Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 72 , Issue 8
Showing 1-33 articles out of 33 articles from the selected issue
  • Yoshinori Hirata
    1999 Volume 72 Issue 8 Pages 1647-1664
    Published: 1999
    Released: November 01, 2004
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    Photophysical and photochemical primary processes of diphenylacetylene (DPA) derivatives and related compounds have been reviewed. Curious photophysical properties of the low lying excited singlet states of DPA, such as an exceptionally slow S2 → S1 internal conversion, a distinct temperature effect of the S2 lifetime, and a strong excitation energy dependence of the fluorescence yield, were correlated with the S2–S1 energy gap. Contradictions of the assignments of the lowest excited singlet states of DPA were resolved and the mechanism of the S2 → S1 internal conversion was proposed from the comparison of the dynamic behavior of DPA with that of diphenylpolyenes. The small S2–S1 energy gap as well as the large displacement between the potential curves of the upper and lower electronic states can be a reason why the S2 state of the DPA derivatives is exceptionally long-lived. The DPA derivatives of which the intramolecular charge-separated states are formed in polar solvents were used as probe molecules of the solvent–solute interaction. Significant enhancement of the charge recombination of aminophenyl(phenyl)acetylene in protic solvents should be due to the interaction between amino nitrogen atom of the solute molecule and the hydrogen-bonded solvent oligomer.
  • Norihiro Tokitoh, Tsuyoshi Matsumoto, Renji Okazaki
    1999 Volume 72 Issue 8 Pages 1665-1684
    Published: 1999
    Released: November 01, 2004
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    The recent applications of an extremely bulky and efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (denoted as Tbt in this article), to the kinetic stabilization of a series of doubly bonded compounds between germanium and heavier chalcogen atoms (we coin the expression “germanium-containing heavy ketones” for this family of heavier congeners of germanone) are described. Combination of a Tbt group with some other bulky aromatic or alkyl substituent enabled us to synthesize the novel germanium-containing double-bond species [Tbt(R)Ge=X; R = 2,4,6-triisopropylphenyl (Tip) or bis(trimethylsilyl)methyl (Dis)] such as germanethiones (X = S), germaneselones (X = Se), and germanetellones (X = Te) as stable crystalline compounds, while the germanone [Tbt(Tip)Ge=O], the most reactive species among the germanium-containing heavy ketones, was found to be very difficult to isolate and was evidenced only by the trapping reactions. The X-ray crystallographic analysis of the isolated germanium-containing heavy ketones revealed a completely trigonal planar geometry around their germachalcogenocarbonyl units and their ideally doubly bonded character, which was also confirmed by their spectroscopic data.
  • Ken-ichi Okamoto, Chieko Sasaki, Yasunori Yamada, Takumi Konno
    Type: Article
    1999 Volume 72 Issue 8 Pages 1685-1696
    Published: 1999
    Released: November 01, 2004
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    Novel pentanuclear complexes, [Pd{Pd(aet)}{M(aet)2}{M(aet)3}2]4+ (M = Rh (1); Ir (2); aet = 2-aminoethanethiolate) and [Pd2{Pd(aet)2}{Co(aet)3}2]4+ (4), were prepared by the reactions of fac(S)-[M′(aet)3] (M′ = M, Co) with Na2[PdCl4]. Molecular structures for 1, 2 and 4 were determined by X-ray diffraction. In 1 and 2, two Pd atoms forming the parallel planes are spanned by the aggregation of two octahedral fac(S)-[M(aet)3] units and cis(N)-[M(S)2(aet)2] unit. In these complexes, one of the aet ligands in the starting fac(S)-[M(aet)3] transfers from the M ( = Rh, Ir) atom to the Pd one. Two Pd atoms in 4 are bridged by two fac(S)-[Co(aet)3] units and cis(S)-[Pd(aet)2] unit. In this complex, two aet ligands transfer to the Pd one. The methylation reaction for one non-bridging S atom in 1 gave the corresponding complex [Pd{Pd(aet)}{Rh(aet)(smaet}{Rh(aet)3}2]5+ (3; smaet = S-methyl-2-aminoethanethiolate), whose structure was also determined by X-ray diffraction. For all of the complexes, the chiral configurations are selectively regulated owing to the octahedral units (Δ or Λ) and the bridging sulfur atoms (R or S), and they are characterized on the basis of the electronic absorption, circular dichroism (CD) and 13C NMR spectral behavior. The binding modes of the octahedral units in 1, 2, and 4 are also discussed in relation to their stereochemical behavior.
