Design, synthesis, and insecticidal activity of novel 1-alkoxy-2-nitroguanidines

In searching for new insecticidal lead compounds, a series of novel 1-alkoxy-2-nitroguanidine, guadipyr analogues bearing alkoxy groups were designed, synthesized and confirmed by ¹H NMR, ¹³C NMR, high-resolution mass spectrometry and X-ray diffraction. The primary bioassays showed that most of these compounds exhibited moderate to good insecticidal activity against Myzus persicae and Aphis gossypii. Especially, the precise insecticidal assay showed that compounds 4-02, 4-07 and 4-08 displayed excellent in vitro activity with IC₅₀ values lower than 10 μg mL^-1 to M. persicae which is comparable to guadipyr. On the other hand, the toxicity of compound 4-07 and guadipyr against honey bees was much lower than imidacloprid. The results indicated that the flexible chain on the nitrogen atom was the most crucial factor on honey bee toxicity, which existed in both neonicotinoids and guadipyr series.