bluuebunny/crossref_metadata_2025 huggingface dataset:
Friedel-Crafts Reactions Catalyzed by Rare Earth Metal Trifluoromethanesulfonates
Authors: Kawada Atsushi , Mitamura Shuichi , Matsuo Jun-ichi , Tsuchiya Takehiro , Kobayashi Shu
Published: September 2002

Rare earth metal trifluoromethanesulfonates (rare earth metal triflates, RE(OTf)3) were found to be efficient catalysts for Friedel-Crafts acylation and alkylation. In the presence of a catalytic amount of RE(OTf)3, acylation of aromatic compounds having electron-donating substituents such as anisole, thioanisole, and mesitylene with acid anhydrides proceeded smoothly to afford the corresponding aromatic ketones in high yields. Although RE(OTf)3 alone is not effective for acylation of less reactive aromatics such as toluene, the combination of RE(OTf)3 and lithium perchlorate (LiClO4) enhanced the catalytic activity dramatically. Friedel-Crafts acylation reactions using rare earth metal perfluoroalkanesulfonates were also successfully performed in supercritical carbon dioxide (scCO2). Moreover, in the presence of a catalytic amount of RE(OTf)3, aromatic compounds reacted with benzyl chloride smoothly to afford the corresponding alkylation products in high yields. In these reactions, RE(OTf)3 could be easily recovered after the reactions were completed and could be reused without loss of activity.
Studies on the Conformations of Antimicrobial Salicylanilide Derivatives by Spectroscopy
Authors: Suezawa Hiroko , Hirota Minoru , Yuzuri Tomoaki , Hamada Yoshiki , Takeuchi Isao , Sugiura Michiharu
Published: September 2002

Conformations of variously substituted salicylanilides were determined by NMR spectroscopy. The salicylanilide molecules are fairly rigid, taking either the OH…O=C hydrogen bonded (I) or the NH…O hydrogen bonded (II) conformation. The preference between the two intramolecularly hydrogen bonded conformations is affected by the 3- and/or 2′(6′)-substitutent(s). In general, conformation (I) exists overwhelmingly, while conformation (II) becomes predominant in 3-chloro or 2-O-acetylated salicylanilide in inert solvents. These two intramolecular hydrogen bonds were weakened or destroyed to a great extent in dimethyl sulfoxide.
Reactions of 2,2-Dialkylvinyl Iodonium Salt with Halide Ions
Authors: Okuyama Tadashi , Sato Koichi , Ochiai Masahito
Published: September 2002

Reactions of (E)- and (Z)-2-methyl-5-phenyl-1-pentenyl(phenyl)iodonium (1) salts with halide ions were examined in various solvents at 50 or 60 °C. The main products are those of substitution, 1-halo-2-methyl-5-phenyl-1-pentenes, mainly of inversion but involving some retained products. Varying amounts of rearranged products are also formed. Reaction follows pseudo-first-order kinetics at [1] << [halide ion]. The observed rate constants show curved dependence on halide concentration typical of reactions involving a pre-equilibrium formation of the adduct, λ3-haloiodane, and first-, second-, and third-order reaction pathways. The first-order rate constant for the E isomer, (E)-1, is greater than that for (Z)-1, while the opposite is the case for the second- and third-order terms. The main reaction is considered to proceed via a vinylic in-plane SN2 mechanism to lead to inversion while some retention routes via out-of-plane SN2 and/or ligand coupling mechanism are also possible. Competing rearrangement reactions occur by the β-alkyl participation and no evidence for formation of the primary vinylic cation was obtained.
Synthesis and Structure of Sterically Congested, New Alkenes, syn- and anti-9,9′-Bibenzonorbornenylidenes
Authors: Sugihara Yoshiaki , Noda Koichi , Nakayama Juzo
Published: September 2002

Sterically congested alkenes, syn- and anti-9,9′-bibenzonorbornenylidenes (1a) and (1b), were synthesized starting from 9-benzonorbornenone in good overall yields and were isolated in pure form. Their structures were elucidated by analyses of NMR spectra and established by X-ray crystallographic analysis. Structures of the two episulfides, which served as precursors leading to 1a and 1b, were also determined by X-ray crystallographic analysis.
Structural and Stereochemical Studies of Tris[2-(trifluoromethyl)phenyl]borane: Spontaneous Resolution, Stereodynamics, and Intramolecular C-F···B Interactions
Authors: Toyota Shinji , Asakura Mitsuhiro , Oki Michinori , Toda Fumio
Published: September 2002

The structure and stereochemistry of the title organoboron compound, prepared from the corresponding organolithium compound and BCl3, were studied by spectroscopic methods and molecular orbital calculations. The X-ray crystal structure analysis shows that molecules take a propeller-shaped structure of nearly C3 symmetry, in which three CF3 groups lie at the same side of the boron sp2 plane. This compound crystallizes as conglomerates to give single crystals consisting of one or the other enantiomeric forms, both of which are CD active in the solid state. In solutions, molecules exist as a mixture of two conformational isomers, the C3 and C1 symmetric forms. Interconversion between the two isomers was observed by the variable temperature 19F NMR, the barriers to isomerization being 8 and 6 kcal mol-1 for two independent processes in the two ring flip mechanism. The presence of C-F···B interactions was supported by the short F···B contacts (ca. 2.80 Å) in the X-ray structure and by the chemical shift of 19F NMR in solutions.
The Effect of D-Amino Acid-Containing Basic Peptides with Different Hydrophobicity on the Antimicrobial and Cytotoxic Activity
Authors: Kiyota Taira , Yanagida Ryoko , Oka Masahito , Miyoshi Mie , Lee Sannamu , Sugihara Gohsuke
Published: September 2002

