Design, synthesis and structure-activity relationship of novel coumarin derivatives

Discovery of new N-Phenylamide Isoxazoline derivatives with high insecticidal activity and reduced honeybee toxicity

Isoxazoline is a novel structure with strong potential for controlling agricultural insect pests, but its high toxicity to honeybees limits its development in agriculture. Herein, a series of N-phenylamide isoxazoline derivatives with low honeybee toxicity were designed and synthesized using the intermediate derivatization method. Bioassay results showed that these compounds exhibited good insecticidal activity. Compounds 3b and 3f showed significant insecticidal effects against Plutella xylostella (P. xylostella) with median lethal concentrations (LC50) of 0.06 and 0.07 mg/L, respectively, comparable to that of fluralaner (LC50 = 0.02 mg/L) and exceeding that of commercial insecticide fluxametamide (LC50 = 0.52 mg/L). It is noteworthy that the acute honeybee toxicities of compounds 3b and 3f (LD50 = 1.43 and 1.63 μg/adult, respectively) were significantly reduced to 1/10 of that of fluralaner (LD50 = 0.14 μg/adult), and were adequate or lower than that of fluxametamide (LD50 = 1.14 μg/adult). Theoretical simulation using molecular docking indicates that compound 3b has similar binding modes with fluralaner and a similar optimal docking pose with fluxametamide when binding to the GABA receptor, which may contribute to its potent insecticidal activity and relatively low toxicity to honey bees. This study provides compounds 3b and 3f as potential new insecticide candidates and provides insights into the development of new isoxazoline insecticides exhibiting both high efficacy and environmental safety.

Design and Synthesis of Pyrimidine Amine Containing Isothiazole Coumarins for Fungal Control

Developing new fungicides is always crucial to protecting crops. A series of 4-(3,4-dichloroisothiazol-5-yl)-7-(2-((5-(5-pyrimidin-4-yl)amino)ethoxy)-8-methyl) coumarin derivatives were designed and synthesized by Williamson ether condensation and substitution reactions. Structure determinations were clarified by 1H NMR, 13C NMR, and HRMS, and compound 4h crystallized by the fusion method for further structural confirmation. The in vitro bioassay results showed that the target compounds displayed good fungicidal activity against Alternaria solani, Botrytis cinerea, Cercospora arachidicola, Fusarium graminearum, Physalospora piricola, Rhizoctonia solani, and Sclerotinia sclerotiorum. Among them, compounds 4b and 4d showed higher inhibitory activity against R. solani, with EC50 values of 11.3 and 13.7 μg/mL, respectively, and they were more active than the positive control diflumetorim with an EC50 value of 19.8 μg/mL. Molecular docking suggested that compound 4b and diflumetorim may have similar interactions with complex I NADH oxidoreductase. Density functional theory calculation and pesticide-likeness analysis studies gave a rational explanation of their fungicidal activity. These results indicated that compounds 4b and 4d deserved further optimization according to the principle of pesticide-likeness.

Design, Synthesis and Fungicidal Activity of Ester Derivatives of 4-(3,4-Dichloroisothiazole) 7-Hydroxy Coumarin

The development of new fungicides is vital for safeguarding crops and ensuring sustainable agriculture. Building on our previous finding that 4-(3,4-dichloroisothiazole)-7-hydroxy coumarins can be used as fungicidal leads, 44 novel coumarin ester derivatives were designed and synthesized to evaluate whether esterification could enhance their fungicidal activity. In vitro fungicidal bioassays indicated that compound 2ai displayed good activity against Alternaria solani, Botrytis cinereal, Cercospora arachidicola, Physalospora piricola and Sclerotinia sclerotiorum, with an EC₅₀ value ranging from 2.90 to 5.56 μg/mL, comparable to the lead compound 1a, with its EC₅₀ value ranging from 1.92 to 9.37 μg/mL. In vivo bioassays demonstrated that compounds 1a, 2ar and 2bg showed comparable, excellent efficacy against Pseudoperonospora cubensis at a dose of 25 µg/mL. Our research shows that the esterification of 4-(3,4-dichloroisothiazole) 7-hydroxycoumarins results in a fungicidal activity equivalent to that of its lead compounds. Furthermore, our density functional theory (DFT) calculations and 3D-QSAR modeling provide a rational explanation of the structure-activity relationship and offer valuable insights to guide further molecular design.

