Design, synthesis and insecticidal activity of novel phenylpyrazoles containing a 2,2,2-trichloro-1-alkoxyethyl moiety

Design, Synthesis, and Bioactivity of Trifluoroethylthio-Substituted Phenylpyrazole Derivatives

As the first marketed phenylpyrazole insecticide, fipronil exhibited remarkable broad-spectrum insecticidal activity. However, it poses a significant threat to aquatic organisms and bees due to its high toxicity. Herein, 35 phenylpyrazole derivatives containing a trifluoroethylthio group on the 4 position of the pyrazole ring were designed and synthesized. The predicted physicochemical properties of all of the compounds were within a reasonable range. The biological assay results revealed that compound 7 showed 69.7% lethality against Aedes albopictus (A. albopictus) at the concentration of 0.125 mg/L. Compounds 7, 7g, 8d, and 10j showed superior insecticidal activity for the control of Plutella xylostella (P. xylostella). Notably, compound 7 showed similar insecticidal activity against Aphis craccivora (A. craccivora) compared with fipronil. Potential surface calculation and molecular docking suggested that different lipophilicity and binding models to the Musca domestica (M. domestica) gamma-aminobutyric acid receptors may be responsible for the decreased activity of the tested derivatives. Toxicity tests indicated that compound 8d (LC50 = 14.28 mg/L) induced obviously 14-fold lower toxicity than fipronil (LC50 = 1.05 mg/L) on embryonic-juvenile zebrafish development.

Synthesis and evaluation of larvicidal efficacy against C. pipiens of some new heterocyclic compounds emanated from 2-cyano-N'-(2-(2,4-dichlorophenoxy)acetyl)acetohydrazide

Several infectious diseases are transmitted and spread by mosquitoes, and millions of people die annually from them. The mosquito, Culex pipiens is a responsible for the emergence of various Virus in Egypt. So, we devote our work to evaluate the larvicidal efficacy against C. pipiens of some new heterocyclic compounds containing chlorine motifs. The implementation was emanated from using 2-cyano-N'-(2-(2,4-dichlorophenoxy)acetyl)acetohydrazide (3) as scaffold to synthesize some new heterocyclic compounds. The structures of the synthesized compounds were interpreted scrupulously by spectroscopic and elemental analyses. Thereafter, the larvicidal activity against C. pipiens of thirteen synthesized compounds was estimated. Noteworthy, cyanoacetohydrazide derivative 3 and 3-iminobenzochromene derivative 12 showed a fabulous potent efficacy with LC50 equal to 3.2 and 3.5 ppm against C. pipiens, respectively, and are worth being further evaluated in the field of pest control.

Design, synthesis, and biological activity of novel spiro-pyrazolo[1,5-a]quinazolines derivatives as potential insecticides

BACKGROUND

Arylpyrazole insecticides display broad-spectrum insecticidal activity against insect pests. However, the high toxicity toward honeybees associated with fipronil prohibits its agronomic utility. To explore reducing the toxicity of aryl pyrazole analogs to bees, a series of new spiro-pyrazolo[1,5-a]quinazoline derivatives were designed and synthesized.

RESULTS

Bioassay results showed that these compounds exhibited good insecticidal activity. In particular, the insecticidal activity of compound 5f against Plutella xylostella larvae (median lethal contentration, LC₅₀  = 1.43 mg L^-1 ) was equivalent to that of fipronil. Moreover, some compounds also showed good insecticidal activity against Solenopsis invicta. Importantly, the bee toxicity study confirmed that compound 5f had much lower acute oral toxicity, with a median lethal dose (LD₅₀ ) = 1.15 μg bee^-1 that was three to four orders of magnitude greater than that of fipronil (0.0012 μg bee^-1 ). Electrophysiological studies were conducted using honeybee γ-aminobutyric acid receptor heterologously expressed in Xenopus oocytes to explain the reduced bee toxicity of compound 5f. The inhibitory effect of compound 5f (16.29 μmol L^-1 ) was determined to be approximately 700-fold lower than that of fipronil (0.023 μmol L^-1 ).

CONCLUSION

These spiro-pyrazolo[1,5-a]quinazoline derivatives could be potential candidates and lead structures for the discovery of novel insecticides with low bee toxicity. © 2022 Society of Chemical Industry.

