Abstracts of Vol. 26 No. 4

Original Articles

Enantioselective Antifungal Activity of Pefurazoate against Pathogens of Rice Seed Diseases

　　Pefurazoate is a 14α-demethylation inhibitor of 24-methylenedihydrolanosterol (24-MDL) and has an asymmetric carbon atom in its structure.　We previously reported that the antifungal activity of the (S)-(−)-isomer of pefurazoate against Gibberella fujikuroi was about thirty times that of the (R)-(＋)-isomer.　This enantioselective antifungal activity was presumed to be due to an asymmetric molecular shape caused by the binding of a bulky 2-furanylmethyl group to a nitrogen atom adjacent to the asymmetric carbon atom.　Therefore, to further elucidate the difference in antifungal activity between the two enantiomers of pefurazoate, we synthesized optically active N-methyl analogues of pefurazoate, and evaluated their antifungal activity.　Optical (R)-(＋)- and (S)-(−)-isomers of pefurazoate exhibited different activities against Cochliobolus miyabeanus and Pyricularia oryzae as well as Gibberella fujikuroi, but the N-methyl (R)-(＋)- and (S)-(−)-isomers of the pefurazoate analogues had almost the same degree of activity against these three fungi and of inhibition of ergosterol biosynthesis in G. fujikuroi.　These findings strongly suggest that the enantioselective antifungal activity of pefurazoate is due to its asymmetric molecular shape caused by substitution of the furan ring.

Key words:　pefurazoate, enantioselective antifungal activity, 14α-demethylation inhibitor, Gibberella fujikuroi, Cochliobolus miyabeanus, Pyricularia oryzae.

Partition of 2,4-Dichlorophenoxyacetic Acid Derivatives in Phosphatidylcholine Multi-lamellar Vesicles

　　The interaction of 2,4-dichlorophenoxyacetic acid (2,4-D) with multi-lamellar vesicles of dimyristoyl and dipalmitoyl L-α-phosphatidylcholine was examined from the pH dependency of partition and pH- and temperature-dependent polarization of fluorescence probes such as 1,6-diphenyl-1,3,5-hexatriene.　It was strongly suggested that 2,4-D in the undissociated form was located at the region from the neighborhood of the glycerol backbone to a shallow site of the hydrophobic core of the lipid bilayers and that its anionic species was adsorbed at the membrane surface.　Fluorescence study with the derivatives of 2,4-D showed that hydrophobicity and pKa of these acids determined their interaction with membrane.

Key words:　2,4-dichlorophenoxyacetic acid derivatives, pH dependency of partition in synthetic membranes, polarization of fluorescence probes.

Synthesis of (−)-ent-Altholactone, (＋)-7a-epi-Altholactone, (−)-ent-Isoaltholactone and (−)-7a-epi-Isoaltholactone from 2,3-O-Cyclohexylidene-D-glyceraldehyde^１

　　Synthesis of the diastereomers of (＋)-altholactone, an antitumor acetogenin from various Goniothalamus species, was achieved.　Four isomers including 3a,7a-trans-fused analogs were synthesized from 2,3-O-cyclohexylidene-D-glyceraldehyde via twice separation of diastereomers.

Key words:　altholactone, isoaltholactone, goniothalenol, total synthesis.

Synthesis of Both Enantiomers of Altholactone, Isoaltholactone and 5-Hydroxygoniothalamin from Tri-O-acetyl-D-glucal, and Their Biological Activities^１

　　Both enantiomers of altholactone, isoaltholactone and 5-hydroxygoniothalamin were synthesized from tri-O-acetyl-D-glucal, and biological activities of altholactones were examined.　For brine shrimp, the configuration of 3-hydroxy group at convex site was important for lethal activity, while (2S,3S)-configuration was inhibitory to lettuce germination.

Key words:　altholactone, isoaltholactone, 5-hydroxygoniothalamin, total synthesis, tri-O-acetyl-D-glucal.

