Synthesis and insecticidal activity in vitro and vivo of novel benzenesulfonyl derivatives based on potent target subunit H of V-ATPase

Synthetic Modification and Insecticidal Activity of 4-epi-cis-Dihydroagarofuran Derivatives

To synthesize the fundamental framework of dihydroagarofuran, a novel strategy was devised for constructing the C-ring through a dearomatization reaction using 6-methoxy-1-tetralone as the initial substrate. Subsequently, the dihydroagarofuran skeleton was assembled via two consecutive Michael addition reactions. The conjugated diene and trans-dihydroagarofuran skeleton were modified. The insecticidal activities of 33 compounds against Mythimna separata were evaluated. Compounds 11-5 exhibited an LC50 value of 0.378 mg/mL. The activity exhibited a remarkable 29-fold increase compared to positive control Celangulin V, which was widely recognized as the most renowned natural dihydroagarofuran polyol ester insecticidal active compound. Docking experiments between synthetic compounds and target proteins revealed the shared binding sites with Celangulin V. Structure-activity relationship studies indicated that methyl groups at positions C4 and C10 significantly improved insecticidal activity, while ether groups with linear chains displayed enhanced activity; in particular, the allyl ether group demonstrated optimal efficacy. Furthermore, a three-dimensional quantitative structure-activity relationship model was established to investigate the correlation between the skeletal structure and activity. These research findings provide valuable insights for discovering and developing dihydroagarofuran-like compounds.

Diversifying the benzenesulfonamide scaffold for potential V-ATPase inhibitors: synthesis and insecticidal activity evaluation

Celangulin V is a natural β-dihydroagarofuran derivative isolated from Celastrus angulatus which shows insecticidal activity in many agricultural pests. Using celangulin V as a molecular probe, we find out a new pesticide target: subunit H of V-ATPase. To explore the potential application of this novel target, lead sulfonamides have been found through virtual screening. Combined with the previous work, 46 sulfonamide derivatives are designed and synthesized. All target compounds are first screened for their insecticidal activities against Mythimna separata. The results of bioassay reveal that most of the designed compounds exhibit significant insecticidal activities against third-instar larvae of M. separata under the concentration of 10 mg/mL, and compound 8.4 shows the highest activity with LC50 value of 1.72 mg/mL, 15-fold smaller than that of celangulin V (25.89 mg/mL). Molecular docking results further indicated that compound 8.4 might serve as a potential inhibitor of the subunit H of V-ATPase. This study provides a potential sulfonamide candidate compound for the M. separata control.

Design, synthesis and insecticidal activity of benzenesulfonamide derivatives containing various alkynyl, alkenyl and cyclopropyl groups in para position

Celangulin V is a natural β-dihydrofuran sesquiterpene polyester with anti Mythimna separate activity and unique mechanism of action. Further study showed that its target was the H subunit of V-ATPase in the midgut of M. separate. Thus, combined with the previous work, thirty-two benzene sulfonamide derivatives were systematically synthesised to discover efficient and low-budget insecticidal candidates for the H subunit of V-ATPase. Screening results showed that compounds C2, C4, C5, C6 and C8 could significantly cause death of tested third-instar larvae of M. separate, and provided the corresponding LC50 values of 0.844, 0.953, 0.705, 0.599 and 0.887 mg/mL, which were extremely better than Celangulin V (LC50 = 11.5 mg/mL). The docking results indicated that this novel framework might target H subunit of V-ATPase. Given these excellent bioactivity results, this kind of sulfonamide framework could provide a suitable point for exploring highly efficient insecticidal agents.

Design, synthesis and insecticidal activities of 4-propargyloxybenzene sulfonamide derivatives substituted with amino acids

Sixty-nine 4-propargyloxybenzene sulfonamide derivatives with different amino acids as amino substituent were synthesized and evaluated for their insecticidal activity against third-instar Mythimna separate. The bioassay results revealed that some derivatives bearing amino acid ester group performed good insecticidal activity against third-instar M.separata, such as the LC₅₀ values of D18 and D19 were 4.28 and 2.96 mg/ml after 48 h, in particular, the LC₅₀ of D16 was 2.38 mg/ml and the activity was improved by 14 times compared to celangulin V (34.48 mg/ml). The above results provided theoretical and experimental basis for the discovery of novel insecticidal active compounds.

Design, Synthesis, Insecticidal Activities and Molecular Docking of Sulfonamide Derivatives Containing Propargyloxy or Pyridine Groups

The discovery of new highly active molecules from natural products is a common method to create new pesticides. Celangulin V targeting Mythimna separate (M. separate) midgut V-ATPase  H subunit, has received considerable attention for its excellent insecticidal activity and unique mechanism of action. Therefore, combined with our preliminary work, thirty-seven sulfonamide derivatives bearing propargyloxy or pyridine groups were systematically synthesized to search for insecticidal candidate compounds with low cost and high efficiency on the  H subunit of V-ATPase. Bioactive results showed that compounds A2-A4 and A6-A7 exhibited a better bioactivity with median effective concentration (LC₅₀ ) values (2.78, 3.11, 3.34, 3.54 and 2.48 mg/mL, respectively) against third-instar larvae of M. separate than Celangulin V (LC₅₀ =18.1 mg/mL). Additionally, molecular docking experiments indicated that these molecules may act on the H subunit of V-ATPase. Based on the above results, these compounds provide new ideas for the discovery of insecticides.

