Design, synthesis and biological activity of diamide compounds based on 3-substituent of the pyrazole ring.

Background: Diamide insecticides have attracted significant attention due to their high efficacy and low toxicity to non-target organisms since they were introduced to the market. In order to tackle the problems of insecticide resistance and ecological safety, 16 novel nitrobenzene substituted anthranilic diamides with ester, hydroxyl or sulfonyl at the 3-position of the pyrazole ring were designed and synthesized.

Results: All of these compounds possessed good activity against the ryanodine receptor (RyR) from Spodoptera frugiperda and relatively lower activity against mammalian RyR1, showing a better insect-selectivity compared to chlorantraniliprole in a cell-based assay. The molecular docking analysis predicted the binding conformations of these compounds, which showed a good correlation between the insecticidal activity and the binding scores. In vitro studies using a calcium imaging method demonstrated that the novel compounds could not only activate the RyR but may also target the dihydropyridine receptor on the plasma membrane of insect neurons, implicating a similar but not same mode of action.

Conclusion: Substituted anthranilic diamides with an ester at the 3-position of the pyrazole ring exhibited a promising insecticidal activity and better insect-selectivity, which provided insight into the rational design of a new generation of effective diamide insecticides.