Design, Synthesis, Anti‐Oomycete, and Insecticidal Activities of 3β‐Acyloxy‐18β‐Glycyrrhetinic Acid Derivatives

18β-Glycyrrhetinic acid (GA) is a pentacyclic triterpenoid compound mainly extracted from the roots of the leguminous plant licorice. To discover botanical pesticides, twelve 3β-acyloxy-18β-glycyrrhetinic acid derivatives (3a-l) were synthesized, and their structures were characterized by ¹H NMR, ¹³C NMR, and HR-MS. In addition, we assessed the bioactivities of these title compounds as anti-oomycete and insecticidal agents against two serious agricultural pests, Phytophthora capsici and Mythimna separata. Amongst all tested target compounds, (1) Six compounds 3d, 3e, 3h, 3i, 3j, and 3k indicated promising anti-oomycete activity against P. capsici, with EC₅₀ values of 28.27, 29.36, 23.88, 20.03, 23.07, and 25.93 mg/L, respectively. (2) Six compounds showed significant insecticidal activity, the final mortality rates of 3b, 3c, 3f, 3g, 3i, and 3l were 66.7%, 55.6%, 63.0%, 60.7%, 51.9%, and 75.6%, respectively. The anti-oomycete and insecticidal activities of the title compounds were closely related to R, which has a significant impact on its activity.