Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
73 巻 , 5 号
選択された号の論文の30件中1~30を表示しています
  • Masaaki Suzuki, Ryoji Noyori, Bengt Långström, Yasuyoshi Wa ...
    2000 年 73 巻 5 号 p. 1053-1070
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Molecular design to develop a stable biochemical probe for a study of the role of prostacyclin (PGI2) in the brain led to the discovery of (15R)-16-m-tolyl-17,18,19,20-tetranorisocarbacylin (referred to as 15R-TIC), that selectively bind to a novel PGI2 receptor, IP2, expressed in the central nervous system (CNS). This artificial prostaglandin with the 15R configuration exhibits high binding affinity for the IP2 receptor in the thalamus (IC50 = 32 nM) and weak affinity for the peripheral-type PGI2 receptor, IP1, in the NTS (IC50 = 1.2 μM). The length of the ω side-chain and the position of the methyl substituent on the aromatic ring strongly influence the binding characteristics. The features of the IP2 receptor were elucidated by quantitative mapping, specificity studies, and Scatchard analysis, as well as by a study using knockout mice with a tritium-labeled 15R-TIC and related radioligands. In order to conduct in vivo PET studies, a rapid methylation reaction using methyl iodide and an excess amount of an aryltributylstannane has been developed. This has successfully been applied to the synthesis of short-lived 11C-incorporated PET tracers, 15R-[11C]TIC and its methyl ester. The PET experiments accomplished the imaging of the IP2 receptor in the brain of living rhesus monkeys through intravenous administration. The elimination of the C(15) chirality results in 15-deoxy-TIC with ten-fold higher affinity and selectivity for the IP2 receptor than original 15R-TIC. Neither 15R-TIC nor 15-deoxy-TIC inhibit platelets aggregation, up to 400 nM, while PGI2 derivatives which bind with the IP1 receptor show a very potent inhibitory effect at a several nM level. Notably, these artificial CNS-specific PGI2 ligands, like the unstable natural PGI2 itself, prevent the apoptotic cell death of hippocampal neurons induced under high (50%) oxygen atmosphere and by xanthine and xanthine oxidase or serum deprivation. The difference in the binding potency between 15R-TIC and 15-deoxy-TIC for the IP2 receptor correlates well with the extent of the prevention of the neuronal cell death (IC50 values of 300 and 30 nM, respectively, under high oxygen atmosphere). 15R-TIC protects CA1 pyramidal neurons against ischemic damage in gerbils. Thus the designed TICs have neuronal survival-promoting activity both in vitro and in vivo, providing the possibility as a new type of chemotherapeutic agents for applications in neurodegeneration.
  • Naoki Asao, Yoshinori Yamamoto
    2000 年 73 巻 5 号 p. 1071-1087
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Hydrosilylation, hydrostannation, carbosilylation, and carbostannation of unactivated alkynes with organosilanes, or organostannanes proceed effectively in the presence of catalytic amounts of Lewis acids to produce the corresponding vinylsilyl or vinylstannyl compounds in a highly regio- and stereoselective way. Although it is well known that transition metal catalyzed hydrometalations and carbometalations, in general, proceed in a cis-manner, the Lewis acid-catalyzed reactions proceed in a trans-manner exclusively. The coordination of a triple bond to Lewis acids is proposed as a key step for the Lewis acid catalyzed reactions.
  • Norihiro Kato, Hiroto Hasegawa, Fujio Takahashi
    2000 年 73 巻 5 号 p. 1089-1095
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Fast-responsive deswelling of poly(N-isopropylacrylamide) gel after a freeze-dry (FD) treatment was investigated by means of SEM images and a kinetic method using a N-isopropylacrylamide (NIPAAm) monomer from the viewpoint of the mesoscopic structure comprising a partitioned polymer-network.
    It was deduced from SEM images that an elastic frame comprising a partitioned polymer-network is formed by a hydrophobic interaction between polymer chains in the FD-treated gel. Fast-deswelling of the FD-treated gel results from the elasticity of a partitioned polymer-network caused water to release. The kinetic parameters on deswelling of both the conventional gel and the FD-treated gel were determined in the presence of an NIPAAm monomer. This monomer in solution is considered to play two directly-opposed roles in making a skin on the surface of the conventional gel: One is for disturbing the formation of hydrogen bonding between amide groups in the polymer; the other is for accelerating the separation of hydrated water from isopropyl groups in the polymer. Cracking the surface of a conventional gel was investigated in connection with the monomer.
  • Nahoko Iimura, Yuji Ohashi, Hirotaka Hirata
    2000 年 73 巻 5 号 p. 1097-1103
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Seven crystalline molecular complexes were formed between perfumes such as guaiacol, 2-methylindole, and skatole and cationic surfactants such as hexadecyl-, tetradecyl-, dodecyl-, and decyltrimethylammonium bromide from an aqueous or methanol solution at low temperatures (< 10 °C). The crystal structures were determined by X-rays. The structures are very similar to each other, that is, the perfume molecules are packed in the layers of the alkyl chains of the surfactant molecules. Those packings are substantially the same as the common packing pattern observed in complexes between the surfactants and the aromatic compounds. The thermal analysis showed that the volatilization temperatures of the perfumes increased significantly when the perfumes are packed in the complex crystals. Moreover, the molar loss ratio of the perfume with increasing the temperature decreased with increasing the length of the alkyl chain of the surfactant. This suggests that thermal stability of the perfumes can be controlled by forming the complexes with the surfactants containing different alkyl chains.
