Structural Optimization of Natural Plant Products: Construction, Pesticidal Activities, and Toxicology Study of New 2-Isopropanol-4-methoxy-7-alkyl/aryloxycarbonyl-(E)-vinyl-2,3-dihydrobenzofurans

Recently, the structural optimization of natural bioactive products has been one of the important ways to discover new pesticide candidates. Based on osthole as a lead compound, herein, a series of new 2-isopropanol-4-methoxy-7-alkyl/aryloxycarbonyl-(E)-vinyl-2,3-dihydrobenzofuran derivatives were synthesized. Steric configurations of compounds 3, 4, 6, 9, 11, 29, and 31 were confirmed by X-ray monocrystallography. Notably, an efficient method for preparation of 2-isopropanol-2,3-dihydrobenzofurans from osthole by the epoxidation and rearrangement reactions was developed. Against Plutella xylostella Linnaeus, compound 31 (R = CH₂CH₂Ph; LC₅₀: 0.759 mg/mL) displayed a 1.9-fold insecticidal activity compared to that of osthole; against Tetranychus cinnabarinus Boisduval, compound 34 (R = (CH₂)₉CH₃; LC₅₀: 0.401 mg/mL) exhibited a 3.3-fold acaricidal activity and good control effects compared to those of osthole. By the scanning electron microscope (SEM) imaging method, it was demonstrated that the acaricidal activity of compound 34 may be related to the damage of the cuticle layer crest of T. cinnabarinus. Compound 34 could be further studied as a potential acaricide.