Design, synthesis, herbicidal activity, in vivo enzyme activity evaluation and molecular docking study of acylthiourea derivatives as novel acetohydroxyacid synthase inhibitor

Synthesis, Herbicidal Activity against Barnyard Grass, and Photolytic Behavior of Aryl 2,6-Dipyrimidinoxybenzoates

In this study, we investigated the characteristics and herbicidal potential of bispyribac phenolic esters, which belong to the 2-(pyrimidin-2-yloxy)benzoic acid (PYB) class of acetohydroxyacid synthase (AHAS-)-inhibiting herbicides. These herbicides are primarily used for controlling Poaceae and broadleaf weeds. Among them, bispyribac-sodium stands out as a representative in this class. Surprisingly, other bispyribac esters, including alkanol and phenol esters exhibit considerably reduced herbicidal activity compared to bispyribac-sodium. In contrast, oxime esters (e.g., pyribenzoxim) demonstrate high activity. To further understand and develop novel PYB herbicides, we synthesized and screened a series of bispyribac phenolic esters while investigating their photochemical behaviors. Several compounds displayed excellent herbicidal activity, with compounds Ia-19 and Ic showing impressive 90% effective dosages for fresh weight inhibition of barnyard grass, measuring 0.55 and 0.60 g a.i./hm2, respectively. These values were approximately half of bispyribac-sodium or pyribenzoxim. The results indicate that the herbicidal activity of phenolic esters is influenced by both their binding ability to the AHAS enzyme and their decomposition into bispyribac acid. For instance, bispyribac phenol ester exhibited considerably reduced receptor affinity compared to bispyribac-sodium, and faced challenges in transforming into bispyribac acid, explaining its diminished herbicidal activity. However, introducing a photosensitive nitro group led to a complete transformation. This modification improved its affinity with AHAS and accelerated its decomposition into bispyribac acid, further accelerated by photocatalysis. Consequently, nitro-containing compounds displayed heightened herbicidal activity. The findings from this study open possibilities for structural optimization of phenolic esters through quantitative structure-activity relationship analysis, potentially regulating their activity-releasing period. Furthermore, the high activity of aromatic heterocyclic esters offers new insights into developing novel PYB herbicides.

Design, synthesis and biological activity determination of novel phenylpyrazole protoporphyrinogen oxidase inhibitor herbicides

Protoporphyrinogen oxidase (PPO, EC 1.3.3.4) is the last common enzyme in the biosynthetic pathway in the synthesis of heme and chlorophyll. The high-frequency use of PPO inhibitor herbicides has led to the gradual exposure of pesticide damage and resistance problems. In order to solve this kind of problem, there is an urgent need to develop new PPO inhibitor herbicides. In this paper, 16 phenylpyrazole derivatives were designed by the principle of active substructure splicing through the electron isosterism of five-membered heterocycles. Greenhouse herbicidal activity experiments and in vitro PPO activity experiments showed that the inhibitory effect of compound 9 on weed growth was comparable to that of pyraflufen-ethyl. Crop safety experiments and cumulative concentration experiments in crops showed that when the spraying concentration was 300 g ai/ha, wheat, corn, rice and other cereal crops were more tolerant to compound 9, among which wheat showed high tolerance, which was comparable to the crop safety of pyraflufen-ethyl. Herbicidal spectrum experiments showed that compound 9 had inhibitory activity against most weeds. Molecular docking results showed that compound 9 formed one hydrogen bond interaction with amino acid residue ARG-98 and two π-π stacking interactions with amino acid residue PHE-392, indicating that compound 9 had better herbicidal activity than pyraflufen-ethyl. It shows that compound 9 is expected to be a lead compound of phenylpyrazole PPO inhibitor herbicide and used as a herbicide in wheat field.

