Design, Synthesis, and Biological Activity of Novel Fungicides Containing a 1,2,3,4-Tetrahydroquinoline Scaffold and Acting as Laccase Inhibitors.

Laccase is a novel target for fungicides. We previously developed a new fungicide, 4-chlorocinnamaldehyde thiosemicarbazide (PMDD-5Y), as a laccase inhibitor. The introduction of active groups of natural products into the framework of a pesticide molecular structure is an effective method for discovering active lead compounds, and it has applications in the discovery of new pesticides. In this work, PMDD-5Y was selected as a lead compound, and we designed and synthesized a series of novel sulfonyl hydrazide derivatives containing the natural product scaffold 1,2,3,4-tetrahydroquinoline. The new compounds had antifungal activities against several fungi, especially and . One compound () displayed very good activity against and , with EC values of 3.32 and 2.78 μg/mL, respectively. The results of an enzyme activity assay showed that had the best inhibitory activity against laccase, with an EC value of 14.85 μg/mL. This was more active than the lead compound PMDD-5Y and the positive control cysteine. Using a molecular docking method, we studied the binding mode of the title compounds with laccase. The structural features of these new laccase inhibitors as fungicides will advance research and impact the field of discovering more potent fungicides to control diseases in agriculture.