In the course of studies on novel sulfonamide derivatives, we found that 4, N-dimethyl-N-(2-phenyloxiran-2-ylmethyl) benzenesulfonamide was herbicidally active. In spite of its high activity, the compound did not have enough stability for practical use. To improve the stability and herbicidal activity by molecular modification, a series of sulfonamide derivatives with phenyl substituted oxirane moiety were prepared. Among them, N-[2-(3-chlorophenyl) oxiran-2-ylmethyl]-4-cyano-N-methylbenzenesulfonamide possessed the highest herbicidal activity with enough thermal stability. Halohydrin derivatives were also prepared as an alternative solution for the stability. Among them, N-(3-bromo-2-hydroxy-2-phenypropyl)-4-chloro-N-difluoromethyl-3-methylbenzensulfonamide was the most favorable for herbicide. Both compounds showed excellent herbicidal activity against grass weeds and some of broad leaf weeds in paddy condition with selectivity to transplanted rice.

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In the course of studies on sulfonamides with aryl substitutedoxirane moiety, we found that compounds having a pyridyl group on 2-position of the oxiran-2-ylmethyl moiety possessed herbicidal activity. As a result of elaborate study, 4-chloro-N-[2-(6-chloropyridin-2-yl)oxiran-2-ylmethyl]-3, N-dimethylbenzenesulfonamide and N-[2-(6-chloropyridin-2-yl) oxiran-2-ylmethyl]-N-methyl-5, 6, 7, 8-tetrahydronaphthalene-2-sulfonamide were discovered as potential rice herbicides. The former compound showed complete control of Echinochloa oryzicola (barnyardgrass) up to 2 leaf stage and broad herbicidal spectrum. The latter compound showed remarkable selectivity between rice and Echinochloa oryzicola.

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The effect of the surfactant Triton X-100, α-[4-(1, 1, 3, 3-tetramethylbutyl)phenyl] -ω-hydroxypolyoxy-1, 2-ethanediyl, on solubilization of epicuticular wax of mature tomato (Lycopersicon esculentum Mill.) fruit was investigated. The surfactant solubilized the unsaturated hydrocarbons, hexacosene and tritriacontadiene, and the triterpenols, α- and β-amyrins; solubilization was concentration dependent above the critical micelle concentration. Only traces or nondetectable quantities of saturated hydrocarbons were solubilized. Our data provide a definitive evidence that the surfactant solubilized selective constituents of epicuticular wax. Based on calculation of the logarithm of octanol/water partition coefficients for wax constituents, it appears that the mechanism of surfactant solubilization of the constituents was not solely related to the hydrophobicity of the constituents, but may involve pi-pi interaction, van der Waals interaction or molecular conformation of the solubilized constituents. This solubilization of epicuticular wax may decrease the diffusive resistance of the cuticular membrane and, hence, facilitate penetration of surfactant-formulated foliar applied agrochemicals.

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Practical synthetic routes for the preparation of 1-(7-chlorobenzothiazol-2-yl)-1-methylethylamine (VII), a key intermediate of the barnyardgrass-controlling herbicide, 3-[[1-(7-chlorobenzothiazol-2-yl)-1-methyl]ethyl]-2, 3-dihydro-6-methyl-5-phenyl-4H-1, 3-oxazin-4-one (MI-3069), were investigated. As the result, the intermediate VII was prepared in an excellent overall yield by cyclization of 2-amino-2-methylpropionitrile with 2-amino-6-chlorothiophenol, which was synthesized by hydrogenation of 2-nitro-6-chlorothiophenol derived from 2, 3-dichloronitrobenzene. This practical route consisted of shorter steps with relatively cheaper reactants than the reported method.

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Metabolism of 50 herbicides and 7 other chemicals with different structures and modes of action was examined in the microsomes from the recombinant yeast strains expressing each of 11 human P450 species. Of these, 27 herbicides and 6 other chemicals were mainly metabolized by CYP1A1, CYP1A2, CYP2B6, CYP2C9, CYP2C18, CYP2C19, CYP2D6 and CYP3A4. The metabolites of atrazine (AT), chlortoluron (CT), fenitrothion (FT), methoxychior (MXC), pyributicarb (PC), simazine (SZ) and simetryn (ST) were identified by co-chromatography with the authentic standards as well as LC/MS and GC/MS of their derivatives. Based on these results, three major P450 species CYP1A1, CYP2B6 and CYP2C19 in different families and subfamilies were selected and then co-expressed in the transgenic potato plant T1977, which showed cross-tolerance toward the herbicides acetochlor (AC), AT, CT, methabenzthiazuron (MT), metolachlor (MC), norflurazon (NR) and PC. The T1977 plant showed a higher activity in the metabolism of each of [¹⁴C] CT, [¹⁴C] AT, [¹⁴C] PC and [¹⁴C] MXC than the control. In T1977, [¹⁴C] PC was almost completely metabolized to m-tert-butylphenol(BP), O-demethylated PC (DMPC), hydroxylated BP (BPOH) and unknown metabolites. Also, [¹⁴C] MXC was rapidly metabolized in T1977 through O-demethylation to yield mono-demethylated and di-demethylated metabolites, which were mainly deposited as glucosides in the plants. These results strongly suggested that three P450 species expressed in T1977 coordinately functioned and actively metabolized the herbicides and the insecticide. The transgenic plants expressed human P450 species metabolizing xenobiotics seem to be useful for generation of transgenic crops with low pesticide residues as well as for phytoremediation of pesticide residues.