In order to investigate the structure-activity relationships between the hydrophobicity, differences in the number of positive charged amino acids and D-amino acids as well as their action mechanism with different bio-membranes, we designed and synthesized two sets of 12-mer model peptides originating from an amphiphilic antimicrobial model peptide and a D-amino acid-containing non-amphiphilic peptide. The introduction of D-amino acid in peptides led not only to decreases in the hydrophobicity, helical content, and hemolytic activity, but to an increase in the antimicrobial activity against Gram-positive and -negative bacteria. The relative peptide hydrophobicity was estimated in terms of the peptide elution time, expressed by linear trifluoroacetic acid (TFA)-water to TFA-acetonitrile gradients on C18 reverse-phase high-performance liquid chromatography (RP-HPLC). The retention behavior of model peptides on RP-HPLC is correlated with the activity and selectivity for mammalian cells, Gram-positive and -negative bacteria: The α-helical amphiphilic structure is required for cytolytic ability against mammalian cells, but is not necessary for bacterial activity. Additionally, the peptides have different hydrophobicity regions in which they show their optimum activity against both bacteria and erythrocytes. In the highest hydrophobisity region the peptides display high levels of hemolytic activity. At medium hydrophobicity levels, the peptides are able to display to high levels of activity against Gram-positive bacteria. In the lowest hydrophobisity regions the peptides are able to display high levels of activity against Gram-negative bacteria. This may be useful in designing clinically effective antimicrobial peptides with highly potent activity and high bacterial selectivity.
Directive Effect of the 2- and 3-Axial Hydroxy Groups That Appeared in the Complex Metal Hydride Reduction of Cyclohexanones
Authors: Senda Yasuhisa , Kikuchi Nobuhito , Inui Ayuko , Itoh Hiroki
Published: September 2002

A significant directive effect of the 2-axial hydroxy group appeared in the LiAlH4, NaBH4, and Zn(BH4)2 reduction of cyclohexanone, while the 3-axial hydroxy group exhibited a steric hindrance. The distance between the carbonyl carbon and the hydroxy group which interacts with the hydride reagent is mainly responsible for such a difference. In the reduction of Na[B(OAc)3H], both the 2- and 3-axial hydroxycyclohexanones exclusively gave the products which were obtained by the hydride approaching from the side of the hydroxy group. The key point of this stereoselectivity is the formation of Na[B(OAc)2(OR)H], which is far more reactive than the parent hydride, by exchanging the acetate ion with the alkoxide.
Absolute Conformation and Chiroptical Properties. VII. 9(1′)-Msc and Psc Forms of 9-(2-Fluoro-1,1-dimethylethyl)- and 9-(1,1-Dimethylpropyl)-11,12-bis(methoxycarbonyl)-9,10-dihydro-9,10-ethenoanthracenes
Authors: Toyota Shinji , Yoshida Satoshi , Kojima Hiroharu , Oki Michinori
Published: September 2002

The racemic forms of sc-9-(2-fluoro-1,1-dimethylethyl)- and 9-(3-iodo-1,1-dimethylpropyl)-11,12-bis(methoxycarbonyl)-9,10-dihydro-9,10-ethenoanthracene were prepared by treatment of the corresponding carboxylic acid with xenon difluoride and by reduction of 9-(1,1-dimethyl-3-oxopropyl) compound followed by a reaction with iodine in the presence of imidazole, respectively. The fluoro and the iodo compounds were resolved on a chiral column. The absolute conformations of these compounds were determined by deriving them by the same methods from the carboxylic acid and the aldehyde of known absolute conformations. Reduction of the iodo compound with Raney nickel in 1-propanol afforded optically active sc-9-(1,1-dimethylpropyl) compound. In the CD spectrum, the Psc-(-) fluoro compound showed a broad and large trough at ca. 240 nm, similarly with the other halogen compounds, and a stronger Cotton effect at ca. 220 nm than the other halogen compounds. The Psc-(+)-9-(1,1-dimethylpropyl) compound showed a quite different CD spectrum from those of other halogen compounds. Thus the importance of the halogen, though remote from any chromophore, in determining the CD spectra of the title compounds and analogous ones was confirmed.
Radical Cyclization of N-Allyl-2-halo Amide in Water
Authors: Wakabayashi Katsuyu , Yorimitsu Hideki , Shinokubo Hiroshi , Oshima Koichiro
Published: September 2002

Triethylborane-induced radical cyclization of N-allyl-2-iodo amide proceeded smoothly in water to give the corresponding γ-lactam in good yield. Radical cyclization in acidic media was also effective. Chloroacetamide, combined with sodium iodide, was available as a substrate for the atom transfer radical cyclization in water to furnish the iodomethyl-substituted γ-lactam.
Structure and Dynamics of Silica and Acrylamide Gels
Authors: Song Youngjun , Im Seung Soon , Han Yang-Kyoo , Sohn Daewon
Published: September 2002

The structure and dynamics of silica and acrylamide gels were studied using a probe diffusion technique of dynamic light scattering (DLS). Latex particles, diameter = 0.05 μm, embedded in the gel network serve as a probe through their diffusion behavior within the network. A quantitative analysis of the homogeneity of the gel is introduced based on a shift of the correlation function of the dynamic light scattering. The lag time of the particles' correlation function in a completed inorganic silica gel is increased by increasing the contents of the gel network; but the particles' diffusion coefficient in a viscoelastic (acrylamide) gel lowers the f(A)max, the maximum value of the y-axis in the correlation function. The silica gel makes a more homogeneous and compact structure than that of a PAA gel, which has partial heterodyning, by increasing the solid contents of the network density.
Radiation-Induced Coloration of Photochromic Dithienylethene Derivatives in Polymer Matrices
Authors: Irie Setsuko , Irie Masahiro
Published: September 2002

The high-energy radiation-induced coloration of photochromic dithienylethenes was studied in various polymer matrices with the aim of developing a reusable color plastic dosimeter. Upon γ-irradiation, polystyrene films containing 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene 1a and 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene 2a turned red and blue, respectively. The red and blue colors disappeared upon irradiation with visible light, and the films could be reused. In both films the absorption intensities of the colors increased linearly with the absorbed dose. Although radiation-induced coloration was clearly detected in polystyrene films, a color change was scarcely observed in poly(methyl methacrylate) (PMMA) and poly(N-vinyl carbazole) containing 1a and 2a. Excitation energy transfer from polymers to dithienylethenes is considered to play a role in the coloration process in polymer films.
Fatigue Mechanism of Photochromic 1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene
Authors: Higashiguchi Kenji , Matsuda Kenji , Kobatake Seiya , Yamada Taro , Kawai Tsuyoshi , Irie Masahiro
Published: September 2002