  • Tanveer Alam, Kamaluddin
    1999 Volume 72 Issue 8 Pages 1697-1703
    Published: 1999
    Released: November 01, 2004
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    Copper(II) and zinc(II) hexacyanoferrates(II) have been found to be effective adsorbents for aminopyridines, such as 2-amino-, 3-amino-, and 4-aminopyridines. The maximum adsorption was found at neutral pH (pH = 7.0). The adsorption trend followed a Langmuir adsorption isotherm. The Langmuir constants, KL and XM, were determined. The overall adsorption trend was found to be in the order 3-amino- > 4-amino- > 2-aminopyridine. Infrared spectral studies of the adsorption adducts indicate that adsorption takes place through an interaction between the adsorbate molecule and the outer divalent metal ion of metal hexacyanoferrates(II). The results of the present study suggest the importance of metal hexacyanoferrates(II) and metal ions in the stabilization of biomolecules from degradation on primitive earth.
  • Yoshihisa Fujiwara, Kohji Yoda, Taro Tomonari, Takeshi Aoki, Yukimi Ak ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1705-1715
    Published: 1999
    Released: November 01, 2004
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    The magnetic field effects on the lifetimes of radical pairs (RPs) comprising anthrasemiquinone (AQH·) and alkyl radicals generated in Brij35, HDTCl, and SDS micellar solutions of anthraquinone (AQ) and n-alkyl anthraquinone-2-carboxylates (AQ-n) were studied by laser flash photolysis in high magnetic fields up to 13 T. The RP lifetimes of AQ and AQ-n in the three surfactants increased along with increasing the magnetic field from 0 to about 2 T. The RP lifetimes of AQ in Brij35 and HDTCl drastically decreased in a magnetic field from 3 to 13 T, whereas the RP lifetimes of AQ in SDS were almost constant in the same range of the magnetic field. The increase in the three surfactants was explained by spin-lattice relaxation (SLR) modulated by anisotropic hyperfine and electron dipole–dipole interactions. The drastic decrease in Brij35 and HDTCl was interpreted by SLR modulated by an anisotropic Zeeman interaction. The parameters of the anisotropic g-value and the rotational correlation time for an anisotropic Zeeman interaction were obtained. The constant RP lifetimes in SDS at a high magnetic field were interpreted referring to an escape process of AQH· from the micelle core.
  • Ayori Mitsutake, Masayuki Irisa, Yuko Okamoto, Fumio Hirata
    1999 Volume 72 Issue 8 Pages 1717-1729
    Published: 1999
    Released: November 01, 2004
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    We employed Monte Carlo simulated annealing to classify the low-energy conformations of Met-enkephalin in the gas phase and in aqueous solution. In order to include the free energy of cavity formation in aqueous solution, we used the method of extended scaled particle theory. This is the first attempt to combine the Monte Carlo simulated annealing method and the extended scaled particle theory. We conducted 20 Monte Carlo simulated annealing runs of 10000 Monte Carlo sweeps both in the gas phase and in aqueous solution. It was found that the obtained conformations (20 each) can be classified into 3 groups of similar structure both in the gas phase and in aqueous solution. We studied in detail the structural characteristics of the classified conformations. It was found that the cavity-formation effects of aqueous solution do not drastically change the backbone structures obtained in the gas phase. The relation between the solvent-accessible surface area and the cavity-formation free energy was studied in detail. The results show unambiguously that the cavity-formation free energy is not neccessarily proportional to the accessible surface area, at least for a small peptide.
  • Masaaki Yokota, Hidehiro Uekusa, Yuji Ohashi
    Type: Article
    1999 Volume 72 Issue 8 Pages 1731-1736
    Published: 1999
    Released: November 01, 2004
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    Two crystal forms of (−)-trans-4-(p-fluorophenyl)-3-(3,4-methylenedioxyphenoxymethyl)piperidine hydrochloride salt (paroxetine HCl) have been analyzed by X-rays. One form (Form I) is obtained as a hemihydrate and the other (Form II) is crystallized as the propan-2-ol solvate. The crystal of Form I belongs to the monoclinic system and the space group is P21. The unit-cell dimensions are; a = 14.5888(10), b = 10.1591(7), c = 13.0255(10) Å, β = 107.095(3)°, and V = 1845.2(2) Å3. There are two crystallographically independent protonated paroxetine molecules with different conformations and chloride anions, and one water molecule in an asymmetric unit. The crystal of Form II also belongs to the monoclinic system and the space group is P21. The unit-cell dimensions are; a = 11.6504(7), b = 5.7374(3), c = 16.4107(10) Å, β = 90.959(2)°, and V = 1096.79(11) Å3. There are one protonated paroxetine molecule, one chloride anion, and one solvent propan-2-ol molecule in an asymmetric unit. The protonated paroxetine molecule in Form II has a different conformation from those in Form I. The solvent propan-2-ol molecule is disordered in the channel formed by paroxetine molecules and chloride anions. The crystal was easily decomposed in open air at room temperature because the propan-2-ol molecules are easily released through the channel.
