Synthesis of paeonol ester derivatives and their insecticidal, nematicidal, and anti-oomycete activities

Background Paeonol is extracted and isolated as a rich and sustainable natural bioresource from the root bark of Paeonia suffruticosa , the derivatives of which exhibit numerous biological activities. It is well known that ester compounds play a very important role in pest control, such as organophosphorus, carbamate and pyrethroid pesticides. Results To discover biorational natural product-based pesticides, three series of (60) paeonol ester derivatives ( 7a–t , 8g , p , 9g , p , 10g–j , n–u , 11g , u , 12g , u , 13a–p , 14b , c , and 15b , c ) were prepared by structural modification of paeonol, and their structures were well characterized by proton nuclear magnetic resonance ( 1 H-NMR), carbon-13 nuclear magnetic resonance ( 13 C-NMR), high-resolution mass spectrometry (HRMS), and melting point. Furthermore, we assessed the compounds as insecticidal, nematicidal, and anti-oomycete agents against three serious agricultural pests, Mythimna separata , Heterodera glycines , and Phytophthora capsici . Among all tested compounds: (i) compound 8p showed more significant insecticidal activity than toosendanin, and the final mortality rates of 8p and toosendanin against M. separata (1 mg mL −1 ) were 70.4%, and 51.9%, respectively; (ii) compound 7a exhibited more promising nematicidal activity than paeonol, and the median lethal concentration (LC 50 ) values of 7a and 1 against H. glycines were 15.47 and 50.80 mg L −1 , respectively; (iii) compounds 7n and 13m displayed more significant anti-oomycete activity compared to zoxamide against Phytophthora capsici , and the median effective concentration (EC 50 ) values of 7n , 13m , and zoxamide were 23.72, 24.51, and 26.87 mg L −1 , respectively; and the protective effect of the compounds against Phytophthora capsici in vivo further confirmed the effectiveness of the agents. Conclusion This study suggested that the introduction of a nitro at the C5 or C3 position of paeonol could improve its bioactivity against M. separata , H. glycines , and Phytophthora capsici . © 2022 Society of Chemical Industry.