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.

Pd(II)-Catalyzed Fujiwara-Moritani Reactions for the Synthesis and Functionalization of Substituted Coumarins

Highly substituted coumarins, privileged and versatile scaffolds for bioactive natural products and fluorescence imaging, are obtained via a Pd(II)-catalyzed direct C-H alkenylation reaction (Fujiwara-Moritani reaction), which has emerged as a powerful tool for the construction and functionalization of heterocyclic compounds because of its chemical versatility and its environmental advantages. Thus, a selective 6-endo cyclization led to 4-substituted coumarins in moderate yields. Selected examples have been further functionalized in C3 through a second intermolecular C-H alkenylation reaction to give coumarin-acrylate hybrids, whose fluorescence spectra have been measured.

Discovery of Novel 3,4-Dichloroisothiazole-Containing Coumarins as Fungicidal Leads

Natural products are one of the resources for discovering novel fungicidal leads. As a natural fungicide, osthole was used as a coumarin-based lead compound for the development of novel fungicides. Here, a series of 3,4-dichloroisothiazole-containing 7-hydroxycoumarins were rationally designed, synthesized, and characterized by introducing a bioactive substructure, 3,4-dichloroisothiazole, into the coumarin skeleton. In vitro bioassay indicated that compound 7g displayed good activity against Rhizoctonia solani, Physalospora piricola, Sclerotinia sclerotiorum, and Botrytis cinerea. Its median effective concentration (EC₅₀) value against each of these fungi fell between 0.88 and 2.50 μg/mL, which was much lower than that of osthole against the corresponding pathogen (between 7.38 and 74.59 μg/mL). In vivo screening validated that 7k exhibited 100%, 60%, and 20% efficacy against R. solani Kühn at 200, 100, and 50 μg/mL, respectively. RNA sequence analysis implied that growth inhibition of R. solani by 7k might result from potential disruptions of fungal membrane formation and intracellular metabolism. Furthermore, a field experiment with cucumber plants indicated that 7b showed 62.73% and 74.03% efficacy against Pseudoperonospora cubensis (Berk. & Curt.) Rostov. at rates of 12.5 g a.i./ha and 25 g a.i./ha, respectively, which showed no significant difference between 7b and osthole at 30 g a.i./ha. Our studies suggested that 7b, 7g, and 7k might be used as fungicidal leads for further optimization.

Design, synthesis and fungicidal activity of 3,4-dichloroisothiazolocoumarin-containing strobilurins

Twenty-one novel 3,4-dichloroisothiazolocoumarin-containing strobilurins were rationally designed and synthesized. Preliminary bioassay showed that compounds 7c, 7h and 7l exhibited over 80% inhibitory rate against Sclerotinia sclerotiorum at 50 μg/mL, 7c exhibited good activity against S. sclerotiorum with median effective concentration (EC₅₀) of 4.08 μg/mL, while the positive control coumoxystrobin showed EC₅₀ of 1.00 μg/mL. In addition, 7d showed better fungicidal activity with a lower EC₅₀ value of 7.65 μg/mL against Botrytis cinerea than that of positive control trifloxystrobin with its EC₅₀ value of 21.96 μg/mL. This study indicated that 3,4-dichloroisothiazolocoumarin-containing strobilurin was a promising fungicide lead deserved for further study.

Design, synthesis and herbicidal evaluation of novel uracil derivatives containing an isoxazoline moiety

BACKGROUND

Glyphosate is the most widely used and successful herbicide discovered to date, but its utility is now threatened by the occurrence of several glyphosate-resistant weed species. Saflufenacil is a relatively new herbicide developed by BASF in 2010. It is a highly effective selective herbicide showing excellent control on broadleaf weeds (more than 90 species), significantly superior to other protoporphyrinogen oxidase (PPO) inhibitor herbicides at the level of weeds controlled. It is also effective against glyphosate-resistant Conyza canadensis if used in combination with glyphosate. A series of novel uracil-based PPO inhibitors containing an isoxazoline moiety were designed via the intermediate derivatization method, synthesized using a key saflufenacil raw material as starting material and evaluated for herbicidal activity.

RESULTS

The target compounds were characterized by ¹ H NMR and high-resolution electrospray mass spectra. Bioassays indicated that some title compounds can control efficiently and effectively both broadleaf weeds and grassy weeds at low doses, especially the glyphosate-resistant weeds C. canadensis and Eleusine indica.

