Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 75 , Issue 7
Showing 1-28 articles out of 28 articles from the selected issue
  • Tomoaki Tanase
    Type: scientific monograph
    2002 Volume 75 Issue 7 Pages 1407-1422
    Published: 2002
    Released: July 15, 2002
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    This paper reviews the recent development of linearly ordered multinuclear transition-metal complexes, which have been of increasing interest as potential nanostructured molecular units and their precursors. In particular, it focuses on our recent results of platinum-based homo- and heteromultimetallic complexes supported by the tridentate phosphine ligands, bis(diphenylphosphinomethyl)phenylphosphine (dpmp). The synthetic strategy involved the metal core expansion using the diplatinum precursors having two uncoordinated phosphine pendants, syn- and anti-[Pt2(μ-dpmp)2(RNC)2]2+ (11 and 12), which allowed us to gain access to versatile homo- and heterotrinuclear complexes with Pt2M cores. Reactions of 11 with d10 and d8 metal fragments afforded the Pt–Pt–M metal frameworks (M = Pt, Pd, Au, Ag, Cu, Ir, Rh), and in contrast, those of 12 gave the Pt–M–Pt ones (M = Pt, Pd, Rh). The inserted position of the additional metal interestingly depends on the two dpmp arrangement of the starting diplatinum complexes. The corresponding chemistry of palladium and gold complexes is also described. Since the metal–metal bonded triplatinum complex, linear-[Pt3(μ-dpmp)2(RNC)2](PF6)2 (16), was regarded as a minimal model for the surface of metal catalysts, its reactions with various small organic molecules were examined. Further, the axial ligand exchange reactions of 16 with bulky aromatic bisisocyanide led to a one-dimensional assemblage of the linear Pt3 units, resulting in rigid rod-like cluster polymers, and the reduction of 16 afforded the linearly ordered hexaplatinum cluster molecules supported by four dpmp ligands through a direct combination of the two linear Pt3 fragments.
  • Yoshio Umezawa, Takeaki Ozawa, Moritoshi Sato
    Type: scientific monograph
    2002 Volume 75 Issue 7 Pages 1423-1433
    Published: 2002
    Released: July 15, 2002
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    Methods of analysis for bioactive substances that are based on cellular signaling pathways are discussed and compared with the binding assay and bioassay. For nondestructive analysis of chemical processes in living cells, we have developed some general methods and new intracellular fluorescent probes for detecting 1) second messengers, cGMP, diacylglycerol and phosphatidylinositol-3,4,5-triphosphate, 2) protein phosphorylation, 3) protein conformational changes, and 4) protein-protein interactions in live cells under a confocal laser microscope. The approaches for the present probe developments are use of fluorescence resonance energy transfer for reporting binding of substrates (analytes) to molecular recognition domains in dual-fluorophore conjugated probe molecules, and use of protein splicing chemistry for detecting protein-protein interactions. Key molecules and steps of cellular signaling pathways were visualized in relevant live cells using developed fluorescent probe molecules. These probes were found of general importance not only for fundamental biology studies, but also for assay and screening methods for chemicals that inhibit or facilitate cellular signaling pathways. Changes in cellular signals were thereby observed in nongenomic pathways of steroid hormones upon treatment of the target cells with steroid hormones and xenoestrogens. This method of analysis appears to be a rational approach to high-throughput prescreening of biohazardous chemicals such as endocrine disrupting chemicals that disrupt these cellular signaling pathways.
  • Eiji Shirakawa, Tamejiro Hiyama
    Type: scientific monograph
    2002 Volume 75 Issue 7 Pages 1435-1450
    Published: 2002
    Released: July 15, 2002
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    Carbon–tin bonds in alkynyl-, allyl-, acyl-, alkenyl-, and arylstannanes were found to add to carbon–carbon unsaturated bonds of alkynes, 1,3-dienes and 1,2-dienes in the presence of a catalytic amount of palladium or nickel complexes to give alkenyl- or allylstannanes having various functional groups. Mechanisms are proposed that start with oxidative addition of a carbon–tin bond, or palladacycle formation followed by β-tin elimination or by the reaction with an organostannane.