Design, Synthesis and Bioactivity of Novel Pyrimidine Sulfonate Esters Containing Thioether Moiety

Pesticides play an important role in crop disease and pest control. However, their irrational use leads to the emergence of drug resistance. Therefore, it is necessary to search for new pesticide-lead compounds with new structures. We designed and synthesized 33 novel pyrimidine derivatives containing sulfonate groups and evaluated their antibacterial and insecticidal activities. Results: Most of the synthesized compounds showed good antibacterial activity against Xanthomonas oryzae pv. Oryzae (Xoo), Xanthomonas axonopodis pv. Citri (Xac), Pseudomonas syringae pv. actinidiae (Psa) and Ralstonia solanacearum (Rs), and certain insecticidal activity. A₅, A₃₁ and A₃₃ showed strong antibacterial activity against Xoo, with EC₅₀ values of 4.24, 6.77 and 9.35 μg/mL, respectively. Compounds A₁, A₃, A₅ and A₃₃ showed remarkable activity against Xac (EC₅₀ was 79.02, 82.28, 70.80 and 44.11 μg/mL, respectively). In addition, A₅ could significantly improve the defense enzyme (superoxide dismutase, peroxidase, phenylalanine ammonia-lyase and catalase) activity of plants against pathogens and thus improve the disease resistance of plants. Moreover, a few compounds also showed good insecticidal activity against Plutella xylostella and Myzus persicae. The results of this study provide insight into the development of new broad-spectrum pesticides.

Crystal structure of the insecticide ethiprole (C13H9Cl2F3N4OS): a case study of whole-mol-ecule configurational disorder

The crystal structure of ethiprole {systematic name: 5-amino-1-[2,6-di-chloro-4-(tri-fluoro-meth-yl)phen-yl]-4-ethane-sulfinyl-1H-imidazole-3-carbo-nitrile}, C₁₃H₉Cl₂F₃N₄OS, a phenyl-pyrazole-based insecticide, is presented. The pyrazole ring carries four substituents: an N-bound 2,6-di-chloro-4-tri-fluoro-methyl-phenyl ring and C-bound amine, ethane-sulfinyl, and cyano groups. The sulfur atom of the ethane-sulfinyl group is trigonal-pyramidal and stereogenic. The structure exhibits whole-mol-ecule configurational disorder due to superposition of enanti-omers. The crystal packing is dominated by strong N-H⋯O and N-H⋯N hydrogen bonds, which form R ⁴ ₄(18) and R ² ₂(12) ring motifs. Since the ethiprole mol-ecule is quite small, and structure solution and refinement were straightforward, the structure presents a convenient instructional example for modelling whole-body disorder of a non-rigid mol-ecule. To this end, a step-by-step overview of the model-building and refinement process is also given. The structure could form the basis of a useful classroom, practical, or workshop-style example.

Design, synthesis, and insecticidal activities of novel 5-substituted 4,5-dihydropyrazolo[1,5-a]quinazoline derivatives

BACKGROUND

Chemical pesticides are the main measures for pest control, but have caused growing resistance of pests and brought a series of environmental problems. Development of high-efficient insecticidal molecules with novel scaffolds is therefore particularly urgent.

RESULTS

Based on a [5 + 1] annulation reaction with 5-amino-1H-phenylpyrazole and dialkyl bromomalonate, 27 novel five-substituted 4,5-dihydropyrazolo[1,5-a]quinazolines were designed following the intermediate derivatization method and synthesized. Bioassay results indicated that most of the test compounds displayed good insecticidal activities against Plutella xylostella, Spodoptera frugiperda, and Solenopsis invicta. In particular, the insecticidal activities of compounds 4a, 4f, and 4m against P. xylostella [median lethal concentration (LC₅₀ ) values ranged from 3.87 to 5.10 mg L^-1 ] were comparable to that of indoxacarb (LC₅₀ = 4.82 mg L^-1 ). In addition, compounds 4a and 9e showed similar high insecticidal activities against Spodoptera frugiperda (mortality rate = 79.63% and 72.12%) at 100 mg L^-1 , comparable to that of fipronil (mortality rate: 68.44%); compound 9a showed possible delayed toxicity against Solenopsis invicta (mortality rate: 95.66%) after 5 days of treatment at 1.0 mg L^-1 .

CONCLUSION

Due to their high insecticidal activities against P. xylostella, compound 4m, 4a, and 4f could be considered as qualified candidates for novel insecticide. Several other 4,5-dihydropyrazolo[1,5-a]quinazolines with relatively high bioactivity, such as compounds 9a and 9e, are also worth further optimization as potential insecticide or anticide candidates.