  • Yasuo Kameda, Kentaro Sugawara, Takayoshi Hosaka, Takeshi Usuki, Osamu ...
    2000 年 73 巻 5 号 p. 1105-1112
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Polarized Raman scattering, X-ray, and time-of-flight (TOF) neutron-diffraction measurements were carried out for highly concentrated aqueous phosphoric acid solutions, in order to deduce detailed structural information on both the PO4-intramolecular geometry and intermolecular hydrogen bonds in the solution. Isotropic Raman spectra observed for (H3PO4)x(H2O)1-x with x = 0.1—0.6 exhibited a single band assigned to the symmetrical stretching vibrational mode of the PO4 structural unit, which suggests that all P-O bonds in the unit are spectroscopically equivalent. The results of X-ray and neutron-diffraction measurements for the 53 mol% phosphoric acid solution indicated that the structure of the PO4 unit is a regular tetrahedron with a P-O bond-length of 1.540(3) Å. From a least-squares fit to the observed X-ray and neutron intermolecular interference terms, the nearest-neighbor intermolecular distances, reflecting intermolecular hydrogen-bonded interactions in the solution, were determined to be r(O…D) = 1.77(1) Å and r(O…O) = 2.73(2) Å, respectively, which are both ca. 0.1 Å shorter than those observed for pure liquid water. Therefore, it has been clarified that a strongly hydrogen-bonded network exists in such concentrated aqueous phosphoric acid solutions.
  • Takashi Imai, Masahiro Kinoshita, Fumio Hirata
    2000 年 73 巻 5 号 p. 1113-1122
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Salt effects on the stability and on the solvation structure of a peptide in a variety of aqueous solutions of the alkali-halide ions are studied by means of the reference interaction site model (RISM) theory. The order of salt effect on the peptide stability is consistent with the experimental results; the order follows the Hofmeister series. The results are further analyzed in order to clarify the nature of the salt effect which determines the Hofmeister series and to find the reason why the Hofmeister series applies so generally to a variety of solutes in aqueous solutions. A heuristic model for explaining salt effects on the solvation structure of the peptide is proposed based on changes in the peptide-water pair correlation functions due to the ion perturbation.
  • Junko N. Kondo, Lianhai Lu, Yoshiko Takahara, Ken-ichi Maruya, Kazunar ...
    2000 年 73 巻 5 号 p. 1123-1129
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    By IR observation, Lewis acid sites of medium strength were found by CO adsorption on a mesoporous Ta-TMS-1 while no basic sites were detected by CO2 adsorption. Methyl migration of methoxy species and formation of methoxy species from adsorbed dimethyl ether were quantitatively demonstrated.
  • Akinari Sonoda, Yoji Makita, Kenta Ooi, Norio Takagi, Takahiro Hirotsu
    2000 年 73 巻 5 号 p. 1131-1133
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    We have found a unique pH dependence of the fractionation of boron isotopes with N-methyl-D-glucamine resin in aqueous solution systems. The fractionation is due to the adsorption of 10B isotopes from the solution phase to the resin phase. For pH values less than 7, the boron-isotope separation factors are 1.027, indicating that 10B isotopes are concentrated in the resin more selectively than 11B isotopes. On the other hand, for the pH values greater than 11, the factors are 0.998, revealing no fractionation of boron isotopes. In the intermediate pH range, the factors are decreased significantly with an increase in pH. This finding confirms that 10B is fractionated as boron complexes with a tetrahedral coordination geometry in resin phase more selectively than as those with a planar trigonal coordination geometry in solution phase, while 11B exhibits the opposite relation. This finding will provide a very important basis for separation of boron isotopes with novel chelating resins in aqueous solution systems.
  • Akira Tatehata, Shigeo Yamada, Akira Muraida
    2000 年 73 巻 5 号 p. 1135-1142
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The product distribution of the three geometrical isomers and the stereoselectivity of the u-fac isomer in the oxidation of [Co(dien)2]2+ (dien = diethylenetriamine) by optically active anionic cobalt(III) complexes were significantly influenced by the geometrical arragement of the coordinated atoms in the oxidants, reflecting the differences in the stabilization of the precursor assemblies due to the hydrogen bonding interactions between the reactants. Solvent effects on the isomer proportions and the stereoselectivity were examined in water, methanol, ethanol, formamide, dimethylformamide, and dimethyl sulfoxide. The results are explained in terms of the differences in the degree of oxidant-solvent interactions depending on acceptor number of solvents.
