The structure-activity relationships of α-cyanobenzyl 3-(2, 2-dichlorovinyl)-2, 2-dimethyl-cyclopropanecarboxylates having various substituents at the 3-position of the benzyl group have been analyzed with physicochemical substituent parameters and regression techniques. The knockdown activity with and without synergists, PB and NIA, against the housefly, Musca domestica L., is correlated to the hydrophobicity, steric bulkiness, and stereo-electronic properties of the 3-substituents. Without synergists, the variation in the knockdown activity is related to that in the lethal activity with the addition of the hydrophobic term, while with synergists, both variations are directly related to each other. Synergistic effects on the knockdown activity are not so remarkable, and these compounds are detoxified depending on the structure of the 3-substituent even under synergistic conditions.

View full abstract

Herbicidal properties of a new post-emergence herbicide, sethoxydim {(±)-2-(1-ethoxyiminobutyl)-5-[2-(ethylthio)propyl]-3-hydroxycyclohex-2-enone} were evaluated mainly in a greenhouse. Sethoxydim showed excellent activity against gramineous plants other than annual bluegrass (Poa annua) and significant selectivity between grassy weeds and bloadleaved crops. Most annual grasses and perennial grasses were perfectly controlled at 0.2-0.4kg/ha and at 0.5-1.0kg/ha, respectively, whereas bloadleaved crops showed extremely high tolerance to sethoxydim. Sethoxydim was 7-8 times more active against johnsongrass (Sorghum halepence) than alloxydim-sodium. It appeared that sethoxydim was rapidly absorbed and readily basipetally translocated. Sethoxydim showed higher activity in postemergence treatment than in pre-emergence treatment. It was presumed that the cause of low activity of sethoxydim in pre-emergence treatment was attributable to its short persistence and high movement in soil.

View full abstract

Sethoxydim {(±)-2-(1-ethoxyiminobutyl)-5-[2-(ethylthio)propyl]-3-hydroxycyclohex-2-enone} was evaluated as a postemergence herbicide for gramineous weeds in field trials. Sethoxydim showed excellent herbicidal activities to gramineous weeds at the rate of 0.3kg/ha and excellent selectivities to broadleaved crops. Tank-mixture with mineral oil improved its activities without crop injury, and application of 0.2kg/ha of sethoxydim with 3liter/ha mineral oil was as effective as that of 0.3kg/ha of sethoxydim. Annual bluegrass (Poa annua) and broadleaved weeds were resistant in spite of mixing with mineral oil. Broadleaved crops showed satisfactory tolerance, but gramineous crops except red fescue (Festuca rubra) were very sensitive, as well as gramineous weeds, to sethoxydim. Sethoxydim gave good efficacy in foliar application, but its efficacy was poor in practical preemergence treatment. The short persistence in soil seemed to be one of the factors contributing to low activity in preemergence treatment. It was indicated that crops including gramineous crops could be sown beyond 21 days after treatment of sethoxydim. Stable efficacy was obtained in low water volume application and rainfall immediately after application did not reduce its efficacy. As the lack of efficacy on broadleaved weeds were shown, tank-mixtures or sequential treatments with broadleaved herbicides in soybean or sugar beet field were conducted. Adequate control on both grasses and broadleaved weeds was achieved by this combination of methods.

View full abstract

The effects of environmental factors of soil on the residual amount of the fumigant chloropicrin in soil were investigated. Chloropicrin in soils under laboratory conditions disappeared rapidly in Tokyo and Chiba soils. The residual amounts decreased more rapidly with increasing soil temperature. When the moisture content of soil was 20% of maximum water holding capacity, the residual amount showed the minimum level. When the soil was pretreated with chloropicrin, the disappearance of chloropicrin was extremely retarded. In field tests, the disappearance to a 0.1ppm level of chloropicrin needed about 25 and 70 days in Tokyo and Chiba soils, respectively.

View full abstract

Flowable formulation containing melt crystal of S-3552 gave good physico-chemical properties, especially lower viscosity, while the one containing recrystallized material showed high viscosity. Herbicidal activity of S-3552 Fowable formulation is almost the same or little inferior to that of EC formulation. Addition of specified surfactant to fiowable formulation itself or its spray liquid improved herbicidal activity of S-3552 fiowable formulation. Addition of the surfactant to the formulation caused remarkable crystal growth after storage, which was supposed to be due to Ostwald ripening. S-3552 fiowable formulation has characteristics such as lower irritation on mucous membrane and lower acute oral toxicity in mouse than EC formulation.

