Preparation of oximoether derivatives of osthole and their pesticidal properties

To explore non-food bioactive products for pesticide candidates, and high value-added application of crop plants in agriculture, by using osthole (a natural coumarin isolated from a Chinese herbal medicine Cnidium monnieri) as a lead compound, a series of osthole derivatives containing oximoether groups were synthesized, and evaluated for their agricultural activities against Tetranychus cinnabarinus and Mythimna separata. The key steric configurations of eight derivatives were confirmed by X-ray crystallography. Especially compound 4r showed potential insecticidal activity (>2-fold of osthole) against M. separata, and 4g displayed good acaricidal activity against T. cinnabarinus (LC₅₀ = 0.566 mg/mL, > 2-fold of osthole). Their structure–activity relationships were also concluded. It will pave the way for future application of osthole derivatives as coumarin-kind botanical pesticides in crop protection.