The discovery of HNPC‐A3066: a novel strobilurin acaricide

Abstract

BACKGROUND: Although more than ten strobilurin analogues have been commercialized since 1996 as fungicides, only one was available as an acaricide as of 2003. To search for novel strobilurin analogues with unique biological activities, a synthetic screening programme was carried out. RESULTS: Syntheses of compounds analogous to the commercialized fungicide metominostrobin and the acaricide fluacrypyrim led to the discovery of a lead compound, (E)-2-[2-[[3,5-bis(trifluoromethyl)phenoxy]methyl]phenyl]-2-(methoxyimino)-N-methylacetamide (3b), that showed moderate acaricidal activity against Tetranychus urticae Koch. Compound 3b has a 3,5-(CF(3))(2)-phenoxymethyl group instead of the unsubstituted phenoxy substituent in metominostrobin. Optimization of compound 3b was achieved by introducing an oxime ether bridge along with an alkylthio(alkyl) branch in place of the oxymethylene chain between two aromatic moieties, as well as by replacing the methoxyiminoacetamide group with a methoxyacrylate structure, leading to (E)- methyl 2-[2-[[[(Z)[1-(3,5-bis(trifluoromethyl)phenyl)-2-methylthioethylidene]amino]oxy] methyl]phenyl]-3-methoxyacrylate (6c) and (E)- methyl 2-[2-[[[(Z)[1-(3,5-bis(trifluoromethyl)phenyl)-1-methylthiomethylidene]amino]oxy]methyl]phenyl]-3-methoxyacrylate (9a, HNPC-A3066). CONCLUSION: The above two compounds (6c, 9a) were shown to exhibit potent acaricidal and fungicidal activity. Compound 9a (HNPC-A3066) also exhibits larvicidal and ovicidal activities against various acarids. The acaricidal potency is comparable with those of commercial acaricides such as fluacrypyrim, tebufenpyrad and chlorfenapyr.