Synthesis and Pesticidal Activities of New Quinoxalines

Design and Synthesis of Unsymmetric Benzils, Quinoxalines, and Evaluations of their Anticancer Activities against Human Non-Small Lung Cancer Cells

Quinoxaline and its derivatives exhibit a broad spectrum of biological activity, making them valuable for various therapeutic applications. However, most quinoxalines are synthetically produced due to their scarcity in nature. In this article, a series of unsymmetric benzils were synthesized and subsequently condensed with 1,2-diaminobenzene to produce unsymmetric quinoxalines. The novel synthetic benzils and quinoxalines were evaluated for their anticancer activities against human non-small-cell lung cancer (NSCLC) cells harboring different gene mutations, to explore their potential as anticancer agents. Among these synthesized molecules, compound 5 g demonstrated inhibitory effects comparable to those of cisplatin.

The Hoverfly Attracting Property of a Methyl Salicylate-Containing (E)-β-Farnesene Analog (3e) and Potential Mechanism by Mediating the EcorOBP15 and EcorOR3

Using natural enemies provides a sustainable method to control major agricultural pests. Hoverflies are significant natural enemies of aphids and efficient pollinators. Herbivore-induced plant volatiles (HIPVs), including (E)-β-farnesene (EBF) and methyl salicylate (MeSA), are key olfactory cues mediating hoverflies behavior. Our previous work identified compound 3e, an EBF analog containing a MeSA moiety, exhibited aphid-repelling and ladybug-attracting activities. However, whether 3e can attract hoverflies remains unknown. Therefore, this study explored the attractant property and potential mechanism of 3e toward hoverflies. Laboratory bioassays and field trials indicated 3e has an obvious hoverfly attracting property. The attraction mechanism studies demonstrate that, similar to EBF, 3e can interact with EcorOBP15 and EcorOR3, with its greater chemical softness, larger hydrophobic and charge regions enhancing these interactions. Furthermore, 3e exhibited low toxicity to honeybees (Apis mellifera) and hoverflies (Eupeodes corollae). Consequently, 3e could be a promising eco-friendly behavioral regulator for integrated aphid management in sustainable agriculture.

Synthesis and modification of novel thiazole-fused quinoxalines as new insecticidal agents against the cotton leafworm Spodoptera litura: design, characterization, in vivo bio-evaluation, toxicological effectiveness, and study their mode of action

Herein, novel thiazolo[4,5-b]quinoxalin-2-ones 2-6 and thiazolo[4,5-b]quinoxalin-2(3H)-imines 7-9 were synthesized and characterized using elemental analysis, IR spectroscopy, and 1H/13C NMR to confirm their structures. The efficacy of the newly designed thiazolo-quinoxalines 2, 3, 4, 5, 7, 8, and 9 against the cotton leafworm S. litura (2nd and 4th instar larvae) was evaluated, and results revealed insecticidal activity with variable and good mortality percentages. A SAR study was also discussed. Additionally, compound 3 exhibited the highest insecticidal activity, with mortality% values ranging from 86% ± 7.21% to 97% ± 1.52% and from 66.00% ± 6.24% to 86.33% ± 6.90% at concentrations of 625-2500 mg L-1 against the 2nd and 4th instar larvae, respectively. The probit analysis revealed that the thiazolo[4,5-b]quinoxalin-2(3H)-one derivative 3, after 5 days of treatment, exhibited LC50 values of 141.02 and 366.73 mg L-1 for the 2nd and 4th instar larvae, respectively. The LT50 values ranged from 0.52 to 1.92 days for the 2nd larval instar and from 1.95 to 2.47 days for the 4th larval instar. The corresponding toxicity index (TI) values were 86.21% for the 2nd instar and 78.47% for the 4th instar larvae. The mode of action of compound 3 was assessed through physiological, histological, and SEM analyses on the 4th larval instar. The physiological bioassay revealed a significant increase in total carbohydrate and protein levels compared to the control group. However, the enzymatic study showed a significant decrease (P < 0.05) in the levels of aspartate aminotransferase (AST/GOT), alanine aminotransferase (ALT/GPT), and alkaline phosphatase (AlP), while acetylcholinesterase (AChE) levels significantly increased. SEM analysis revealed malformations in the external body, while histological examination demonstrated severe damage to the gut epithelium and regenerative cells in the midgut tissues.

Design, Synthesis, and Antimicrobial Activity Evaluation of Novel Isocryptolepine Derivatives against Phytopathogenic Fungi and Bacteria

This research adopted the Fischer indole synthesis method to continue constructing a novel drug-like chemical entity based on the guidance of isocryptolepine and obtained four series of derivatives: Y, Da, Db, and Dc. The antimicrobial activity of these derivatives against plant pathogens was further evaluated. The results showed that Dc-2 had the best antifungal effect against Botrytis cinerea, and its EC50 value was up to 1.29 μg/mL. In addition, an in vivo activity test showed that the protective effect of Dc-2 on apples was 82.2% at 200 μg/mL, which was better than that of Pyrimethanil (45.4%). Meanwhile, it was found by scanning electron microscopy and transmission electron microscopy that the compound Dc-2 affected the morphology of mycelia. The compound Dc-2 was found to damage the cell membrane by PI and ROS staining. Through experiments such as leakage of cell contents, it was found that the compound Dc-2 changed the permeability of the cell membrane and caused the leakage of substances in the cell. According to the above studies, compound Dc-2 can be used as a candidate lead compound for further structural optimization and development.