Synthesis and insecticidal activities of 4-(propargyloxy) benzenesulfonamide derivatives

A series of 4-(propargyloxy) benzenesulfonamide derivatives with different substituents on the benzene ring were synthesized and evaluated for their insecticidal activity. Some of the compounds showed good insecticidal activity against Mythimna separata, and the LC₅₀ value of the most active compound B2.5 was 0.235 mg/ml. Ultrastructural changes in the midgut epithelial cells of Mythimna separata were observed using transmission electron microscopy, and severe structural damage was found in microvilli, mitochondria and rough endoplasmic reticulum. It indicates that the possible site of action of these benzenesulfonamides is the cytoplasmic membrane and endomembrane system of the midgut epithelial cells. The above provides a basis for the development of novel insecticidal active compounds with a novel mechanism of action.

Design, Synthesis and Bioactivity of Novel Low Bee-Toxicity Compounds Based on Flupyrimin

Neonicotinoids are important insecticides for controlling aphids in agriculture. Growing research suggested that neonicotinoid insecticides are a key factor causing the decline of global pollinator insects, such as bees. Flupyrimin (FLP) is a novel nicotinic insecticide with unique biological properties and no cross-resistance, and is safe for pollinators. Using FLP as the lead compound, a series of novel compounds were designed and synthesized by replacing the amide fragment with a sulfonamideone. Their structures were confirmed by ¹H NMR, ¹³C NMR and HRMS spectra. Bioassay results showed that compound 2j had good insecticidal activity against Aphis glycines with an LC₅₀ value of 20.93 mg/L. Meanwhile, compound 2j showed significantly lower acute oral and contact toxicity to Apis mellifera. In addition, compound 2j interacted well with the protein in insect acetylcholine binding protein (AChBP). The molecular docking on honeybee nicotinic acetylcholine receptor (nAChR) indicated that the sulfonamide group of compound 2j did not form a hydrogen bond with Arg173 of the β subunit, which conforms to the reported low bee-toxicity conformation. In general, target compound 2j can be regarded as a bee-friendly insecticide candidate.

Facile synthesis, larvicidal activity, biological effects, and molecular docking of sulfonamide-incorporating quaternary ammonium iodides as acetylcholinesterase inhibitors against Culex pipiens L

Insecticides participate with a vital role in our lives especially in preventing the spread of human diseases via controlling the dangerous pests. It is a challenge to identify alternatives to the ordinary insecticides with new mode of action to be used for mosquitoes' control in an environmentally sustainable manner. Using a facile two-step procedure, three novel series of sulfonamide-incorporating quaternary ammonium iodides (3a-i, 4a-i and 5a-i) were synthesized and their chemical structures were successfully characterized. The uncharged sulfonamide intermediates (2a-i) were constructed through simple amidation of the corresponding (hetero)aryl sulfonyl chlorides then the cationic target molecules were formed by quaternizing the tertiary nitrogen with methyl, ethyl, and allyl iodides. The larvicidal activities and biological effects of most synthesized compounds against Culex pipiens L. were extensively investigated and they exhibited good and comparable activities to temephos. Among these hybrids, 4a showed the most potent activity with LC₅₀ = 26.71 ppm. Additionally, the developmental durations of larval and pupal stages were significantly prolonged after treatment with all concentrations of 4h. At high concentration (160 ppm) of 4a and 4b, no adults emerged due to the complete death of pupae, and consequently zero growth index. Moreover, the results of the molecular docking demonstrated that the activities of compounds correlate partially to their binding with acetylcholinesterase (AChE) and it is not the sole parameter for determining the activity.

Design, synthesis, and insecticidal activities of propargyloxy-naphthalene-sulfonamide derivatives

In our previous studies, a kind of novel benzenesulfonamides was found to be a candidate insecticidal compounds. It was shown that propargyloxy and sulfonamide groups are pharmacodynamic groups. One hundred and twenty-six (126) naphthalenesulfonamides derivatives with propargyloxy functionality were designed and synthesized, and their insecticidal activities were determined. Some of them showed outstanding activity, with LC₅₀ values as low as 0.202 mg ml^-1, much lower than that of the positive control celangulin V (23.9 mg ml^-1). In addition, the structure-activity relationships were discussed, and molecular docking was used to verify the binding mode of the compound and the target receptor.

Synthesis and Insecticidal Activity Evaluation of Virtually Screened Phenylsulfonamides

The fastest and most effective way to control pests is to use pesticides. However, with the accumulation of pesticide resistance and the difficulties of rapidly producing new pesticides, it is of great significance to create new pesticides through new synthetic methods. In this study, we report a computer-aided drug design (CADD)-assisted method to obtain two lead sulfonamides by homology modeling and virtual screening. On this basis, the lead compounds were synthesized from p-chlorocresol by four steps of esterification, sulfonation, sulfonamidation, and amidation. Further, 71 derivatives were synthesized by optimizing the lead compounds, and their insecticidal activities against Mythimna separata were evaluated by the leaf-dipping method. Notably, seven sulfonamides (5a, 5g, 5h, 5m, 6b, 6g, and 6m) with excellent insecticidal activity were obtained, and the possible binding modes between receptors and active groups in sulfonamides were verified by structure-activity relationship and docking simulation, which provided theoretical support for the subsequent development of these novel candidate insecticides.