A series of novel 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxylic acid amides were synthesized and their activities were tested against seven phytopathogenic fungi by an in vitro mycelia growth inhibition assay. Most of them displayed moderate to excellent activities. Among them N-(2-(5-bromo-1H-indazol-1-yl)phenyl)-3-(difluoro-methyl)-1-methyl-1H-pyrazole-4-carboxamide (9m) exhibited higher antifungal activity against the seven phytopathogenic fungi than boscalid. Topomer CoMFA was employed to develop a three-dimensional quantitative structure-activity relationship model for the compounds. In molecular docking, the carbonyl oxygen atom of 9m could form hydrogen bonds towards the hydroxyl of TYR58 and TRP173 on SDH.

A series of novel aromatic carboxylic acid amides were synthesized and tested for their activities against six phytopathogenic fungi by an in vitro mycelia growth inhibition assay. Most of them displayed moderate to good activity. Among them N-(2-(1H-indazol-1-yl)phenyl)-2-(trifluoromethyl)benzamide (3c) exhibited the highest antifungal activity against Pythium aphanidermatum (EC50 = 16.75 µg/mL) and Rhizoctonia solani (EC50 = 19.19 µg/mL), compared to the reference compound boscalid with EC50 values of 10.68 and 14.47 µg/mL, respectively. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were employed to develop a three-dimensional quantitative structure-activity relationship model for the activity of the compounds. In the molecular docking, a fluorine atom and the carbonyl oxygen atom of 3c formed hydrogen bonds toward the hydroxyl hydrogens of TYR58 and TRP173.

By combining the sub-structures of strobilurin and guadipyr analogues in one molecule, a series of compounds was designed and synthesized. Some compounds showed excellent insecticidal activity or fungicidal activity.

BACKGROUND Strobilurin fungicides are some of the most potent and successful agrochemicals. However, continued use of traditional strobilurins has led to the emergence of fungicide‐resistant biotypes. Thus, a supply of new strobilurin fungicides is highly valuable. In this study, a series of novel methoxyacrylate analogs containing a cyano‐substituted hydrazine moiety as the side chain was synthesized and evaluated for their anti‐plant pathogenic activities. RESULTS Compounds 2‐04, 2‐05, 2‐07 and 2‐14 exhibited a relatively broad range of fungicidal activity. Compounds 2‐04, 2‐13 and 2‐14 exhibited good fungicidal activity against Sclerotinia sclerotiorum with median effective concentrations (EC50) of 3.84, 3.50 and 3.80 μg mL−1, respectively. Most of these compounds showed excellent inhibition of spore germination in Magnaporthe grisea at 25 μg mL−1. Moreover, in an in vivo test, compounds 2‐02, 2‐04, 2‐07 and 2‐13 exhibited potent fungicidal activities against the tested plant diseases at 400 μg mL−1. Notably, compound 2‐07 showed comparable or better activity than the commercially positive controls, azoxystrobin and procloraz, against powdery mildew of cucumber and rice blast fungus in the field trails at the same application dosages. CONCLUSON This study indicated that methoxyacrylate analogs containing a cyano‐substituted hydrazone side chain can serve as potential fungicidal candidates for crop protection. © 2019 Society of Chemical Industry

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