Continuous operation of nano-catalytic ozonation using membrane separation coupling system: Influence factors and mechanism

The application of nano-catalysts in improving the ozonation removal efficiency for refractory organic compounds has been extensively investigated. However, cost-effective nano-catalysts separation remains a challenge. In this study, membrane separation processes were employed to separate nano-MgO catalysts from an ozonation system. A continuous nano-catalytic ozonation membrane separation (nCOMS) coupling system was successfully constructed for treating quinoline. The results showed that long hydraulic retention time (HRT) and high nano-MgO dosage could improve the quinolone removal efficiency but shorten operation cycles. At the optimal operation conditions of HRT = 4 h and nano-MgO dosage = 0.2 g/L, the nCOMS system achieved a stable quinoline removal efficiency of 85.2% for 240 min running with a transmembrane pressure lower than 10 kPa. The quinoline removal efficiency contribution for ozonation, catalysis and membrane separation was 57.1%, 24.9% and 18.0%, respectively. Compared to ozonation membrane separation system, the fouling rate index of the nCOMS system increased by 60% under optimal conditions, but the irreversible fouling was reduced to 28%. In addition, the nCOMS system exhibited reduced adverse effects of coexisting natural organic matter (NOM) on quinoline removal and membrane fouling. In conclusion, the nCOMS system demonstrated higher quinoline removal efficiency, lower irreversible fouling, and reduced adverse effect of coexisting NOM, thereby signifying its potential for practical applications in advanced treatment of industrial wastewater.

Novel Insecticidal Butenolide-Containing Methylxanthine Derivatives: Synthesis, Crystal Structure, Biological Activity Evaluation, DFT Calculation and Molecular Docking

The design of novel agrochemicals starting from bioactive natural products is one of the most effective ways in the discovery and development of new pesticidal agents. In this paper, a series of novel butenolide-containing methylxanthine derivatives (Ia-Ir) were designed based on natural methylxanthine caffeine and stemofoline, and the derivatized insecticide flupyradifurone of the latter. The structures of the synthesized compounds were confirmed via 1H-NMR, 13C NMR, HRMS and X-ray single crystal diffraction analyses. The biological activities of the compounds were evaluated against a variety of agricultural pests including oriental armyworm, bean aphid, diamondback moth, fall armyworm, cotton bollworm, and corn borer; the results indicated that some of them have favorable insecticidal potentials, particularly toward diamondback moth. Among others, Ic and Iq against diamondback moth possessed LC50 values of 6.187 mg ⋅ L-1 and 3.269 mg ⋅ L-1, respectively, - 2.5- and 4.8-fold of relative insecticidal activity respectively to that of flupyradifurone (LC50=15.743 mg ⋅ L-1). Additionally, both the DFT theoretical calculation and molecular docking with acetylcholine binding protein were conducted for the highly bioactive compound (Ic). Ic and Iq derived from the integration of caffeine (natural methylxanthine) and butenolide motifs can serve as novel leading insecticidal compounds for further optimization.

Design, Synthesis, and 3D-QASR of 2-Ar-1,2,3-triazole Derivatives Containing Hydrazide as Potential Fungicides

A series of novel 2-Ar-1,2,3-triazole derivatives were designed and synthesized based on our previously discovered active compound 6d against Rhizoctonia solani. Most of these compounds exhibited good antifungal activity against R. solani at a concentration of 25 μg/mL. Based on the results of biological activity, we established a three-dimensional quantitative structure-activity relationship (3D-QSAR) model that guided the synthesis of compound 7y. Compound 7y exhibited superior activity against R. solani (EC50 = 0.47 μg/mL) compared to the positive controls hymexazol (EC50 = 12.80 μg/mL) and tebuconazole (EC50 = 0.87 μg/mL). Furthermore, compound 7y demonstrated better protective activity than the aforementioned two commercial fungicides in both detached leaf assays and greenhouse experiments, achieving 56.21% and 65.75% protective efficacy, respectively, at a concentration of 100 μg/mL. The ergosterol content was determined and molecular docking was performed to explore the mechanism of these active molecules. DFT calculation and MEP analysis were performed to illustrate the results of this study. These results suggest that compound 7y could serve as a novel 2-Ar-1,2,3-triazole lead compound for controlling R. solani.

Novel Pyrazole-4-Carboxamide Derivatives Containing Oxime Ether Group as Potential SDHIs to Control Rhizoctonia solani

In the search for novel succinate dehydrogenase inhibitor (SDHI) fungicides to control Rhizoctonia solani, thirty-five novel pyrazole-4-carboxamides bearing either an oxime ether or an oxime ester group were designed and prepared based on the strategy of molecular hybridization, and their antifungal activities against five plant pathogenic fungi were also investigated. The results indicated that the majority of the compounds containing oxime ether demonstrated outstanding in vitro antifungal activity against R. solani, and some compounds also displayed pronounced antifungal activities against Sclerotinia sclerotiorum and Botrytis cinerea. Particularly, compound 5e exhibited the most promising antifungal activity against R. solani with an EC50 value of 0.039 μg/mL, which was about 20-fold better than that of boscalid (EC50 = 0.799 μg/mL) and 4-fold more potent than fluxapyroxad (EC50 = 0.131 μg/mL). Moreover, the results of the detached leaf assay showed that compound 5e could suppress the growth of R. solani in rice leaves with significant protective efficacies (86.8%) at 100 μg/mL, superior to boscalid (68.1%) and fluxapyroxad (80.6%), indicating promising application prospects. In addition, the succinate dehydrogenase (SDH) enzymatic inhibition assay revealed that compound 5e generated remarkable SDH inhibition (IC50 = 2.04 μM), which was obviously more potent than those of boscalid (IC50 = 7.92 μM) and fluxapyroxad (IC50 = 6.15 μM). Furthermore, SEM analysis showed that compound 5e caused a remarkable disruption to the characteristic structure and morphology of R. solani hyphae, resulting in significant damage. The molecular docking analysis demonstrated that compound 5e could fit into the identical binding pocket of SDH through hydrogen bond interactions as well as fluxapyroxad, indicating that they had a similar antifungal mechanism. The density functional theory and electrostatic potential calculations provided useful information regarding electron distribution and electron transfer, which contributed to understanding the structural features and antifungal mechanism of the lead compound. These findings suggested that compound 5e could be a promising candidate for SDHI fungicides to control R. solani, warranting further investigation.