CONCLUSION

This work provides a basis for further studies of 9b for control of a wider range of weeds, particularly for glyphosate-resistant weeds.

Synthesis of Novel 6-Aryloxy-4-chloro-2-phenylpyrimidines as Fungicides and Herbicide Safeners

Fenclorim is a commercial herbicide safener with fungicidal activity used for chloroacetanilide herbicides, which might be suitable as a lead compound for screening novel fungicides. However, little has been reported so far on the structure-activity relationship of fungicidal activities of fenclorim or its analogues. Here, a series of 4-chloro-6-substituted phenoxy-2-phenylpyrimidine derivatives was synthesized by a substructure splicing route using fenclorim as a lead compound. The structures of synthesized derivatives were characterized by ¹H NMR, ¹³C NMR, and HRMS. Their fungicidal and herbicide safening activities were then evaluated. The results revealed that compound 11 had the best fungicidal activity against Sclerotinia sclerotiorum and Thanatephorus cucumeris, which was better than that of the control pyrimethanil. Moreover, compounds 3, 5, and 25 exhibited excellent safening activities against fresh weight, plant height, and root length, respectively. Such activities were significantly improved when compared to fenclorim. In summary, these findings look promising for the preparation of new fungicides and herbicide safeners based on the structure of fenclorim.

4-Methylumbelliferone fused oxazole thioether derivatives: synthesis, characterization and antifungal activities

Series of thioether derivatives containing 4-methylumbelliferone fused oxazole moiety were designed and synthesised, their structures were fully characterized by ¹H NMR, ¹³C NMR and HR-ESI-MS as well. Moreover, the in vitro antifungal potency of the title compounds were preliminarily evaluated for their possible use as a fungicide. Meanwhile, ethyl thioethers 3aa and 3ba displayed remarkable inhibitory effect against the mycelium growth of Valsa mali and Botrytis cinerea with EC₅₀ of 12-16 μg/mL. Furthermore, compounds 3aa and 3ba also exhibited > 88% protective and curative effect against B. cinerea on tomato fruits at 90 μg/mL. Additionally, the environmental toxicity of the title compounds against the brine shrimp Artemia salina were evaluated as well. The results indicated that most of the title compounds exhibited weak toxic to aquatic organism A. salina.

Design, Synthesis, and Structure-Activity Relationship of Novel Spiropyrimidinamines as Fungicides against Pseudoperonospora cubensis

Harmful fungus and the developed resistance to available fungicides seriously threaten the yield and quality of crops; thus, the search for new, highly efficient, and resistance-overcoming fungicides remains a quite urgent goal of agricultural scientists. In this study, a series of novel spiropyrimidinamine derivatives were designed and synthesized by employing the intermediate derivatization method (IDM). Their structures were identified by ¹H NMR, elemental analyses, and MS spectra. The structure of compound 5 was further confirmed by X-ray diffraction. Bioassays indicated that a number of the title compounds exhibited some fungicidal activities against Pseudoperonospora cubensis. Especially, compound 5 displayed excellent activity (EC₅₀ = 0.422 mg/L), significantly higher than those of the commercialized fungicides cyazofamid, flumorph, and diflumetorim. The structure-activity relationship was also discussed. It was concluded that compound 5 with super fungicidal potency and a novel structure is a promising agrochemical fungicide candidate for further development.

Design, Synthesis, and Structure-Activity Relationship of New Arylpyrazole Pyrimidine Ether Derivatives as Fungicides

To explore a novel fungicide effectively against cucumber downy mildew (CDM), a series of new arylpyrazole containing pyrimidine ether derivatives were designed and synthesized by employing the intermediate derivatization method (IDM). The structures of synthesized compounds were identified by ¹H NMR, ¹³C NMR, elemental analyses, MS, and X-ray diffraction. Bioassays demonstrated that some of the title compounds exhibited excellent fungicidal activities against CDM. Especially, compound 7 (EC₅₀ = 1.22 mg/L) displayed significantly higher bioactivity than that of commercial fungicides diflumetorim and flumorph and nearly equal effect to that of cyazofamid. The relationship between the structure and fungicidal activity of the synthesized compounds was discussed as well. The study showed that compound 7 was a promising fungicide candidate for further development.