  • Hironori Tsutsui, Mitsuru Kitamura, Koichi Narasaka
    Type: technical report
    2002 Volume 75 Issue 7 Pages 1451-1460
    Published: 2002
    Released: July 15, 2002
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    Various pyrrole derivatives are synthesized from γ,δ-unsaturated ketone O-pentafluorobenzoyloximes by treatment with catalytic amounts of Pd(PPh3)4 and triethylamine via alkylideneaminopalladium(II) intermediates generated by oxidative addition of the oximes to the Pd(0) complex.
  • Sadakatsu Nishikawa, Kazuhiko Ishikawa
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 7 Pages 1461-1467
    Published: 2002
    Released: July 15, 2002
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    Ultrasonic absorption coefficients were measured in aqueous solutions of propylamine at 25 °C in both the absence and presence of 2.01 g dm-3 (poly(vinyl alcohols) (PVA’s)) with the number average degree of polymerization of 500, 900, 1500, and 2000. No excess absorption was observed in solutions without propylamine. A single relaxational absorption was observed in the concentration range from 0.0241 to 0.201 mol dm-3 of propylamine in both the presence and absence of PVA’s. The relaxational absorption was attributed to a perturbation of the equilibrium associated with a proton-transfer reaction from the concentration dependence of the relaxation frequency and the maximum absorption per wavelength. The rate and equilibrium constants and the standard volume change of the reaction were determined in individual solutions with PVA’s. As a result, it was found that the diffusion-controlled reaction rate constant remains constant, or increases slightly, even though the solution viscosity increases. The effect of the polymers on the reaction was interpreted in terms of an interaction between the PVA’s and the reaction intermediate and a solvent structural change.
  • Masataka Eda, Takashi Kamachi, Kazunari Yoshizawa, Tetsuo Toraya
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 7 Pages 1469-1481
    Published: 2002
    Released: July 15, 2002
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    The energy profile of the diol dehydratase reaction is discussed from theoretical calculations at the B3LYP/6-311G* level of density functional theory. The differences between the energy diagrams of models with and without K+ ion are rather small except for the substrate binding and the OH group migration. The most important role of K+ ion in the diol dehydratase catalysis is to fix substrates and intermediates in proper positions in order to ensure the hydrogen abstraction and recombination between them and the adenosyl group. In the course of the reaction, substrates and reaction intermediates would always be kept bound to K+ ion until the release of product aldehyde from the active site. Given the neutral radical state of the substrate, the OH group migration proceeds in a concerted mechanism. In this process, K+ ion can work as an inhibitor of intramolecular hydrogen bond, which decreases the activation energy by 4.0 kcal/mol, due to the destabilization of reactant 1,2-dihydroxypropyl radical. The lowering of the activation energy by K+ ion, however, is rather small, and thus the contributions of active-site amino acid residues to the OH group migration must be taken into consideration to explain that the hydrogen abstraction is the rate-determining step for the overall reaction.
  • Mitsuo Yamamoto, Koichi Yamashita, Masayoshi Sadakata
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 7 Pages 1483-1491
    Published: 2002
    Released: July 15, 2002
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    Previous experiments on the reactions of O- with CF4 and CHF3 using a selected ion flow tube (SIFT) have indicated that many species, such as CF3-, F-, and HF2-, are produced in the O- + CHF3 reaction, although no reaction proceeds in the O- + CF4 reaction under thermal conditions. Ab initio molecular orbital calculations were carried out in this study to clarify the reason for the difference in the reactivity between these two reactions. Potential energy surfaces (PESs) for the possible reaction channels were computed at the UMP2/6-31+G** level. Although the SN2-type reactions, such as the CF3O- + F channel, are exothermic, the calculated activation energy for the O- + CF4 reaction is rather high, 222 kJ/mol. The energies of the transition states in the O- + CHF3 reaction are below that of the reactant. We may conclude that the difference in reactivity between the two reactions is attributable to the charge distribution of each molecule. The H atom in CHF3 has a large effect on increasing the reactivity because the positively charged H atom attracts O-, whereas O- has difficulty approaching the CF4 molecule because of the four negatively charged F atoms.