(NH4)2S2O8 promoted tandem radical cyclization of quinazolin-4(3H)-ones with oxamic acids for the construction of fused quinazolinones under metal-free conditions

A novel cascade radical addition/cyclization reaction of non-activated olefins and oxamic acids has been proposed. Under transition metal-free conditions, 36 quinazolinone derivatives containing an amide moiety were successfully synthesized, with the highest yield being 81%. This method involves the preparation of aminoacyl fused quinazolinone derivatives under mild conditions, offering advantages such as a high yield, a broad substrate compatibility, and a high atom economy.

Sodium sulfide-promoted regiodefined redox condensation of o-nitroanilines with aryl ketones to benzo[a]phenazines and quinoxalines

Inexpensive sodium sulfide trihydrate was found to promote unprecedented 6e-regio-predefined redox condensation of o-nitroanilines with α-tetralones to benzo[a]phenazines. The method was also successfully extended to acetophenones and higher homologs as reducing partners to provide 2-phenylquinoxalines. Compared to traditional approaches toward benzo[a]phenazine and quinoxaline cores starting with o-phenylenediamines, the present strategy could afford these heterocycles with well-defined regiochemistry based on the structure of starting o-nitroanilines.

Recent Methods for the Synthesis of Quinoxaline Derivatives and their Biological Activities

Quinoxaline derivatives have been incorporated into numerous marketed drugs used for the treatment of various diseases. Examples include glecaprevir (Mavyret), voxilaprevir (Vosevi), Balversa (L01EX16) (erdafitinib), carbadox, XK469R (NSC698215), and becampanel (AMP397). These quinoxaline derivatives exhibit a diverse range of pharmacological activities, including antibacterial, antitubercular, antiviral, anti-HIV, anti-inflammatory, antifungal, anticancer, antiproliferative, antitumor, kinase inhibition, antimicrobial, antioxidant, and analgesic effects. Recognizing the significance of these bioactive quinoxaline derivatives, researchers have dedicated their efforts to developing various synthetic methods for their production. This review aimed to compile the most recent findings on the synthesis and biological properties of quinoxaline derivatives from 2015 to 2023.

Synthesis, Herbicidal Activity, Mode of Action, and In Silico Analysis of Novel Pyrido[2,3-d]pyrimidine Compounds

Natural products are a main source of new chemical entities for use in drug and pesticide discovery. In order to discover lead compounds with high herbicidal activity, a series of new pyrido[2,3-d] pyrimidine derivatives were designed and synthesized using 2-chloronicotinic acid as the starting material. Their structures were characterized with 1H NMR, 13C NMR and HRMS, and the herbicidal activities against dicotyledonous lettuce (Lactuca sativa), field mustard (Brassica campestris), monocotyledonous bentgrass (Agrostis stolonifera) and wheat (Triticum aestivum) were determined. The results indicated that most of the pyrido[2,3-d] pyrimidine derivatives had no marked inhibitory effect on lettuce at 1 mM. However, most of the pyrido[2,3-d] pyrimidine derivatives possessed good activity against bentgrass at 1 mM. Among them, the most active compound, 3-methyl-1-(2,3,4-trifluorophenyl)pyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione (2o), was as active as the positive controls, the commercial herbicides clomazone and flumioxazin. Molecular simulation was performed with molecular docking and DFT calculations. The docking studies provided strong evidence that 2o acts as an herbicide by inhibition of protoporphyrinogen oxidase. However, the physiological results indicate that it does not act on this target in vivo, implying that it could be metabolically converted to a compound with a different molecular target.

Facile synthesis, crystal structure, quantum calculation, and biological evaluations of novel selenenyl sulfide compounds as potential agrochemicals

BACKGROUND

In order to design compounds with fresh molecular skeleton to break through the limitation of available agrochemicals, a series of 36 novel selenenyl sulfide compounds were chemically synthesized, and their biological activities were fully evaluated against tobacco mosaic virus (TMV), 14 plant pathogenic fungi, three insect species and plant acetohydroxyacid synthase (AHAS).

RESULTS

All the target compounds were characterized by proton nuclear magnetic resonance (¹ H-NMR), carbon-13 (¹³ C)-NMR, selenium-77 (⁷⁷ Se)-NMR, and high-resolution mass spectrometry (HRMS). The crystal structure of 10j indicated that the Se-S bond was successfully constructed. Compounds 10d, 10h, 10s, 10u, 10aa, 10ac, 10ae, 10ag, and 10ai exhibited 40%, 43%, 39%, 41%, 47%, 46%, 47%, 42%, and 39% anti-TMV activities at 500 mg L^-1 , better than that of ribavirin. The median effective concentration (EC₅₀ ) against Sclerotinia sclerotiorum of 10ac was 6.69 mg L^-1 and EC₅₀ values against Physalospora piricola and Pyricularia grisea of 10z were 12.25 mg L^-1 and 15.27 mg L^-1 , respectively, superior to the corresponding values of chlorothalonil. Compounds 10c and 10v demonstrated 100% larvicidal activity against Culex pipiens pallens at 5 mg L^-1 , while 10a displayed 100% insecticidal activity against Mythimna separata at 200 mg L^-1 . Compounds 10c, 10j, and 10o showed > 60% inhibitions against plant AHAS at 10 μmol L^-1 . From the quantum calculation, highest occupied molecular orbital (HOMO) was considered as a factor that affects the anti-TMV activity.

CONCLUSION

The preliminary results suggested that more efforts should be devoted to exploring the selenenyl sulfides for the discovery of new leads of antiviral agent, fungicide, insecticide or AHAS inhibitors as potential agrochemicals for crop protection. © 2023 Society of Chemical Industry.

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.

