Abstract
Cyclic imides belong to a well-known class of organic compounds with various biological activities, promoting a great interest in compounds with this functional group. Due to the structural complexity of some molecules and their spectra, it is necessary to use several spectrometric methods associated with auxiliary tools, such as the theoretical calculation for the structural elucidation of complex structures. In this work, the synthesis of epoxy derivatives of 5-methylhexahydroisoindole-1,3-diones was carried out in five steps. Diels–Alder reaction of isoprene and maleic anhydride followed by reaction with m-anisidine afforded the amide (2). Esterification of amide (2) with methanol in the presence of sulfuric acid provided the ester (3) that cyclized in situ to give imides 4 and 4-ent. Epoxidation of 4 and 4-ent with meta-chloroperbenzoic acid (MCPBA) afforded 5a and 5b. The diastereomers were separated by silica gel flash column chromatography, and their structures were determined by analyses of the spectrometric methods. Their structures were confirmed by matching the calculated 1H and 13C NMR chemical shifts of (5a and 5b) with the experimental data of the diastereomers using MAE, CP3, and DP4 statistical analyses. Biological assays were carried out to evaluate the potential herbicide activity of the imides. Compounds 5a and 5b inhibited root growth of the weed Bidens pilosa by more than 70% at all the concentrations evaluated.
Highlights
In 2050, it is estimated that the global population will reach the mark of 9.1 billion people
Diels–Alder reaction reactionofofisoprene isopreneand and maleic anhydride followed by nucleophilic
The results reported by CP3 were obtained by comparing differences in calculated data with differences in experimental chemical shifts for equivalent nuclei
Summary
In 2050, it is estimated that the global population will reach the mark of 9.1 billion people. World food production will need to increase by 70–100%. Weeds are agricultural pests and cause the highest percentage of loss of income from food production. They compete with the plantations for sunlight, water, and nutrients, harbor insects and pathogens (fungi, bacteria, and viruses), promoting losses in production. Weeds destroy native habitats, threatening plants and animals in the local ecosystem [1,2]. Cyclic imides belong to an important class of organic compounds, being important in synthetic, pharmacological, and industrial chemistry. Imides are compounds with high biological potential because they are electrically neutral and hydrophobic, being able to cross biological membranes [3,4,5]. Herbicidal activity stands out and some commercial herbicides are presented in Figure 1 [6]
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