Discovery of a Novel Class of Acylthiourea-Containing Isoxazoline Insecticides against Plutella xylostella

Isoxazoline structures are widely found in natural products and are rich in biological activities. This study discloses the development of a series of novel isoxazoline derivatives by introducing acylthiourea fragments to access insecticidal activity. All synthetic compounds were examined for their insecticidal activity against Plutella xylostella, with results showing moderate to strong activity. Based on this, the structure-activity relationship analysis was carried out via the constructed three-dimensional quantitative structure-activity relationship model to further guide the structure optimization, resulting in the optimal compound 32. The LC₅₀ of compound 32 against Plutella xylostella was 0.26 mg/L, demonstrating better activity than the positive control, ethiprole (LC₅₀ = 3.81 mg/L), avermectin (LC₅₀ = 12.32 mg/L), and compounds 1-31. The insect GABA enzyme-linked immunosorbent assay demonstrated that compound 32 might act on the insect GABA receptor, and the molecular docking assay further illustrated the mode of action of compound 32 with the GABA receptor. In addition, the proteomics analysis indicated that the action of compound 32 on Plutella xylostella was multi-pathway.

Design, synthesis, characterization and insecticidal screening of novel anthranilic diamides comprising acyl thiourea substructure

BACKGROUND

Mosquito-borne pathogens constitute a major health problem worldwide. The extermination of the mosquito remains a significant issue in public health. Chemical insecticides have been used to control mosquitoes for decades. However, resistance has become a limiting factor for their control. The anthranilic diamide insecticides possess excellent insecticidal activities against Lepidoptera and its resistant strains by draining internal calcium stores on activating insect ryanodine receptors. However, the reports on the effect on mosquitoes are scarce and hence a series of novel anthranilic diamides comprising acyl thiourea substructure were synthesized and their insecticidal activities against three vector mosquito larvae namely, Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi were evaluated as per WHO protocol. Also investigated the morphological observations of treated larvae.

RESULTS

Novel anthranilic diamides containing an acyl thiourea substructure were synthesized and structures were established by ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, Fourier transform infrared (FTIR) and high-resolution mass spectrometry (HR-MS). Mosquito larvicidal activity of the title compounds 6-a-s revealed that compound 6-l exhibited marked larvicidal activities against C. quinquefasciatus and A. aegypti 3rd instar larvae with median lethal concentrations (LC₅₀ ) values of 0.0044 mm and 0.0070 mm, respectively, for 48 hours of treatment. Compound 6-g exhibited larvicidal activity against An. stephensi with LC₅₀ value of 0.0085 mm. Peculiar morphological alterations in the body of the treated larvae leading to death were observed on microscopic examination.

CONCLUSION

Novel anthranilic diamides containing an acyl thiourea substructure were designed, synthesized and characterized. Their bioassay results demonstrated significant mosquito larvicidal activity with striking morphological alterations in the body, which should ensure forthcoming designs of highly active diamide derivatives as mosquito larvicides. © 2022 Society of Chemical Industry.

Design, synthesis and fungicidal evaluation of novel psoralen derivatives containing sulfonohydrazide or acylthiourea moiety

To search a novel lead structure for antiphytopathogenic fungus agent, a series of novel psoralen derivatives possessing sulfonohydrazide or acylthiourea structure were designed and synthesized, and their fungicidal activity against seven phytopathogens was evaluated. Their structures were confirmed by melting points, ¹H NMR, ¹³C NMR and HRMS, and the typical crystal structure was determined by X-ray diffraction for validation. Preliminary fungicidal activity showed that some of the title compounds exhibited certain-to-high fungicidal activity. Compound I-13 exhibited good fungicidal activity against Botrytis cinerea, Cercospora arachidicola and Physalospora piricola with EC₅₀ values of 12.49, 13.22 and 12.12 μg/mL, respectively. Compounds II-9 and II-15 showed over 90% inhibition against B. cinerea at 50 μg/mL in vitro. In particular, II-9 exhibited significant higher fungicidal activity with a lower EC₅₀ value of 9.09 μg/mL than the positive control YZK-C22 (13.41 μg/mL). Our studies found that sulfonohydrazide or acylthiourea-containing psoralen derivatives were promising fungicide leads deserve for further study.