  • Krishanu Ray, Hiroo Nakahara
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 7 Pages 1493-1501
    Published: 2002
    Released: July 15, 2002
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    The monolayer properties of octadecylamine at various pHs on the Naphthalene Red (NR) aqueous solution were studied from the measurements of surface pressure–area isotherms. It was observed that the presence of the azo dye substituted with the –OH group (NR) in the subphase affects the compressibility of the octadecylamine monolayer. The adsorbability of the cationic Langmuir–Blodgett (LB) films was investigated by NR as an adsorbate. The cationic LB films before and after the azo dye adsorption were characterized by UV–vis absorption and emission spectroscopy, polarized visible absorption, X-ray diffraction, FTIR spectroscopy, and atomic force microscopy. Strong dipole–dipole interaction between the NR molecules in functionalized LB films was observed in accordance with the exciton model. It was found that the adsorption of the azo dye induced rearrangement of the layer structure of the cationic LB films where the hydrocarbon chains of the amine molecules exhibited an interdigitated structure and the azo dye molecules adsorbed in the LB films were oriented in an edge-on configuration. Furthermore, the substituent position of the –OH group of NR plays a crucial role in the different ways on the orientation of the other azo dyes in organized assembly.
  • Naoki Kishimoto, Hideyuki Ogasawara, Koichi Ohno
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 7 Pages 1503-1513
    Published: 2002
    Released: July 15, 2002
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    Ionization of 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,4-cyclohexadiene (CHD), and 2,5-norbornadiene (NBD) with He*(23S) metastable atoms was studied by (collision-energy/electron-energy-resolved) two-dimensional Penning ionization electron spectroscopy. Anisotropic interaction around the molecule was investigated by determining collision energy dependence of partial ionization cross sections (CEDPICS) and spatially anisotropic distribution of ionized molecular orbitals (MOs). The negative slope of CEDPICS for HOMO was smaller than that for the next HOMO of DABCO and CHD; this was due to the repulsive interaction around the σCC,CH bond region, which is related to the through-bond interaction via the electron distribution. The trend of CEDPICS for DABCO was confirmed by classical trajectory calculations. For NBD, the negative CEDPICS for the next HOMO was larger than that for HOMO; this was due to the attractive endo region for the in-phase next HOMO with the through-space interaction.
  • Alka Anant Phulambrikar, Chinmay Chatterjee
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1515-1519
    Published: 2002
    Released: July 15, 2002
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    The kinetics of the hydrolysis of 4-nitrophenyl glycine ester (PNPG) catalysed by [Co(OH)(trien)(OH2)]2+, [Co(OH)(tren)(OH2)]2+ and [Co(OH)(en)2(OH2)]2+ complexes has been studied spectrophotometrically in weakly basic aqueous media (pH = 6.5 to 7.4). Kinetic experiments were carried out as a function of the pH, complex concentration and temperature. The rate of hydrolysis increases linearly with the complex concentration with a trend to wards rate saturation, suggesting the formation of associative species in a pre-equilibrium step. The pseudo-first order rate constant, kobs, increases rapidly with a decrease in the hydrogen-ion concentration. The complexes promote the hydrolysis of 4-nitrophenyl glycinate significantly, and the acceleration rate is about 400–600. An attack of external OH- on the chelated ester is suggested as a probable mechanism for the hydrolysis. The lower rate enhancements observed in the present study could probably be ascribed to a weaker cobalt(III) alkoxy carbonyl interaction in the chelate, owing to a decreased nucleophilicity of the carbonyl oxygen in the p-nitrophenyl ester. The activation parameters for all three complex-promoted reactions are found to be comparable, thus suggesting a common mechanism operative in all complex catalysed reactions.
  • Yucang Liang, Maochun Hong, Rong Cao, Weiping Su, Yingjun Zhao, Jiabao ...
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1521-1526
    Published: 2002
    Released: July 15, 2002
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    The hydrothermal reactions of Ln2O3, Zn(NO3)2·6H2O, pyrazine-2,3-dicarboxylic acid (H2pzdc) and H2O resulted in the formation of three isostructural coordination polymers [Ln2Zn(pzdc)4(H2O)6·2H2O]n (Ln = Gd, 1; Nd, 2; and Sm, 3). The crystal structures of complexes 1 and 2 were determined by X-ray diffraction methods. Compounds 1, 2 and 3 are isomorphous and crystallize in the monoclinic space group P21/n with a = 6.1196(2), b = 22.5318(8), c = 11.9617(1) Å, β = 91.766(2), V = 1648.56(8) Å3, Z = 2 for 1, a = 6.1644(3), b = 22.6577(12), c = 12.0384(6) Å, β = 91.513(2), V = 1680.8(2) Å3, Z = 2 for 2. X-ray diffraction analyses confirm that complexes 1 and 2 possess a 3-D brick-like framework structure, each framework being surround by metal atoms, with a size of 16.37×6.12 Å, accommodating two water molecules as guests. The Ln(III) ions in compounds 1 to 3 are coordinated by seven oxygen and two nitrogen atoms. In addition, the zinc(II) ions are bonded by two carboxyl oxygen, two nitrogen and two apical carboxyl oxygen atoms in an octahedral geometry. The excitation spectrum and luminescent properties of 1 and 3 were studied qualitatively.
