Synthesis, Crystal Structure, Herbicidal Activity, and SAR Study of Novel N-(Arylmethoxy)-2-chloronicotinamides Derived from Nicotinic Acid

Novel "Phenyl-Pyrazoline-Oxadiazole" Ternary Substructure Derivatives: Synthesis, Insecticidal Activities, and Structure-Activity Relationship Study

In recent years, isoxazole insecticides or parasiticides targeting the γ-aminobutyric acid receptor, such as fluralaner or fluxametamide, featured a novel chemical structure and exhibited potent insecticidal activity with no-cross resistance. Thus, many research institutes have tried to modify the structures of these agents to find a new insecticide. Previously, the majority of researchers stuck to the "phenyl-isoxazole-phenyl" structure, making modifications only to other components. In this study, the "phenyl-isoxazole-phenyl" ternary motif was modified for the first time based on bioisosterism theory. A series of new derivatives carrying pyrazoline and 1,3,4-oxadiazole moieties were designed and synthesized to investigate their insecticidal activities against the diamondback moth (Plutella xylostella) and fall armyworm (Spodoptera frugiperda). Preliminary bioassay data showed that some of the target compounds exhibited good insecticidal activities against P. xylostella and S. frugiperda. Especially, compound A21 showed insecticidal activity against P. xylostella (LC50 = 1.2 μg/mL) better than commercial insecticide ethiprole (LC50 = 2.9 μg/mL) but worse than parasiticide fluralaner (LC50 = 0.5 μg/mL). Similarly, compound A21 exhibited insecticidal activity to S. frugiperda (LC50 = 13.2 μg/mL) better than commercial insecticide fipronil (LC50 = 78.8 μg/mL) but worse than fluralaner (LC50 = 0.7 μg/mL). Compound A21 could serve as a potential lead compound to control P. xylostella and S. frugiperda. The three-dimensional quantitative structure-activity relationship model revealed that the further introduction of an electron-donating group in the 2- or 3-site may increase the insecticidal activity of A21. Molecular dynamics simulations showed that the hydrogen bond of A21 and receptor was important for the binding receptor. This study has identified a new substructure called "phenyl-pyrroline-oxadiazole" instead of the previously known "phenyl-isoxazole-phenyl" substructure, offering a useful guide for the design of novel insecticide molecules.

Understanding the Effects of Ligand Configuration on Protoporphyrinogen IX Oxidase with Rationally Designed 3-(N-Phenyluracil)but-2-enoates

Protoporphyrinogen IX oxidase (PPO, EC 1.3.3.4) is a promising target for green herbicide discovery. However, the ligand configuration effects on PPO activity were still poorly understood. Herein, we designed 3-(N-phenyluracil)but-2-enoates using our previously developed active fragments exchange and link (AFEL) approach and synthesized a series of novel compounds with nanomolar ranges of Nicotiana tabacum PPO (NtPPO) inhibitory potency and promising herbicidal potency. Our systematic structure-activity relationship investigations showed that the E isomers of 3-(N-phenyluracil)but-2-enoates displayed improved bioactivity than their corresponding Z isomers. Using molecular simulation studies, we found that the E isomers showed a relatively lower entropy change and could sample more stable binding conformation to the receptor than the Z isomers. Our density functional theory (DFT) calculations showed that the E isomers showed higher chemical reactivity and lower electronic chemical potential than their corresponding Z isomers. Compound E-Ic emerged as the optimal compound with a Ki value of 3.0 nM against NtPPO, exhibiting a broader spectrum of weed control than saflufenacil at 37.5-75 g ai/ha and also safe to maize at 75 g ai/ha, which could be considered as a promising lead herbicide for further development.

Design, synthesis and insecticidal activity of novel Isoxazoline Acylhydrazone compounds

BACKGROUND

Nowadays, the diamondback moth has ascended to become one of the most formidable pests plaguing cruciferous vegetables. Consequently, the exigency for the development of efficacious pesticide candidates for crop protection has never been more paramount. In response to this pressing need, this study presents a compendium of novel isoxazoline derivatives, incorporating acylhydrazone moieties, synthesized with the express purpose of serving as potential insecticides.