  • Hiroshi Ichikawa, Atsushi Yoshida, Hirotaka Kagawa, Jun’ichi Aih ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1737-1740
    Published: 1999
    Released: November 01, 2004
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    The kinetic energy of electrons in a one-dimensional box has the property of a linear additivity with respect to the unit length. This property coincides with that of the π electrons of linear polyenes. Both properties lead to an understanding of why the ‘π energy’ or the Hückel energy includes information about the nuclear configuration based on the molecular virial theorem. This article shows that the linear additivity is a property of the kinetic energy of particles that move in a one-dimensional box, and thus assures that the Hückel energy is another expression of the kinetic energy of π electrons. The reason for the coincidence of both methods is interpreted as meaning that they seek the same stationary wave functions. Thus, we may fairly say that the so-called Hückel energy, ‘π energy’, or the empirical π energy is a quantitative quantity of the kinetic energy of π electrons.
    If the interpretation that the ‘π energy’ is the kinetic energy of π electrons is adopted, the explanation for a regular hexagon structure of benzene made by Shaik et al. is reversed.
  • Hua Huang, Sadakatsu Nishikawa, Shaojun Dong
    Type: Article
    1999 Volume 72 Issue 8 Pages 1741-1747
    Published: 1999
    Released: November 01, 2004
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    Ultrasonic absorption coefficients were measured for butylamine in heavy water (D2O) in the frequency range from 0.8 to 220 MHz and at concentrations from 0.0278 to 2.5170 mol dm−3 at 25 °C; two kinds of relaxation processes were observed. One was found in relatively dilute solutions (up to 0.5 mol dm−3), which was attributed to the hydrolysis of butylamine. In order to compare the results, absorption measurements were also carried out in light water (H2O). The rate and thermodynamic parameters were determined from the concentration dependence of the relaxation frequency and the maximum absorption per wavelength. The isotope effects on the diffusion-controlled reaction were estimated and the stability of the intermediate of the hydrolysis was considered while comparing it with the results for propylamine in H2O and D2O. Another relaxation process was observed at concentrations greater than 1 mol dm−3 in D2O. In order to examine the solution characteristics, proton NMR measurements for butylamine were also carried out in D2O. The chemical shifts for the γ- and δ-proton in butylamine molecule indicate the existence of an aggregate. From profiles of the concentration dependence of the relaxation frequency and the maximum absorption per wavelength of sound absorption, the source of the relaxation was attributed to an association–dissociation reaction, perhaps, associated with a hydrophobic interaction. The aggregation number, the forward and reverse rate constants and the standard volume change of the reaction were determined. It was concluded from a comparison with the results in H2O that the hydrophobic interaction of butylamine in D2O is stronger than that in H2O. Also, the isotope effect on this reaction was interpreted in terms of the solvent structure.
  • Kaori Asano, Kazuhiro Inoue, Motohiro Nakano, Yuji Miyazaki, Michio So ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1749-1757
    Published: 1999
    Released: November 01, 2004
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    Heat capacities of the molecule-based antiferromagnet MnCu(obbz)·5H2O (obbz = oxamidobis(benzoato)) have been measured at temperatures from 0.1 to 300 K by means of adiabatic calorimetry. A phase transition due to three-dimensional antiferromagnetic ordering was observed at 2.18 K, above which a heat capacity hump appeared, arising from the short-range ordering characteristic of a low-dimensional magnet. The enthalpy and entropy gained at the magnetic phase transition were evaluated to be 48.6 J mol−1 and 12.1 J K−1 mol−1, respectively. This entropy gain is close to the value R ln 5 ( = 13.4J K−1 mol−1) expected for the spin-manifold of the S = 2 ground state. The heat capacity hump above the magnetic transition temperature is explained well by the S = 2 one-dimensional ferromagnetic Heisenberg model with the exchange interaction J/kB = 0.75 K, where kB is the Boltzmann constant. These results confirm that the present complex behaves as a one-dimensional ferrimagnet, in which strong antiferromagnetic coupling exists between a pair of spins of Mn(II) (S = 5/2) and Cu(II) (S = 1/2) but the magnetic interaction is very weak between the pairs. A first-order phase transition was also found at 268.4 K. This transition may arise from orientational order–disorder mechanism of the crystalline water molecules in the complex.
  • Shinsaku Fujita
    Type: Article
    1999 Volume 72 Issue 8 Pages 1759-1768
    Published: 1999
    Released: November 01, 2004
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    The ring flipping (F) and the N-inversion (I) of piperidine are discussed by presuming a quadruplet of conformers as a model. After an extended pseudo-point group is defined, the concept of FI-energeticity is proposed. The flexible piperidine derivatives are enumerated on the basis of the model by the unit-subduced-cycle-index approach. The enumerated derivatives are classified into FI-isoenergetic (Types I, I′, and II) and FI-anisoenergetic (Types III and IV) by means of their extended pseudo-point groups.
