Synthesis and phloem mobility of acidic derivatives of the fungicide fenpiclonil

A series of derivatives of the phenylpyrrole fungicide fenpiclonil was synthesized in which a carboxyl group was present at various sites of this non-phloem-mobile molecule. Using the Kleier model, all these acidic analogues were predicted to be moderately phloem-mobile, especially the N-substituted derivatives. One of these latter molecules, N-carboxymethyl-3-cyano-4-(2,3-dichlorophenyl)pyrrole, exhibited some fungicidal activity on the pathogenic fungus Eutypa lata, and was then tested as a phloem-mobile pesticide in the Ricinus system. The compound was indeed mobile in the sieve tubes and was not degraded to fenpiclonil in the phloem sap under our experimental conditions. Its concentration in the sap was closely correlated to the percentage of the undissociated form of the molecule in the external medium, and was similar under acidic conditions (external pH 4.6-5.0) to that of the herbicide glyphosate.     

Some laboratory investigations relevant to the possible use of new pyrethroids in control of mosquitoes and tsetse flies

Cypermethrin, fenvalerate, permethrin, (S)-α-cyano-3-phenoxybenzyl (1R,cis)-3-(2, 2-dibromovinyl)-2, 2-dimethylcyclopropanecarboxylate (NRDC 161) and (R,S)-α-cyano-3-phenoxybenzyl 2, 2,3, 3-tetramethylcyclopropanecarboxylate (S-3206; WL 41706) have been tested against adult mosquitoes (Anopheles stephensi) and tsetse flies (Glossina austeni). They possess many of the necessary characteristics such as high intrinsic toxicity, low volatility, and high stability but vary considerably in the contact action of their spray residues.     

Photolysis of Diuron

The major photoproducts observed in the photolysis of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] ( 2 ) in aqueous solution resulted from a heterolytic substitution of chlorine by OH (photohydrolysis). A wavelength effect was observed: at 254 nm the formation of 3-(4-chloro-3-hydroxyphenyl)-1,1-dimethylurea ( 3 ) accounted for more than 90% of the conversion, whereas when the solution was irradiated in ‘black light’ (85% of photons emitted at 365 nm, about 7% at 334 nm), the major photoproduct was 3-(3-chloro-4-hydroxyphenyl)-1,1-dimethylurea ( 4 ). The presence of methanol favoured the photoreduction into 3-(3-chlorophenyl)-1,1-dimethylurea ( 5 ). Completely different reactions were observed when 2 was irradiated in dry aerobic conditions on silica. They resulted from elimination or oxidation of methyl groups. The main photoproducts initially formed were 3-(3,4-dichlorophenyl)-1-methyl urea ( 6 ) and 3-(3,4-dichlorophenyl)-1-formyl-1-methylurea ( 7 ). In the second stage ( 6 ) was transformed into (3,4-dichlorophenyl)-urea ( 8 ) and 3-(3,4-dichlorophenyl)-1-formylurea ( 9 ); some other minor products such as monuron ( 1 ) were also identified. The formation rate of 6 and 7 was much slower on clay (montmorillonite or kaolin) than on silica. In contrast with products 6 and 8 , the formation of 7 and 9 needed the presence of oxygen: they did not appear when diuron was irradiated in deoxygenated C₂Cl₃F₃. It can be concluded that the photolysis of diuron is highly dependent on the conditions of irradiation. © 1997 SCI.     

Action of fungicidal triazoles of the diclobutrazol series on ustilago maydis

Diclobutrazol [(2RS, 3RS)-1-(2, 4-dichlorophenyl)-4, 4-dimethyl-2-(1,2, 4-triazol-1-yl)pentan-3-ol] decreased the rate of growth of Ustilago maydis during the log phase. Marked changes in sterol composition were observed with a decrease in ergosterol and an increase in methyl-sterols, indicating a block in the removal of the 14-methyl group. The inhibition was of rapid onset (<4 h). Changes in other lipid constituents were minor and there was no build up of unsaturated fatty acids. The fungicidal activity resides in the (2R, 3R)-isomer, which is known to be more potent in blocking a yeast 14-demethylase enzyme than the (2S, 3S)-isomer. This relationship held in the 4-chlorophenyl homologues, which as a group were less fungicidal and less potent inhibitors than the 2, 4-dichlorophenyl compounds. The evidence presented indicates that the primary lesion caused by the fungicide was a build up of membrane sterols containing extra methyl groups; this, in combination with a loss of ergosterol, is believed to prevent proper membrane ordering and thus to cause a loss of membrane function.     