View full abstract

A number of benzoyl (pyridyloxyphenyl) ureas were synthesized, and the larvicidal and embryocidal activities were tested against the common cutworm, Spodoptera litura, and the house fly, Musca domestica. Correlation of the activities by means of physicochemical parameters reveals that not only the hydrophobicity of the whole molecule, but the susceptibility to the degradative metabolism is the controlling factor of the insecticidal activity. As to the embryocidal activity, the latter factor was estimated to be more important. The excellent insecticidal activity of chlorfluazuron (IKI-7899) seems to be due to the slow detoxication in the insect body.

View full abstract

A respiration burst of rice leaf tissue slices infected by compatible blast fungus race with or without the application of probenazole or incompatible blast fungus race, or stimulated by one of the hyphal components was quantitatively analysed. A time at maximum rate of the augmentation phase and a half life time of the auto-inactivation phase were respectively determined. A time-sequential orderliness along either line of the time of maximum rate or the half life time was observed. A high correlation coefficient between the values of time of maximum rate and half life time was also observed. By the application of probenazole, both the time of maximum rate and half life time of respiration burst were shifted as in an incompatible combination even in a compatible infection. Superoxide anion and hydrogen peroxide generation were also observed when glucose was used as a respiratory substrate. The major oxidative product of glucose seemed to be gluconate.

View full abstract

Following the foliar application of polyoxyethylene sorbitan ¹⁴C-monooleate, the ¹⁴C-label was traced in tobacco and kidney bean leaves. The autoradiographs showed radioactivity in the treated spot only, indicating that 14C is not readily mobile from the spot to other untreated parts. Even though dimethylsulfoxide, isobutyl alcohol or acetone was included at the concentration of 1% as penetrants, no changes in the distribution pattern of ¹⁴C were found. Most of the radioactivity applied to the leaves could be washed off with water. The remaining small amounts of radioactivity were detected in the wax fraction and in the cell homogenate. In addition, cellular location of ¹⁴C was examined on micro-autoradiographs. Although the ¹⁴C-label was translocated into epidermal cells from wax layer, no further movement took place.

View full abstract

A combination of chemical and photochemical techniques was used to prepare analogues of endrin in which the chlorine atoms at C-1 and C-8 (bridge-end) of the hexachloronorbornene system of this insecticide are retained, whilst those at C-9, C-10 (ethylenic) and C-11 (dichloromethano-bridge) are variously replaced by hydrogen atoms. Similar derivatives were prepared of dieldrin analogues in which the unchlorinated methano-bridge (C-12) is missing or replaced by an oxygen atom.

View full abstract

Photodegradation of bromobutide [N-(1-methyl-1-phenylethyl)-2-bromo-3, 3-dimethyl-butanamide], (P1), in water was studied using ¹⁴C preparations labeled separately at the phenyl ring or carbonyl group. Upon exposure to sunlight, P1 was photodecomposed with half-lives of ca. 13 weeks in distilled water, 12 weeks in sea water, 11 weeks in paddy field water and 1.3 weeks in 2% aqueous acetone. The photoreactions involved were oxidation at one of the gem-dimethyl or tert-butyl methyl group, hydroxylation at the phenyl ring, substitution of bromine by hydroxyl group, cleavage of the amide, carbon-bromine or benzylic carbon-nitrogen bond, and photomineralization of the phenyl and carbonyl carbon to ¹⁴CO₂. Most of the photochemical reactions can be rationalized by a mechanism involving free radical intermediates. The carbon-bromine bond cleavage and photomineralization to ¹⁴CO₂ were predominant in any water tested. The hydroxylation at the phenyl ring was much enhanced by UV irradiation of P1 in distilled water containing hydrogen peroxide or by treatment with Fenton's reagent, and consequently involvement of hydroxyl radical in the reaction was suggested. However, singlet molecular oxygen was unreactive to P1.

View full abstract

Chemical modifications were performed on the four structural parts (1. carboxylic acid part, 2. aliphatic chain part, 3. benzene ring, and 4. pyridine ring) of the mother-skeleton of 2-(4-pyridyloxyphenoxy) propionic acid herbicide. By means of evaluating the herbicidal activity of each derivative, the role of each structural part was investigated. As a result it was understood that the partial structure of D-2-phenoxy-propionic acid is most important as essential moiety, that the pyridyloxy structure carries the responsibility to control the hydrophobicity and structure of total molecule for the optimum herbicidal activity and is important to realize systemic activity in the plant tissue, one of the characteristics of this series of herbicides, and that the derivatives with trifluoromethyl group on position 5 and in addition with or without halogen atom on position 3 of the pyridine nucleus afford the optimum activity.