RESULTS

The structures of these derivatives were confirmed using Proton nuclear magnetic resonance (1 H NMR), Carbon-13 nuclear magnetic resonance (13 C NMR), and high-resolution mass spectrometry (HR-MS). Most of these derivatives demonstrated effective insecticidal activities against Plutella xylostella. Notably, compound E3 exhibited exceptional insecticidal activity against Plutella xylostella (LC50  = 0.19 mg L-1 ), surpassing the effectiveness of ethiprole (LC50  = 3.28 mg L-1 ), and comparable to that of fluxametamide (LC50  = 0.22 mg L-1 ). Interestingly, compound E3 also displayed potent insecticidal activity against Pyrausta nubilalis (LC50  = 0.182 mg L-1 ) and Chilo suppressalis (LC50  = 0.64 mg L-1 ), and the LC50 values of fluxametamide were 0.23 mg L-1 (P. nubilalis) and 2.26 mg L-1 (C. suppressalis), respectively. The molecular docking results revealed that the compound E3 can form a hydrogen bond and two Pi-Pi bonds with the active sites of GABA receptors. In addition, the DFT calculations were also performed to study the relationship between insecticidal activities. The structure-activity relationships suggested that the identity of the R substituent was crucial for their pesticidal activities.

CONCLUSION

The results of the present study suggest that isoxazoline acylhydrazone derivatives could be promising candidates against P. xylostella and other Lepidopteran pests. © 2023 Society of Chemical Industry.

Design, Synthesis, and Herbicidal Activity of Pyrazole Amide Derivatives as Potential Transketolase Inhibitors

The design and synthesis of new herbicidal active compounds based on a new target are of great significance for the development of new herbicides. Transketolase (TK) plays a key role in the Calvin cycle of plant photosynthesis and has been confirmed as a potential candidate target to develop and discover new herbicides. To obtain compounds with ultraefficient targeting of TK, a series of pyrazole amide derivatives were designed and synthesized through structural optimization for lead compound 4u based on TK as the new target. The bioassay results showed that compounds 6ba and 6bj displayed a highly inhibitory effect with the root inhibition of about 90% against Digitaria sanguinalis (DS) and 80% against Amaranthus retroflexus (AR) and Setaria viridis (SV) by the small cup method, which was better than the positive control mesotrione and nicosulfuron. Furthermore, compounds 6ba and 6bj exhibited an excellent inhibitory effect with the inhibition of about 80% (against DS) and over 80% (against SV) at the dosage of 150 g of active ingredient/ha by the foliar spray method. The TK enzyme activity inhibition test showed that the inhibition effect of target compounds against TK was consistent with the results of herbicidal activities. Also, molecular docking analysis showed that compounds 6ba and 6bj went deep into the active cavity of TK, bound to TK by a strong interaction, and might act on the enzyme TK. Above of all, compounds 6ba and 6bj are promising herbicide lead compounds targeting TK. Hence, they could be developed into more efficient herbicides by further structural optimization.

Novel Pyrazole Acyl(thio)urea Derivatives Containing a Biphenyl Scaffold as Potential Succinate Dehydrogenase Inhibitors: Design, Synthesis, Fungicidal Activity, and SAR