Novel Sulfonylurea Derivatives as Potential Antimicrobial Agents: Chemical Synthesis, Biological Evaluation, and Computational Study

Methicillin-resistant Staphylococcus aureus (MRSA) is a worldwide health threat and has already tormented humanity during its long history, creating an urgent need for the development of new classes of antibacterial agents. In this study, twenty-one novel sulfonylurea derivatives containing phenyl-5-vinyl and pyrimidinyl-4-aryl moieties were designed and synthesized, among which, nine compounds exhibited inhibitory potencies against Gram-positive bacterial strains: MRSA (Chaoyang clinical isolates), S. aureus ATCC6538, vancomycin-resistant Enterococci-309 (VRE-309), and Bacillus subtilis ATCC 6633. Especially, 9i and 9q demonstrated inhibitory activities against the four bacterial strains with minimum inhibitory concentrations (MICs) of 0.78-1.56 μg/mL, and quite a few of other MRSA clinical strains with MICs of 0.78 μg/mL, superior to those of the positive controls vancomycin (MIC of 1 μg/mL) and methicillin (MIC of >200 μg/mL). This is the very first time that sulfonylurea derivatives have been identified as promising inhibitors against different MRSA clinical isolates. In addition, all the MIC values of the synthesized compounds against Candida albicans were greater than 100 μg/mL. Since the reported anti-Candida activities of sulfonylureas were due to acetohydroxyacid synthase (AHAS) inhibition, the molecular target against MRSA for the target sulfonylureas was thought to be a different mode of action. Density functional theory (DFT) calculations were finally performed to understand the structure-activity relationships, based on which, significant differences were observed between their HOMO maps for compounds with strong antibacterial activities and weak anti-MRSA effects. The present results hence provide valuable guidance for the discovery of novel agents to treat bacterial infections, especially against MRSA.

Sustainable synthesis of azobenzenes, quinolines and quinoxalines via oxidative dehydrogenative couplings catalysed by reusable transition metal oxide–Bi(iii) cooperative catalysts

Heterogeneous catalytic oxidative dehydrogenative processes for N-heterocycles are presented, which enable waste-minimized (additive-, oxidant-, base-free), efficient cyclisations/couplings via transition metal oxide–Bi(iii) cooperative catalysis.

Synthesis and Pesticidal Activity of New Niacinamide Derivatives Containing a Flexible, Chiral Chain

Natural products are a source for pesticide or drug discovery. In order to discover lead compounds with high fungicidal or herbicidal activity, new niacinamide derivatives derived from the natural product niacinamide, containing chiral flexible chains, were designed and synthesized. Their structures were confirmed by ¹H NMR, ¹³C NMR and HRMS analysis. The fungicidal and herbicidal activities of these compounds were tested. The fungicidal activity results demonstrated that the compound (S)-2-(2-chloronicotinamido)propyl-2-methylbenzoate (3i) exhibited good fungicidal activity (92.3% inhibition) against the plant pathogen Botryosphaeria berengriana at 50 μg/mL and with an EC₅₀ of 6.68 ± 0.72 μg/mL, which is the same as the positive control (fluxapyroxad). Compound 3i was not phytotoxic and could therefore be used as a fungicide on crops. Structure-activity relationships (SAR) were studied by molecular docking simulations with the succinate dehydrogenase of the fungal mitochondrial respiratory chain.

Comprehensive Overview of β-Methoxyacrylate Derivatives as Cytochrome bc1 Inhibitors for Novel Pesticide Discovery

β-Methoxyacrylate derivatives represent a new class of pesticides, which have attracted increasing attention owing to their unique structure, broad biological activity, and unique mechanisms of action. They inhibit mitochondrial respiration via preventing electron transfer at the Qo site of the cytochrome bc₁ complex and thus are identified as cyt bc₁ inhibitors. A variety of β-methoxyacrylate derivatives have been reported by many research groups for discovery of novel pesticides with improved expected activities. This review focuses on development of β-methoxyacrylate derivatives with great significance as pesticides such as fungicides, acaricides, insecticides, herbicides, and antiviral agents. In addition, the structure-activity relationships (SARs) of β-methoxyacrylate derivatives are summarized. Moreover, the cause of resistance to β-methoxyacrylate fungicides and some solutions are also introduced. Finally, the development trend of β-methoxyacrylate derivatives as pesticides is explored. We hope the review will give a guide to develop novel β-methoxyacrylate pesticides in the future.

Convenient Synthesis of N-Heterocycle-Fused Tetrahydro-1,4-diazepinones

A general approach towards the synthesis of tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepin-4-one, tetrahydro[1,4]diazepino[1,2-a]indol-1-one and tetrahydro-1H-benzo[4,5]imidazo[1,2-a][1,4]diazepin-1-one derivatives was introduced. A regioselective strategy was developed for synthesizing ethyl 1-(oxiran-2-ylmethyl)-1H-pyrazole-5-carboxylates from easily accessible 3(5)-aryl- or methyl-1H-pyrazole-5(3)-carboxylates. Obtained intermediates were further treated with amines resulting in oxirane ring-opening and direct cyclisation-yielding target pyrazolo[1,5-a][1,4]diazepin-4-ones. A straightforward two-step synthetic approach was applied to expand the current study and successfully functionalize ethyl 1H-indole- and ethyl 1H-benzo[d]imidazole-2-carboxylates. The structures of fused heterocyclic compounds were confirmed by ¹H, ¹³C, and ¹⁵N-NMR spectroscopy and HRMS investigation.

Synthesis, crystal structure, herbicidal activity and mode of action of new cyclopropane-1,1-dicarboxylic acid analogues

A new series of cyclopropane-1,1-dicarboxylic (CPD) acid analogues were designed and synthesized. CPD is an inhibitor of ketol-acid reductoisomerase (KARI), an enzyme of the branched chain amino acid pathway in plants. The structures of CPD analogues were characterized by ¹H NMR and HRMS. The structure of N,N'-bis(4-(tert-butyl)phenyl)cyclopropane-1,1-dicarboxamide was further elucidated by X-ray diffraction. The herbicidal activities of these compounds were tested against lettuce (Lactuca sativa) and bentgrass (Agrostis stolonifera). Most of these compounds exhibited low herbicidal activity against both plant species. Among them, N,N'-bis(2-ethylphenyl)cyclopropane-1,1-dicarboxamide displayed moderate activity against bentgrass. Inhibition of KARI activity by the CPD analogues was also assessed experimentally and by molecular docking simulation with results supporting inhibition of KARI as their mode of action. These results provide the basis for design of more effective KARI inhibitors.