Coumarin: a novel player in microbial quorum sensing and biofilm formation inhibition

Antibiotic resistance is a growing threat worldwide, causing serious problems in the treatment of microbial infections. The discovery and development of new drugs is urgently needed to overcome this problem which has greatly undermined the clinical effectiveness of conventional antibiotics. An intricate cell-cell communication system termed quorum sensing (QS) and the coordinated multicellular behaviour of biofilm formation have both been identified as promising targets for the treatment and clinical management of microbial infections. QS systems allow bacteria to adapt rapidly to harsh conditions, and are known to promote the formation of antibiotic tolerant biofilm communities. It is well known that biofilm is a recalcitrant mode of growth and it also increases bacterial resistance to conventional antibiotics. The pharmacological properties of coumarins have been well described, and these have included several that possess antimicrobial properties. More recently, reports have highlighted the potential role of coumarins as alternative therapeutic strategies based on their ability to block the QS signalling systems and to inhibit the formation of biofilms in clinically relevant pathogens. In addition to human infections, coumarins have also been found to be effective in controlling plant pathogens, infections in aquaculture, food spoilage and in reducing biofouling caused by eukaryotic organisms. Thus, the coumarin class of small molecule natural product are emerging as a promising strategy to combat bacterial infections in the new era of antimicrobial resistance.

Design, synthesis, and herbicidal activity of novel quaternary ammonium salt derivatives

A series of novel quaternary ammonium salt derivatives were designed and synthesized by introducing the herbicide carboxylic acid into substituted aminoacetanilide compounds which derived from herbicides alachlor or acetochlor, using the intermediate derivatization methods in an attempt to obtain novel candidates for weed control. The herbicidal activity assays in greenhouse demonstrated that some of the title compounds exhibited good herbicidal activities against velvet leaf, youth-and-old age, barnyard grass, and foxtail. Especially, III9 gave the best activity (EC₅₀ (ga.i/ha): YOA 34.1, VEL 33.6, FOX 15.9, BYG 36.2). The field trials indicated that III9 had better herbicidal activity than the commercial herbicide imazethapyr to control broadleaf weeds at 150ga.i/ha. The present work demonstrated that the quaternary ammonium salt derivatives can be used as potential lead compounds for discovering novel herbicides with improved activity. III9 itself is worthy of being further developed as an herbicidal candidate. Further syntheses, structure optimization studies, and field trials around III9 are in progress.

Design, Synthesis, and Structure-Activity Relationship of New Pyrimidinamine Derivatives Containing an Aryloxy Pyridine Moiety

The pyrimidinamine diflumetorim is an ideal template for the discovery of agrochemical lead compounds due to its unique mode of action, novel chemical structure, and lack of reported resistance. To develop a new pyrimidinamine fungicide effective against cucumber downy mildew (CDM), a series of new pyrimidinamine derivatives containing an aryloxy pyridine moiety were designed and synthesized by employing the recently reported intermediate derivatization method (IDM). The structures of all compounds were identified by ¹H NMR, elemental analyses, HRMS, and X-ray diffraction. Bioassays demonstrated that some of the title compounds exhibited excellent fungicidal activities against CDM. Compound 9 gave the best activity (EC₅₀ = 0.19 mg/L), which is significantly better than the commercial fungicides diflumetorim, flumorph, and cyazofamid. The relationship between structure and fungicidal activity of the synthesized pyrimidinamines was explored. The study showed that compound 9 is a promising fungicide candidate for further development.

Evaluation of antifungal activities and structure-activity relationships of coumarin derivatives

BACKGROUND

Osthol is a natural coumarin and lead compound that has been developed into commercial fungicides in China. Natural coumarins comprise five major subtypes: simple coumarins, linear furanocoumarins, angular furanocoumarins, linear pyranocoumarins and angular pyranocoumarins. Studies pertaining to the antifungal activities of linear pyranocoumarins are few, and no reports exist for the antifungal activities of angular pyranocoumarins. In order to discover more antifungal natural coumarins, we synthesised a series of simple natural coumarins and isolated several plant-based furanocoumarins and pyranocoumarins using previously described methods. The compounds were biologically evaluated against some plant fungal pathogens.