Synthesis and biological activities of novel trifluoromethylpyridine amide derivatives containing sulfur moieties

A series of trifluoromethylpyridine amide derivatives containing sulfur moieties (thioether, sulfone and sulfoxide) was designed and synthesized. Their antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo), Ralstonia solanacearum (R. solanacearum) and insecticidal activities against P. xylostella were evaluated. Notably, the half-maximal effective concentration (EC50) value of sulfone-containing compound F10 is 83 mg L-1 against Xoo, which is better than that of commercial thiodiazole copper (97 mg L-1) and bismerthiazol (112 mg L-1). Thioether-containing compounds E1, E3, E5, E6, E10, E11 and E13 showed much higher activities against R. solanacearum with the EC50 value from 40 to 78 mg L-1, which are much lower than that of thiodiazole copper (87 mg L-1) and bismerthiazol (124 mg L-1). Generally, most of the sulfone-containing compounds and sulfoxide-containing compounds showed higher activities against Xoo than that of the corresponding thioether-containing compound, but most of the thioether-containing compounds contributed higher antibacterial activities against R. solanacearum. Furthermore, title compounds E3, E11, E24 and G2 showed good insecticidal activities of 75%, 70%, 70% and 75%, respectively.

Enantioselective endocrine-disrupting effects of the phenylpyrazole chiral insecticides in vitro and in silico

The phenylpyrazole chiral insecticides, including the widely used fipronil, ethiprole, and flufiprole, have generated a worldwide interest due to their environmental toxicity. However, up to now,only few studies focused on their their potential endocrine-disrupting effects (EDEs). In this study, we investigated the endocrine hormonal disorder caused by the fipronil, ethiprole, and flufiprole enantiomers in vitro and in silico approach. Results of the luciferase reporter assay indicated that the enantiomers of fipronil, ethiprole, or flufiprole have shown stereoselective endocrine-disrupting effects. S-(-)-ethiprole and S-(-)-flufiprole have anti-thyroidal disorder effects whereas R-(-)-fipronil, R-(+)-ethiprole, and R-(+)-flufiprole showed anti-estrogenic disorder effects. The results of the molecular dynamics simulations revealed that the happened EDEs could be partially attributed to the enantioselective specific receptor binding affinities. It also suggested that Vander Waals interactions plays an important role in the binding procedure. This study could provide helpful information for the explanation of enantioselectivity in the EDEs of chiral phenylpyrazole pesticides at the molecular level.

Design, Synthesis, and Insecticidal Activity of Novel Doramectin Derivatives Containing Acylurea and Acylthiourea Based on Hydrogen Bonding

Our recent investigation on the insecticidal activities of several doramectin derivatives preliminarily revealed that the presence of hydrogen bonds at the C4″ position of the molecule with target protein γ-aminobutyric acid (GABA) receptor was crucial for retaining high insecticidal activity. As a continuation of our research work on the development of new insecticides, two series of novel acylurea and acylthiourea doramectin derivatives were designed and synthesized. The bioassay results indicated that the newly synthesized compounds (5o, 5t, and 6t) exhibited higher insecticidal activity against diamondback moth, oriental armyworm, and corn borer than the control compounds doramectin, commercial avermectins, chlorbenzuron, and lead compound 3g in our laboratory. Specifically, compound 5t was identified as the most promising insecticide against diamondback moth, with a final mortality rate of 80.00% at the low concentration of 12.50 mg/L, showing approximately 7.75-fold higher potency than the parent doramectin (LC₅₀ value of 48.1547 mg/L), 6.52-fold higher potency than commercial avermectins (LC₅₀ value of 40.5507 mg/L), and 3.98-fold higher potency than compound 3g (LC₅₀ value of 24.7742 mg/L). Additionally, molecular docking simulations revealed that compound 5t (2.17, 2.20, 2.56, and 2.83 Å) displayed stronger hydrogen-bond action in binding with the GABA receptor, better than that of compound 5o (1.64 and 2.15 Å) and compound 6t (2.20 and 2.31 Å) at the C4″ position. This work demonstrated that these compounds containing hydrogen-bond groups might contribute to the improvement of insecticidal activity and supply certain hints toward structure optimization design for the development of new insecticides.

One pot solvothermal synthesis of novel fluorescent phloem-mobile phenylpyrazole amide pesticides fused olefin moieties to enhance insecticidal bioactivities and photodegradation properties

