to evaluate the activities of the designed target compounds against the eggs and larvae of the spider mite (<i>Tetranychus cinnabarinus</i>). Most of the target compounds exhibited good efficacy in controlling the larvae and eggs of <i>T. cinnabarinus</i>. Based on these results, a three-dimensional quantitative structure-activity relationship (3D-QSAR) model was established to guide the construction of compound <b>7l</b>. Notably, compound <b>7l</b> exhibited a better activity against <i>T. cinnabarinus</i> eggs (LC₅₀ = 0.0035 mg/L) compared to etoxazole (LC₅₀ = 0.2990 mg/L). Greenhouse bioassays indicated that compound <b>7l</b> exhibits excellent acaricidal activity against egg of <i>T. cinnabarinus</i>, which is better than the etoxazole at 1.0 mg/L. Additionally, some of the compounds showed inhibitory effects against <i>Dickeya zeae</i> (<i>D. zeae</i>), <i>Xanthomonas campestris pv campestris</i> (<i>Xcc</i>), <i>Xanthomonas oryzae pvoryza</i> (<i>Xoo</i>), and <i>Xanthomonas oryzae pvoryzicola</i> (<i>Xoc</i>). Furthermore, compounds <b>7l</b> not only exhibited relatively potent against <i>Plutella xylostella</i> activities (LC₅₀ = 24.0 mg/L) but also had low toxicity (LC₅₀ > 11.0 μg/bee) to <i>Apis mellifera</i>. In conclusion, the current experimental results suggest that oxazoline derivatives containing an S-S moiety have the potential to serve as lead compounds for the development of novel acaricide agents.