View full abstract

On exposure to sunlight, fenitrothion was photodecomposed with the half-lives of 0.6-1.0 days in distilled water, 1.5, 1.0, and 0.9 days in buffer solutions at pH3, 7 and 9 respectively, and 0.9-1.1 days in natural river and sea water. The quantum yield was determined to be 8.0×10^-4 (at 313nm in distilled water), and the half-life of disappearance at 40 degree north latitude was calculated to be 1.4 days in fall. Fenitrothion applied on two kinds of soil thin layer plates promptly disappeared through photodegradation and volatilization, with the half-life of approximately 1 day. The insecticide underwent photo-induced oxidation of P=S to P=O, oxidation of the aryl methyl group to the carboxyl group, reduction of the nitro group to the amino group, coupling of the carboxy group with the amino group leading to the formation of the dimeric compound, cleavage of the P-O-aryl or P-O-methyl linkage, isomerization, formation of the benzoisoxazole derivative with subsequent formation of the seven-membered ring (azepine derivative) through Beckmann rearrangement, and photomineralization of the aromatic ring to carbon dioxide in water, and oxidation of P=S to P=O and cleavage of the P-O-aryl linkage on soil. The formation of the major photoproducts in water was pH dependent. The carboxy derivative oxidized at the aryl methyl group of fenitrothion was predominant in distilled water at pH5.9 and in buffer solutions at pH3 and 7, while the dimeric compound, composing of the carboxy derivative of fenitrothion and the corresponding amino analog, was more predominantly formed in buffer solutions at pH7 and9, and natural river (pH7.4) and sea (pH7.8) water. On prolonged exposure to sunlight, these photoproducts were degraded further to ¹⁴CO₂ and the unextracted residues, which were considered to be the polymerized compounds like humic acid and other highly polar products. Fenitrothion underwent hydrolysis through neutral (pH independent) and basecatalyzed processes below pH7 and above pH10 respectively, while both reactions occurred between pH7 and pH10. The half-lives of disappearance by hydrolysis within the ranges of pH5-9, normally found in natural water, were about 200-630 days at 15°C, 17-61 days at 30°C, and 4-8 days at 45°C. The product cleaved at the P-O-aryl linkage was predominant above pH10, while the product cleaved at the P-O-methyl linkage was predominant below pH8. The rates and pathways of degradation of fenitrothion by photolysis and hydrolysis in natural river and sea water were similar to those in buffer solutions at the same pH.

View full abstract

Upon a single oral dose of the photo-decarboxylated derivative of fenvalerate (decarboxy-fenvalerate), [2-(3-phenoxyphenyl)-3-(4-chlorophenyl)-4-methylpentanenitrile] labeled with ¹⁴C in the chlorophenyl and benzyl rings to both male and female rats at the rate of 4mg/kg, the radiocarbon was readily absorbed, metabolized and almost completely eliminated mainly in the feces within a few days. The radiocarbon was mainly located in the liver and gastrointestinal contents, and hardly translocated to other tissues, as evidenced by the whole-body autoradiogram taken at 1, 3, 6, 9 and 24hr after oral administration of the ¹⁴C-labeled preparations. The ¹⁴C residues in tissues 7 days after treatment were generally quite low. Decarboxy-fenvalerate was metabolized in rats via hydroxylation at the methyl group with subsequent oxidation to the carboxylic acid, and hydroxylation at the 2′-, 3′-, 4′- or 6-position of the 3-phenoxybenzyl moiety, and at the benzyl methine carbon bearing the cyano group. The resultant oxidation products were excreted in bile mainly as the glucuronide conjugates, and hardly excreted in the urine. The glucuronide conjugates underwent significant enterohepatic circulation, during which the biliary metabolites were deconjugated by gut microflora and excreted into the feces. There was no substantial difference in the nature and amounts of the metabolites, and in the patterns of the ¹⁴C excretion and tissue residues between male and female rats, and between the two ¹⁴C-labeled compounds.

View full abstract

[in Japanese]

View full abstract

The tanned pupal cuticle was formed in vitro when the wandering stage larval epidermis of Manduca sexta was cultured in the presence of 5μg/ml of β-ecdysone for 4 days. Since metamorphosis occurs in response to two releases of ecdysone, epidermis was explanted from feeding final-instar larvae (day 3, weighing 6.5-7.0g) before the first release of ecdysone and was cultured in Grace's medium. During the first 24hr of exposure to 1μg/ml of β-ecdysone in vitro, the epidermis changed its cellular commitment to that for pupal cuticle formation. Juvenile hormone inhibited the change of the cellular commitment and the tissue subsequently formed larval cuticle in the presence of JH. The epidermis of the last instar larvae was found to convert JH I into JH-acid. This esterase activity increased as a function of larval age and was considered to be involved in elimination of intracellular JH from the target tissues in preparation for metamorphosis. The nuclei were isolated and assayed for specific JH binding using the competitive nuclear exchange assay. Specific binding was found only for epidermal nuclei from larvae before the change in commitment of the cells. Diflubenzuron was found to inhibit both endocuticle deposition and β-ecdysone-initiated pupal cuticle synthesis by using the in vitro culture technique. Both effects were due to its inhibition of chitin synthesis. When larvae were injected with ¹⁴C-glucosamine after treatment of difiubenzuron (DFB), ¹⁴C-UDP-N-acetylglucosamine (UDP-AGA) was found to accumulate in vivo. However, chitin synthetase was not inhibited by DFB. Peritrophic membrane in the midgut of Mamestra brassicae final instar larvae was used as a target to study the mode of inhibition of chitin synthesis by DFB. Chitin synthesis was not inhibited only when DFB and UDP-AGA were applied inside the midguts. When ¹⁴C-AGA was applied outside the midguts, the amount of the radio-labeled compounds transported across the microvilli membrane was about 1/4 as much in the DFB-treated tissues as in the control tissues. The results lead the conclusion that DFB seems to be an inhibitor of UDP-AGA transport across the microvilli membranes.