RESULTS

Several of the 35 coumarins evaluated here exhibited strong activities against specific fungal species, including compound 25 (Pd-D-V, a linear pyranocoumarin), compound 26 (libanorin, an angular furanocoumarin) and compound 34 (disenecioyl khellactone, an angular pyranocoumarin). Compound 25 exhibited a high activity against Sclerotinia sclerotiorum (EC₅₀ = 13.2 µg mL^-1 ); compound 34 displayed a strong antifungal activity against Botrytis cinerea (EC₅₀ = 11.0 µg mL^-1 ).

CONCLUSION

This study demonstrates that several natural coumarins (one linear pyranocoumarin and one angular pyranocoumarin in particular) exhibit strong antifungal activities. These results call for further studies, where these coumarins can be examined as potential lead compounds for developing novel antifungal agents. © 2016 Society of Chemical Industry.

Design, Synthesis and Antifungal Activity of Coumarin Ring-Opening Derivatives

Based on our initial design, we synthesized two series of coumarin ring-opening derivatives by the reactions of hydrolysis and methylation. Results of antifungal screening in vitro showed that the target compounds exhibited potent activity against the six common pathogenic fungi. Compounds 6b, 6e, 6g, 6i, 7b and 7c were identified as the most active ones, and the EC₅₀ values of these active compounds were further tested. Compared to the commonly used fungicide Azoxystrobin (0.0884 µM), compounds 6b (0.0544 µM) and 6e (0.0823 µM) displayed improved activity against Botrytis cinerea.

Microwave-assisted Synthesis and antifungal activity of coumarin[8,7-e][1,3]oxazine derivatives

The synthesis of novel coumarin[8,7-e][1,3]oxazine derivatives through a microwave-assisted three-component one-pot Mannich reaction is described in this study. All the target compounds were evaluated in vitro for their antifungal activity against Botrytis cinerea, Colletotrichum capsici, Alternaria solani, Gibberella zeae, Rhizoctonia solani, and Alternaria mali. The preliminary bioassays showed that 5e, 5m, and 5s exhibited good antifungal activity and the most active compound was 5m with an [Formula: see text] value as low as 2.1 nM against Botrytis cinerea.

Efficient Approach To Discover Novel Agrochemical Candidates: Intermediate Derivatization Method

Intensive competition of intellectual property, easy development of agrochemical resistance, and stricter regulations of environmental concerns make the successful rate for agrochemical discovery extremely lower using traditional agrochemical discovery methods. Therefore, there is an urgent need to find a novel approach to guide agrochemical discovery with high efficiency to quickly keep pace with the changing market. On the basis of these situations, here we summarize the intermediate derivatization method (IDM) between conventional methods in agrochemicals and novel ones in pharmaceuticals. This method is relatively efficient with short time in discovery phase, reduced cost, especially good innovated structure, and better performance. In this paper, we summarize and illustrate "what is the IDM" and "why to use" and "how to use" it to accelerate the discovery of new biologically active molecules, focusing on agrochemicals. Furthermore, we display several research projects in our novel agrochemical discovery programs with improved success rate under guidance of this strategy in recent years.

Discovery of pyridine-based agrochemicals by using Intermediate Derivatization Methods

Pyridine-based compounds have been playing a crucial role as agrochemicals or pesticides including fungicides, insecticides/acaricides and herbicides, etc. Since most of the agrochemicals listed in the Pesticide Manual were discovered through screening programs that relied on trial-and-error testing and new agrochemical discovery is not benefiting as much from the in silico new chemical compound identification/discovery techniques used in pharmaceutical research, it has become more important to find new methods to enhance the efficiency of discovering novel lead compounds in the agrochemical field to shorten the time of research phases in order to meet changing market requirements. In this review, we selected 18 representative known agrochemicals containing a pyridine moiety and extrapolate their discovery from the perspective of Intermediate Derivatization Methods in the hope that this approach will have greater appeal to researchers engaged in the discovery of agrochemicals and/or pharmaceuticals.

Design, synthesis, and herbicidal activity of novel substituted 3-(pyridin-2-yl)benzenesulfonamide derivatives

A series of novel substituted 3-(pyridin-2-yl)benzenesulfonamide derivatives were designed and synthesized using 2-phenylpridines as the lead compound by intermediate derivatization methods in an attempt to obtain novel compound candidates for weed control. The herbicidal activity assay in glasshouse tests showed several compounds (II6, II7, II8, II9, II10, II11, III2, III3, III4, and III5) could efficiently control velvet leaf, youth-and-old age, barnyard grass, and foxtail at the 37.5 g/ha active substance. Especially, the activities of II6, II7, III2, and III4 were proved roughly equivalent to the saflufenacil and better than 95% sulcotrione at the same concentration. The result of the herbicidal activity assay in field tests demonstrated that II7 at 60 g/ha active substance could give the same effect as bentazon at 1440 g/ha active substance to control dayflower and nightshade, meanwhile II7 showed better activity than oxyfluorfen to control arrowhead and security to rice. The present work indicates that II7 may be a novel compound candidate for potential herbicide.