  • Akiyo Yamauchi, Takashi Hayashita, Ayako Kato, Norio Teramae
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1527-1532
    Published: 2002
    Released: July 15, 2002
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    Crown ether probes C3-12C4 and C3-18C6, in which the pyrenyl moieties as fluorophore and benzo-12-crown-4 or benzo-18-crown-6 acting as ion recognition sites are connected by a trimethylene spacer, have been synthesized. Their supramolecular function for alkali metal ion sensing in water is compared with that of the previously designed C3-15C5/γ -CyD complex sensor. The C3-12C4, C3-15C5, and C3-18C6 are found to selectively form 2 : 1 complexes with Na+, K+, and Cs+, respectively, in the presence of γ -CyD and to exhibit pyrene dimer emission in water. These results demonstrate that the selectivity of the crown ether probe/γ -CyD complexes can be tuned by simply altering their crown ether ring size. The apparent 2 : 1 binding constants of the probes with alkali metal ions are determined at the optimum γ -CyD concentrations for each probe. For C3-12C4/γ -CyD complex, the accurate binding constant could not be obtained due to the relatively large deviation for the response. However, the fitting curve reveals that the binding constant is about 107 M-2. The 2 : 1 binding constants of the C3-15C5/γ -CyD complex for K+ and C3-18C6/γ -CyD complex for Cs+ are (3.8 ± 1.3)×109 M-2 and (5.8 ± 4.6)×107 M-2, respectively. These values are considerably larger than those of the corresponding benzocrown ethers in organic solvents. In the suparamolecular sensing system, the dimer formation of the probes inside the γ -CyD is selectively promoted by alkali metal ion binding in water. This is a novel sensing mechanism in which the dynamic molecular recognition events are successfully utilized for ion sensing in water.
  • Young-A Lee, Ok-Sang Jung
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1533-1537
    Published: 2002
    Released: July 15, 2002
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    Stable mono- and bis(methoxo)platinum(IV) species via the oxidation of PtII to PtIV have been prepared and characterized. The reaction of [PtII(fpd)(dpda)] (fpd = 9-fluorenylidenepropanedioate; dpda = 2,2-dimethyl-1,3-propanediamine) with hydrogen peroxide in methanol at room temperature affords [PtIV(OH)(OCH3)(fpd)(dpda)], and further reaction at boiling methanol produces a bis(methoxo)platinum(IV) compound, [PtIV(OCH3)2(fpd)(dpda)]. The bis(methoxo)platinum(IV) compound can be prepared by the direct reaction of [PtII(fpd)(dpda)] with hydrogen peroxide in boiling methanol or by the simple stirring of [PtIV(OH)2(fpd)(dpda)] in boiling methanol. The crystal structures of [PtII(fpd)-(dpda)]·2(CH3)2NCHO (Pna21, a = 10.125(2) Å, b = 26.141(4) Å, c = 10.845(6) Å, V = 2870(2) Å3, Z = 4, R = 0.0370), [PtIV(OH)2(fpd)(dpda)]·3C2H5OH (P21/a, a = 10.312(2) Å, b = 22.044(5) Å, c = 14.225(3) Å, β = 110.25(2)°, V = 3034(1) Å3, Z = 4, R = 0.0572), and [PtIV(OCH3)2(fpd)(dpda)]·1.5CH3OH·0.5C2H5OH·0.5H2O (P1-, a = 13.333(2) Å, b = 15.386(3) Å, c = 18.446(5) Å, α = 66.80(2), β = 69.06(2)°, γ = 68.84(1), V = 3140(1) Å3, Z = 2, R = 0.0437) have been solved and refined. For [PtIV(OCH3)2(fpd)(dpda)], the 9-fluorenylidene moiety of fpd ligand snugly interacts with the methoxo group (C(22)···C(9), 3.34 Å; C(22)-H···C(9), 2.65 Å). The mono- and bis(methoxo)platinum(IV) compounds are stable even in solution.
