Biological activities of nitromethylene analogues of imidacloprid with a 4,5-dimethylated imidazolidine ring

Abstract

Four nitromethylene analogues of imidacloprid (CH-IMIs) having a 4,5-dimethylated (diMe) imidazolidine ring were stereospecifically synthesized to evaluate their affinity for the nicotinic acetylcholine receptors of the housefly Musca domestica. Among the analogues, the 4S,5R-diMe analogue showed the highest receptor affinity (K_i=0.39 nM). The insecticidal activity against M. domestica of the synthesized compounds was also measured under synergistic and nonsynergistic conditions. Under nonsynergistic conditions, the insecticidal activity of the 4S,5R-diMe analogue was the highest. The order of the insecticidal potency of the four diMe-CH-IMIs (4S,5R->4R,5S-=4R,5R->4S,5S-diMe analogues) was the same as that of the receptor affinity. Piperonyl butoxide (PBO) did not synergize with the test compounds, but both PBO and NIA16388 applications strengthened the activity of analogues other than the 4S,5S-diMe analogue. This suggests that the configuration of the substituents on the imidazolidine ring should influence the metabolism process of CH-IMI in houseflies.

Keywords: Musca domestica; insecticidal activity; neonicotinoids; nicotinic acetylcholine receptor; piperonyl butoxide.