Expedient discovery of novel oxime ester derivatives of piperine/piperine analogs as potent pesticide candidates and their mode of action against Tetranychus cinnabarinus Boisduval

Abstract

AbstractBACKGROUNDNowadays, pest infestation and resistance have appeared as a consequence of repeated and extensive use of pesticides. Thus, development of new effective pesticide candidates in crop protection is highly desirable. Herein, a series of new piperine derivatives containing oxime ester scaffolds were regioselectively and stereoselectively prepared as pesticidal agents.RESULTSSteric configurations of compounds 2, 5z and 13e were definitively determined by single‐crystal X‐ray diffraction. Against Tetranychus cinnabarinus, notably, compounds 5f [median lethal concentration (LC50) = 0.14 mg mL−1] and 5v (LC50 = 0.13 mg mL−1) showed >107‐fold greater acaricidal activity than piperine (LC50 = 15.02 mg mL−1), which were comparable to the commercial acaricide spirodiclofen. Against Aphis citricola, compound 5d (LD50 = 19.12 ng aphid−1) exhibited 6.1‐fold more potent aphicidal activity than piperine (LD50 = 116.06 ng aphid−1). Additionally, through scanning electron microscopy, the toxicology study suggested that the acaricidal activity of piperine derivatives may be related to damage of the cuticle layer crest of T. cinnabarinus.CONCLUSIONThe structure–activity relationships suggested that 3,4‐dioxymethylene of piperine was crucial for its acaricidal activity; and introduction of a certain length of aliphatic chain at the C‐2 position was beneficial to the aphicidal and acaricidal activities. Compounds 5f and 5v are potential leads for further structural modification as acaricidal agents. © 2023 Society of Chemical Industry.