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In the course of our studies on compounds having 2-aryl substituted oxiran-2-ylmethyl structure, we found that compounds with indan-1, 3-dione moiety showed potent herbicidal activity against mainly gramineous weeds in paddy field and upland field. As a result of elaborate study, we found Indanofan; 2-[2-(3-chlorophenyl)oxiran-2-ylmethyl]-2-ethylindan-1, 3-dione that controlled Echinochloa oryzicola at the rate of 0.10-0.15kg a. i./ha with excellent selectivity to transplanted rice plant. Indanofan was registered in 1999 as a herbicide for transplanted rice.

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Vapor pressures of carbamate and thiocarbamate pesticides were estimated from their chemical structures by using the newly developed thermodynamic equations. The equations were derived from the modified Watson method by optimizing a parameter and introducing the concept of a number of possible hydrogen-bonding sites for better estimation of vapor pressures. This method could successfully estimate the vapor pressures of the tested pesticides and correctly predict vapor pressures, ranging from 10^-5 to 10¹ Pa at 298K, of other pesticides not being utilized in the optimization procedure.

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An imidacloprid-related nitromethylene compound and its alkyl congeners at the imidazolidine NH site were prepared and their insecticidal and nerve-excitatory and -blocking activities were measured. In the insecticidal test with the male adult American cockroach by the injection method, metabolic inhibitors, more or less, increased the activity of tested compounds. The NH mother compound was the most active among the nitromethylene compounds and was as active as imidacloprid under the synergistic conditions. The N-alkyl congeners were less active than the NH compound under the conditions. In both of the nerve excitatory and blocking activities measured with a central nerve cord of the American cockroach, the NH compound was the most active among the nitromethylene series compounds and was less active than imidacloprid. A good correlation was not observed between the nerve activities. Quantitative analyses showed that the insecticidal activity measured with the metabolic inhibitors was better correlated with the nerve-blocking activity than with the nerve-excitatory activity. When factors of transport of the compounds within the insect body and/or interaction with target sites were considered separately by use of the hydrophobicity parameter, the correlation with the nerve-blocking activity was significantly improved.

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In the screening process we found that two 1, 2, 4-oxadiazole compounds showed antifungal activity against Trychophyton mentagrophytes. Microscopic observation revealed that these compounds inhibited mycelial growth with morphological changes without inhibition of germination. When treated with the oxadiazoles, ergosterol of Candida albicans decreased strikingly and much squalene was accumulated. These results firmly suggested that the compounds were new squalene epoxidase inhibitors. We synthesized the related oxadiazoles and thiadioazoles having various substituents to investigate the structure-activity relationships. Among the synthesized compounds, 3-(2, 6-dichlorophenyl)-5-(4-chloroanilino)-1, 2, 4-thiadiazole (51) showed the highest fungicidal activity against Botrytis cinerea, and accumulated squalene remarkably. This compound is of interest as a new lead of squalene epoxidase inhibitors.

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A series of new 3-(5-alkoxy-2, 4-dihalophenyl)-5-alkylidene-1, 3-imidazolidine-2, 4-dione derivatives was synthesized and their herbicidal activities against various weeds were examined. The herbicidal activities varied with the substituents on the benzene ring and the compounds having a 5-alkynyloxy-4-chloro-2-fluorophenyl group exhibited relatively higher herbicidal activities. In the case of monocyclic Imidazolidinedione derivatives, introduction of an isopropylidene group at the 5-position and a lower alkyl group at the 1-position of the imidazolidinedione ring was most effective in enhancing the activity. In the case of bicyclic imidazolidinedione derivatives, 5, 6-dihydroimidazo [1, 5-a] pyridine derivatives gave a higher selectivity than tetrahydroimidazo [1, 5-a] pyridine derivatives, therefore, it was thought that the presence of a double bond was important for the crop safety. Among the compounds synthesized, a bicyclic imidazolidinedione compound, 2-(4-chloro-2-fluoro-5-propargyloxyphenyl)-5, 6-dihydroimidazo[1, 5-a]pyridine-1, 3[2H, 7H]-dione is considered to be the most promising candidate as a corn herbicide.

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1′-Acetoxychavicol acetate (1a), identified from the rhizomes of a Zingiberaceae plant as an anti-ulcer and insecticidal material, and its positional (meta and ortho) isomers were synthesized from hydroxybenzaldehydes. These racemic mixtures were resolved by HPLC equipped with a chiral column (Chiralpak AS or AD), and the absolute configuration of the separated enantiomers was studied with the corresponding 1′-hydroxy derivatives. Examination of the ¹H NMR data of their esters with (S)- and (R)-α-methoxy-α-(trifluoromethyl)phenylacetic acids by a modified Mosher's method indicated that the dextrorotatory enantiomers with a shorter Rt possess the R configuration, while the levorotatory enantiomers with a longer Rt possess the same S configuration as natural . Both enantiomers of each compound showed almost the same insecticidal activity against the adzuki bean weevil (ABW). On the other hand, the (S)-enantiomers exhibited a stronger repellent effect against ABW females than the (R)-enantiomers, while a similar effect by the two stereoisomers was observed against the males. The number of eggs laid on adzuki beans was efficiently decreased when the beans were treated with the (S)-enantiomers, especially with (S)-.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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