As part of a program to discover novel succinate dehydrogenase inhibitor fungicides, a series of new pyrazole acyl(thio)urea compounds containing a diphenyl motif were designed and synthesized. Their structures were confirmed by 1H NMR, HRMS, and single X-ray crystal diffraction analysis. Most of these compounds possessed excellent activity against 10 fungal plant pathogens at 50 μg mL-1, especially against Rhizoctonia solani, Alternaria solani, Sclerotinia sclerotiorum, Botrytis cinerea, and Cercospora arachidicola. Interestingly, compounds 3-(difluoromethyl)-1-methyl-N-((3',4',5'-trifluoro-[1,1'-biphenyl]-2-yl)carbamoyl)-1H-pyrazole-4-carboxamide (9b, EC50 = 0.97 ± 0.18 μg mL-1), 1,3-dimethyl-N-((3',4',5'-trifluoro-[1,1'-biphenyl]-2-yl)carbamoyl)-1H-pyrazole-4-carboxamide (9a, EC50 = 2.63 ± 0.41 μg mL-1), and N-((4'-chloro-[1,1'-biphenyl]-2-yl)carbamoyl)-1,3-dimethyl-1H-pyrazole-4-carboxamide (9g, EC50 = 1.31 ± 0.15 μg mL-1) exhibited activities against S. sclerotiorum that were better than the commercial fungicide bixafen (EC50 = 9.15 ± 0.05 μg mL-1) and similar to the positive control fluxapyroxad (EC50 = 0.71 ± 0.11 μg mL-1). These compounds were not significantly phytotoxic to monocotyledonous and dicotyledonous plants. Structure-activity relationships (SAR) are discussed by substituent effects/molecular docking, and density functional theory analysis indicated that these compounds are succinate dehydrogenase inhibitors.

Synthesis, acaricidal activity, and structure-activity relationships of novel phenyl trifluoroethyl thioether derivatives containing substituted benzyl groups

BACKGROUND

To discover and develop novel acaricidal compounds, a series of 2-fluoro-4-methyl/chlorine-5-((2,2,2-trifluoroethyl)thio)aniline/phenol compounds containing N/O-benzyl moieties were synthesized based on lead compound LZ-1.

RESULTS

The activity of these compounds against carmine spider mites (Tetranychus cinnabarinus) was determined using the leaf-spray method. Bioassays indicated that most of the designed target compounds possessed moderate to excellent acaricidal activity against adult T. cinnabarinus. The median lethal concentrations of 25b and 26b were 0.683 and 2.448 mg L-1 against adult mites, respectively; exceeding those of bifenazate (7.519 mg L-1 ) and lead compound LZ-1(3.658 mg L-1 ). Compound 25b exhibited 100% mortality in T. cinnabarinus larvae at 10 mg L-1 .

CONCLUSION

Continuing the study of these compounds in field trials, we compared the efficacy of mite killing by compound 25b with the commercial pesticide spirodiclofen and showed that mite control achieved 95.9% and 83.0% lethality at 10 and 22 days post-treatment. In comparison, spirodiclofen showed 92.7% lethality at 10 days and 77.2% lethality at 22 days post-treatment at a concentration of 100 mg L-1 . Results showed that 25b produced more facile and long-lasting control against T. cinnabarinus than the commercial acaricide spirodiclofen. Density functional theory analysis and electrostatic potential calculations of various molecular substitutions suggested some useful models to achieve other highly active miticidal compounds. © 2023 Society of Chemical Industry.

Design, Synthesis, and Antifungal Activity of Novel 2-Ar-1,2,3-Triazole Derivatives

Triazoles are crucial molecular frameworks in the development of fungicidal compounds. Although there has been extensive research on triazole derivatives for fungicide discovery, the investigation of 2-Ar-substituted-1,2,3-triazoles remains in progress. This study reports the synthesis and evaluation of the fungicidal activity of 27 distinct 2-Ar-substituted-1,2,3-triazole derivatives. These derivatives were synthesized from anilines through a three-step process, with the key step being the Cu(II)-catalyzed annulation reaction of readily accessible alkyl 3-aminoacrylates with aryldiazonium salts. All derivatives were novel, and their structures were characterized using 1H NMR, 13C NMR, and high-resolution mass spectrometry. Their antifungal activity was tested against five phytopathogenic fungi. Twelve of the target compounds exhibited better performance than the positive control hymexazol in the fungal test. Notably, compound 6d demonstrated the most potent inhibition against Botryosphaeria dothidea with an EC50 value of 0.90 mg/L. The structure-activity relationships are also discussed in this paper. Preliminary studies on the antifungal mechanism of compound 6d revealed that it inhibits ergosterol synthesis and alters the morphology and ultrastructure of the B. dothidea mycelium. These results suggest that the designed 2-Ar-substituted-1,2,3-triazole-containing hydrazone derivatives warrant further investigation as potential lead compounds for novel antifungal agents.