In order to find a novel type of fluorescent phloem-mobile insecticides, a facile one-pot solvothermal strategy via fipronil addition-elimination substitution reaction with the corresponding acyl chloride derivatives has been employed to construct series of phenylpyrazole amide derivatives (PAs) fused olefin moieties in high yields. The investigation for insecticidal bioactivities of PAs against 3rd instar larvae of Plutella xylostella exhibited better activities than that of fipronil, which can be elucidated by enhanced phloem mobility and calcium ions' coordination with amide N-C=O, CC double bonds and chloride ions, extended conjugate moieties and decreasing steric hindrance of the stereoscopic structure. The introduction of amide units conferred phloem mobility to PAs, which was evaluated by the hydrophobic parameters determined with reversed-phase HPLC through the chromatographic capacity factor. By introducing conjugate moieties and organic chromophore into phenylpyrazole parent structure to increase their conjugation degree and light absorption abilities, PAs exhibited good photodegradation properties. The relationships between extended conjugate moieties of parent structure, electronegativity of substituted groups and photodegradation properties have been discussed. The olefin units connected to PAs caused electronic absorption and fluorescent wavelengths bathochromic shifted. Under simulated solar irradiation, PAs can be reconverted into fipronil parent fragments by photodegradation, thereby enhancing their insecticidal activity. The fluorescent quantum yields of PAs were almost 4 times that of fipronil, which also laid a foundation for the natural degradation and fluorescence detection of insecticide residues.

Engineering of Peglayted Camptothecin Into Nanomicelles and Supramolecular Hydrogels for Pesticide Combination Control

As a famous quinoline alkaloid, camptothecin (CPT) presented the significant anti-tumor activity, as well as the interesting insecticidal activities, but the low solubility, poor hydrophobicity and cuticular penetration of CPT have been severely limited the field application. In this study, we conjugated the camptothecin with polyethylene glycol, forming amphiphilic copolymer, mPEG-CPT, which could be self-assembled into micelles, or formed a hydrogel with α-CD by super-cross-linking to combine delivery with acetamiprid or nitenpyram. Results showed that the nitenpyram or acetamiprid loaded hydrogels showed dual phase release behavior, while the micelles displayed a synchronous and fast release profile. Moreover, these four nanopesticides showed potent or superior insecticidal activities and a synergetic effect against Brevicoryne brassicae, Tetranychus cinnabarinus, and Bursaphelenchus xylophilus. This finding indicated that micelles and hydrogels could be used as effective carriers for pesticide combination control.

Degradation products and pathway of ethiprole in water and soil

Ethiprole and its degradation products were identified and quantified using UHPLC-Q-TOF/MS. Indoor culture experiments and UHPLC-Q-TOF/MS are used to study the hydrolysis, photolysis, and soil degradation behavior of ethiprole in water and soil. The differences in ethiprole degradation products across a range of environmental conditions such as pH, light, and oxygen availability were compared in order to improve understanding of the ethiprole degradation pathway and the toxicity of the degradation products. Eleven degradation products were identified using UHPLC-Q-TOF/MS and MetaboLynx XS Training software, and two new degradation products (M401 and M312) were characterized by ¹H NMR and HR MS. Three degradation products M401, M399, and M312 were detected in samples using a UHPLC-MS/MS protocol established in this study. Tests of acute toxicity of the three degradation products on Brachydanio rerio, Pseudokirchneriella subcapitata, and Daphnia magna Straus found that the toxicity of M401 to Daphnia magna Straus was greater than that of the parent compound, indicating that ethiprole degradation should be carefully monitored in given the environmental risk posed by its degradation products.

Synthesis and insecticidal activity studies of novel phenylpyrazole derivatives containing arylimine or carbimidate moiety

Phenylpyrazole insecticides are successful for crop protection and public hygiene by blocking gamma-aminobutyric acid (GABA)-gated chloride channels and glutamate-gated chloride (GluCl) channels. A series of novel phenylpyrazoles containing arylimine or 1-methoxyaryl groups were designed and synthesized. The addition reaction of methanol to the imines 1-11 was investigated and the cayno addition products 13-15 were obtained. The compounds 1-15 were confirmed by ¹H NMR and elemental analysis. The results of bioassay indicated that some compounds exhibited comparable bioactivity to fipronil against a broad spectrum of insects such as bean aphid (Aphis craccivora), mosquito (Culex pipiens pallens), diamondback moth (Plutella xylostella) and Oriental armyworm (Mythimna separata). Especially, the foliar contact activity against bean aphid of compound 7 at 10 µg mL^-1 was 68%, the larvacidal activity against mosquito of compounds 5, 13 and 15 at 0.0025 µg mL^-1 was 100%, the larvacidal activity against diamondback moth of compounds 9 and 11 at 0.05 µg mL^-1 was 100%, the larvacidal activity against Oriental armyworm of compound 9 at 1 µg mL^-1 was 100%. The 3-cayno moiety on pyrazole ring was essential for the high insecticidal activities against bean aphid, diamondback moth and Oriental armyworm, while the 3-carbimidate moiety on pyrazole ring was crucial to the excellent high insecticidal activities against mosquito.