  • Kalyan Kali Sen Gupta, Biswajit Pal, Nandini Bhattacharjee, Saktiprosa ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1769-1774
    Published: 1999
    Released: November 01, 2004
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    The kinetics and mechanism of the reduction of tris(pyridine-2-carboxylato)manganese(III) by azide ion in Na(pic)–picH [where Na(pic) = sodium salt of pyridine-2-carboxylic acid and picH = pyridine-2-carboxylic acid] have been studied. The reaction appears to proceed through the intermediate formation of a hepta-coordinated 1 : 1 complex between [MnIII(pic)3] and N3 ion, which then decomposes to give the free radical () and diaquabis(pyridine-2-carboxylato)manganese(II). The free radical further reacts with [MnIII(pic)3] to give nitrogen as the product of oxidation. During the reduction, pyridine-2-carboxylate ion is generated and the coordination sphere of the parent complex is altered, thereby indicating that the reaction takes place by an inner-sphere mechanism. The enthalpy change (ΔH°) and change in entropy (ΔS°) associated with the equilibrium step are −61 ± 4 kJ mol−1 and −169 ± 14 J K−1 mol−1, whereas the enthalpy of activation (ΔH) and the entropy of activation (ΔS) associated with the slowest step are found to be 91 ± 4 kJ mol−1 and 11 ± 14 J K−1 mol−1, respectively.
  • Haruo Naruke, Toshihiro Yamase, Masahiko Kaneko
    Type: Article
    1999 Volume 72 Issue 8 Pages 1775-1779
    Published: 1999
    Released: November 01, 2004
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    Europium decavanadate, [Eu(H2O)8]2[V10O28]·8H2O, crystallizes in triclinic, , a = 9.413(1), b = 9.885(1), c = 23.556(4)Å, α = 81.31(2), β = 82.08(2), γ = 89.51(2)°, V = 2145.8(5)Å3, Z = 2. There are two crystallographically independent [Eu(H2O)8]3+ cations and two centrosymmetric [V10O28]6− anions in a unit cell. Each [Eu(H2O)8]3+ cation achieves eight-fold coordination by aqua-ligands with an approximately square-antiprismatic configuration. The Eu–O distances for the [Eu(H2O)8]3+ cations were found to be 2.38(1)—2.54(1) Å (mean 2.44 ± 0.02 Å). The crystal structure consists of two crystallographically inequivalent [Eu(H2O)8]2[V10O28] layers and interstitial water molecules, the former being piled up alternately along the c-direction, and the latter linking the two adjacent layers with hydrogen-bonds.
  • Kenichi Oyaizu, Agus Haryono, Yukio Nishimura, Kimihisa Yamamoto, Eish ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1781-1784
    Published: 1999
    Released: November 01, 2004
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    The crystal structure of a μ-oxo heterometallic porphyrin [(pip)(tpp)CrIIIOFeIII(tpp)] (pip = piperidine) not only confirmed the proposed oxidation state of chromium and iron atoms, but also revealed a unique coordination environment around chromium(III), which is substantially protruded from the porphyrin plane.
  • Toshio Takayanagi, Eiko Wada, Mitsuko Oshima, Shoji Motomizu
    1999 Volume 72 Issue 8 Pages 1785-1791
    Published: 1999
    Released: November 01, 2004
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    Ion associability of some alkylammonium-type ion association reagents with the positional isomers of aromatic anions has been examined in an aqueous solution through electrophoretic mobility changes of the corresponding anions in capillary zone electrophoresis. Ion associability of the alkylammonium ions was investigated for monovalent and divalent cationic groups, considering the hydrophilicity and hydrophobicity of cationic groups and the hydration of the ionic sites. When such monovalent cationic reagents as hexylmethylammonium, hexyltrimethylammonium, and hexyltriethylammonium ions were used, the ion associability increased with an increase in the number and bulkiness of alkyl groups of the cations. On the other hand, hexylammonium ion, a primary ammonium ion, showed different behavior: Higher ion associability was obtained with aromatic anions possessing two carboxylate groups at adjacent positions. Also ion associability of the primary diammonium ions with phthalate and naphthalene-2,3-dicarboxylate ions was the highest among their positional isomers, which was the reverse behavior from that obtained with quaternary diammonium ions. Such characteristic ion associability in the primary ammonium ions could be explained from the hydrophilicity of the ionic groups of the pairing ions: A primary ammonium group is more ion associable with hydrophilic anionic groups.