  • Isao Ando, Hiroto Miyake, Kikujiro Ujimoto, Hirondo Kurihara
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1539-1545
    Published: 2002
    Released: July 15, 2002
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    Silver-deposited gold electrodes were prepared in order to investigate the role of deposited silver onto a gold electrode in the electrochemical behavior of p-benzoquinone at the electrode. Using the electrodes as a working electrode, the electrochemical behavior of p-benzoquinones was examined in acetonitrile and aqueous solutions. In the acetonitrile solution, cyclic voltammograms for p-benzoquinone derivatives were measured and the relations between the potentials of the second-redox peak and the sum of Hammett’s σ value were examined. A potential-pH diagram was obtained for p-bezoquinone in an aqueous solution. Both relations were also obtained at other solid electrodes. The mechanism for a redox reaction at a silver-deposited gold electrode was considered based on a comparison of the observation data at the electrode with different materials.
  • Tsutomu Mizuta, Koji Nakayama, Shizuka Aoki, Katsuhiko Miyoshi
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1547-1552
    Published: 2002
    Released: July 15, 2002
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    Two types of diphosphido ligands, mpe and ppe (mpe = MePCH2CH2PMe2- and ppe = PhPCH2CH2PPh2-), were used as a bridging unit in the edge-sharing bis-squareplanar complexes, [{Pt(dppe)}2(μ-mpe or μ-ppe)]Cl2 (dppe = Ph2PCH2CH2PPh2), which were prepared by the reaction of [Pt(dppe)(H2mpe or H2ppe)]Cl2 with [PtCl2(dppe)] in the presence of Na2CO3. X-ray crystal structure analyses were performed for the following diplatinum complexes: [{Pt-(dppe)}2(μ-mpe)]X2 (X = Cl- and I-) and [{Pt(dppe)}2(μ-ppe)]X2 (X = Cl- and BArf-), and their palladium analogs: [{Pd(dppe)}2(μ-ppe)]X2 (X = I- and BArf-) (BArf- = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anion). Regarding an M2P6 core framework, all of the dinuclear complexes in the above six crystals adopted a common bent form reported previously. It is only in [{Pd(dppe)}2(μ-ppe)]2+ that a chloride or iodide anion is incorporated into a “pocket” located under the bent bis-squareplanes to allow the two metal centers to interact simultaneously with the halide anion. The factors responsible for the above interaction mode are discussed.
  • Hisashi Shimakoshi, Masaomi Koga, Yoshio Hisaeda
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1553-1558
    Published: 2002
    Released: July 15, 2002
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    New dicobalt complexes, [CoIII2LBr4], with monoanionic ligands (L) have been synthesized by the reaction of a tetraamine and oximes, followed by an aerobic reaction with CoBr2·6H2O. The complexes were characterized by elemental analyses, IR, ESR, and NMR as well as mass spectroscopies. The redox behavior of the complexes was examined in DMF by means of cyclic voltammetry in comparison with that of the corresponding mononuclear complex. Redox waves identified to CoIII/CoII and CoII/CoI for [CoIII2L] were observed at -0.19 V and -0.69 V vs Ag/AgCl, respectively. These potentials are quite similar to those for the corresponding mononuclear complex. An electrogenerated [CoI2L] species reacts with methyl p-toluenesulfonate to give an organocobalt complex. Two-electron reduction of the dinuclear organocobalt compound yields an unstable intermediate that undergoes rapid decomposition by cleavage of the cobalt–carbon bond. The dimethylated complex, which has cobalt–carbon bonds at one axial site of each cobalt, was disproportionated to a tetramethylated complex, involving two cobalt–carbon bonds at both axial sites, and a dicobalt(I) species by two-electron reduction. The tetramethylated cobalt complex was inactive for an electrochemical reduction, but transformed into the dimethylated complex via cleavage of the cobalt–carbon bonds upon electrochemical oxidation.