The fatigue mechanism of photochromic 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene was studied in hexane solution. Upon irradiation with ultraviolet light, two kinds of by-products were produced in addition to normal photochromic reactions. The major by-product was isolated by HPLC, and was characterized by 1H NMR and absorption spectroscopies and X-ray crystallographic analysis. A minor by-product was also isolated and analyzed with a mass spectrometer. Based on the molecular structural analysis a possible photofatigue mechanism of the dithienylethene was proposed.
The Structure of Sulfur Adsorbed on Pt-Na2O/Al2O3 Catalyst and Its Influence on Isobutane Dehydrogenation
Authors: Kobayashi Junya , Shimizu Takashi , Mizushima Takanori
Published: September 2002

The structures of the sulfur species on a sulfurized Pt-Na2O/Al2O3 catalyst were characterized by Extended X-ray Absorption Fine Structure (EXAFS) and temperature-programmed reaction (TPR) experiments. EXAFS indicated that PtS2 is formed on a surface of Pt particles. A TPR experiment using deuterium indicated that HS- is the major species on the catalyst and that the HS- bridges the PtS2 and Na2S particles. This HS- was effective in enhancing the selectivity for isobutane dehydrogenation.
Photo-Induced Electron-Transfer Reactions of Cyclic Organosilanes and Related Compounds
Authors: Kako Masahiro , Nakadaira Yasuhiro
Published: September 2002

Under photo-induced ET conditions in the presence of CCl4 and BF4-, a Si-Si σ-bond readily undergoes chlorinative and fluorinative cleavage, and gives the corresponding chloro- and fluoro-silanes in good yields. In contrast co-photolysis of an aromatic nitrile with a disilane and a tetraalkyl group 14 metal effects selective silylation and alkylation of the nucleus at the position where spin density is high on its radical anion. Chlorination with CCl4 and the intra-molecular trap with the hydroxy group have clarified the radical cationic nature of the intermediate in the photo-induced electron transfer reactions of organooligosilanes. On the other hand, on photo-induced electron transfer, 7-silabicyclo[2.2.1]heptadiene derivatives undergo skeletal rearrangement to give 2-silabicyclo[3.2.0]heptadiene and 1-silabicyclo[2.2.1]heptadiene derivatives which are also the products from the direct photolysis. 7,8-Disilabicyclo[2.2.2]octadiene derivatives afford 1,2-dimethoxydisilane and 1,2-difluorodisilane, respectively on photo-induced electron transfer in the presence of methanol and BF4-. 1,2-Disilacyclohexadiene derivatives undergo ring contraction to give the corresponding silacyclopentadienes under photo-induced electron transfer conditions. Structural and electronic characteristics of the radical cation derived from these cyclic unsaturated organosilanes by MO calculations have been discussed.
Asymmetric Synthesis of β-Amino Acids by Addition of Chiral Enolates to Nitrones via N-Acyloxyiminium Ions
Authors: Kawakami Toru , Ohtake Hiroaki , Arakawa Hiroaki , Okachi Takahiro , Imada Yasushi , Murahashi Shun-Ichi
Published: September 2002

N-Acyloxyiminium ions, generated by the reaction of nitrones with acyl halides, are highly reactive species and undergo facile reaction with a wide range of nucleophiles, such as ketene silyl acetals, titanium(IV) and boron enolates, hydrido- and allyltin(IV) reagents, and alkynyltitanium(IV) reagents, to give α-substituted amine derivatives. Optically active β-amino acids can be prepared by the reaction of N-acyloxyiminium ions with both boron and titanium(IV) enolates bearing chiral auxiliaries. Reversal of diastereoselectivity was observed by the reactions of the boron and titanium(IV) enolates. Using these reactions, all of the four stereoisomers of α-methyl-β-phenylalanines, for example, can be prepared highly diastereoselectively. Cyclic N-acyloxyiminium ions are useful for the asymmetric synthesis of pyrrolidine and piperidine alkaloids; (5R,8R,8aS)-5-cyano-8-methylindolizidine, which is a common key intermediate for synthesis of 5-substituted 8-methylindolizidines, was prepared selectively.
Intramolecular Assistance of Electron Transfer from Heteroatom Compounds. Electrochemical Oxidation of 2-(2-Pyridyl)ethyl-Substituted Ethers, Sulfides, and Selenides
Authors: Watanabe Mitsuru , Suga Seiji , Yoshida Jun-ichi
Published: September 2002

Organoheteroatom compounds having a 2-(2-pyridyl)ethyl group were synthesized and their oxidation potentials were determined by rotating disk electrode voltammetry. The oxidation potentials were found to be less positive than those of the corresponding compounds having a phenyl group in place of the pyridyl group. The dynamic coordination of the pyridyl group to the heteroatom, which stabilizes the cation radical intermediate, seems to be responsible for facilitating the electron transfer. The magnitude of the intramolecular assistance increases along with an increase in the oxidation potential of the parent compounds. This tendency can be explained in terms of the energy match between the nonbonding p orbital of the pyridyl nitrogen and the HOMO of the parent heteroatom compound.
Solubility Prediction Using Statistical Mechanics
Authors: Parsafar Gholamabbas , Keshavarzi Ezat
Published: September 2002

In the present work, a new expression for the chemical potential of a component in its pure and mixed state has been derived using the classical partition function and the Linear Isotherm Regularity, LIR. Using this approach, we are able to interpret all contributions of ideal and non-ideal terms which appear in the chemical potential. The derived chemical potential satisfies Raoult's and Henry's laws. We may also predict the solubility using the chemical potential without any adjustable parameter when the solvent and solute have molecular similarity, like NH3 in H2O. However, for cases in which the solvent and solute molecules are significantly differ, one adjustable parameter must be considered. Success in predicting the solubility in different systems is due to the generality of the used equation of state, LIR.
Accurate Density-Functional Calculation of Core-Electron Binding Energies of Some Substituted Benzenes
Authors: Takahata Yuji , Chong Delano Pun
Published: September 2002