  • Masayoshi Nishiura, Naoko Okano, Tsuneo Imamoto
    1999 Volume 72 Issue 8 Pages 1793-1801
    Published: 1999
    Released: November 01, 2004
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    X-Ray structural analyses of the rare earth(III) trifluoromethanesulfonates (triflates) with urea derivatives are described. The reactions of anhydrous rare earth triflates with 8 equiv of tetrahydro-2-pyrimidinone (trimethyleneurea (PU)) in methanol give [M(pu)8](OTf)3 (OTf = triflate) (M = Sm: 1a; M = Y: 1b; M = Nd: 1c; M = Eu: 1d; M = Gd: 1e; M = Tb: 1f; M = Dy: 1g; M = Ho: 1h; M = Yb: 1i), and [Sc(pu)6](OTf)3 (2). X-Ray crystallographic analyses of these complexes indicate that a pair of PU ligands are interacting with each other through the hydrogen bonds. The reaction of anhydrous samarium(III) triflate with 6 equiv of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (1,3-dimethyltrimethyleneurea (DMPU)) in tetrahydrofuran (THF) affords [Sm(dmpu)6](OTf)3 (3) which has a hexa-coordinated octahedral structure. Anhydrous samarium(III) triflate reacts with 5 equiv of 1,3-dimethyl-2-imidazolidinone (DMI) to give [Sm(Otf)2(dmi)5]OTf (4) which has a hepta-coordinated pentagonal bipyramidal structure. Five DMI ligands in 4 coordinate to the samarium atom in a propeller-like fashion.
  • Masafumi Goto, Nobuhiro Tsuruda, Sachiko Fujioka, Hiromasa Kurosaki
    Type: Article
    1999 Volume 72 Issue 8 Pages 1803-1806
    Published: 1999
    Released: November 01, 2004
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    Sodium tetracyano((S)-2-aminomethylpyrrolidine = S-pyrda)ferrate(II) and -cobaltate(III) and tetracyano(2-aminomethylpiperidine = pipda)ferrate(II) and -cobaltate(III) were prepared. These complexes afforded well-separated 1H NMR spectra sufficient to delineate their structures in solution. The major conformation of the coordinated pyrda and pipda differs in the condensation mode of the five-membered chelate ring and the heterocycles, i.e. cis- and trans-, respectively, this leads to the different orientation of the heterocycle of the diamines. The comparison of the 1H and 13C chemical shifts and the electronic structure is described from the viewpoint of the isoelectronic structures with different electric charges.
  • Mitsuaki Narita, Koji Sode, Shokichi Ohuchi
    Type: Article
    1999 Volume 72 Issue 8 Pages 1807-1813
    Published: 1999
    Released: November 01, 2004
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    Using both dihedral angles and hydrogen-bond definitions, 225 type-I α-turns were extracted from 125 analyzed proteins. The extracted α-turns were built up from 5% (1125) of the total amino acid residues (23286) found in the proteins. The type-I α-turn is an independent kind of secondary structural unit, although it has been frequently classified as (i, i+1) double β-turns. Both the nucleation of a helix with the type-I β-turn and its propagation with the repetitive addition of the type-I β-turn suggest that the origin of the helix in a globular protein might be the type-I β-turn. Single amino acid preferences for specific locations at type-I α-turns were compared to those at type-I β-turns and the ends of helices. The result indicates that the type-I α-turn, the type-I β-turn, and the helix are of similar kin. Similarities in the structure and amino acid preferences for specific locations among them suggest that the amino acid residues on defined positions along both turns could be properly assigned to the corresponding helix elements.
  • Chiyo Yamamoto, Eiji Yashima, Yoshio Okamoto
    1999 Volume 72 Issue 8 Pages 1815-1825
    Published: 1999
    Released: November 01, 2004
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    The calculations of interaction energies between cellulose tris(phenylcarbamate) (CTPC) or cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) and trans-stilbene oxide (1) or benzoin (2) were performed by various methods. The purpose was to gain insight into the mechanism for the chiral recognition on phenylcarbamate derivatives of cellulose which are useful chiral stationary phases for HPLC. The calculations were roughly divided into two methods: 1) Enantiomers were generated around the NH proton and the C=O oxygen of the carbamoyl group of CTPC and CDMPC which are considered to be the most important adsorption sites, and then the interaction energy was calculated. 2) Enantiomers were randomly generated by the Monte Carlo method on the surface of CTPC and CDMPC, and then the interaction energy was calculated. The results of both calculations were in good agreement with the results in the chromatographic resolution of 1 and 2 by CTPC and CDMPC.
  • Michio Iwai, Hisashi Yamada, Yoshinori Ishii, Kouichi Tamura, Mineo Ni ...