  • Wanzhi Chen, Fenghui Liu, Xiaozeng You
    Type: Introduction
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1559-1560
    Published: 2002
    Released: July 15, 2002
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    Two adducts of [Cd(SCN)2] and isonicotinonitrile, [Cd(SCN)2(pyCN)n] (pyCN = isonicotinonitrile, n = 1, 2), have been synthesized and characterized by X-ray diffraction analysis. The coordination environment of the cadmium atoms in both 1 and 2 is a distorted octahedron with a 2S4N coordination geometry. Compound 1 crystallizes via the SCN- functionality, resulting in infinite linear chains. Compound 2 crystallizes via both SCN- and isonicotinonitrile functionality, thus forming an infinite 3D framework material based on 22- and 8-membered rings.
  • Wanzhi Chen, Kazuko Matsumoto
    Type: Introduction
    Subject area: AI
    2002 Volume 75 Issue 7 Pages 1561-1562
    Published: 2002
    Released: July 15, 2002
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    N,N′-Dialkylimidazolium salts, [m-C6H4(CH2ImMe)2]-[PtCl4] (Im = imidazolium) (1) and [Mes2Im][PtCl3(H2O)] (Mes2Im = N,N′-di(2,4,6-trimethylphenyl)imidazolium) (2), were prepared and characterized by X-ray diffraction. Compound 2 is the first structurally characterized aquatrichloroplatinate compound.
  • Hiroshi Yamaguchi, Hiroaki Kodama, Satoshi Osada, Masood Jelokhani-Nia ...
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 7 Pages 1563-1568
    Published: 2002
    Released: July 15, 2002
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    2-Aminoisobutyric acid (Aib,1 2-amino-2-methylpropionic acid) is an unusual amino acid, which is present in some antimicrobial peptides. To elucidate the impact of Aib residues on the conformation and biological activity of ion channel forming peptides, Aib residues in Ac-(Aib-Lys-Aib-Ala)5-NH2 were partially and fully replaced by Ala residues. A total of three analogs were thus synthesized. Two of these analogs, Ac-(Aib-Lys-Ala-Ala)5-NH2 (BKAA-20) and Ac-(Ala-Lys-Aib-Ala)5-NH2 (AKBA-20), had similar amino acid composition and were not hemolytic. BKAA-20 exhibited comparable antimicrobial activity to gramicidin S against Gram-positive bacteria (minimum inhibitory concentration: ∼3.13 µg ml-1), whereas AKBA-20 was not active. Single-channel measurements showed that there was a clear correlation between the antimicrobial activity and the ion channel activity in these analogs. The third analog, Ac-(Ala-Lys-Ala-Ala)5-NH2, was biologically inactive. Circular dichroism spectroscopy revealed that the helix forming propensities of BKAA-20 and AKBA-20 were independent of the position of Aib residues in negatively charged phospholipid vesicles, as mimics of external cell membranes of bacteria. However, different positions of Aib residues in BKAA-20 and AKBA-20 affected their antimicrobial activity. It is indicated that the introduction of Aib residues into the peptide backbone not only promotes the generation of stable helical conformations, but also modulates the antimicrobial activity. The results of this study can implicate a deeper understanding of the role of Aib residues in the structure-activity relationships of helical pore forming peptides, which in turn promotes the rational design of effective antimicrobial peptides.
  • Masashi Hojo, Tadaharu Ueda, Masanori Yamasaki, Akihiko Inoue, Sumio T ...