Systemic Stereoselectivity Study of Etoxazole: Stereoselective Bioactivity, Acute Toxicity, and Environmental Behavior in Fruits and Soils

This is the first systemic assessment of the stereoselectivity of etoxazole enantiomers. Etoxazole's stereoselective bioactivity was assessed against target organisms ( Tetranychus urticae eggs and Tetranychus cinnabarinus eggs), and its acute toxicity was assessed toward nontarget aquatic organisms ( Daphnia magna and Danio rerio). Additionally, stereoselective elimination was investigated in three species of fruits (grape and strawberry grown in a greenhouse and apple grown in an open field) and in field soil. The ovicidal activity of (+)-( S)-etoxazole against Tetranychus urticae and Tetranychus cinnabarinus eggs was about 16 and 24 times higher, respectively, than that of (-)-( R)-etoxazole. Inconsistent order of etoxazole isomer toxicity was found toward different aquatic organisms: (+)-( S)-etoxazole showed nearly 8.7 times higher acute toxicity than (-)-( R)-etoxazole toward Daphnia magna, whereas (-)-( R)-etoxazole was ∼4.5 times more toxic to Danio rerio than (+)-( S)-etoxazole. Stereoselective degradation of etoxazole enantiomers showed significant variation in various fruits and field soil. The (+)-( S)-etoxazole was preferentially dissipated in grape and strawberry fruits grown under greenhouse condition, whereas (-)-( R)-etoxazole degraded faster than its antipode in apple fruits and soils under open-field condition. Overall, the stereoselectivity of etoxazole enantiomers should be fully considered in comprehensive environmental health risk in future work.

Design, synthesis, insecticidal activity and molecular docking of doramectin derivatives

A series of new doramectin derivatives containing carbamate, ester and sulfonate were synthesized, and their structures were characterized by ¹H and ¹³C nuclear magnetic resonance (NMR) and high-resolution mass spectrum (HRMS). Their insecticidal activities against oriental armyworm, diamondback moth, and corn borer were evaluated and compared with the parent doramectin and commercial avermectins, metolcarb, fenpropathrin. Among all compounds, three compounds (3a, 3g and 3h) showed excellent insecticidal effect. In particular, compound 3g containing cyclopropyl carbamate against oriental armyworm, diamondback moth, and corn borer, exhibited the most promising insecticidal activity with the final mortality rate of 66.67%, 36.67%, 40.00% at the concentration of 12.5 mg/L, respectively. The LC₅₀ values of 3g were 5.8859, 22.3214, and 22.0205 mg/L, showing 6.74, 2.23, 2.21-fold higher potency than parent doramectin (LC₅₀ values of 39.6907, 49.7736, and 48.6129 mg/L) and 6.83, 1.93, 3.36-fold higher potency than commercial avermectins (LC₅₀ values of 40.2489, 42.9922, and 73.9508 mg/L). Additionally, molecular docking simulations revealed that 3g displayed stronger hydrogen-bonding action in binding with the GABA receptor than parent doramectin, which were crucial for keeping high insecticidal activity. The present work demonstrated that these compounds containing alkyl carbamate group could be considered as potential candidates for the development of novel pesticides in the future.

Synthesis, Nematicidal Activity and Docking Study of Novel Pyrazole-4-Carboxamide Derivatives Against Meloidogyne incognita

Background:

A series of novel 2,6-dichloro-4-(trifluoromethyl)phenyl)-3-(difluoromethyl)- 1H-pyrazole-4-carboxamide derivatives were designed and synthesized.

Methods:

All the title compounds were confirmed by 1H NMR and MS.

Results and Conclusion:

The primarily nematicidal activity results indicated that some of them exhibited moderate control efficacy against the tomato root-knot nematode disease caused by Meloidogyne incognita.

Facile Three-Component Synthesis, Insecticidal and Antifungal Evaluation of Novel Dihydropyridine Derivatives

In an attempt to find the neonicotinoid insecticides, twenty novel dihydropyridine derivatives were designed, "green" synthesized via one pot facile three-component reaction and evaluated for their bioactivities against Tetranychus cinnabarinus, Myzus persicae, Brevicoryne brassicae, Fusarium oxysporum f. sp. vasinfectum, Magnaporthe oryzae, Sclerotinia sclerotiorum and Botrytis cinereal. All of the tested compounds showed potent insecticidal activity, and some were much better in comparison with imidacloprid (IMI). Especially, compounds 3d (LC₅₀: 0.011 mM) and 5c (LC₅₀: 0.025 mM) were 12.2- and 5.4-fold more active than IMI (LC₅₀: 0.135 mM) against T. cinnabarinus, respectively. Moreover, out of all the derivatives, compound 3d (LC₅₀: 0.0015 mM) exhibited the strongest insecticidal activity against B. brassicae and compound 3i (LC₅₀: 0.0007 mM) displayed the strongest insecticidal activity against M. persicae. Surprisingly, when the concentration of compound 4 was 50 mg/L, the inhibition rate against F. oxysporum and S. sclerotiorum reached 45.00% and 65.83%, respectively. The present work indicated that novel dihydropyridine derivatives could be used as potential lead compounds for developing neonicotinoid insecticides and agricultural fungicides.

