Design, Synthesis, Anti-Oomycete, Antifungal, and Nematicidal Activities of 2'-Acyloxyfenjuntong Derivatives

In order to discover highly bioactive Fenjuntong compounds, 10 2'-acyloxyfenjuntong derivatives (3a-j) were synthesized by structural modification of Fenjuntong, and their structures were well characterized by ¹H NMR, ¹³C NMR, and HRMS. Furthermore, the bioactivities of these compounds as anti-oomycete, antifungal, and nematicidal agents against three serious agricultural pests, Phytophthora capsici, Fusarium graminearum, and Heterodera glycines were evaluated. Among all tested compounds, first, compound 3a exhibited promising anti-oomycete against P. capsici, with an EC₅₀ value of 35.00 mg/L. Second, compounds 3d and 3f displayed promising antifungal against F. graminearum, with EC₅₀ values of 52.60 and 39.41 mg/L, respectively. Third, compounds 3g, 3i, and 3j showed significant nematicidal activity against H. glycines, with LC₅₀ values of 36.29, 30.19, and 35.43 mg/L, respectively. The results demonstrate that introducing acyloxy pharmacophores at the phenolic hydroxyl position of Fenjuntong not only significantly enhances its biological activity against P. capsici, F. graminearum, and H. glycines, but also yields target compounds that uniformly more active than Fenjuntong itself. Moreover, these important results lay the foundation for further optimization of Fenjuntong toward the development of potential new pesticides.