Ovicidal and Insecticidal Activities of Pyriproxyfen Derivatives with an Oxime Ester Group

Based on the structural framework of a pyriproxyfen metabolite, nineteen oxime ester derivatives were synthesized via reaction of the carboxylic acids with 4-(2-(2-pyridinyloxy)ethoxy)benzaldehyde oxime. The corresponding structures were comprehensively characterized by (1)H-nuclear magnetic resonance (NMR), (13)C-NMR, and electrospray ionization high-resolution mass spectrometry (ESI-HRMS). All of the compounds were screened for their insecticidal activities against Plutella xylostella and Myzus persicae, and for their ovicidal activities against Helicoverpa armigera eggs. The results obtained show that most of the oxime ester derivatives displayed moderate to high insecticidal activities and ovicidal activities at a concentration of 600 μg/mL. In particular, the ovicidal activity of compounds 5j, 5o, 5p, 5q, and 5s was determined to be 100%. Importantly, some of the compounds presented even higher biological activities than the reference compound pyriproxyfen. For example, compound 5j displayed an insecticidal activity value of 87.5% against Myzus persicae, whereas the activity value of pyriproxyfen was 68.3% at a concentration of 600 μg/mL. Among the synthesized compounds 5j and 5s exhibited broad biological activity spectra.