Investigation of Novel Pesticides with Insecticidal and Antifungal Activities: Design, Synthesis and SAR Studies of Benzoylpyrimidinylurea Derivatives

In order to find pesticides with insecticidal and antifungal activities, a series of novel benzoyl pyrimidinylurea derivatives were designed and synthesized. All target compounds were identified by ¹H-NMR spectroscopy and HRMS. Insecticidal and antifungal activity of these compounds were evaluated and the structure-activity relationships (SAR) were clearly and comprehensively illustrated. Compound 7, with low toxicity to zebrafish (LC50 = 378.387 µg mL-1) showed 100% inhibition against mosquito (Culex pipiens pallens) at 0.25 µg mL-1. Both compounds 19 and 25 exhibited broad-spectrum fungicidal activity (>50% inhibitory activities against 13 phytopathogenic fungi), which were better than those of the commercial pesticide pyrimethanil (>50% inhibitory activities against eight phytopathogenic fungi). Furthermore, compounds 19 and 25 exhibited protective activity against Sclerotinia sclerotiorum on leaves of Brassica oleracea L. during in vivo experiments.

Natural Product-Based Pesticide Discovery: Design, Synthesis and Bioactivity Studies of N-Amino-Maleimide Derivatives

Natural products are an important source of pesticide discovery. A series of N-amino-maleimide derivatives containing hydrazone group were designed and synthesized based on the structure of linderone and methyllinderone which were isolated from Lindera erythrocarpa Makino. According to the bioassay results, compounds 2 and 3 showed 60% inhibition against mosquito (Culex pipiens pallens) at 0.25 µg·mL−1. Furthermore, the results of antifungal tests indicated that most compounds exhibited much better antifungal activities against fourteen phytopathogenic fungi than linderone and methyllinderone and some compounds exhibited better antifungal activities than commercial fungicides (carbendazim and chlorothalonil) at 50 µg·mL−1. In particular, compound 12 exhibited broad-spectrum fungicidal activity (>50% inhibitory activities against 11 phytopathogenic fungi) and compounds 12 and 14 displayed 60.6% and 47.9% inhibitory activity against Rhizoctonia cerealis at 12.5 µg·mL−1 respectively. Furthermore, compound 17 was synthesized, which lacks N-substituent at maleimide and its poor antifungal activity against Sclerotinia sclerotiorum and Rhizoctonia cerealis at 50 µg·mL−1 showed that the backbone structure of N-amino-maleimide derivatives containing hydrazone group was important to the antifungal activity.

Synthesis of Novel Amino Acid-Fipronil Conjugates and Study on Their Phloem Loading Mechanism

To develop a new pesticide with phloem mobility, a series of new amino acid–fipronil conjugates were designed and synthesized based on derivatization at the 3-position of the pyrazole ring of fipronil. Experiments using a Ricinus communis seedling system showed that all tested conjugates were phloem mobile except for the isoleucine–fipronil conjugate, and that the serine–fipronil conjugate (4g) exhibited the highest concentration in phloem sap (52.00 ± 5.80 μM). According to prediction with log Cf values and uptake experiments with Xenopus oocytes, the phloem loading process of conjugate 4g involved both passive diffusion and an active carrier system (RcANT15). In particular, compared with for a previously reported glycinergic–fipronil conjugate (GlyF), passive diffusion played a more important role for conjugate 4g in the enhancement of phloem mobility. This study suggests that associating a nutrient at a different position of an existing pesticide structure could still be effective in obtaining phloem-mobile derivatives, but the distinct physicochemical properties of resultant conjugates may lead to different phloem loading mechanisms.

