Synthesis and fungicidal evaluation of novel chalcone-based strobilurin analogues

Strobilurin derivatives have become one of the most important classes of agricultural fungicide due to a novel action mode, wide fungicidal spectrum, lower toxicity toward mammalian cells, and environmentally benign characteristics. To discover new strobilurin analogues with high activity against resistant pathogens, a series of new chalcone-based strobilurin derivatives are designed and synthesized by integrating a chalcone scaffold with a strobilurin pharmacophore. The preliminary bioassay showed that some of the chalcone analogues exhibited good in vivo fungicidal activities against Pseudoperoniospora cubensis and Sphaerotheca fuliginea at the dosage of 200 microg mL(-1). Two compounds, (E)-methyl 2-[2-({3-[(E)-3-(2-chlorophenyl)acryloyl]phenoxy}methyl)phenyl]-3-methoxyacrylate (1e) and (E)-methyl 2-[2-({3-[(E)-3-(3-bromophenyl)acryloyl]phenoxy}methyl)phenyl]-3-methoxyacrylate (1l), were found to display higher fungicidal activities against P. cubensis (EC90=118.52 microg mL(-1) for 1e and EC90=113.64 microg mL(-1) for 1l) than Kresoxim-methyl (EC90=154.92 microg mL(-1)) and were identified as the most promising candidates for further study. The present work demonstrated that strobilurin analogues containing chalcone as a side chain could be used as a lead structure for further developing novel fungicides. To our knowledge, this is the first report about the syntheses and fungicidal activities of chalcone-based strobilurin derivatives.