The core electron binding energies (CEBE's) of benzene, seven monosubstituted benzenes (Ph-X) and one disubstituted benzene (p-NH2-C6H4-NO2) were calculated using density-functional theory (DFT). The unrestricted generalized transition-state (uGTS) model was employed. The DeMon DFT program with a combined functional of Becke's exchange (B88) with Perdew's correlation (P86) was used. The average absolute deviation of the calculated CEBE's of the title compounds was 0.3 eV when the cc-pVDZ basis set was used. The ``CEBE shift'' of the ring carbon in Ph-X was calculated while taking the CEBE on the ring carbon in Ph-H as a reference. The thus-calculated CEBE shifts agree with experiment within the value of the average absolute deviation, 0.1 eV. The signs and quantitative numerical values of the CEBE shifts are very close to the corresponding Hammett σ constants.
Computer Simulation Study of Patterns of Copper and Silver Dendrites Grown from Aqueous Solution in High Magnetic Field
Authors: Duan Wenyong , Fujiwara Masao , Tanimoto Yoshifumi
Published: September 2002

The magnetic field effects (MFEs) on the patterns and yields of silver and copper dendrites generated from Cu2+/Zn and Ag+/Cu liquid-solid redox reactions are simulated with the aid of a biased random walk model. In the present model, multi-particles are generated to represent metal ions, and their trajectories walk randomly with superimposed drifts. Comparing the simulation patterns and yields with the experimental ones, it is confirmed that the convection of solution induced by the magnetic force is responsible for the observed MFEs on the dendrites in a high magnetic field gradient (ca. 400 T2 m-1).
X-Ray Crystal Structure Analysis of Silicon Phthalocyanines: Study of the Relationship between Intermolecular Interaction and Photochemical Sensitivity
Authors: Kojima Yuko , Osano Yasuko T , Ohashi Toyoshi
Published: September 2002

This paper reports on the crystal structures of the three silicon phthalocyanines: dichlorosilicon phthalocyanine [SiCl2Pc], dimethoxysilicon phthalocyanine [Si(Ome)2Pc] and bis(tetrahydrofurfuryloxy)silicon phthalocyanine [Si(thff)2Pc]. We found that although Si(Ome)2Pc and Si(thff)2Pc show sensitivity for an electrophotographic photoreceptor, SiCl2Pc doesn't have photosensitivity. It is known that the difference in the photochemical property of phthalocyanines is related to the crystal structures. Although it is difficult for these materials to obtain single crystals with sufficient size for single crystal X-ray analysis, it is very important to determine the crystal structures in order to understand the mechanism concerning the performance of the electrophotographic photoreceptor. In this work we determined the crystal structures from very small (micrometer-sized) single crystals. The compounds crystallized in space group P21/n for SiCl2Pc, Z = 2 with unit-cell parameters a = 10.261(1) Å, b = 14.618(2) Å, c = 9.072(1) Å, β = 98.51(1)°; in space group P1- for Si(Ome)2Pc, Z = 1 with unit-cell parameters a = 11.606(4) Å, b = 7.583(3) Å, c = 8.304(3) Å, α = 96.46(3)°, β = 105.23(3)°, γ = 74.87(3)°; and in space group P1- for Si(thff)2Pc, Z = 1 with unit-cell parameters a = 10.234(6) Å, b = 10.266(7) Å, c = 9.761(6) Å, α = 98.93(2)°, β = 117.94(2)°, γ = 68.83(2)°. All molecules in the three crystals have a symmetry center on Si atom. In the crystal structure, although SiCl2Pc has π-π stacking extended in only one direction (along c-axis), Si(Ome)2Pc and Si(thff)2Pc have intermolecular interactions extended in all directions in the crystals. Si(Ome)2Pc includes water molecules in the crystal, which form hydrogen bonds. We discuss the relationship between the intermolecular interactions and the photochemical property of silicon phthalocyanines.
Polarographic Behavior and Determination of Pendimethalin in Formulations, and Environmental Samples
Authors: Sreedhar Mallipattu , Damodar Janmanchi , Jyothi Nimmagadda Venkata Vijaya , Reddy Srinivasulu Reddy Jayarama
Published: September 2002

A differential pulse polarographic (DPP) method for the determination of pendimethalin is described based on the reduction of a nitro group at a dropping mercury electrode in BR buffers of pH 2.0 to 12.0 using 25% acetone-water mixtures as a solvent. Also, a cyclic voltammetry (CV) technique has been used to study the behavior of pendimethalin at a hanging mercury drop electrode. The differential pulse polarographic method described here has been applied to the determination of pendimethalin in formulations, grains, soils and spiked water samples. Both standard addition and calibration methods were used for the analytical measurements. The lower detection limit was found to be 1.87 × 10-8 M (M = mol dm-3).
Study on an Estimation of the Contributed Energy to the Transfer Free Energies of Complex Ions. Part I. [Fe(CN)2n(phen)(3-n)](2-2n)+ from Water to a Water-ethanol Mixed Solvent
Authors: Tarui Takao
Published: September 2002