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 7 Pages 1569-1576
    Published: 2002
    Released: July 15, 2002
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    The cleavage of C–O bonds in two fluoran-based dyes by the addition of alkali metal (M+ = Li+, Na+) and alkaline earth metal (M2+ = Mg2+, Ba2+) perchlorates in acetonitrile solution was examined by means of UV-visible absorption and 1H and 13C NMR spectroscopy at room temperature. Although the 1H NMR signals of the xanthene part of Rhodamine B base (3′,6′-bis(diethylamino)fluoran) were shifted toward lower fields, those of the isobenzofuran (or the benzoate) part were not shifted much upon the addition of M+ and M2+. The appearance of 13C signals at 163.6 and 162.4 ppm (vs TMS) in the presence of Li+ and Ba2+, respectively, confirmed the formation of the zwitterions from Rhodamine B base. The assignments of the 1H and 13C signals were performed by the HMBC method. The colored zwitterion of a practical black color former, 2′-anilino-6′-dibutylamino-3′-methylspiro[3H-isobenzofuran-1, 9′-(9H)xanthene]-3-one, was produced by the addition of M+ and M2+. The 13C NMR signals at 162.2 and 159.8 ppm in the presence of 2.0 mol dm-3 Mg(ClO4)2 and Ba(ClO4)2, respectively, gave conclusive evidence of the formation of the sp2-hybrid carbon center for the black color former. The interaction between the metal ions and the zwitterions from the fluoran-based dyes decreased as Mg2+ > Ba2+ > Li+ > Na+. The 1 : 1 complex formation constants with the metal ions for both dyes were evaluated based on the UV-visible absorption data. The smaller formation constants of the black color former, compared with those of Rhodamine B base, indicate some more difficulty in the cleavage of the γ-lactone ring, which is probably based on the asymmetric structure of the compound, i.e, only a single dibutylamono-group at the 3′- and 6′-positions. The evidence for the formation of both the trityl cation and the benzoate ion was obtained by the 1H NMR signals from trityl benzoate in the presence of Mg(ClO4)2 in CD3CN containing a small amount of CF3SO3D. The C–Cl bond cleavage of 4-methoxy, 4,4′-dimethoxy, and 4,4′,4′′-trimethoxytrityl chlorides, through the chemical interaction between Ba2+ and Cl- in acetonitrile soluition, was justified by our 13C NMR results.
  • Tsutomu Shiragami, Yoshito Andou, Yuichiro Hamasuna, Futoshi Yamaguchi ...
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 7 Pages 1577-1582
    Published: 2002
    Released: July 15, 2002
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    The substituent effects on the reduction potentials (E1/2red), the proton dissociation constants of a hydroxo ligand (Ka), and the fluorescence quantum yields (Φ) in aryloxo(hydroxo)tetraarylporphyrinatoantimony(V) complexes were investigated. The E1/2red and Ka values were affected by substituents in the axial aryloxo ligand but, little affected by substituents in the porphyrin ring. Since E1/2red of tetraarylporphyrinatoantimony(V) complexes were higher than those of other metal-porphyrin complexes, it was suggested that the metal orbital greatly contributed to the LUMO level of the complex which can be related to the E1/2red and Ka values. Therefore, the substituent effects of the axial aryloxo ligand on the E1/2red and Ka values were attributed to the electron density of the antimony ion, which affected the LUMO level of the complexes. Moreover, the Φ of the porphyrin moiety depended on both the oxidation potential of the axial aryloxo ligands and the polarity of the solvent used. The fluorescences of the porphyrin moiety were quenched by the axial aryloxo ligands at rate constants of 108 – 1011 s-1.
  • Chung-gi Shin, Akihiro Okabe, Akinori Ito, Akio Ito, Yasuchika Yonezaw ...
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 7 Pages 1583-1596
    Published: 2002
    Released: July 15, 2002
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    The useful synthesis of the main central 2,3,6-trisubstituted pyridine skeleton [the protected Fragment A-B-C] of a macrobicyclic antibiotic, cyclothiazomycin, was first accomplished. First, the 2-[2-(2-substituted thiazol-4-yl)]-4,5-dihydrothiazole-4-carboxylate [Fragment A derivative], attached to the 6-substituent of the main pyridine skeleton, was synthesized by two consecutive thiazolations of the protected Ser thioamide derivative with 3-bromopyruvate, and then thiazolination of the C-terminal Ser residue of the sequence. Secondly, an efficient synthesis of the central 2-(2-{2-[(1R)-1-aminoethyl]pyridin-6-yl}thiazol-4-yl)-4,5-dihydrothiazole-4-carboxylate [Fragment B derivative] was also achieved by thiazolation of the formyl group of the 2-(1-aminoethyl)-6-formylpyridine derivative, and then thiazolination. Thirdly, a convenient synthesis of the protected dehydrotetrapeptide [Fragment C derivative], which is bound to the 2-substituent of the pyridine skeleton, was attained by the usual stepwise elongation of the appropriate α-amino acids and β-elimination of a Thr residue of the sequence. Finally, the facile fragment condensation of the three Fragments thus obtained gave the protected Fragment A-B-C derivative via Fragment A-B. Furthermore, the configurational structures of the three Fragments (A, B, and C) were also investigated.