Synthesis of Novel α-Trifluoroanisole Derivatives Containing Phenylpyridine Moieties with Herbicidal Activity

To find novel herbicidal compounds with high activity and broad spectrum, a series of phenylpyridine moiety-containing α-trifluoroanisole derivatives were designed, synthesized, and identified via nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). Greenhouse-based herbicidal activity assays revealed that compound 7a exhibited > 80% inhibitory activity against Abutilon theophrasti, Amaranthus retroflexus, Eclipta prostrate, Digitaria sanguinalis, and Setaria viridis at a dose of 37.5 g a.i./hm2, which was better than fomesafen. Compound 7a further exhibited excellent herbicidal activity against Abutilon theophrasti and Amaranthus retroflexus in this greenhouse setting, with respective median effective dose (ED50) values of 13.32 and 5.48 g a.i./hm2, both of which were slightly superior to fomesafen (ED50 = 36.39, 10.09 g a.i./hm2). The respective half-maximal inhibitory concentration (IC50) for compound 7a and fomesafen when used to inhibit the Nicotiana tabacum protoporphyrinogen oxidase (NtPPO) enzyme, were 9.4 and 110.5 nM. The docking result of compound 7a indicated that the introduction of 3-chloro-5-trifluoromethylpyridine and the trifluoromethoxy group was beneficial to the formation of stable interactions between these compounds and NtPPO. This work demonstrated that compound 7a could be further optimized as a PPO herbicide candidate to control various weeds.

Synthesis, Structure, and Antifungal Activities of 3-(Difluoromethyl)-Pyrazole-4-Carboxylic Oxime Ester Derivatives

Fifteen new pyrazole-4-carboxylic oxime ester derivatives were conveniently synthesized, and their structures were confirmed by 1H NMR, 13C NMR, HRMS, and X-ray diffraction. Antifungal assays indicated that some of these compounds possessed good activity against S. sclerotiorum, B. cinerea, R. solani, P. oryae, and P. piricola at 50 ppm. Structure-activity relationships (SAR) were studied by molecular docking simulation.

Green Design, Synthesis, and Molecular Docking Study of Novel Quinoxaline Derivatives with Insecticidal Potential against Aphis craccivora

An efficient and environmentally friendly method was established for designing novel 3-amino-1,4-dihydroquinoxaline-2-carbonitrile (1) via the reaction of bromomalononitrile and benzene-1,2-diamine under microwave irradiation in an excellent yield (93%). This targeted amino derivative was utilized for the construction of a series of Schiff bases (8-13). A new series of thiazolidinone derivatives (15-20) were synthesized in high yields (89-96%) via treatment of thioglycolic acid with Schiff bases (8-13) under microwave irradiation in high yields (89-96%). Moreover, new pyrimidine derivatives (26-30 and 35-38) were prepared by treatment of compound 1 with arylidenes (21-25) and/or alkylidenemalononitriles (31-34) using piperidine as a basic catalyst under microwave conditions. Based on elemental analyses and spectral data, the structures of the new assembled compounds were determined. The newly synthesized quinoxaline derivatives were screened and studied as an insecticidal agent against Aphis craccivora. The obtained results indicate that compound 16 is the most toxicological agent against nymphs of cowpea aphids (Aphis craccivora) compared to the other synthesized pyrimidine and thiazolidinone derivatives. The molecular docking study of the new quinoxaline derivatives registered that compound 16 had the highest binding score (-10.54 kcal/mol) and the thiazolidinone moiety formed hydrogen bonds with Trp143.

Design, Synthesis, and Antifungal Activities of Hymexazol Glycosides Based on a Biomimetic Strategy

Hymexazol (HYM) is irreplaceable for treating soil-borne diseases due to its high efficiency and low cost, as a broad-spectrum fungicide. However, when HYM is absorbed by plants, it is rapidly converted into two glycoside metabolites, and the antifungal activities of these glycosides are inferior to that of HYM. Therefore, in this study, to maintain strong antifungal activity in vitro and in vivo, HYM was glycosylated with amino sugars that have diverse biological activities to simulate plant glycosylation. The antifungal experiment proved that glycoside 15 has the highest antifungal activity, and N-acetyl glucosamine and HYM had obvious synergistic effects. According to the structure-activity relationship studies, glycoside 15 had greater numbers of active electron-rich regions and front-line orbital electrons due to the introduction of N-acetyl glucosamine. Moreover, glycoside 15 can significantly promote plant growth and induce an increase in plant defense enzyme activity. Additionally, compared to HYM, the results of electron microscopy and proteomics revealed that glycoside 15 has a unique antifungal mechanism. The promising antifungal activity and interactions with plants mean that glycoside 15 is a potential green fungicide candidate. Furthermore, this research conducted an interesting exploration of the agricultural applications of amino sugars.

Chemical synthesis, biological activities, and molecular simulations of novel sulfonylurea compounds bearing ortho-alkoxy substitutions

A series of 51 novel sulfonylurea compounds with ortho-alkoxy substituent at phenyl ring were chemically synthesized and spectroscopically characterized. The biological activities of the target compounds were evaluated using the enzyme inhibition against acetohydroxyacid synthase (AHAS; EC 2.2.1.6) from fungal or plant source, as well as cell-based antifungal assay and greenhouse pot herbicidal assay. Among the target compounds, 6e showed desirable antifungal activity against Candida albicans standard isolate sc5314 with minimum inhibition concentration (MIC) of 0.39 mg/L (0.98 μM) after 24 h, and 6a demonstrated promising pre-emergence herbicidal activity against Echinochloacrus-galli at 30 g/ha dosage. Representative compounds 6a, 6e, and 6i showed no cell cytotoxicity even at 40 mg/L concentration. Theoretical DFT calculations indicated HOMO maps should be considered to understand the structure-activity relationships. The present study has hence provided useful information for further discovery of novel antifungal agents or selective herbicides.