The solubilities of [Fe(phen)3](ClO4)2·H2O, [Fe(CN)2(phen)2]·0.5H2O, [Fe(phen)3][Fe(CN)4phen]·8H2O, and [Fe(phen)3]2[Fe(CN)6]·3.5H2O in ethanol-water mixed solvents were measured at 25.0 ± 0.1 °C, and the transfer free energy of each complex ion from water to water-ethanol mixed solvent was calculated. From the obtained data, the transfer free energies were split into contributions from 1,10-phenanthroline-solvent, cyano ligand-solvent interaction energies, and electrostatic energies. The ratio of the contributed energy from 1,10-phenanthroline vs. transfer free energy of free (non-coordinated) 1,10-phenanthroline is almost constant at about 0.6—0.7 over the whole mole-fraction range. There is thus a possibility to estimate the contributed energy from the transfer free energy of the free ligand in the future. On the other hand, the contributed energy from the cyano ligand can not be obtained by multiplying a certain coefficient to the transfer free energy of the free cyanide ion. The contributed energy from electrostatic energy changes in a somewhat different manner, as expected by the Born equation. However, the estimated transfer free energy as the sum of each contributed energy obtained by a least-squares method is in fair agreement with the observed transfer free energy of each complex ion. It has been confirmed that the proposed conception of the contributed energy to the transfer free energy is a useful means to predict the unknown transfer free energy of complex ions.
Magnetic Properties of the Octahedral Chromium Chalcogenide Cluster Complexes [Cr6Se8(PEt3)6], [Cr6Se8(H)(PEt3)6], and [Cr6S8(H)(PEt3)6]
Authors: Kamiguchi Satoshi , Saito Taro , Mori Wasuke
Published: September 2002

The magnetic data of chromium chalcogenide cluster complexes [Cr6Se8(PEt3)6] (1), [Cr6Se8(H)(PEt3)6] (2), and [Cr6S8(H)(PEt3)6] (3) have been analyzed using the Heisenberg-Dirac-Van Vleck Hamiltonian. The analysis has shown that all of these complexes display an antiferromagnetic interaction between chromium atoms and that the coupling constants decrease in the order 2 > 3 > 1. This interaction is mediated by Cr-(μ3-E)-Cr bridges (E = Se, S) and Cr-Cr bonds. In a comparison of the two hydride clusters, the selenide 2 has a larger antiferromagnetic coupling than the sulfide 3. The shorter Cr-Cr distances in 2 (mean 2.66 Å) than those in 1 (mean 2.81 Å) seem to cause larger antiferromagnetic interaction through the Cr-Cr bonds.
Substitution of Five-Membered Heteroarenes and Uracils with Trifluoroacetaldehyde Ethyl Hemiacetal
Authors: Gong Yuefa , Kato Katsuya , Kimoto Hiroshi
Published: September 2002

A number of α-(trifluoromethyl)heteroarylmethanols 2a—c are conveniently obtained in good yields by substitution of pyrole, furan, and thiophene with trifluoroacetaldehyde ethyl hemiacetal (TFAE); 2b and 2c are formed only in the presence of a catalyst such as ZnCl2. Analogous methanols 8a and 8b are also prepared by catalytic substitution of uracils with TFAE in moderate yields.
Antiferromagnetic Adducts of Copper(II) Propionate with Pyridyl Nitronyl Nitroxides
Authors: Mikuriya Masahiro , Azuma Hiroshi , Nukada Ryoji , Sayama Yasuyoshi , Tanaka Katsunori , Lim Jong-Wan , Handa Makoto
Published: September 2002

Copper(II) propionate was reacted with 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-oxide (p-nitpy), 2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-oxide (m-nitpy), and 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-oxide (o-nitpy) to isolate three complexes, which were characterized by measurements of the infrared and electronic spectra, as well as the magnetic susceptibilities. Single-crystal X-ray analyses reveal that the former two complexes are adducts of dimeric copper(II) propionate, [Cu2(pro)4(p-nitpy)2] (1) (Hpro = C2H5COOH) and [Cu2(pro)4(m-nitpy)2] (2), and that the latter complex is bis(picolinato)copper(II) dihydrate (3·2H2O).
Structures and Magnetic Properties of Ruthenium(II,III) Pivalate Cation Dimers Axially Coordinated by Pyridyl Nitronyl Nitroxide Radicals through Their Pyridyl Nitrogen Atoms
Authors: Sayama Yasuyoshi , Handa Makoto , Mikuriya Masahiro , Hiromitsu Ichiro , Kasuga Kuninobu
Published: September 2002

Adduct complexes of ruthenium(II,III) pivalate dimer with pyridyl nitronyl nitroxide radicals, [Ru2(O2CCMe3)4(L)2]X (L = 2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-N-oxide (m-nitpy) and 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-N-oxide (p-nitpy); X = BF4 and BPh4), have been prepared and characterized. The dimeric cores, which are axially coordinated by the pyridyl nitrogen atoms of the radical ligands, not by the nitroxide oxygen atoms, have been crystallographically confirmed for complexes with m-nitpy (X = BF4) and p-nitpy (X = BPh4) using an X-ray diffraction method. The magnetic interactions between the radical and Ru(II,III) dimer through the pyridyl group and the radicals of the neighboring cation units through the space are weak.
Analysis of Reactions of Aromatic Anions with Quaternary Ammonium Ions in Ion Association-Nonionic Micellar Electrokinetic Chromatography
Authors: Takayanagi Toshio , Fushimi Kana , Motomizu Shoji
Published: September 2002

Reactions in ion association-nonionic micellar electrokinetic chromatography have been analyzed using mobility change in capillary electrophoresis. Several quaternary ammonium ions and aromatic anions were used as pairing cations and anions, respectively, and three kinds of nonionic surfactant were used to form micelles in an aqueous solution. The apparent electrophoretic mobility of the analyte anions decreased with increasing concentrations of nonionic surfactant and/or pairing cation. The equilibrium reactions participating in this electrophoresis system are binding of anions to nonionic surfactant micelle (KB), ion association of anions with pairing cation (Kass), and distribution of the formed ion associates to the nonionic surfactant micelle (KB,IA). The equilibrium constants were determined by non-linear least-squares analyses by applying the analyses to the mobility decreases. Equilibrium constants of KB and KB,IA for monovalent anions were found to be larger than those for divalent anions, and KB,IA values for each anions were larger than their KB values. The results obtained can be explained from distribution phenomena of analytes between aqueous and organic phases.
ORMOSIL Composite Phosphors Incorporated with Lanthanide Complexes
Authors: Li Hui-hui , Inoue Satoshi , Ueda Daisuke , Machida Ken-ichi , Adachi Gin-ya
Published: September 2002