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.

Hydrogen bonded dimers in the crystal structure of 2-chloro-N-((3,5-dimethylphenyl)carbamoyl)-nicotinamide, C30H28Cl2N6O4

C30H28Cl2N6O4, monoclinic, P21/n (no. 14), a = 15.812(5) Å, b = 8.820(3) Å, c = 22.615(7) Å, β = 109.814(10)°, V = 2967.2(16) Å3, Z = 8, Rgt (F) = 0.0489, wRref (F 2) = 0.1302, T = 296(2) K.

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.

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.

The crystal structure of 2-chloro-N-((2-chlorophenyl)carbamoyl)nicotinamide, C13H9Cl2N3O2

C13H9Cl2N3O2, monoclinic, P21/n (no. 14), a = 7.918(2) Å, b = 12.766(3) Å, c = 13.767(4) Å, β = 103.413(9)°, V = 1353.6(6) Å3, Z = 4, Rgt (F) = 0.0382, wRref (F 2) = 0.1019, T = 296(2) K.

Hydrogen bonded dimers in the crystal structure of 2-chloro-N-(phenylcarbamoyl)nicotinamide, C26H20Cl2N6O4

C26H20Cl2N6O4, orthorhombic, Pbca (no. 61), a = 7.7316(6) Å, b = 24.8021(19) Å, c = 26.074(2) Å, V = 4999.9(7) Å3, Z = 8, R gt (F) = 0.0674, wR ref (F 2) = 0.1625, T = 296(2) K.

Synthesis, Insecticidal Activities, and 3D-QASR of N-Pyridylpyrazole Amide Derivatives Containing a Phthalimide as Potential Ryanodine Receptor Activators

To develop potent and environment-friendly insecticides, novel N-pyridylpyrazole amide derivatives containing a phthalimide were designed and synthesized. The preliminary bioassay results showed that most of the target compounds exhibited good insecticidal activities. For oriental armyworm (Mythimna separata), compounds E₅, E₂₉, E₃₀, and E₃₃ displayed higher than 90% lethal rates at 25 mg L^-1. In particular, compound E₃₃ displayed 60% mortality at a lower concentration of 6.25 mg L^-1. Besides, compound E₃₃ also showed a 30% lethal rate at 5 mg L^-1 against diamondback moth (DBM) (Plutella xylostella). Molecular docking between the most active compound E₃₃ and DBM ryanodine receptor (RyR), comparative molecular field analysis (CoMFA), and density functional theory (DFT) calculations were conducted and discussed. Furthermore, according to vitro studies using a calcium imaging technique, compound E₃₃ was a potent novel lead targeting insect RyR.

Synthesis and pesticidal activity of new 1,3,4-oxadiazole thioether compounds containing a trifluoromethylpyrazoyl moiety