Separation and identification of short-lived free radicals formed by photolysis of the pyrethroid insecticide fenvalerate

Using a spin-trap reagent 3-nitrosodurene (1,2,4,5-tetramethyl-3-nitrosobenzene), the short-lived free radicals generated by ultraviolet irradiation of fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] in degassed benzene or dichloromethane, were scavenged as the more stable nitroxide radicals. These radicals were separated by high-performance liquid chromatography and identified individually by electron-spin resonance spectroscopy, as well as by gas chromatography/mass spectrometry. As a result, they were found to be the spin adduct mixtures of the 4-chloro-α-isopropylbenzyl and α-cyano-3-phenoxybenzyl radicals, which are involved in the photo-induced decarboxylation process of fenvalerate. Discrimination of the radicals was also performed by the isotope-labelling method whereby the benzylic proton in the acid moiety was deuteriated. The spin numbers of the nitroxides decreased by about five-fold when photolysis was carried out in oxygenated benzene solution. N-Benzylidene-tert-butylamine N-oxide trapped both radicals but much less efficiently. The nitroxide of the 4-chloro-α-isopropylbenzyl radical was predominant at 25°C or –40°C, but the proportion of the α-cyano-3-phenoxybenzyl nitroxide radical increased at the lower temperature.     

Acaricidal properties of some synthetic unconjugated allenic anilides

Seven unconjugated allenic anilides with the allenic moiety situated at the 3, 4 position were synthesized and evaluated for acaricidal activity against Boophilus microplus (Canestrinii). The order of toxicity (% adult mortality) of the anilides against adult B. microplus at 0.5 μg tick^?1 was: N-(3-chloro-4-methyl-phenyl)-5-methylhexa-3, 4-dienamide, (I) = N-(4-bromophenyl)-5-methylhexa-3, 4-dienamide(III)(100%) > N-(4-bromophenyl)-deca-3, 4-dienamide (VI)(68%) > N-(3, 4-dichlorophenyl)-5-methylhexa-3, 4-dienamide (II) (32.3%) > N-(3, 4-dichlorophenyl)-5-methylhepta-3, 4-dienamide (IV) (28%) > N-(3-chloro-4-methylphenyl)-5-ethylhepta-3, 4-dienamide (VII) (24%) > N-(4-bromophenyl)-5-methylhepta-3, 4-dienamide (V) (20%). Comparison of the relative potencies (in parenthesis) at 1.5 μg tick^?1 of the anilides with three commercial acaricides: pyrenone, lindane and carbaryl, revealed the following orders of activities: in comparison with pyrenone: pyrenone = I = II (1) > VI(0.93) > II (0.67) > IV (0.55) > VII (0.46) > VI (0.37); in comparison with lindane: I = HI (6.06) > VI (5.65) > II (4.04) > IV (3.36) > VII (2.76) > V (2.39) > lindane (1.0). All anilides were more toxic than carbaryl which gave no mortality at 1.5 μg tick^?1. The need for developing more effective control agents for B. microplus is highlighted by the high levels of resistance found in some Jamaican populations of the pest. Resistance of the orders of 31- to 227-fold had been reported against lindane and between 15- and 67-fold to carbaryl.     

Metabolism of imazalil by wild-type and DMI-resistant isolates of Penicillium italicum

Metabolism of imazalil (1-[2-(2,4-dichlorophenyl)-2-(2-propenyloxy)ethyl]-1H-imidazole) inPenicillium italicum isolates with a wild-type sensitivity and with various degrees of resistance to sterol demethylation inhibitors was studied in liquid cultures. The metabolite 1-[2(2,4-dichlorophenyl)-2-(2,3-dihydroxypropyloxy)ethyl]-1H-imidazole (R42243) was detected in the culture filtrate after prolonged incubation. The metabolism occurred in the propenyl side chain of imazalil probably through epoxidation and hydratation. This is the first report of such a conversion of imazalil in fungi. R42243 was much less toxic toP. italicum than imazalil. Therefore, the metabolism can be regarded as a detoxification step. Both wild-type and resistant isolates metabolized imazalil, but metabolism by resistant isolates was faster than by the wild-type isolate. This is probably caused by a relatively strong inhibition of growth of the wild-type isolate by the fungicide. Results indicate that the detoxification of imazalil does not operate as a mechanism of resistance. This conclusion was confirmed by the fact that resistant isolates showed cross-resistance to miconazole and R42243, which had a similar structure as imazalil except for the propenyl side chain.     

