Increasing numbers of novel pesticides
have been applied in agriculture.
However, traditional evaluation of pesticides does not distinguish
between their enantiomers, which may lead to inaccurate results. In
this study, systematic research on the chiral insecticide fluxametamide
was conducted at the enantiomeric level. The methods for enantioseparation
and semipreparative separation of fluxametamide enantiomers were developed.
The optical rotation and absolute configuration of two enantiomers
were determined, and their stability was verified in solvents and
soils. Enantioselective bioactivities against four target pests (Plutella xylostella, Spodoptera exigua, Aphis gossypii, and Tetranychus cinnabarinus) were tested. Acute toxicities of fluxametamide enantiomers toward
honeybees were also evaluated. S-(+)-Isomer exhibited
52.1–304.4 times and 2.5–3.7 times higher bioactivity
than R-(−)-isomer and rac-fluxametamide, respectively. Meanwhile, rac-fluxametamide
was more toxic than S/R-isomer,
and S-(+)-isomer showed >30-fold higher acute
toxicity
than R-(−)-isomer. Molecular docking studies
were performed with γ-aminobutyric acid receptor (GABAR) to
monitor the mechanism of stereoselective bioactivity. The better Grid
score of S-(+)-fluxametamide (−60.12 kcal/mol)
than R-(−)-enantiomer (−56.59 kcal/mol)
indicated higher bioactivity of S-(+)-isomer than
of R-(−)-isomer. The dissipation of fluxametamide
in cabbage, Chinese cabbage, and soil was nonenantioselective under
field conditions. Development of S-(+)-fluxametamide
could maintain the high-efficacy and low-risk properties, which should
attract attention of producers, applicators, and managers of pesticides.
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