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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
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Item Syntheses of epoxides, and structural analysis of (E)N-hexyl-3-(trans-3-methyloxiran-2-yl)prop-2-enamide by spectroscopic techniques and DFT calculations(Journal of Molecular Structure, 2018-08-05) Aguiar, Alex R.; Alvarenga, Elson S.; Oliveira, Ramon P.; Carneiro, Vania Maria T.; Moura, Luciano G.Pyrethroids are three membered ring compounds similar to the natural pyrethrins produced by the flowers of Chrysanthemum cinerariaefolium and C. coccineum. Pyrethroids are insecticides and may also have insect repellent properties and are generally harmless to humans. Due to our interest in compounds with insecticidal activity, we have synthesized seven epoxides (2a-g), which are structurally similar to pyrethroids. The epoxides were prepared by stereospecific and regioselective epoxidation of seven dienamides (1a-g) with meta-chloroperbenzoic acid. The energies for two attainable epoxides (2g and 2g′) at their respective equilibrium geometries were calculated, and we have shown that the title epoxide (2g) is more stable than the candidate epoxide (2g′) (trans)N-hexyl-3-((E)-prop-1-en-1-yl)oxirane-2-carboxamide by 13.37 kJ mol−1. Experimental and calculated nuclear magnetic resonance chemical shifts were compared for both candidate epoxides (2g and 2g′), and a better match was achieved for the title compound (2g). The complementarity of Raman and infrared (IR) spectroscopies is a feature that can be explored for the characterization of this class of compound. This is shown by the bands around 3092 cm−1 in the Raman and absent in the IR spectra. On the other hand a strong peak at 1625 cm−1 in the IR is tiny in the Raman. Therefore the title compound was completely identified by NMR, IR, and Raman spectroscopies, and this protocol can be extended to the herein prepared epoxide analogues.Item Synthesis, insecticidal activity, and phytotoxicity of novel chiral amides(Pest Management Science, 2019) Aguiar, Alex R.; Alvarenga, Elson S.; Silva, Eliete M. P.; Farias, Elizeu S.; Picanço, Marcelo C.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.