Lanthanide complexes, [Eu(phen)2]Cl3 and [Tb(bpy)2]Cl3, were doped into organically modified silicate (ORMOSIL) matrices over a wide range of composition. The features and luminescence behavior of the resultant composite products were strongly dependent on the matrix composition. Transparent ORMOSIL composite phosphor disks were obtained under the optimized complex concentration and matrix composition, as well as with careful control of the drying process. Luminescence property varieties of the composites based on various matrix compositions were studied and interpreted from the viewpoint of local chemical environment around the doped complex molecules. Those for composite phosphors incorporated with [Eu(phen)2]Cl3 were additionally characterized by the 5D0-7F2 to 5D0-7F1 emission intensity ratio. Illustrative models of the lanthanide complex-containing sol-gel derived composites were proposed.
Practical Synthesis of [3-(2H3)Methyl]mevalonolactone and Incorporation Experiment of [3-(2H3)Methyl]mevalonolactone and [13C]Labeled Acetate in the Biosynthesis of Isoprenoidal Diether Lipids of Halophilic Archaea
Authors: Yamauchi Noriaki , Natsubori Yoshiaki , Murae Tatsushi
Published: September 2002

The biosynthesis of the saturated isoprenoid portion of membrane lipids of the halophilic archaea Natrinema pallidum was investigated. At first, a practical method for the synthesis of [3-(2H3)methyl]mevalonate was developed. Then, incorporation experiments of [3-(2H3)methyl]mevalonate into the lipid core indicated that the isoprenoid portion was derived from mevalonate. However, a [2-13C]acetate-incorporation experiment revealed a significant difference in the degree of 13C enrichment between the expected position from the mevalonate pathway, the CH2 groups (and at one terminal CH3 group) and the CH3 groups in the saturated isoprenoid chain. These results suggest that (1) the mevalonate pathway exists and is active, and (2) a part of acetoacetyl-CoA is not derived from an acetate in the biosynthesis of the isoprenoidal lipid-core of the archaebacterium.
Syntheses of Penta-O-benzyl-myo-inositols, O-β-L-Arabinosyl-(1 → 2)-sn-myo-inositol, O-α-D-Galactosyl-(1 → 3)-sn-myo-inositol, and O-α-D-Galactosyl-(1 → 6)-O-α-D-galactosyl-(1 → 3)-sn-myo-inositol
Authors: Koto Shinkiti , Hirooka Motoko , Yoshida Toyosaku , Takenaka Kazuhiro , Asai Chizuru , Nagamitsu Toshiki , Sakuma Hiroaki , Sakurai Michiyo , Masuzawa Shinichi , Komiya Mitsuo , Sato Tadaaki , Zen Shonosuke , Yago Kazuo , Tomonaga Fumiya
Published: September 2002

Two-step conversions of myo-inositol into (±)-2,3,4,5,6- and 1,3,4,5,6-penta-O-benzyl-myo-inositols are described. Starting from these monohydroxy derivatives of myo-inositol, O-β-L-arabinopyranosyl-(1 → 2)-sn-myo-inositol from Japanese green tea [SENCHA], Camellia sinensis, and O-α-D-galactopyranosyl-(1 → 3)-sn-myo-inositol (galactinol) as well as its homolog, O-α-D-galactopyranosyl-(1 → 6II)-galactinol, were synthesized by way of the in situ activating glycosylation procedure.
Exploration of the Role of Phenylalanine in the Thrombin Receptor Tethered-Ligand Peptide by Substitution with a Series of Trifluorophenylalanines
Authors: Matsushima Ayami , Fujita Tsugumi , Okada Kazushi , Shirasu Naoto , Nose Takeru , Shimohigashi Yasuyuki
Published: September 2002

The thrombin receptor-tethered ligand SFLLRNP (abbreviation formed by one letter amino acid codes expressing Ser-Phe-Leu-Leu-Arg-Asn-Pro) consists of the Phe-2 residue essential for the receptor activation. In order to explore the molecular characteristics of this Phe-2-phenyl, a series of trifluorophenylalanines [(F3)Phe] was incorporated into this S/Phe/LLRNP for evaluation of their ability to induce the human platelet aggregation. A complete set of (F3)Phe in the L-configuration, namely, (2,3,4-F3)Phe, (2,3,5-F3)Phe, (2,3,6-F3)Phe, (2,4,5-F3)Phe, (2,4,6-F3)Phe, and (3,4,5-F3)Phe, was prepared from trifluorobenzyl bromides and diethyl acetamidomalonate. S/(2,3,4-F3)Phe/LLRNP was equipotent to S/Phe/LLRNP, while (2,4,5-F3)Phe-containing analog was almost twice as potent as those. (2,4,6-F3)Phe-analog exhibited about a half of the activity of S/Phe/LLRNP. (3,4,5-F3)Phe-, (2,3,5-F3)Phe-, and (2,3,6-F3)Phe-analogs were very weak. The analysis of these assay results suggested that Phe-2-phenyl of SFLLRNP is in the edge-to-face CH/π interaction with the receptor aromatic group, utilizing the Phe-2-phenyl edge along with benzene hydrogens at position 2-3 or 5-6. The computer-assisted semi-empirical molecular orbital calculations by MOPAC showed that the fluorine atom decreases the electron density of its ortho, meta, and para hydrogens, and thus increases their acidity more strongly in that order. All these suggested that H → F replacements reinforce the edge-to-face CH/π interaction to enhance biological activity. The H → F replacement on the Phe-phenyl group was found to render an effective structural examination; i.e., to identify the hydrogens in the CH/π interaction, and to intensify the CH/π interaction.
Flavin Receptors. Effect of the Acidity of Melamine Derivatives Bearing a 2-Arylguanidinium Ion on 6-Azaflavin Binding in Chloroform
Authors: Moriya Hideki , Kajiki Takeshi , Watanabe Shigeki , Kondo Shin-ichi , Yano Yumihiko
Published: September 2002