Control of insects in cotton crops in africa with some pyrethroid

Cotton yield results are presented for trials in Senegal, the Ivory Coast, Chad and Morocco in which the pyrethroids permethrin, biopermethrin, 3-phenoxybenzyl (1R,cis)-3-(2,2-dichlorovinyl)-2, 2-dimethylcyclopropanecarboxylate (NRDC 167) and (S)-α-cyano-3-phenoxybenzyl (1R,1 S)-cis,trans-3-(2,2-dibromovinyl-2, 2-dimethylcy-clopropanecarboxylate (NRDC 156) were compared with the compounds currently used for insect control. NRDC 156 gave marked yield increases at rates as low as 12.5 g.a.i./ha, the other pyrethroids needing higher rates to give comparable results. Control of mites, Hemitarsonemus lata and Tetranychus urticae was not satisfactory, however.     

Inhibition of the photochemical activity of the isolated photosystem ii reaction centre by 2-cyanoacrylates

Certain derivatives of the 2-cyanoacrylates are potent inhibitors of photosystem II (PSII) mediated electron flow. These compounds block electron flow by binding to the D1 polypeptide as do many other types of photosystem II herbicides. In this paper we report the action of these species of 2-cyanoacrylates on the photochemical activity of the isolated PSII reaction centre consisting of the D1 and D2 polypeptides but free of other chlorophyll-binding proteins. The three species tested were 2-ethoxyethyl 2-cyano-3-(4-chlorobenzylamino)-3-isopropylacrylate (cyanoacrylate 1), isopropyl 2-cyano-3-(N-methylanilino)acrylate (cyanoacrylate II) and methoxymethyl 2-cyano-3-(4-chlorobenzylthio)-3-mercapto-acrylate sodium salt (cyanoacrylate III). Unlike the case with thylakoid membranes or PSII enriched membranes, cyanoacrylate III was a more potent inhibitor than cyanoacrylate I of the photoreduction of 2,6-dichlorophenol indophenol (DCPIP) in the isolated PSII reaction centre. This cyanoacrylate was also more effective than diuron (DCMU) in blocking DCPIP reduction in the reaction centre complex. Moreover, unlike DCMU and cyanoacrylates I and II, cyanoacrylate III was more effective in inhibiting the quinone-dependent photoreduction of cytochrome b559 in isolated PSII reaction centres. It is concluded that the hydrophilic nature of cyanoacrylate III gives it greater potency with the isolated reaction centre and that its site of action is likely to be closer to the histidine ligands involved in the binding of non-haem iron rather than in the Q_B binding niche. (See footnote on page 331 for nomenclature of cyanoacrylates).     

Structure—activity relationships in pyrethroid esters derived from substituted 2-phenoxy-3-methylbutanoic acids

Non-cyclopropane pyrethroid esters of different substituted 2-phenoxy-3-methylbutanoic acids have been synthesised using the three alcohols—3-phenoxybenzyl alcohol, α-cyano-3-phenoxybenzyl alcohol and 3, 4-methylene-dioxybenzyl alcohol. Among the 35 esters synthesised and tested against Culex quinquefasciatus Say, the Bancroftian filariasis vector, for both larvicidal and adulticidal activities, α-cyano-3-phenoxybenzyl 2-(4-fluorophenoxy)-3-methylbu-tanoate, with an LC₅₀ value of 2.5 × 10^?3 mg litre^?1 for larvicidal activity, and α-cyano-3-phenoxybenzyl-2-(4-chlorophenoxy)-3-methylbutanoate, with an LD₅₀ value of 30 times; 10^?4 ug insect^?1 for adulticidal activity, were found to be as effective as fenvalerate, a well-known non-cyclopropane pyrethroid ester. Structure-activity studies showed that the insecticidal activity is dependent on the nature and position of the substituent in the phenyl ring of the acid moiety and also on the type of alcohol moiety.     