In order to find new lead compounds with high pesticidal activity, a series of 1,3,4-oxadiazole thioether compounds (5 series) were designed by using penthiopyrad as a synthon. They were synthesized easily via five steps by using ethyl 4,4,4-trifluoro-3-oxobutanoate and triethyl orthoformate as starting materials. The synthesized compounds were characterized by ¹H NMR, ¹³C NMR and HRMS. The compound 2-(benzylthio)-5-(1-methyl-3-(trifluoromethyl)-1H-pyrazol-4-yl)-1,3,4-oxadiazole (5a) was further determined by X-ray single-crystal diffraction. It crystallized in the monoclinic system, space group P2₁/c, Z = 4. All the 1,3,4-oxadiazole thioether derivatives were screened for fungicidal activity against ten fungi and herbicidal activity against two weeds. The bioassay results indicated that some of the synthesized 1,3,4-oxadiazole compounds exhibited good fungicidal activity (> 50% inhibition) against the plant pathogens Sclerotinia sclerotiorum and Rhizoctonia solani at 50 μg/mL. Some of them exhibited certain herbicidal activity, and compounds 2-((3-chlorobenzyl)thio)-5-(1-methyl-3-(trifluoromethyl)-1H-pyrazol-4-yl)-1,3,4-oxadiazole (5e) and 2-((4-bromobenzyl)thio)-5-(1-methyl-3-(trifluoromethyl)-1H-pyrazol-4-yl)-1,3,4-oxadiazole (5 g) had bleach effect. Molecular docking is to find the best fit orientation of the 2-((4-bromobenzyl)thio)-5-(1-methyl-3-(trifluoromethyl)-1H-pyrazol-4-yl)-1,3,4-oxadiazole (5 g) molecule with the SDH protein (PDB: 2FBW). The docking results indicate that the compound 5 g and the lead compound penthiopyrad have similar binding interactions with SDH and carbonyl is a key group for these compounds.

Scaffold-Hopping Approach To Identify New Chemotypes of Dimpropyridaz

Dimpropyridaz is a pyrazole carboxamide insecticide with a novel mode of action, currently under worldwide development by BASF, providing excellent activity against sucking pests. A series of dimpropyridaz analogues were designed to investigate the impact of bioisosteric heterocyclic replacements on the biological activity and molecular properties. Focus was given to prepare analogues where the 4-pyridazinyl moiety was replaced by 5-pyrimidinyl, 2-pyrimidinyl, 3-pyridazinyl, and 2-pyrazinyl groups. Five different synthetic routes were developed for the preparation of these analogues, delivering the target compounds in moderate to good yields. We explained some aspects of the observed structure-activity relationship by a density functional theory (DFT) calculation and DFT-derived Multiwfn and VMD program models. These findings provide first insights into the important role of the 4-pyridazinyl heterocyclic moiety in the pyrazole carboxamide insecticide chemical class and the mechanism of action of dimpropyridaz.

Bioisosteric-Replacement-Driven Lead Optimization of Tyclopyrazoflor

A heterocyclic replacement strategy has been applied attempting to further optimize the biological properties of the new insecticide tyclopyrazoflor, a pyridinyl-pyrazole compound with excellent activity against sap-feeding insects recently discovered by Corteva. Our research program on this novel chemical class of insecticide was targeted to evaluate the importance of both the pyridyl and pyrazole moieties on the biological activity, properties, and structure-activity. Synthetic methodologies have been developed delivering our designed target compounds in moderate to good yields. In our attempt to rationalize the biological activity differences of tyclopyrazoflor analogues, a potential surface analysis based on a density functional theory (DFT) calculation and DFT-derived Multiwfn and VMD program model was performed. Furthermore, the SwissBioisostere online database was applied as a great source for inspiration for bioisosteric replacements.

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.

Isolation, Synthesis, and Fungicidal Activity of Isopropyl (3-methyl-1-oxo-1-((1-((4-(prop-2-yn-1-yloxy)phenyl)thio)propan-2-yl)amino)butan-2-yl)carbamate Diastereomers against Phytophthora capsici

Two isopropyl (3-methyl-1-oxo-1-((1-((4-(prop-2-yn-1-yloxy)phenyl)thio)propan-2-yl)amino)butan-2-yl)carbamate diastereomers were isolated. Fungicidal activities indicated that the isolated four chiral compounds possessed excellent activity against P. capsici with the EC50 value of 4a (1.30 μg/mL), 4b (0.078 μg/mL), 4c (1.85 μg/mL), and 4d (44.4 μg/mL). Among them, compound 4b exhibited remarkably high activities against Phytophthora capsici, which is better than that of positive control dimethomorph. Its R and S isomers showed that chiral influences the activity against P. capsici.