    1999 Volume 72 Issue 8 Pages 1827-1835
    Published: 1999
    Released: November 01, 2004
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    The primary structure of human IGF-I, except for the disulfide bond system, has been reported by Rinderknecht and Humbel. IGF-I afforded the corresponding characteristic peptide fragments on V8 protease digestion, which contained Cys6, Cys47, Cys48, and Cys52. Two possible fragments, Type I with Cys6–Cys47 and Cys48–Cys52 and Type II with Cys6–Cys48 and Cys47–Cys52 of h-IGF-I(4-9,47-53), were chemically synthesized. The disulfide bond system of IGF-I was unequivocally determined to be the Type-II form along with Cys18–Cys61. Interestingly, the Type-I system was included in the disulfide bond isomer produced as the main by-product in the refolding step on IGF-I synthesis by the recombinant DNA method.
  • Takashi Karatsu, Hajime Itoh, Nobuko Yoshikawa, Akihide Kitamura, Kats ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1837-1849
    Published: 1999
    Released: November 01, 2004
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    Rotational isomerism between s-cis and s-trans rotamers of (E)-1-(2-anthryl)-2-phenylethene (E-2APE) and (E)-1-(2-anthryl)-3,3-dimethyl-1-butene (E-2ADB) were investigated by comparing the absorption, emission and transient absorption spectra with those of the model compounds. The s-trans isomer is more stable than the s-cis rotamer in the ground state; however, the s-cis isomer is more stable than the s-trans rotamer in the excited state (the lowest singlet and triplet excited state). In the triplet excited state, s–transs–cis one-way rotational isomerization is observed with activation energies of 30 and 18 kJ mol−1 for E-2APE and E-2ADB, respectively. Explanations of why the s-cis rotamer is more stable than the s-trans rotamer in the excited state and less stable in the ground state are proposed using the HOMO and LUMO coefficients estimated by a MOPAC93 (PM3) calculation.
  • Toshiyuki Ohe, Takumi Tanaka, Masashi Kuroda, Chan Sik Cho, Kouichi Oh ...
    1999 Volume 72 Issue 8 Pages 1851-1855
    Published: 1999
    Released: November 01, 2004
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    Triarylbismuthines readily reacted with a catalytic amount of palladium(II) acetate in methanol under air to give the corresponding biaryls in high yields. The presence of oxygen was indispensable for this catalytic coupling, biaryl formation being quite slow under nitrogen. Oxygen absorption was observed during the reaction and a Pd-oxygen complex prepared separately worked effectively as a reagent for this coupling even under inert gas.
  • Masato Oikawa, Tetsuya Shintaku, Harald Sekljic, Koichi Fukase, Shoich ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1857-1867
    Published: 1999
    Released: November 01, 2004
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    The synthesis of regiospecifically 13C-labeled compounds of a biosynthetic precursor of lipid A and its analogue with shorter acyl chains is described. D-(6-13C)Glucose was converted into a suitably protected glucosamine derivative via 1,6-anhydro-β-D-(6-13C)glucose. After coupling with glycosyl donors, the desired compounds were synthesized through a 6-step reaction sequence. The total yields were 1.7% for the biosynthetic precursor, and 6.4% for the short acyl analogue, respectively, for a total of 18 steps from D-(6-13C)glucose.
  • Hironori Tsutsui, Tomoko Ichikawa, Koichi Narasaka
    Type: Article
    1999 Volume 72 Issue 8 Pages 1869-1878
    Published: 1999
    Released: November 01, 2004
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    Primary amines are prepared by the electrophilic amination of Grignard reagents with benzophenone O-sulfonyloxime derivatives. 4,4′-Bis(trifluoromethyl)benzophenone O-sulfonyloximes react with alkyl Grignard reagents in the presence of a catalytic amount of CuCN in tetrahydrofuran-hexamethylphosphoric triamide to give N-alkylimines, which are readily hydrolyzed to primary amines. 3,3′,5,5′-Tetrakis(trifluoromethyl)benzophenone O-p-tolylsulfonyloxime is arylated to the corresponding N-arylimines with aryl Grignard reagents in ether–toluene, and hydrolysis of the resulting imines gives aniline derivatives.
