Novel Piperidine Amide Derivatives Containing a Tetrazole Moiety: Safe Synthesis Methods, Molecular Design, Antioomycete Evaluation, and Action Mechanism.

The novel piperidine amide derivatives containing a tetrazole moiety were first constructed using a safer synthetic method in which sodium azide was substituted with diphenyl azidophosphate (DPPA). Compound D16 (EC50 = 0.0025 μg/mL), which was screened using an in vitro test against oomycetes, exhibited excellent inhibitory activity against P. capsici and showed little difference in efficacy compared to picarbutrazox (0.0010 μg/mL). The control efficacy in vivo of compound D16 against P. capsici was evaluated using bell pepper fruits, leaves, and potted plants as the hosts. SEM, TEM, and fluorescence microscopy experiments indicated that compound D16, as picarbutrazox, exerted a certain degree of damage to P. capsici mycelium, leading to organelle loss and cell apoptosis. Furthermore, compound D16 at 0.05 μg/mL potently inhibited spore germination of P. capsici by 87.2%. This research on novel piperidine amide derivatives containing a tetrazole moiety provides a valuable reference for new antioomycete agents.