Design, Synthesis, and Molecular Docking Studies of Some New Quinoxaline Derivatives as EGFR Targeting Agents

The synthesis of some new quinoxaline derivatives (IVa-n) and their structure determination using 1H NMR, 13C NMR and mass spectral analysis was described herein. The in vitro anti-cancer activity of the these compounds (IVa-n) revealed that the compound1-((1-(4-bromophenyl)-1H-1,2,3-triazol-4-yl)methyl)-2-(tetrazolo[1,5-a]quinoxalin-4-yl)pyrazolidine-3,5-dione (IVd) has shown promising activity, whereas, compounds 1-((1-phenyl-1H-1,2,3-triazol-4-yl)methyl)-2-(tetrazolo[1,5-a]quinoxalin-4-yl)pyrazolidine-3,5-dione (IVa), 1-(tetrazolo[1,5-a]quinoxalin-4-yl)-2-((1-(m-tolyl)-1H-1,2,3-triazol-4-yl)methyl)pyrazolidine-3,5-dione (IVb), 1-((1-(3,5-dimethoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)-2-(tetrazolo[1,5-a]quinoxalin-4-yl)pyrazolidine-3,5-dione (IVh) and 1-((1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)methyl)-2-(tetrazolo[1,5-a]quinoxalin-4-yl)pyrazolidine-3,5-dione (IVi) exhibited good to moderate activity against four human cancer cell lines such as HeLa, MCF-7, HEK 293T, and A549 as compared to the doxorubicin. Predominantly, the compound displayed excellent activity over HeLa, MCF-7, HEK 293T, and A549 with IC50 values of 3.20 ± 1.32, 4.19 ± 1.87, 3.59 ± 1.34, and 5.29 ± 1.34 μM, respectively. Moreover, molecular docking studies of derivatives (IVa-n) on EGFR receptor suggested that the most potent compound strongly binds to protein EGFR (pdbid:4HJO) and the energy calculations of in silico studies were also in good agreement with the obtained IC50 values.

Supplementary Information

The online version contains supplementary material available at 10.1134/S1068162022030220.

Benzamides Substituted with Quinoline-Linked 1,2,4-Oxadiazole: Synthesis, Biological Activity and Toxicity to Zebrafish Embryo

To develop new compounds with high activity, broad spectrum and low-toxicity, 17 benzamides substituted with quinoline-linked 1,2,4-oxadiazole were designed using the splicing principle of active substructures and were synthesized. The biological activities were evaluated against 10 fungi, indicating that some of the synthetic compounds showed excellent fungicidal activities. For example, at 50 mg/L, the inhibitory activity of 13p (3-Cl-4-Cl substituted, 86.1%) against Sclerotinia sclerotiorum was superior to that of quinoxyfen (77.8%), and the inhibitory activity of 13f (3-CF₃ substituted, 77.8%) was comparable to that of quinoxyfen. The fungicidal activities of 13f and 13p to Sclerotinia sclerotiorum were better than that of quinoxyfen (14.19 mg/L), with EC₅₀ of 6.67 mg/L and 5.17 mg/L, respectively. Furthermore, the acute toxicity of 13p was 19.42 mg/L, classifying it as a low-toxic compound.

Synthesis, Anti-Potato Virus Y Activities, and Interaction Mechanisms of Novel Quinoxaline Derivatives Bearing Dithioacetal Moiety

Quinoxaline and its derivatives are important functional molecules with a broad range of applications. Disclosed here is a design and synthesis of a series of novel quinoxaline derivatives containing dithioacetal moieties as well as their antiviral activities against potato virus Y (PVY). The compound D30 was developed on the basis of the three-dimensional quantitative structure-activity relationship. The anti-PVY activity test showed that the half maximal effective concentration of the anti-PVY protective activity of compound D30 is 197 μg/mL, which was better than the control agents ningnanmycin (423 μg/mL) and xiangcaoliusuobingmi (281 μg/mL). Significantly, compound D30 can increase defense enzyme activity and chlorophyll content, promote photosynthesis by accelerating carbon fixation in tobacco, and further improve plant disease resistance. All of these results suggest that compound D30 could be employed as a lead compound for novel PVY inhibitor discovery.

Discovery of evodiamine derivatives as potent insecticide candidates

In the search for novel more effective insecticides, natural products could be used as ideal template compounds due to their good environmental compatibility, various bioactivities, unique scaffolds and mode of action. We have found that natural product evodiamine, the main active component from the fruits of Evodia rutaecarpa (Juss.) Benth, displayed obvious insecticidal activities against lepidoptera pests. To continue our research, a series of evodiamine derivatives 3a-3aa were rationally designed and synthesized. The larvicidal activities results indicated that most of target compounds displayed better efficacy than evodiamine, matrine, and rotenone against Mythimna separata, Plutella xylostella and Helicoverpa armigera, among which 3z exhibited excellent larvicidal activities (65% at 2.5 mg/L against M. separata, 75% at 1.0 mg/L against P. xylostella, and 85% 10 mg/L against H. armigera, respectively), much better than evodiamine (0%), matrine (0%), and rotenone (0%). The preliminary structure activity relationships demonstrated that the fluorine atom at the E ring of evodiamine had a positive influence on the larvicidal activity. The calcium imaging experiment studies indicated that 3z could act on the ryanodine receptor (RyR) of M. separata and was an effective calcium activator for RyR.

