Prodrug-Oriented Molecular Design of Neonicotinoids: Preparation of Imidacloprid-Related 5,5-Dimethoxy-1,3-diazacyclohexane Derivatives and Their Insecticidal Activity
作者:Shinzo KAGABU、Manabu HIBI、Keiichiro NISHIMURA
DOI:10.1271/bbb.69.705
日期:2005.1
Prodrug-oriented molecular design was attempted for the potent acyclic neonicotinoid insecticide, clothianidin (1-(2-chloro-5-thiazolylmethyl)-3-methyl-2-nitroguanidine). Molecules bearing a CH2COCH2 bridge linking the 1,3-NH ends of clothianidin or their acetals would possibly be hydrolyzed, regenerating the mother compounds. This strategy was used to prepare seven acetals of clothianidin-based molecules that combined 2-chloro-5-thiazolylmethyl, 6-chloro-3-pyridylmethyl or 3-tetrahydrofurfuryl with a nitroimine, cyanoimine or nitromethylene group. The key intermediate, 1,3-diamino-2,2-dimethoxypropane, was prepared from the dihydroxyacetone dimer in four steps. A selected acetal showed a characteristic nerve-impulse pattern for neonicotinoids on an excised American cockroach ganglion, although the neuroblocking activity was fairly low. Some acetals were highly insecticidal against the pea aphid at 0.8–20 ppm 7 days after a spray treatment, this being in a contrast to their far weaker activity by injection into American cockroaches. The biological results suggest that the intrinsic insecticidal activities of the acetals are weak, but would exhibit enhanced activity if hydrolyzed in an external environment.
针对强效的非环状新烟碱类农药克洛噻啶(1-(2-氯-5-噻唑基甲基)-3-甲基-2-硝基氨基脲),进行了以前药为导向的分子设计。带有CH2COCH2桥的分子将克洛噻啶的1,3-NH末端或其缩醛链连接在一起,这些分子可能会被水解,从而再生母体化合物。该策略用于合成七种以克洛噻啶为基础的缩醛分子,这些分子结合了2-氯-5-噻唑基甲基、6-氯-3-吡啶基甲基或3-四氢呋喃基与硝基亚胺、氰亚胺或硝基亚甲基基团。关键中间体1,3-二氨基-2,2-二甲氧基丙烷是通过四步从二羟基丙酮二聚体中合成的。选择的一种缩醛在切除的美洲蟑螂神经节上显示出新烟碱类的特征神经冲动模式,尽管其神经阻断活性相对较低。某些缩醛在喷雾处理后7天内,对豌豆蚜虫表现出0.8–20 ppm的高杀虫活性,这与通过注射到美洲蟑螂中的活性较弱形成对比。生物结果表明,这些缩醛的固有杀虫活性较弱,但如果在外部环境中水解,则可能会表现出增强的活性。