  • Shinji Toyota, Mitsuhiro Asakura, Tadahiro Futawaka, Michinori Oki
    Type: Article
    1999 Volume 72 Issue 8 Pages 1879-1885
    Published: 1999
    Released: November 01, 2004
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    Rates of the dissociation of the intramolecular B–N coordination bond in two series of phenylborane derivatives, the boronate and diethylborane complexes, with –CHMeNMe2 or –CMe2NMe2 group at the o-position were determined by the NMR lineshape analysis or saturation transfer method. The new organoboron compounds were synthesized from the corresponding organolithium compounds with appropriate boron reagents. Comparison of the kinetic data with those of the –CH2NMe2 compounds reveals that the barrier height to the dissociation, namely the kinetic basicity of the amine ligand, is increased as the molecule possesses more methyl groups at the benzylic position for both of the series of boron compounds. The X-ray structure of one of the boronate complexes and the NMR titration measurements of model amines indicate that the basicity of the amine ligand is not affected much by the methyl substitution in the coordinated form. Therefore, the substituent effect on the kinetic basicity is mainly ascribed to the destabilization of the transition state by the geminal dimethyl groups rather than to any inductive or steric effects at the initial state, especially for the –CMe2NMe2 compounds.
  • Hiroyuki Higuchi, Masatoshi Shinbo, Masanobu Usuki, Makoto Takeuchi, Y ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1887-1898
    Published: 1999
    Released: November 01, 2004
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    Complexes of vinylene-bridged bis- and tris(octaethylporphyrin)s (bis(OEP)–M and tris(OEP)–M) with d8 transition-metal ions (M = Ni(II), Pd(II), and Pt(II)) were synthesized. Metalation of (E)-bis(OEP)–H2 was carried out under the same conditions as for the corresponding octaethylporphyrin complex (OEP–M), to afford a mixture of complexes bearing the vinylene-linkages with (E)- and (Z)-configurations. On the other hand, metalation of tris(OEP)–H2 afforded the single product of which two vinylene-linkages remained holding the same (E,E)-configuration as that in the free-base. 1H NMR spectra varied more drastically for (Z)-bis(OEP)–M, with respect to those of OEP–M, while electronic absorption spectra did more drastically for the (E)-isomers. Their electronic properties at the ground state were examined, proving that the interaction between the constituent OEP rings through the vinylene-linkages is more intensive for tris(OEP)–M than for bis(OEP)–M and more intensive for the Ni complex than for the Pd and Pt ones.
  • Kazushi Okada, Tetsujo Sujaku, Rie Nakashima, Takeru Nose, Yoshinari Y ...
    Type: Article
    1999 Volume 72 Issue 8 Pages 1899-1904
    Published: 1999
    Released: November 01, 2004
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    Nociceptin is a neuropeptide that binds to and activates the opioid receptor-like ORL1 receptor. In order to explore the structural elements necessary for receptor recognition and activation, we designed and synthesized a series of nociceptin analogues, in which nonpolar amino acid residues such as Gly6, Ala7, Ala11, Leu14, and Ala15were substituted respectively by Trp. [Trp6]- and [Trp7]nociceptins exhibited rather weak activities (5—15% of nociceptin), and [Trp11]- and [Trp15]nociceptins also showed reduced activities (40—50%). These results suggested that the space available for these particular residues are relatively restricted. By contrast, the Trp/Leu-substitution at position 14 retained full receptor binding activity, and the resulting [Trp14]nociceptin exhibited an increased biological activity in the functional assay using [35S]GTPγS. This suggested that the receptor residue interacting with nociceptin-Leu14 is the aromatic amino acid.
  • Masaaki Ichinohe, Akira Sekiguchi, Masae Takahashi, Hideki Sakurai
    Type: Article
    1999 Volume 72 Issue 8 Pages 1905-1910
    Published: 1999
    Released: November 01, 2004
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    A series of dialkali metal complexes, [(HMe2Si)2C=C(SiMe2H)2]2−[M+(ligand)n]2 (M = Li, Na, K, Rb, Cs), were prepared by the reaction of tetrakis(dimethylsilylethylene) with alkali metals. These complexes exhibit Si–H alkali metal agostic interactions and have been characterized by spectroscopic and structural methods. Spectroscopic evidence for the interaction of the hydrogen on the silicon atom with alkali metals include (1) an unusually small value of the silicon-hydrogen coupling constant (1JSi–H) in NMR spectra and (2) low-energy Si–H stretching frequency in the infrared spectra. The smallest cation, Li+, can interact with SiH most strongly.
  • Kyoko Nozaki, Fumitoshi Shibahara, Yohei Itoi, Eiji Shirakawa, Tetsuo ...
    1999 Volume 72 Issue 8 Pages 1911-1918
    Published: 1999
    Released: November 01, 2004
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    When polymer-immobilized chiral phosphine-phosphite–Rh(I) complexes were used, the asymmetric hydroformylation of styrene gave 2- and 3-phenylpropanals with a substrate/catalyst ratio of 2000, iso/normal ratios of 84/16 to 89/11, and 89% R enantiomeric excess of 2-phenylpropanal; these results were at the highest level in catalytic activity, regio-, and enantioselectivities. Recovery-reuse of the catalyst was examined. Asymmetric hydroformylation of vinyl acetate, (Z)-2-butene, and 3,3,3-trifluoropropene was also successfully performed with the polymer-supported catalysts.