The pKa's of melamine derivatives bearing a 2-arylguanidinium ion and their binding constants for 6-aza-10-dodecylisoalloxazine (6-azaflavin) were nicely correlated with the Hammett σ of the substituents. However, the rates of the oxidations of N-benzyl-1,4-dihydronicotinamide (BNAH) and dithiothreitol (DTT) by 6-azaflavin were not affected by the substituents of the receptors in CHCl3.
Interactions of a Dye and a Solvent with Poly(N-isopropylacrylamide) Gel in Relation to Its Phase-Transition Behavior
Authors: Murase Yasuyuki , Onda Tomohiro , Tsujii Kaoru , Tanaka Toyoichi
Published: September 2002

The binding of a dyestuff and the sorption of a solvent to a polymer gel have been studied in relation to the phase-transition behavior of the gel. Binding or sorption isotherms of a dye (erythrosine B) and a solvent (benzyl alcohol) to a polymer gel (poly(N-isopropylacrylamide) : NIPA) were measured and found first to be Langmuir- and BET-type curves, respectively. A single Langmuir-type adsorption isotherm and the superposition of the two isotherms of the dye were fit for the collapsed (40 °C) and swollen states (25 °C) of the gel, respectively. The phase-transition behavior of the NIPA gel was not affected at all by binding of the dye, but was highly altered by the addition of benzyl alcohol. A reentrant-type phase transition of the NIPA gel was observed with increasing concentration of benzyl alcohol at 25 °C. It is quite interesting to note that the gel shrinks when the concentration of the solvent inside the gel attains its solubility limit (ca. 0.4 mol dm-3), and swells again when it reaches the solubility in the bulk solution phase (outside the gel). At the stage of re-swelling, the solution in the gel interior consists of almost pure benzyl alcohol. These results indicate that the NIPA gel shows a selective sorption of benzyl alcohol, and separates it from its aqueous solutions.
The Role of Deltorphin II Phenylalanine Residue in Binding to the δ Opioid Receptor
Authors: Honda Takeshi , Shirasu Naoto , Chuman Yoshiro , Okada Kazushi , Fujita Tsugumi , Nose Takeru , Shimohigashi Yasuyuki
Published: September 2002

Deltorphin II is a peptide ligand specific for the δ opioid receptor. In order to elucidate the role of Phe3 in binding to the δ opioid receptor, we synthesized a series of analogs in which Phe3 was replaced by various amino acids such as Ala, cyclohexylalanine (Cha), fluorophenylalanines, and other alkyl-side chain amino acids (Val, Leu, and norleucine (Nle)). It was found that [Cha3]deltorphin II and [Nle3]deltorphin II retain almost a full receptor binding affinity. The results indicated that the Phe3-phenyl group of deltorphin II can be substituted by the alkyl groups such as cyclohexyl and propyl in the interaction with the δ receptor.
New Organogelators Bearing Both Sugar and Cholesterol Units: an Approach toward Molecular Design of Universal Gelators
Authors: Amaike Masato , Kobayashi Hideki , Shinkai Seiji
Published: September 2002

The gelators of organic solvents are classified into two categories on the basis of their basic intermolecular forces: hydrogen-bonded or nonhydrogen-bonded. To utilize these two interactions cooperatively for organogel formation we newly synthesized seven gelators (1—7) and two reference compounds (8 and 9) which have both a cholesterol moiety and a saccharide moiety within one molecule. The solubility of 1—7 changed drastically from totally insoluble one to very soluble one depending on the saccharide absolute configuration. In general, the gelator became very insoluble when it includes many equatorial OH groups, whereas it became very soluble when it includes many axial OH groups. Gelators 2 and 5 bearing two equatorial OH groups and one axial OH group acted as good gelators and in several cases the sol-gel phase-transition temperatures (measured in a sealed tube) were higher than the boiling points. The SEM observations of the xerogels established that the stable gels contain the entangled fibrous network. These results indicate that a very stable organogel can be designed by a cooperative coagulative effect of a cholesterol-cholesterol interaction and a saccharide-saccharide interaction.
Rhodium-Catalyzed Enantioselective Michael Addition of (1-Cyanoethyl)phosphonate: Synthesis of Optically Active Phosphonic Acid Derivatives with Phosphorus-Substituted Quaternary Asymmetric Carbon Center
Authors: Sawamura Masaya , Hamashima Hitoshi , Ito Yoshihiko
Published: September 2002

Asymmetric Michael addition of diethyl (1-cyanoethyl)phosphonate with vinyl ketones or acrylaldehyde in the presence of 0.01 molar amount of a rhodium catalyst prepared in situ from Rh(acac)(CO)2 and a trans-chelating chiral diphosphine ligand (R,R)-(S,S)-2,2′′-bis[1-(diphenylphosphino)ethyl]-1,1′′-biferrocene (PhTRAP) in benzene at 3 °C gave optically active phosphonates having a phosphorus-substituted quaternary asymmetric carbon center with high enantiomeric excesses (92—93% ee) in high yields. The Michael addition product from acrylaldehyde was converted into an optically active (1-aminoalkyl)phosphonic acid derivative.
Reactivities of Stable Rotamers. XLIII. Diazotization of 2-Methyl-2-(1,2,3,4-tetrachloro- and 1,4-dimethoxy-9-triptycyl)propylamine Rotamers
Authors: Oki Michinori , Yoshida Satoshi , Taguchi Yasushi , Minato Ichiro , Nobuoka Koji , Fukada Norihiro , Toyota Shinji , Tanaka Toshimasa , Tanaka Yasuhiro , Yamamoto Gaku
Published: September 2002