Synthesis and Pharmacological Activities of Pyrazole Derivatives: A Review

Pyrazole and its derivatives are considered a pharmacologically important active scaffold that possesses almost all types of pharmacological activities. The presence of this nucleus in pharmacological agents of diverse therapeutic categories such as celecoxib, a potent anti-inflammatory, the antipsychotic CDPPB, the anti-obesity drug rimonabant, difenamizole, an analgesic, betazole, a H2-receptor agonist and the antidepressant agent fezolamide have proved the pharmacological potential of the pyrazole moiety. Owing to this diversity in the biological field, this nucleus has attracted the attention of many researchers to study its skeleton chemically and biologically. This review highlights the different synthesis methods and the pharmacological properties of pyrazole derivatives. Studies on the synthesis and biological activity of pyrazole derivatives developed by many scientists around the globe are reported.

Synthesis and Pharmacological Activities of Pyrazole Derivatives: A Review

Pyrazole and its derivatives are considered a pharmacologically important active scaffold that possesses almost all types of pharmacological activities. The presence of this nucleus in pharmacological agents of diverse therapeutic categories such as celecoxib, a potent anti-inflammatory, the antipsychotic CDPPB, the anti-obesity drug rimonabant, difenamizole, an analgesic, betazole, a H2-receptor agonist and the antidepressant agent fezolamide have proved the pharmacological potential of the pyrazole moiety. Owing to this diversity in the biological field, this nucleus has attracted the attention of many researchers to study its skeleton chemically and biologically. This review highlights the different synthesis methods and the pharmacological properties of pyrazole derivatives. Studies on the synthesis and biological activity of pyrazole derivatives developed by many scientists around the globe are reported.

Synthesis, biological activities and structure-activity relationships for new avermectin analogues

In an effort to discover new molecules with good insecticidal activities, more than 40 new avermectin derivatives were synthesized and evaluated for their biological activities against three species of arachnids, insects and nematodes, namely, Tetranychus Cinnabarinus, Aphis craccivora and Bursaphelenchus xylophilus. All the tested compounds showed potent inhibitory activities against three insect species. Notably, the majority of compounds exhibited high selectivity against T. cinnabarinus, some of which were much better in comparison with avermectin. Especially compounds 9j (LC50: 0.005 μM) and 16d (LC50: 0.002 μM) were 2.5- and 4.7-fold more active than avermectin (LC50: 0.013 μM), respectively, against T. cinnabarinus. Moreover, compounds 9b, 9d-f, 9h, 9j, 9l, 9n, 9p, 9r, 9v and 17d showed superior activities with LC50 values of 2.959-5.013 μM compared to that of 1 (LC50: 6.746 μM) against B. xylophilus. Meanwhile, the insecticidal activities of compounds 9f, 9g, 9h, and 9m against A. craccivora were 7-8 times better than that of avermectin, with LC50 values of 7.744, 5.634, 6.809, 7.939 and 52.234 μM, respectively. Furthermore, QSAR analysis showed that the molecular shape, size, connectivity degree and electronic distribution of avermectin analogues had substantial effects on insecticidal potency. These preliminary results provided useful insight in guiding further modifications of avermectin in the development of potential new insecticides.

Novel hydrazone derivatives containing pyridine amide moiety: Design, synthesis, and insecticidal activity

A series of novel hydrazone derivatives containing pyridine amide moiety were designed, synthesized, and evaluated for their insecticidal activity. Bioassays indicated that some of the target compounds exhibited good insecticidal activities against Nilaparvata lugens (N. lugens), Plutella xylostella (P. xylostella), Mythimna separata (M. separata), Helicoverpa armigera (H. armigera), Pyrausta nubilalis (P. nubilalis), and Culex pipiens pallens (C. pipiens pallens). In particular, compound 5j revealed excellent insecticidal activity against C. pipiens pallens, with the 50% lethal concentration (LC50) and the 95% lethal concentration (LC95) values of 2.44 and 5.76 mg/L, respectively, which were similar to those of chlorpyrifos (3.26 and 6.98 mg/L, respectively), tebufenozide (1.22 and 2.49 mg/L, respectively), and RH-5849 (2.61 and 6.37 mg/L, respectively). These results indicated that hydrazone derivatives containing pyridine amide moiety could be developed as novel and promising insecticides.

Synthesis, biological activities, and quantitative structure-activity relationship (QSAR) study of novel camptothecin analogues

In continuation of our program aimed at the development of natural product-based pesticidal agents, three series of novel camptothecin derivatives were designed, synthesized, and evaluated for their biological activities against T. Cinnabarinus, B. brassicae, and B. xylophilus. All of the derivatives showed good-to-excellent activity against three insect species tested, with LC50 values ranging from 0.00761 to 0.35496 mmol/L. Remarkably, all of the compounds were more potent than CPT against T. Cinnabarinus, and compounds 4d and 4c displayed superior activity (LC50 0.00761 mmol/L and 0.00942 mmol/L, respectively) compared with CPT (LC50 0.19719 mmol/L) against T. Cinnabarinus. Based on the observed bioactivities, preliminary structure-activity relationship (SAR) correlations were also discussed. Furthermore, a three-dimensional quantitative structure-activity relationship (3D-QSAR) model using comparative molecular field analysis (CoMFA) was built. The model gave statistically significant results with the cross-validated q2 values of 0.580 and correlation coefficient r2 of 0.991 and  of 0.993. The QSAR analysis indicated that the size of the substituents play an important in the activity of 7-modified camptothecin derivatives. These findings will pave the way for further design, structural optimization, and development of camptothecin-derived compounds as pesticidal agents.

