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

Nowadays, pest infestation and resistance have appeared due to repeated and extensive use of pesticides. Obviously, 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. Steric configurations of compounds 2, 5z and 13e were undoubtedly determined by single-crystal X-ray diffraction. Against Tetranychus cinnabarinus, notably, compounds 5f (LC50 : 0.14 mg mL-1 ) and 5v (LC50 : 0.13 mg mL-1 ) showed greater than 107 times pronounced acaricidal activity compared to 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 times potent aphicidal activity compared to piperine (LD50 : 116.06 ng aphid-1 ). In addition, through scanning electron microscope, the toxicology study suggested that the acaricidal activity of piperine derivatives may be related to the damage of cuticle layer crest of T. cinnabarinus. The SARs suggested that 3,4-dioxymethylene of piperine was crucial for the 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 can be studied as leads for further structural modification as acaricidal agents. This article is protected by copyright. All rights reserved.