Design, synthesis, and structure-activity relationship of novel aniline derivatives of chlorothalonil

Chlorothalonil with both low cost and low toxicity is a popularly used fungicide in the agrochemical field. The presence of nucleophilic groups on this compound allows further chemical modifications to obtain novel chlorothalonil derivatives. Fluazinam, another commercially available agent with a broad fungicidal spectrum, has a scaffold of diaryl amine structure. To mimic this backbone structure, a variety of (un)substituted phenyl amines was used as nucleophilic agents to react with chlorothalonil to obtain compounds with a diphenyl amine structure. Via an elegant design, two leads, 2,4,5-trichloro-6-(2,4-dichlorophenylamino)isophthalonitrile (7) and 2,4,5-trichloro-6-(2,4,6-trichlorophenylamino)isophthalonitrile (11), with potential fungicidal activity were discovered after a preliminary bioassay screen. These two leads were further modified to obtain final products by replacing the chlorine groups in the phenyl ring in phenyl amine with other functional groups. These functional groups with various electronic properties and spatial characteristics were considered to explore the relationship between structure and fungicidal activity. The results indicate that the electron-withdrawing group NO2 on the 4 position on the right phenyl ring plays a unique role on enhancing the fungicidal activity. The compounds were identified by proton nuclear magnetic resonance and elemental analysis. Bioassays demonstrated that some of the title compounds exhibited excellent fungicidal activities against cucumber downy mildew at 25 mg/L. Compound 20 has been shown as the optimal structure with 85% control against cucumber downy mildew at 6.25 mg/L concentration. The relationship between structure and fungicidal activity is reported. The present work demonstrates that chlorothalonil derivatives can be used as possible lead compounds for developing novel fungicides.

Design, synthesis and structure-activity relationship of novel insecticidal dichloro-allyloxy-phenol derivatives containing substituted pyrazol-3-ols

BACKGROUND

Pyridalyl, consisting of dicholoro-allyoxy-phenol moiety, is a novel class of insecticide showing extraordinary activities against various lepidopterous and thysanopterous pests on cotton and vegetables. To discover further novel insecticides, a series of new dichloro-allyloxy-phenol derivatives containing substituted pyrazol-3-ol moieties were designed and synthesised via the intermediate derivatisation method.

RESULTS

The target compounds were characterised by (1) H NMR, IR, MS and elemental analysis. Bioassays indicated that some of these compounds exhibited good insecticidal activities against diamondback moth (Plutella xylostella) at 6.25 mg L(-1) . The structure-activity relationship is discussed.

CONCLUSION

The present work demonstrates that dichloro-allyloxy-phenol derivatives with substituted phenylpyrazole moieties can be used as lead compounds to develop further novel insecticides.

Synthesis and Bioactivity of Novel Coumarin Derivatives

A series of coumarin derivatives (6-8) containing ( E)-methyl 2-(methoxyimino)-2-phenylacetate, ( E)-2-(methoxyimino )-N-methyl-2-phenylacetamide and methyl methoxy(phenyl)carbamate were synthesized from substituted resorcinols (1) and substituted β-keto esters (2) as starting material via cyclization and condensation reactions. The test results indicated that ( E)-methyl 2-{2-[(3-hexyl-4-methyl-coumarin-7-yloxy)methyl]phenyl}-2-(methoxyimino)acetate (6f) was the optimal structure with good fungicidal activity against cucumber grey mold (CGM) giving 100% control at 100 mg L−1 concentration, much higher than that of coumoxystrobin. Methyl 2-[(3,4-dimethyl-coumarin -7-yloxy)methyl]phenyl(methoxy)carbamate (8a) was another optimal structure with good fungicidal activity against wheat powdery mildew (WPM) showing 100% control at 50 mg L−1 concentration, at the same level as that of the commercial kresoxim-methyl, and very significantly higher than that of coumoxystrobin (no control against WPM at 400 mg L−1).