Optimization of Osthole as a Pesticide Candidate: Synthesis, Crystal Structures, and Agrochemical Properties of Acrylate Derivatives of Isopropenyl 2,3-Dihydrobenzofurans

Abstract

For high-value-added application of osthole derivatives as a pesticide candidate in crop protection, by the use of osthole as a lead compound, a series of novel acrylate derivatives of isopropenyl 2,3-dihydrobenzofurans were prepared by the successive bromination, rearrangement, and esterization reactions. Three-dimensional structures of four compounds were determined by single-crystal X-ray diffraction. The possible mechanism for construction of this new isopropenyl 2,3-dihydrobenzofuran skeleton from the osthole was presented. Against Plutella xylostella Linnaeus, compound 32 (R = PhCH2CH2) displayed 3.5-fold potent insecticidal activity of osthole. Against Tetranychus cinnabarinus Boisduval, compound 40 (LC50: 0.165 mg/mL; R = (CH2)13CH3) showed 8.3-fold pronounced acaricidal activity of osthole (LC50: 1.367 mg/mL); notably, its control effect can be comparable to that of the commercial acaricide spirodiclofen. Additionally, the scanning electron microscopy imaging method demonstrated that compound 40 can destroy the stratum corneum of T. cinnabarinus. Compound 40 can be further explored as a lead acaricidal agent.

Recent Advances and Outlook of Benzopyran Derivatives in the Discovery of Agricultural Chemicals

“…The application of pesticides is crucial for stabilizing and increasing crop yields worldwide . However, over-reliance on pesticides and unreasonable usage of large doses have led to a variety of extremely pronounced problems, such as development of pesticide resistance in insects and the accumulation of highly toxic pesticide residues in the environment. − In recent years, natural products have served as important starting materials for the discovery of new pesticides. − Benzopyran compounds such as coumarin, myricetin, cnidiadin (osthole), and flavonoids are widely found in plants, and exhibit a broad spectrum of biological activities. − Benzopyran has a unique bicyclic structure, and is composed of a benzene ring and a six-membered ring containing one oxygen atom. The two main isomers of benzopyran are benzo-α-pyran and benzo-γ-pyran, while benzodihydropyran, chroman-2-one, chroman-4-one, and 4 H -chromen-4-one contain variations in the scaffold structures of benzopyran (Figure ).…”