Synthesis of novel pyridine-connected piperidine and 2H-thiopyran derivatives and their larvicidal, nematicidal, and antimicrobial activities

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A series of novelpyridine-connected piperidine derivatives (2a-g) and pyridine-connected 2H-thiopyran derivatives (4a-g) were synthesized and screened for larvicidal, nematicidal, and antimicrobial activities. Compound 4e exhibited larvicidal activity against second instar larvae with an LD50 value of 0.8μg/mL. In addition, 4e exhibited high nematicidal activity, with an LD50 value of 3.2μg/mL.Compounds 2e (MIC: 4 μg/mL) and 2d (MIC: 4 μg/mL) exhibited high antibacterial activity against Klebsiella pneumoniae and Escherichia coli, respectively. Compounds 4b (MIC: 0.25 μg/mL) and 4f (MIC: 2 μg/mL) showed high antifungal activity against Candida albicans and Microsporum audouinii, respectively. Therefore, it can be suggested that compounds 2e, 2d, 4e, 4b, and 4f may be useful as lead molecules for the development of new classes ofdrugs with larvicidal,nematicidal,and antimicrobial activities.