Synthesis, insecticidal activity, and phytotoxicity of novel chiral amides

Abstract

The lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), is an important pest of stored grains worldwide. Chemical control is the main method used to manage this pest, but the continuous use of insecticides can lead to the selection of resistant R. dominica strains. Thus, there is a constant demand for the development of new insecticide molecules. This study describes the synthesis of 14 chiral amides and evaluation of their insecticidal activity against R. dominica. Their phytotoxicity to wheat (Triticum sativum) seeds is also evaluated. In the screening assay, compounds 8i and 8j caused 100% and 87% mortality of R. dominica. These values did not differ from the mortality caused by Bifenthrin® (75%). Amide 8i presented similar toxicity (LD50 = 27.98 µmol g^−1, CI95 = 25.14–30.71) and speed of action (LT50 = 22 h, CI95 = 19.34–24.66) to amide 8j (LD50 = 29.37 µmol g^−1, CI95 = 27.43–31.09, and LT50 = 19 h, CI95 = 17.05–20.95) against the pest. Both amides inhibited less than 44% of wheat growth.Among the tested amides, only 8i and 8j were effective in R. dominica control and presented no considerable phytotoxicity towards wheat seeds. Therefore, these amides are promising as insecticides for the management of R. dominica.