Efficacy of Acetamiprid Tablet against Cotton Aphid on Cucumber by Various Application Methods

　　Efficacy of acetamiprid tablet against the cotton aphid on cucumber by various soil application methods was investigated compared to that of its granule applied under the same conditions.　Acetamiprid tablet weighed 0.15 g including 20 mg active ingredient at 1 tablet/plant and controlled-release 2% granule at the dosage of 1 g/plant showed excellent efficacy when they were applied at the center of planting hole, similarly to the granule applied uniformly.　The comparison between the efficacy in row application of tablet and soil surface application of granule suggested the efficacy of both applications became insufficient as the distance between the foot of seedling and application site became longer.　Such a tendency was more remarkable with row application of the tablet than with soil surface application of granule.　The tablet exhibited excellent efficacy at the dosage of 1 tablet/plant by being applied both at the foot of plant in nursery pot before transplanting to the field and at the center of the planting hole.　Besides, efficacy of different sizes of tablet including same amount of acetamiprid was investigated by planting hole application.　There was a tendency that tablet exhibited longer lasting activity as it became larger as far as the weight of 0.15, 0.3 and 0.6 g.　With soil surface application the tendency of efficacy was reversed compared to that with planting hole application.

Key words:　acetamiprid, tablet, granule, cotton aphid, cucumber.

Degradation and Leaching of Herbicide Imazosulfuron in Upland Soils

　　Degradation of imazosulfuron in upland soils was investigated under laboratory conditions using two kinds of ¹⁴C labeled imazosulfuron.　Imazosulfuron degraded with half-life of approximately 40 days, and the major degradation pathway was the hydrolysis of the sulfonylurea bond to give ADPM and IPSN.　The leaching studies of imazosulfuron using non-aged and aged soils were also conducted.　It was found that imazosulfuron was less mobile in soils when the soil column was eluted with 0.02 N CaCl_２ solution after 30 days of aging period of time compared to non-aging.　Main degradation products, ADPM and IPSN, were adsorbed in soils stronger than imazosulfuron.　It was suggested that imazosulfuron dissipates relatively fast in upland soils, and the leaching potential decreases with time.

Key words:　mazosulfuron, labeled compounds, soil degradation, leaching, herbicide.

Influence of Absolute Configuration of Indanofan on Herbicidal Activity１

Key words:　indanofan, herbicide, barnyardgrass (Echinochloa oryzicola), optically active compounds, X-ray crystallography.

Simple Method for Monitoring the Sensitivity of Pyricularia oryzae to Fthalide

Key words:　melanin biosynthesis inhibitor, fthalide, appressoria, Pyricularia oryzae.

2-Methyl-5-pyridyl 2-(Substituted-phenoxy)ethyl Ethers with Precocious Metamorphosis-Inducing Activity

Key words:　2-methyl-5-pyridyl ethers, precocious metamorphosis, silkworm.

Synthesis and Acaricidal Activity of 1-Arylmethyl-2-arylimidazolidines

Key words:　acaricide, preparation of disubstituted imidazolidine, mass spectra of substituted imidazolidine.

Summary of Toxicological Studies on Acequinocyl

　　Acequinocyl, active ingredient of Acequinocyl 15% SC, is a novel naphthoquinone derivative which was synthesized in the 1970s for use in control of plant parasitic mites in the agricultural field.　This novel chemical has a unique mode of action in mite species, namely inhibition of the electron transfer system by binding hydroxy Acequinocyl with the Qo center at complex III in mitochondria after hydrolysis in mite body (Y. Koura et al., 1997), and has excellent miticidal activity against a wide range of plant mite species at all development stages including the egg stage without any cross resistance towards other commercial miticides.　After expending many years in developing formulation which would ensure optimum biological activity, official efficacy trials were initiated in a wide range of crops in co-operation with the Japan Plant Protection Association.　Acequinocyl 15% SC is used widely in Japan to control plant mite species incorporated into IPM program since it was first registered here in 1999, and maintains excellent efficacy without any sign of developing miticide resistance.　This product is also registered in Korea and Taiwan, and many field trials are being conducted with this product in the US and European countries for the purpose of registration in these countries.