  • Hidehiro Nagasawa, Yoshiaki Sugihara, Akihiko Ishii, Juzo Nakayama
    Type: Article
    1999 Volume 72 Issue 8 Pages 1919-1926
    Published: 1999
    Released: November 01, 2004
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    Oxidation of thiophene with dimethyldioxirane at −20 °C and removal of the solvent and volatile materials below −40 °C allowed the isolation of the parent thiophene 1,1-dioxide (1) as colorless crystals in pure form. The 1,1-dioxide 1, which had eluded isolation for a long time despite many efforts, melted at about 6 °C and the melt solidified at room temperature because of the dimeric and trimeric products formation. The structure of 1 was fully characterized by 1H- and 13C NMR, IR, Raman, UV/vis, and Mass spectroscopies. The decomposition of 1 in solution provided the dimer (7) as the principal product along with the trimer (9), whereas the decomposition of a neat sample furnished 7 and 9 in comparable amounts. The half-life of 1 is dependent upon the concentration of 1; 137 and 747 min at 25 °C in 0.12 and 0.025 M CDCl3 solutions (1 M = 1 mol dm−3), respectively. Kinetics of the dimerization of 1 in a dilute solution provided the activation parameters of Ea = 64.4 (±0.3) kJ mol−1, ΔH = 62.0 (±0.3) kJ mol−1, and ΔS = −59.8 (±1.0) J K−1 mol−1. Attempted reactions of 1 with a series of dienophiles and dienes all failed because the dimerization of 1 is much faster than reactions with these additives. An exception is the reaction with cyclopentadiene which gave the Diels–Alder adduct in good yield. The adduct of the dimer 7 with dimethyl acetylenedicarboxylate was found to undergo a retro Diels–Alder reaction to regenerate 1.
  • Adam Košturiak, Ladislav Valko, Jirí Polavka, Milan Brut ...
    1999 Volume 72 Issue 8 Pages 1927-1933
    Published: 1999
    Released: November 01, 2004
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    The paper emphasizes the importance of amorphous metallic alloys thin films for magnetic coatings as well as their characterisation with respect to the mineral acid medium in a more qualitative way. The kinetics and mechanism of the interaction of Fe–Ni–B amorphous alloys films with various concentrations of mineral acids (o-phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid,) were studied. On the basis of the weighing method used we deduced that the overall physically and chemically complicated process consists of simultaneous formation of oxides on the surface of the thin films, their dissolution and moreover dissolution of the metal (Fe, Ni) and metalloid (B) elements through a tendency of all of them to react with hydrogen ions. It should be stressed that dissolution of the two-dimensional amorphous metallic alloys-ribbons significantly differs from such dissolution of the metal bulk systems.
  • Zheng Bao Wang, Takashi Shimada, Hiroyuki Takagi, Cheol-Hee Ahn, Tsune ...
    1999 Volume 72 Issue 8 Pages 1935-1940
    Published: 1999
    Released: November 01, 2004
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    The carbonylation of formaldehyde with carbon monoxide was carried out over two kinds of cation-exchange resins as solid acid catalysts. Effects of reaction conditions on the catalytic performance were studied. From 1H NMR, 13C NMR, IR, and GC-MS analyses of the products obtained, it was found that 1,3-dioxolan-4-one (1,3-DOX-4) is selectively produced over the cation-exchange resins. The carbonylation of formaldehyde with carbon monoxide over the cation-exchange resins proceeds under milder reaction conditions, as compared with HZSM-5 zeolite.
  • Zhi-Kuan Chen, Lian-Hui Wang, En-Tang Kang, Yee-Hing Lai, Wei Huang
    Type: Article
    1999 Volume 72 Issue 8 Pages 1941-1946
    Published: 1999
    Released: November 01, 2004
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    A novel solution processable photoluminescent polymer containing silyl groups has been successfully synthesized through a polycondensation reaction. The polymer was characterized through FT-IR, NMR, UV-vis spectroscopy, photoluminescent spectroscopy (PL), elemental analysis and cyclic voltammetry (CV). A TGA analysis shows that the polymer is stable up to 300 °C both in air and in nitrogen. The UV-vis absorption spectra for both the solution and film samples are very similar. The band gap obtained from the optical spectra is 2.53 eV. The maximum emissions of photoluminescence are at 494 and 507 nm for the solution and film samples, respectively. The UV-vis spectrum of its polymer film also shows a very small temperature dependence. A cyclic voltammogram illustrates that the polymer can be reversibly n-doped and dedoped in a negative sweep and irreversibly p-doped during a positive sweep. All of the results demonstrate that the obtained polymer is a promising green-light emission material for PLED applications.
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