  • Shinichi Ayuba, Norihiko Yoneda, Tsuyoshi Fukuhara, Shoji Hara
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 7 Pages 1597-1603
    Published: 2002
    Released: July 15, 2002
    JOURNALS RESTRICTED ACCESS
    Mono- and difluorinations of sulfides were achieved using a novel fluorinating reagent, IF5–Et3N–3HF. The reagent is applicable for substrates having various electron-withdrawing groups, such as an ester, amide, ketone, nitrile, sulfone, or trifluoromethyl. Because more than one fluorine atom on IF5 is used, a large excess amount of the reagent is not necessary, even for the difluorination reaction.
  • Yao-Nan Xiao, Chun-Xia Zhang
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 7 Pages 1605-1609
    Published: 2002
    Released: July 15, 2002
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    The modes and activities of the interaction of DNA and water-soluble polymeric Schiff-base nickel complexes, prepared by polymeric analogous reaction, have been discussed according to the absorption spectra, circular dichroism spectra, and fluorescent probe results. The polymeric matrix effect and increasing solubility in water can increase the interaction of these water-soluble polymeric metal complexes with DNA.
  • Michio Iwaoka, Shinya Takemoto, Mai Okada, Shuji Tomoda
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 7 Pages 1611-1625
    Published: 2002
    Released: July 15, 2002
    JOURNALS RESTRICTED ACCESS
    Sulfur-containing functional groups of cystine (an SSC group) and methionine (a CSC group) are usually considered as hydrophobic moieties or weak hydrogen-bond acceptors in folded protein structures. However, database analysis as well as theoretical calculations carried out in this study have provided strong evidence for the presence of specific nonbonded interactions between the divalent sulfur atoms (S) and nearby polar non-hydrogen atoms (X). Close S···X (X = O, N, S, C, etc.) atomic contacts were statistically analyzed in 604 high-resolution heterogeneous X-ray structures selected from a protein databank (PDB_SELECT). The S···O interactions found for both SSC and CSC groups showed a specific character as a π(C=O) → σ*(S) orbital interaction based on the directional preferences. The interactions were most frequently observed in α-helices. Ab initio calculations applying the second order Møller–Plesset perturbation theory (MP2) suggested the primary importance of electron correlations. The total stabilization energies were calculated to be ∼3.2 and ∼2.5 kcal/mol for SSC and CSC groups, respectively, including the contribution from a coexisting CH···O hydrogen bond. On the other hand, the S···N interactions observed for a CSC group exhibited structural characters as a π(N) → σ*(S) orbital interaction and an NH···S hydrogen bond, and the S···S interactions for an SSC group showed a structural character as an n(S) → σ*(S) orbital interaction. The S···C(π) interactions should be rather weak and long-range.
  • Masanori Yamada, Kozue Kato, Motoyoshi Nomizu, Masahiro Haruki, Kousak ...
    Type: Others
    Subject area: AM
    2002 Volume 75 Issue 7 Pages 1627-1632
    Published: 2002
    Released: July 15, 2002
    JOURNALS RESTRICTED ACCESS
    We recently demonstrated the preparation of a water-insoluble DNA matrix by UV irradiation. The UV-irradiated DNA matrix selectively accumulated DNA-intercalating compounds and some endocrine disruptors. We evaluated the accumulation of metal ions in the UV-irradiated DNA matrix using a UV-irradiated DNA-film and DNA-immobilized glass beads. When DNA-immobilized glass beads were incubated with an aqueous solution of Hg2+, Cd2+, Pb2+, Zn2+, Cu2+, or Fe3+, the heavy metal ions were accumulated in the DNA-beads. The maximum amounts of the accumulated Hg2+, Cd2+, and Cu2+ in the DNA-beads were approximately 0.21, 0.13, and 0.22 mmol per gram of immobilized-DNA, respectively. The amounts of the accumulated Pb2+, Zn2+, and Fe3+ were lower than that of Hg2+, Cd2+, and Cu2+. Further, Fourier transform infrared (IR) studies using a UV-irradiated DNA-film with heavy metals suggested that the heavy metal ions interacted with not only the nucleic acid bases but also the phosphate groups. In contrast, the DNA-immobilized glass beads could not accumulate Ca2+ and Mg2+. These results suggested that the UV-irradiated DNA could selectively accumulate metal ions. The UV-irradiated DNA matrix has potential utility as a functional material to remove harmful heavy metal ions from contaminated water.
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