Synthesis, Antifungal Activity, and 3D-QASR of Novel 1,2,3,4-Tetrahydroquinoline Derivatives Containing a Pyrimidine Ether Scaffold as Chitin Synthase Inhibitors

The introduction of active groups of natural products into the framework of pesticide molecules is an effective approach for discovering active lead compounds, and thus has been widely used in the development of new agrochemicals. In this work, a novel series of 1,2,3,4-tetrahydroquinoline derivatives containing a pyrimidine ether scaffold were designed and synthesized by the active substructure splicing method. The new compounds showed good antifungal activities against several fungi. Especially, compound 4fh displayed excellent in vitro activity against Valsa mali and Sclerotinia sclerotiorum with EC₅₀ values of 0.71 and 2.47 μg/mL, respectively. 4fh had slightly stronger inhibitory activity (68.08% at 50 μM) against chitin synthase (CHS) than that of polyoxin D (63.84% at 50 μM) and exhibited obvious curative and protective effects on S. sclerotiorum in vivo. Thus, 4fh can be considered as a new candidate fungicide as a chitin synthase inhibitor. An accurate and reliable three-dimensional quantitative structure-activity relationship (3D-QSAR) model presented a useful direction for the further excogitation of more highly active fungicides. Molecular docking revealed that the conventional hydrogen bond mainly affected the binding affinity of 4fh with chitin synthase. The present results will provide a guidance to discover potential CHS-based fungicides for plant disease control in agriculture.

Novel Dioxolane Ring Compounds for the Management of Phytopathogen Diseases as Ergosterol Biosynthesis Inhibitors: Synthesis, Biological Activities, and Molecular Docking

Thirty novel dioxolane ring compounds were designed and synthesized. Their chemical structures were confirmed by ¹H NMR, HRMS, and single crystal X-ray diffraction analysis. Bioassays indicated that these dioxolane ring derivatives exhibited excellent fungicidal activity against Rhizoctonia solani, Pyricularia oryae, Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium oxysporum, Physalospora piricola, Cercospora arachidicola and herbicidal activity against lettuce (Lactuca sativa), bentgrass (Agrostis stolonifera), and duckweed (Lemna pausicostata). Among these compounds, 1-((2-(4-chlorophenyl)-5-methyl-1,3-dioxan-2-yl)methyl)-1H-1,2,4-triazole (D17), 1-(((4R)-2-(4-chlorophenyl)-4-methyl-1,3-dioxolan-2-yl)methyl)-1H-1,2,4-triazole (D20), 1-((5-methyl-2-(4-(trifluoromethyl)phenyl)-1,3-dioxan-2-yl)methyl)-1H-1,2,4-triazole (D22), and 1-((2-(4-fluorophenyl)-1,3-dioxolan-2-yl)methyl)-1H-1,2,4-triazole (D26) had broad spectrum fungicidal and herbicidal activity. The IC₅₀ values against duckweed were 20.5 ± 9.0, 14.2 ± 6.7, 24.0 ± 11.0, 8.7 ± 3.5, and 8.0 ± 3.1 μM for D17, D20, D22, and D26 and the positive control difenoconazole, respectively. The EC₅₀ values were 7.31 ± 0.67, 9.74 ± 0.83, 17.32 ± 1.23, 11.96 ± 0.98, and 8.93 ± 0.91 mg/L for D17, D20, D22, and D26 and the positive control difenoconazole against the plant pathogen R. solani, respectively. Germination experiments with Arabidopsis seeds indicated that the target of these dioxolane ring compounds in plants is brassinosteroid biosynthesis. Molecular simulation docking results of compound D26 and difenoconazole with fungal CYP51 P450 confirmed that they both inhibit this enzyme involved in ergosterol biosynthesis. The structure-activity relationships (SAR) are discussed by substituent effect, molecular docking, and density functional theory analysis, which provided useful information for designing more active compounds.