View full abstract

Both of alloxydim-sodium [Sodium salt of methyl 3-(1-allyloxyaminobutylidene)-6, 6-dimethyl-2, 4-dioxocyclohexylcarboxylate] and sethoxydim (±)-2-(1-ethoxyiminobutyl)-5-[2-(ethylthio) propyl]-3-hydroxycyclohex-2-enone are postemergence herbicides that provide excellent control of a wide range of grass weeds. The studies on them were started from the discovery of a new compound among the benzoxamate (miticide) derivatives having a weak herbicidal activity on grass weed. As a result of the research on the derivatives of various heterocyclic compounds such as pyrans, dimedones and barbituric acids, the dimedone derivatives were found to show the highest activity in postemergence treatment, and an alkoxyamino alkylidene moiety was indispensable on dimedone ring. Thus we selected out a compound from the dimedone derivatives and commercialized it in formulation of alloxydimsodium. It showed excellent activity on annual grasses at 1kg/ha approximately. However, the dosage more than 4kg/ha was needed to control perennial grasses completely, especially johnsongrass (Sorghum halepense). Further investigation was carried out to find out more potent herbicide. Before long, we found that some compounds with additional substituent, sulfur-containing alkyl group at 5-position of 1, 3-dioxocyclohexane ring instead of the gemdimethyl of dimedone, gave excellent control of annual and perennial grasses. A lot of the cyclohexane derivatives with a sulfur-containing alkyl side chain were synthesized and screened. As the result, we picked out a compound (sethoxydim) providing always high activity in field trials. Sethoxydim effectively controlled annual grasses and johnsongrass at 0.2-0.4kg/ha and 0.5kg/ha respectively, and showed excellent selectivity in numerous dicotyledonous crops. Some simulated rainfall and partial droplet application studies revealed that sethoxydim appeared to be readily absorbed and translocated in the plants. Two gramineous species, Festuca rubra and F. myuros were resistant as high as broadleaf weeds, while F. arundinacea and F. pratensis were susceptible. This difference in susceptibility could not explain by absorption, translocation and metabolism. Microscopic studies revealed that sethoxydim attacked the meristematic regions and inhibited the cell divisions, resulting in the occurrence of herbicidal action.

View full abstract

Mepronil, (3′-isopropoxy-2-methylbenzanilide) is a new type of fungicide highly effective against rice sheath blight (Rhizoctonia solani, sasakii type) and many other diseases caused by Basidiomycetes in various agricultural crops. A good number of substituted benzanilide compounds were synthesized and investigated as to their antifungal activities. These studies revealed 2-substituted benzoic acid anilides to be specifically active for Basidiomycetes. The steric effect of the group in the 2-position of the benzoic acid ring may be of the key importance for fungicidal activity. On the other hand, compounds substituted on the aniline ring with 3′-alkyl or 3′-alkoxy group showed stronger activity than 2′- or 4′-substituted and non-substituted compounds. The extent of enhancement depended upon chain length of alkyl groups in 3′-substitution. The fungicidal activity increased with the length of carbon chain showing a peak at carbon number 3 to 5, and then declined steadily as the carbon number in the chain increased further. Mepronil was selected as a most profitable compound, registered as a fungicide and gained commercial acceptance for the control of rice sheath blight and other Basidiomycetes diseases. In comparison with the existing similar compound, 2-methylbenzanilide (common name: mebenil), mepronil was found to have stronger activity both in vitro and in foliar applications but was less systemic and far less phytotoxic than mebenil. Mepronil inhibited glucose oxidation in mycelium of Rhizoctonia solani at the concentration of mycelial growth inhibition. Oxidation of pyruvate and oxalacetate were also inhibited. All of these facts suggest that mepronil has a mode of action similar to the structually related compound, mebenil or carboxin which has a fungicidal spectrum similar to mepronil.

View full abstract