氨基甲酸-2-氯吡啶-5-甲酯化合物的合成与抑菌活性

以芳香硝基化合物、2-氯-5-吡啶甲醇和一氧化碳为原料,在Pd-Fe/Ti O2催化下进行羰基化反应,合成了11个新型氨基甲酸-2-氯吡啶-5-甲酯化合物,其结构经1H NM R和M S表征。初步抑菌活性测定结果表明:在50 mg/L下,大多数目标化合物对4种供试病原菌具有一定的抑制活性,其中化合物3f(4-甲氧基苯基氨基甲酸-2-氯吡啶-5-甲酯、3h(2,4-二氯苯基氨基甲酸-2-氯吡啶-5-甲酯)和3j(3,4-二氯苯基氨基甲酸-2-氯吡啶-5-甲酯)对小麦赤霉病菌Gibberella zeae的抑制率达77.3%以上,3f对苹果轮纹病菌Physalospora piricola的抑制率达82.5%,与对照药多菌灵接近;所有化合物在50 mg/L下对番茄灰霉病菌Botrytis cinerea的抑制活性均优于对照药多菌灵。     

Metabolism of the cis- and trans-isomers of cypermethrin in mice

Metabolism in mice of the separated cis- and trans-isomers of the pyrethroid insecticide cypermethrin (NRDC 149), (RS)-α-cyano-3-phenoxybenzyl (1RS)-cis, trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate, was investigated in each case with preparations that were ¹⁴C-labelled in the benzyl and cyclopropyl moieties. Radioactivity from the trans-isomer was mainly excreted in the urine and that from the cis-isomer in the faeces. Elimination of both isomers was rapid except for a small portion (approximately 2%) of the cis-isomer which was released from the fat with a half-life of approximately 13 days. Metabolism of cypermethrin occurred mainly by ester cleavage and elimination of the cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl- cyclopropanecarboxylic acid moieties as glucuronide conjugates. The α-cyano-3-phenoxybenzyl alcohol released by ester cleavage was mainly converted to 3-phenoxy-benzoic acid which was partly eliminated unchanged, partly conjugated with aminoacids (mainly taurine) and glucuronic acid, and partly oxidised to 3-(4-hydroxyphenoxy) benzoic acid which was excreted as the sulphate conjugate. Metabolites retaining the ester linkage were formed by hydroxylation at various sites in the molecule with more hydroxylation of the cis- than of the trans-isomer occurring.     

7Th international congress of pesticide chemistry

A series of 2-(1,3-dimethyl-4-substituted-5-pyrazolyl)sulfonylimino-5,7-disubstituted-2H-1,2,4-thiadiazolo[2,3-a]pyrimidines was synthesized and tested for herbicidal effects. The compounds showed potent activity and improved selectivity to rice when compared with analogous sulfonylurea derivatives.     

The metabolism of [14C] cymoxanil in the rat

A rat, given a single oral dose of [¹⁴C] cymoxanil, 1-(2-cyano-2-methoxyimino-[2-¹⁴C]-acetyl)-3-ethylurea, eliminated 91% of the radioactivity within 72 h. The urine contained 71%, the faeces 11%, and the expired air about 7% of the radiolabel; no ¹⁴C residue was found in the internal organs. Greater than 70% of the radioactivity in the urine was identified. The major metabolite was characterised as glycine, both free and conjugated, as hippuric acid and phenylaceturic acid [N-(phenylacetyl)-glycine], and probably in the form of polypeptides of low molecular weight. The other metabolites identified included 2-cyano-2-methoxyiminoacetic acid, 2-cyano-2-hydroxyiminoacetic acid and 1-ethylimidazolidine-2, 4, 5-trione. The minor metabolites included succinic acid and 2-oxoglutaric acid which indicated reincorporation of metabolic ¹⁴C. Cymoxanil, as such, was not detected in the urine.     