The title amines were prepared from the corresponding rotamers of carboxylic acids via azides and isocyanates. Diazotization of these amines with isopentyl nitrite and organic acids commonly afforded olefins, that are derived from Wagner-Meerwein type rearrangement of the intervening cation followed by deprotonation. Other products included a cyclic compound derived by the attack of the carbocation on an unsubstituted benzeno bridge and esters derived from the acid which was used for diazotization. These two compounds are the products from the cation prior to the rearrangement. The sc-tetrachloro compound afforded the esters of the organic acids as almost an exclusive product and the sc-dimethoxy compound afforded a cyclized compound which is derived from the nucleophilic reaction of the 1-methoxy group with the cation, followed by demethylation of the resulting oxonium ion. These features are attributed to the strong interaction of the 1-substituent with the intermediate carbocations. In agreement with this interpretation, the formation of the corresponding ester is decreased with decreasing the nucleophilicity of the acid used for the diazotization of the sc-tetrachloro compound.
Catalytic Asymmetric Hydrogenation of α-(Acetamido)acrylates Using TRAP Trans-Chelating Chiral Bisphosphine Ligands: Remarkable Effects of Ligand P-Substituent and Hydrogen Pressure on Enantioselectivity
Authors: Kuwano Ryoichi , Sawamura Masaya , Ito Yoshihiko
Published: September 2002

The catalytic asymmetric hydrogenation of α-(acetamido)acrylates was carried out with the rhodium complexes prepared from [Rh(cod)2]BF4 and trans-chelating chiral bisphosphine ligands, (S,S)-2,2′-bis[(R)-1-(dialkylphosphino)ethyl]-1,1′-biferrocenes [(R,R)-(S,S)-TRAPs]. In the reaction of β-unsubstituted or β-monosubstituted α-(acetamido)acrylates [(E)-RCH=C(NHAc)CO2Me], the selectivity for (R)-hydrogenation product increased with decreasing steric demand of the substrate β-substituent and the ligand P-substituent as well as decreasing hydrogen pressure. The selectivity for the (R)-product in the reaction with EtTRAP-rhodium catalyst at 60 °C and 0.5 kg cm-2 of hydrogen pressure was as follows: R = H, 96% ee; R = Me, 92% ee; R = Ph, 77% ee; R = i-Pr, 57% ee. The remarkable steric and pressure effects caused a dramatic reversal of enantioselectivity in the reaction of methyl 2-(N-acetylamino)cinnamate (R = Ph). For example, the selectivity of 87% (R) with EtTRAP at 60 °C and 0.1 kg cm-2 of hydrogen pressure has reversed to 92% (S) with i-BuTRAP at 15 °C and atmospheric hydrogen pressure. Hydrogenation of the β,β-disubstituted α-(acetamido)acrylates proceeded smoothly at 15 °C and atmospheric hydrogen pressure with high enantioselectivity in favor of the 2S-isomers when EtTRAP or BuTRAP was employed as the chiral ligand.
Diastereoselective Aldol and Reformatsky Reactions of α-Halo Carbonyl Compounds and Aldehydes Mediated by Titanium(II) Chloride
Authors: Kagayama Akifumi , Igarashi Koji , Shiina Isamu , Mukaiyama Teruaki
Published: September 2002

Highly diastereoselective aldol reactions of α-bromo ketones with several aldehydes were successfully carried out by using a combination of titanium(II) chloride and copper or sodium iodide in dichloromethane-pivalonitrile at low temperature. Similarly, Reformatsky reactions of α-bromo thioester with aliphatic aldehydes proceeded to afford β-hydroxy thioesters in good yields under mild conditions.
Interaction Mode of H397A Mutant Carboxypeptidase Y with Protein Substrates Analyzed by the Surface Plasmon Resonance
Authors: Nakase Hiroshi , Jung Giman , Ueno Hiroshi , Hayashi Rikimaru , Harada Yoshinori
Published: September 2002

In order to study the substrate binding mode and subsite properties of carboxypeptidase Y (CPY), the dissociation and association constants, KD and KA, of its catalytically inactive mutant, H397A, were determined by surface plasmon resonance with protein substrates, i.e., α-casein, RCM-RNase A, RCM-lysozyme, and RCM-BSA. KD values obtained for four substrates were in a range of 10-8 to 10-7 M, being equal to Km values of catalytically active wild-type CPY for the same protein substrates. These results suggest that the acylation step is a rate-limiting step in the CPY-catalyzed hydrolysis of protein substrates. Small substrates like N-acylated dipeptides gave Km values in a range of 10-4 to 10-2 M, considerably smaller than those for protein substrates, suggesting the presence of additional subsites in addition to S1′ and S1 in the substrate binding pocket of CPY.
Synthesis of Optically Active 2-Methylchroman Derivatives and Application to Chiral Dopants for Nematic Liquid Crystals
Authors: Shitara Hiroaki , Aoki Yoshio , Hirose Takuji , Nohira Hiroyuki
Published: September 2002

Chiral 2-methylchroman-2-carboxylic acid derivatives were prepared as new chiral dopants for nematic liquid crystals. The starting material, optically active 6-benzyloxy-2-methylchroman-2-carboxylic acid, was newly synthesized as a rigid core structure and resolved by a diastereomeric salt formation method. Its absolute configuration was determined by comparing its circular dichroism spectrum with that of the commercially available (S)-6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid derivative. The helical twisting power of the new dopants was determined and the relationship between their functional groups and flexible terminal structures was studied.
Rotational Isomerism Involving an Acetylenic Carbon II : Effect of 1-Halogen Substituents on Rotamer Population and Rotational Barrier around C(sp)-C(sp3) Bonds in Bis(9-triptycyl)ethynes
Authors: Toyota Shinji , Yamamori Takao , Makino Toshiaki , Oki Michinori
Published: September 2002

A series of (1,4-dimethyl-9-triptycyl)(1-halo-9-triptycyl)ethynes were synthesized to examine the effect of halogen substituents on the rotational isomerism about C(sp)-C(sp3) bonds. The kinetic and thermodynamic data of the isomerization between the ap and sc rotamers were determined by the total lineshape analysis and the intensity of the 1H NMR signals, respectively. The rotational barriers are enhanced with the steric size of halogen atoms from 11.6 (F) to 17.3 (I) kcal mol-1, and there is a linear correlation between the barrier height and van der Waals radius of the 1-substituent. Although large halogen atoms decrease the ratio of the sterically congested sc form, its population tends to be larger than that expected from the steric effect. This finding is attributable to the C-H…X(halogen) interactions between the 1-Me and X groups in the sc form. The possibility of the weak interactions is discussed on the basis of molecular structures optimized by the MM2 calculations.