Synthesis, larvicidal activities and antifungal activities of novel chlorantraniliprole derivatives and their target in the ryanodine receptor

In order to identify novel chlorantraniliprole derivatives as potential insecticides or fungicides, 25 analogues of chlorantraniliprole were synthesized. The insecticidal activities against oriental armyworm and the antifungal activities against five typical fungi of these derivatives were tested. Compounds 2u, 2x and 2y exhibited good activities against oriental armyworm, especially compounds 2u and 2x which showed higher larvicidal activities than indoxacarb. Moreover, all of the tested compounds exhibited activities against five typical fungi. The Ki values of all synthesized compounds were calculated using AutoDock4. The relationship between the Ki values and the results of insecticidal activities against oriental armyworm further indicated that the membrane-spanning domain protein of the ryanodine receptor might contain chlorantraniliprole binding sites.

Design, synthesis and insecticidal activities of N-(4-cyano-1-phenyl-1H-pyrazol-5-yl)-1,3-diphenyl-1H-pyrazole-4-carboxamide derivatives

Twenty novel diphenyl-1H-pyrazole derivatives with cyano substituent were designed and synthesized, and their insecticidal activities were evaluated.

Support vector machine (SVM) classification model based rational design of novel tetronic acid derivatives as potent insecticidal and acaricidal agents

A novel SVM classification model was constructed and applied in the development of novel tetronic acid derivatives as potent insecticidal and acaricidal agents.

A novel fluorescent conjugate applicable to visualize the translocation of glucose-fipronil

The ability to visualize the movement of glycosyl insecticides contributes to learning their translocation and distribution in plants. In our present work, a novel fluorescent glucose-fipronil conjugate N-[3-cyano-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazol-5-yl]-1-(2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-β-D-glucopyranosyl)-1H-1,2,3-triazole-4-methanamine (2-NBDGTF), was obtained via click chemistry. Disk uptake experiments showed that an active carrier-mediated system was involved in the 2-NBDGTF uptake process. Meanwhile, 2-NBDGTF exhibited comparable phloem mobility with GTF in castor bean seedlings. Visualization of 2-NBDGTF uptake and transport experiment showed that this fluorescent glucose-fipronil conjugate could be loaded into sieve tubes after transiting through epidermal cells and mesophyll cells and then translocate from cotyledon to hypocotyl via phloem in castor bean seedlings. The results above determined that it is a promising fluorescence tagging approach for revealing the activities of glycosyl insecticides and 2-NBDGTF is a reasonable and feasible fluorescent surrogate of GTF for tracing the distribution of glucose-fipronil conjugates.

Glucose positions affect the phloem mobility of glucose-fipronil conjugates

In our previous work, a glucose-fipronil (GTF) conjugate at the C-1 position was synthesized via click chemistry and a glucose moiety converted a non-phloem-mobile insecticide fipronil into a moderately phloem-mobile insecticide. In the present paper, fipronil was introduced into the C-2, C-3, C-4, and C-6 positions of glucose via click chemistry to obtain four new conjugates and to evaluate the effects of the different glucose isomers on phloem mobility. The phloem mobility of the four new synthetic conjugates and GTF was tested using the Ricinus seedling system. The results confirmed that conjugation of glucose at different positions has a significant influence on the phloem mobility of GTF conjugates.

Synthesis and Insecticidal Evaluation of Aryl Pyrazole 5-Fluorouracil Compounds

Twenty eight aryl pyrazole derivatives containing 5-fluorouracil were designed and synthesised via the key intermediate 1-aryl-3-methyl-1 H-pyrazole-5-carboxylic acid. The structures of target compounds were confirmed by 1H NMR, FT-IR, EA and their insecticidal activities were evaluated. The bioassays revealed that aryl pyrazole derivatives containing 5-fluorouracil exhibited excellent insecticidal activities against Culex pipiens and Musca domestica at a concentration of 0.1%. Some compounds still showed good insecticidal activities even at a concentration of 0.05%.