Synthesis of cinnamils and quinoxalines and their biological evaluation as anticancer agents

We synthesized multiple cinnamils and quinoxalines to evaluate their anticancer activity. Cinnamils were used as precursors for quinoxalines via condensation with 1,2-diaminobenzene. Among the 26 synthesized compounds reported in this article, we found that cinnamil 3l exhibited its inhibitory effect with an IC50 value of 1.45 ± 0.98 μM, significantly higher than doxorubicin (8.5 ± 0.85 μM) against pancreatic cancer cells (PANC-1). Additionally, cinnamil 3l (IC50 10.98 ± 3.63 μM) showed less cytotoxicity than doxorubicin to Hs68 cells (0.92 ± 1.11 μM). The colony formation assay demonstrated that 3l obviously decreased the PANC-1 cell viability, and Western blot assays confirmed that 3l markedly induced apoptosis of PANC-1 cells through Bax, Bcl-2, and caspase 3 signaling cascades. These results demonstrate that cinnamil 3l has great potential to be further developed as a promising chemotherapeutic agent for pancreatic cancer.

Functionalized quinoxalinones as privileged structures with broad-ranging pharmacological activities

Quinoxalinones are a class of heterocyclic compounds which attract extensive attention owing to their potential in the field of organic synthesis and medicinal chemistry. During the past few decades, many new synthetic strategies toward the functionalization of quinoxalinone based scaffolds have been witnessed. Regrettably, there are only a few reports on the pharmacological activities of quinoxalinone scaffolds from a medicinal chemistry perspective. Therefore, herein we intend to outline the applications of multifunctional quinoxalinones as privileged structures possessing various biological activities, including anticancer, neuroprotective, antibacterial, antiviral, antiparasitic, anti-inflammatory, antiallergic, anti-cardiovascular, anti-diabetes, antioxidation, etc. We hope that this review will facilitate the development of quinoxalinone derivatives in medicinal chemistry.

Synthesis and evaluation of novel 1-(((6-substitutedbenzo[d]thiazol-2-yl)amino)(heteroaryl)methyl)naphthalen-2-ol as pesticidal agents

To discover new agrochemicals with prominent pesticidal properties, a series of novel β-naphthol derivatives containing benzothiazolylamino and various heteroaryl groups (8a-q) were efficiently synthesised via Betti reaction. The bioassay results showed that most of the synthesised compounds exhibited favourable insecticidal potentials, particularly towards oriental armyworm (50–100% at 200 mg·L⁻¹) and diamondback moth (50–95% at 10 mg·L⁻¹). Compounds 8 b, 8f, 8 g, 8j, 8k, 8n, and 8o possessed LC₅₀ values of 0.0988–5.8864 mg·L⁻¹ against diamondback moth. Compounds 8i, 8 l, and 8 m also displayed lethality rates of 30–90% against spider mite at the concentration of 100 mg·L⁻¹. Overall, some compounds could be considered as new insecticidal/acaricidal leading structures for further investigation. The calcium imaging experiments revealed that 8 h, 8i, and viii could activate the release of calcium ions in insect (M. separata) central neurons at a higher concentration (50 mg·L⁻¹). The SAR analysis provided valuable information for further structural modifications.

Sulfur–DMSO promoted oxidative coupling of active methylhetarenes with amines: access to amides

The sulfur–DMSO couple was found to promote the coupling of active methylhetarenes with amines to yield amides under heating conditions. When 2-methylquinoline was used as the methylhetarene component, the reaction could be catalyzed by Fe, Co and Ni salts.

Discovery of a Potent Thieno[2,3-d]pyrimidine-2,4-dione-Based Protoporphyrinogen IX Oxidase Inhibitor through an In Silico Structure-Guided Optimization Approach

A key objective for herbicide research is to develop new compounds with improved bioactivity. Protoporphyrinogen IX oxidase (PPO) is an essential target for herbicide discovery. Here, we report using an in silico structure-guided optimization approach of our previous lead compound 1 and designed and synthesized a new series of compounds 2-6. Systematic bioassays led to the discovery of a highly potent compound 6g, 1-methyl-3-(2,2,7-trifluoro-3-oxo-4-(prop-2-yn-1-yl)-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione, which exhibited an excellent and wide spectrum of weed control at the rates of 30-75 g ai/ha by the postemergence application and is relatively safe on maize at 75 g ai/ha. Additionally, the K_i value of 6g to Nicotiana tabacum PPO (NtPPO) was found to be 2.5 nM, showing 3-, 12-, and 18-fold higher potency relative to compound 1 (K_i = 7.4 nM), trifludimoxazin (K_i = 31 nM), and flumioxazin (K_i = 46 nM), respectively. Furthermore, molecular simulations further suggested that the thieno[2,3-d]pyrimidine-2,4-dione moiety of 6g could form a more favorable π-π stacking interaction with the Phe392 of NtPPO than the heterocyclic moiety of compound 1. This study provides an effective strategy to obtain enzyme inhibitors with improved performance through molecular simulation and structure-guided optimization.

Synthesis, Fungicidal Activity, and Mechanism of Action of Pyrazole Amide and Ester Derivatives Based on Natural Products l-Serine and Waltherione Alkaloids

The development of new green fungicides based on the structural optimization of natural products can effectively solve the problems of low safety and high pathogen resistance of traditional fungicides. In this paper, based on pyrazole amide compound h-I-9 with excellent fungicidal activity discovered in the previous work, a series of l-serine-derived pyrazole amide and waltherione alkaloid-derived pyrazole ester derivatives were synthesized. The structures were successively identified by ¹H NMR, ¹³C NMR, high-resolution mass spectrometry, and X-ray single-crystal diffraction. The in vitro and in vivo fungicidal activity screening demonstrated that compound II-5 showed a good inhibition rate against Physalospora piricola. A transmission electron microscope and fluorescence microscope observation further revealed that compound II-5 may cause damage to the cell membranes and vacuoles, and the hyphae treated with II-5 could produce obvious and easily observed blue fluorescence. The succinate dehydrogenase (SDH) enzymatic activity and molecular docking simulation indicated that compounds I-3 and I-4 may be potential SDH inhibitors against Alternaria sp.