Degradation of the insecticide SD 8280, 2-chloro-1-(2, 4-dichlorophenyl)vinyl dimethyl phosphate,in soils

The degradation of the insecticide SD 8280 [2-chloro-1-(2,4-dichlorophenyl)vinyl dimethyl phosphate] in soil has been examined under laboratory conditions using two soils from rice-growing areas in Japan and one UK soil. In all soils SD 8280 underwent degradation to 1-(2,4-dichlorophenyl)ethanol, 2,4-dichlorobenzoic acid, 2-chloro-1-(2,4-dichlorophenyl)vinyl methyl hydrogen phosphate and 2′,4′-dichloro-acetophenone. These degradation products were present in the soils as free (extractable) compounds and as bound forms and soil binding occurred most extensively with 2,4-dichlorobenzoic acid. Polar products were also formed and these appeared to be in part the result of complexing of degradation products with the soil organic matter. The effect on the degradation of the insecticide of varying the moisture content of one soil was also examined. In soil incubated at 11, 17, 30 and 62% moisture the recovery of SD 8280 after 60 days was 71.0, 12.3, 9.0 and 11.3%, respectively. Although the rate of degradation varied, the same degradation products were detected in all samples.     

The pyrethrins and related compounds. Part XXII. Preparation of isomeric cyano-substituted 3-phenoxybenzyl esters

Preparation of 3-phenoxybenzyl chrysanthemates and their dihalovinyl analogues substituted with a cyano group at the 2-, 6-, (R)-α-, or (S)-α- positions is described. The (R)- and (S)- isomers of α-cyano-3-phenoxybenzyl esters of 2,2-difluoro-, -dichloro-, and -dibromo-vinyl analogues of cis- and trans- chrysanthemic acid are separated chromatographically, as are the separate pairs of enantiomers of fenvalerate, (RS)-α- cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate. An optically active ester of α-cyano-3-phenoxybenzyl alcohol (obtained using D -oxynitrilase) with 2,2,3,3-tetramethylcyclopropanecarboxylic acid is synthesised.     

Advances in the potentiometric determination of pka and log kow of pesticides

The phenylpyrrole fungicide fenpiclonil inhibited the metabolism of glucose in mycelium of Fusarium sulphureum Schlecht at a concentration which only slightly inhibited mycelial growth (EC₁₅). At the same concentration, fenpiclonil also inhibited accumulation and, to a greater extent, phosphorylation of 2-deoxy[U-¹⁴C]glucose in starved mycelium loaded with unlabelled 2-deoxyglucose. Fenpiclonil did not affect cell-free phosphorylation of 2-deoxyglucose or the ATP content of mycelium. Therefore, the primary mode of action of the fungicide may be based on inhibition of transport-associated phosphorylation of glucose. This may cause a cascade of metabolic events which eventually lead to fungal growth inhibition and death. One major event affected by inhibition of transport-associated phosphorylation is the accumulation of polyols, such as glycerol and mannitol, in mycelium. This was not observed in an osmotically sensitive, fenpiclonil-resistant laboratory isolate of the fungus.     

The phototransformation of a bis-2,3-diazabutadienyldisulfide to an aphicidally active 2,3-dihydro-1,3,4-thiadiazole

The pro-insecticide bis-(1-(4-chlorophenyl)-4-(pyrid-3-yl)-2,3-diazabutadien-1-yl)disulfide, I is photochemically transformed to the aphicidally active 5-(4-chlorophenyl)-2-(pyrid-3-yl)-2,3-dihydro-1,3,4-thiadiazole IIa .     

Metabolic fate of methazole in purple and yellow nutsedge

The mechanisms for the tolerance of purple nutsedge (Cyperus rotundus L.) and susceptibility of yellow nutsedge (Cyperus esculentus L.) to methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] were studied. Both species absorbed and translocated[¹⁴C]methazole and metabolites from nutrient solution; however, greater amounts of ¹⁴C per unit weight were detected in yellow than in purple nutsedge. Although intact plants and excised leaves of both species rapidly metabolized methazole to DCPMU [1-(3,4-dichlorophenyl)-3-methylurea], detoxification of DCPMU to DCPU [1-(3,4-dichlorophenyl) urea] occurred more slowly in yellow than in purple nutsedge. Compared to yellow nutsedge, a greater percentage of the radioactivity in purple nutsedge was recovered as polar products. Polar products were converted to the free forms of the parent herbicide and to phytotoxic DCPMU by proteolytic enzyme digestion. Based on the findings of this study, at least three mechanisms (differential absorption, metabolism, and formation of polar products) account for the differential tolerance of these two species to methazole.