Design, Synthesis, Herbicidal Activity, and Molecular Docking Study of 2-Thioether-5-(Thienyl/Pyridyl)-1,3,4-Oxadiazoles as Potent Transketolase Inhibitors

Transketolase (TK) has been regarded as a new target for the development of novel herbicides. In this study, a series of 2-thioether-5-(thienyl/pyridyl)-1,3,4-oxadiazoles were designed and synthesized based on TK as the new target. The preliminary bioassay results indicated that compounds 4l and 4m displayed the best herbicidal activities against Amaranthus retroflexus (AR) and Digitaria sanguinalis (DS), with the inhibition exceeding 90% at 100-200 mg/L in vitro. Moreover, they also displayed higher postemergence herbicidal activities (90% control) against AR and DS than all of the positive controls at 45-90 g [active ingredient (ai)]/ha in a greenhouse. Notably, compounds 4l and 4m showed a broad spectrum of weed control at 90 g ai/ha. More significantly, compound 4l exhibited good crop selectivity against maize at 90 g ai/ha. Both fluorescent binding experiments and molecular docking analyses indicated that compounds 4l and 4m exhibited strong TK inhibitory activities with superior binding affinities than the others. Preliminary mechanism studies suggested that they might exert their TK inhibitory effects by occupying the active cavity of At TK and forming more strong interactions with amino acids in the active site. Taken together, these results suggested that compound 4l was a potential herbicide candidate for weed control in maize fields targeting TK.

The crystal structure of (E)-3-chloro-2-(2-(4-fluorobenzylidene)hydrazinyl)pyridine, C12H9ClFN3

C12H9ClFN3, monoclinic, P21/n (no. 14), a = 10.120(4) Å, b = 13.823(6) Å, c = 16.480(7) Å, β = 91.744(8)°, V = 2304.4(17) Å3, Z = 8, R gt (F) = 0.0402, wR ref (F 2) = 0.0932, T = 113.15 K.

Design, Synthesis, and Biological Activity of Novel Fungicides Containing a 1,2,3,4-Tetrahydroquinoline Scaffold and Acting as Laccase Inhibitors

Laccase is a novel target for fungicides. We previously developed a new fungicide, 4-chlorocinnamaldehyde thiosemicarbazide (PMDD-5Y), as a laccase inhibitor. The introduction of active groups of natural products into the framework of a pesticide molecular structure is an effective method for discovering active lead compounds, and it has applications in the discovery of new pesticides. In this work, PMDD-5Y was selected as a lead compound, and we designed and synthesized a series of novel sulfonyl hydrazide derivatives containing the natural product scaffold 1,2,3,4-tetrahydroquinoline. The new compounds had antifungal activities against several fungi, especially Valsa mali and Sclerotinia sclerotiorum. One compound (4bl) displayed very good in vitro activity against S. sclerotiorum and V. mali, with EC₅₀ values of 3.32 and 2.78 μg/mL, respectively. The results of an enzyme activity assay showed that 4bh had the best inhibitory activity against laccase, with an EC₅₀ value of 14.85 μg/mL. This was more active than the lead compound PMDD-5Y and the positive control cysteine. Using a molecular docking method, we studied the binding mode of the title compounds with laccase. The structural features of these new laccase inhibitors as fungicides will advance research and impact the field of discovering more potent fungicides to control diseases in agriculture.

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.

The crystal structure of (E)-3-chloro-2-(2-(4-methylbenzylidene)hydrazinyl)pyridine, C13H12ClN3

C13H12ClN3, orthorhombic, Fdd2 (no. 43), a = 28.7760(11) Å, b = 41.7393(17) Å, c = 8.5929(3) Å, V = 10,320.8(7) Å3, Z = 32, R gt (F) = 0.0477, wR ref (F 2) = 0.0976, T = 296 K.

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.