Design, Synthesis and Biological Evaluation of Novel Thienylpyridyl- and Thioether-Containing Acetamides and Their Derivatives as Pesticidal Agents

Referring to the structural information of the "hit" compound A from the reported pharmacophore-based virtual screening, a series of novel thienylpyridyl- and thioether/sulfoxide/sulfone-containing acetamide derivatives have been designed and synthesized. The structures of new compounds were confirmed by 1H NMR, 13C NMR and HRMS. The single-crystal structure of A was firstly reported. All the new synthesized compounds were evaluated for insecticidal activities on Mythimna separata Walker and Plutella xylostella L. Through a step-by-step structural optimization, the high insecticidal agents, especially towards Plutella xylostella L., have been found, and thienylpyridyl- and sulfone/thioether-containing acetamides Iq, Io, Ib and A, which are comparable with the control insecticides cartap, triflumuron and chlorantraniliprole in the present study, can be used as novel lead structures for new insecticides innovation research. In addition, some of the compounds, e.g., A, Ih, Id, Io and Iq, also exhibited favourable fungicidal activities against Physalospora piricola, Rhizoctonia cerealis and Sclerotinia sclerotiorum and would provide useful guidance for the design and development of new fungicides.

Advances in Control Strategies against Spodoptera frugiperda. A Review

The strategies for controlling the insect pest Spodoptera frugiperda have been developing over the past four decades; however, the insecticide resistance and the remarkable adaptability of this insect have hindered its success. This review first analyzes the different chemical compounds currently available and the most promising options to control S. frugiperda. Then, we analyze the metabolites obtained from plant extracts with antifeedant, repellent, insecticide, or ovicide effects that could be environmentally friendly options for developing botanical S. frugiperda insecticides. Subsequently, we analyze the biological control based on the use of bacteria, viruses, fungi, and parasitoids against this pest. Finally, the use of sex pheromones to monitor this pest is analyzed. The advances reviewed could provide a wide panorama to guide the search for new pesticidal strategies but focused on environmental sustainability against S. frugiperda.

Discovery of ortho-Alkoxy Substituted Novel Sulfonylurea Compounds That Display Strong Herbicidal Activity against Monocotyledon Grasses

In the present study, we have designed and synthesized a series of 42 novel sulfonylurea compounds with ortho-alkoxy substitutions at the phenyl ring and evaluated their herbicidal activities. Some target compounds showed excellent herbicidal activity against monocotyledon weed species. When applied at 7.5 g ha^-1, 6-11 exhibited more potent herbicidal activity against barnyard grass (Echinochloa crus-galli) and crab grass (Digitaria sanguinalis) than commercial acetohydroxyacid synthase (AHAS; EC 2.2.1.6) inhibitors triasulfuron, penoxsulam, and nicosulfuron at both pre-emergence and postemergence conditions. 6-11 was safe for peanut for postemergence application at this ultralow dosage, suggesting that it could be considered a potential herbicide candidate for peanut fields. Although 6-11 and triasulfuron share similar chemical structures and have close K_i values for plant AHAS, a significant difference has been observed between their LUMO maps from DFT calculations, which might be a possible factor that leads to their different behaviors toward monocotyledon weed species.

Catalyst-free synthesis of novel 1,5-benzodiazepines and 3,4-dihydroquinoxalines using isocyanide-based one-pot, three- and four-component reactions

Reaction of benzimidazolone derivatives, or their thio- or aza-counterparts, with an isocyanide in the presence of acetone unexpectedly gave rise to novel tricyclic benzodiazepine derivatives in good yield by means of a four-component reaction incorporating two moles of acetone. Benzimidazole starting substrates bearing an electron-withdrawing group gave rise instead to dihydroquinoxaline derivatives by means of a three-component reaction. Use of deuterated acetone instead of acetone in the reactions significantly affected yield and reactivity in the four-component reaction but not in the three-component reaction.

Reaction of benzimidazole derivatives with an isocyanide and acetone led to tricyclic benzodiazepine derivatives or dihydroquinoxalines depending on the nature of the substituents R¹ and R².

Design, Synthesis, and Pesticidal Activities of Pyrimidin-4-amine Derivatives Bearing a 5-(Trifluoromethyl)-1,2,4-oxadiazole Moiety

It is important to discover new pesticides with new modes of action because of the increasing evolution of pesticide resistance. In this study, a series of novel pyrimidin-4-amine derivatives containing a 5-(trifluoromethyl)-1,2,4-oxadiazole moiety were designed and synthesized. Their structures were confirmed by ¹H NMR, ¹³C NMR, and HRMS. Bioassays indicated that the 29 compounds synthesized possessed excellent insecticidal activity against Mythimna separata, Aphis medicagini, and Tetranychus cinnabarinus and fungicidal activity against Pseudoperonospora cubensis. Among these pyrimidin-4-amine compounds, 5-chloro-N-(2-fluoro-4-(5-(trifluoromethyl)-1,2,4-oxadiazol-3-yl)benzyl)-6-(1-fluoroethyl)pyrimidin-4-amine (U7) and 5-bromo-N-(2-fluoro-4-(5-(trifluoromethyl)-1,2,4-oxadiazol-3-yl)benzyl)-6-(1-fluoroethyl) pyrimidin-4-amine(U8) had broad-spectrum insecticidal and fungicidal activity. The LC₅₀ values were 3.57 ± 0.42, 4.22 ± 0.47, and 3.14 ± 0.73 mg/L for U7, U8, and flufenerim against M. separata, respectively. The EC₅₀ values were 24.94 ± 2.13, 30.79 ± 2.21, and 3.18 ± 0.21 mg/L for U7, U8, and azoxystrobin against P. cubensis, respectively. The AChE enzymatic activity testing revealed that the enzyme activities of compounds U7, U8, and flufenerim are 0.215, 0.184, and 0.184 U/mg prot, respectively. The molecular docking results of compounds U7, U8, and flufenerim with the AChE model demonstrated the opposite docking mode between compound U7 or U8 and positive control flufenerim in the active site of AChE. The structure-activity relationships are also discussed. This work provided excellent pesticide for further optimization. Density functional theory analysis can potentially be used to design more active compounds.