  • Kenji Nomiya, Ryusuke Noguchi, Takaye Shigeta, Yoshihiro Kondoh, Kazuh ...
    2000 年 73 巻 5 号 p. 1143-1152
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Two types of silver(I)-triphenylphosphine complexes with 2-mercaptonicotinic acid (H2mna) were prepared as [Ag(Hmna)(PPh3)n] (1, n = 2; 2, n = 3); their crystal structures determined by single-crystal X-ray diffraction. These complexes were obtained from reactions of the precursor, [Ag(Hmna)]n, with less excess (3 equiv) and large excess (20 equiv) amounts of PPh3, respectively. Complex 1 was also obtained from a reaction among another precursor [AgCl(PPh3)3], H2mna and aqueous NaOH. The coordination geometry of 1 was a trigonal pyramid with an AgSP2 core; there was a weak interaction between the silver(I) center and the pyridine nitrogen atom, while that of 2 was a distorted tetrahedron with an AgSP3 core. In both 1 and 2, the carboxyl group was protonated and its oxygen atoms did not participate in the coordination. In contrast to the formation of 1 and 2, a related complex, [Ag(Hmba)(PPh3)3] 4 (H2mba = 2–mercaptobenzoic acid), has been obtained from a reaction of [Ag(Hmba)]n with a stoichiometric amount (3 equiv) of PPh3. On the other hand, the gold(I) complex, [Au(Hmna)(PPh3)] 3, with a 2-coordinate AuSP core, was prepared by a stoichiometric reaction among [AuCl(PPh3)], H2mna and aqueous NaOH. Complex 3 in the solid state showed a supramolecular array based on a repetition of hydrogen-bonding interactions between the carboxyl group and the pyridine nitrogen atom, also being contrasted to the related complex, [Au(Hmba)(PPh3)] 5, with a hydrogen-bonding dimer structure in the solid state. In CHCl3, both 1 and 2 were present as several equilibrium species due to a successive dissociation of PPh3 ligands, while 3 was present as an almost monomer. The antimicrobial activities in aqueous media of 15, evaluated by minimum inhibitory concentration (MIC), were also tested.
  • Kenichi Oyaizu, Agus Haryono, Junichiro Natori, Hiroshi Shinoda, Eishu ...
    2000 年 73 巻 5 号 p. 1153-1163
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Acidification of a solution of (μ-oxo)bis[(5,10,15,20-tetraphenylporphyrinato)iron(III)] ([{Fe(tpp)}2O], II) in CH2Cl2 produced equimolar amounts of a hydroxoiron(III) complex [(tpp)FeIII(OH)] (III) and an iron(III) complex [(tpp)FeIII(ClO4)] (IV). The complex IV was isolated as a perchlorate salt, which crystallyzed in the triclinic space group P1-(#2); a = 11.909(3), b = 19.603(4), c = 10.494(3) Å, α = 95.74(2)°, β = 107.91(2)°, γ = 89.14(2)°, V = 2319.1(9) Å3, Z = 2, Dcalc = 1.328 g cm-3, μ(Mo ) = 4.35 cm-1, final R = 0.055 and Rw = 0.050. The crystal structure of IV revealed that ClO4- is coordinated to the iron atom, which may be driven by the preference of iron(III) to be five coordinate rather than four coordinate. Reduction of the complex II in the presence of acid by electrolysis and/or by a reducing agent, such as sodium dithionite, under argon produced [FeII(tpp)]. The addition of O2 to a solution of [Fe(tpp)] in acidic CH2Cl2 in the presence of an equimolar amount of the reducing agent produced the complex III. When the complex II was adsorbed on an electrode surface and placed in aqueous acidic electrolyte solutions, electroreduction of the adsorbate proceeded according to the half-reaction:
    [{Fe(tpp)}2O]+2H++2e-→2[Fe(tpp)]+H2O, at 0.031—0.059 pH V (vs. SCE, pH>1.0). Based on these results, oxo-bridged iron(III) porphyrin dimers were used as electrocatalysts for the reduction of O2. The catalytic reduction of O2 proceeded at potentials in the vicinity of those for II. As a whole, the proportion of H2O as the product increased from 50% for adsorbed [(tpp)FeIIICl] to >90% for the adsorbed dimer. Thus, electroreduction of the dimer adsorbed on a carbon electrode immersed in aqueous acid produced two solid state, cofacially fixed iron(II) porphyrin molecules:
    [PFeIIIOfeIIIP]ad+2H++2e-→[PFeII FeIIP]ad+H2O (P = porphyrin dianion). Coordination of molecular oxygen to the adjacent two iron(II) centers under acidic conditions allowed formation of O2-bridged iron(III) porphyrin [PFeIII(O2)FeIIIP]ad at the electrode surface. Electroreduction of the adsorbate under acidic conditions produced H2O and allowed the reformation of [PFeII FeIIP]ad. The implication is that the electroreduction of the adsorbed oxo-bridged dimer gives a cofacial geometry for PFeII on the electrode, facilitating the coordination and subsequent splitting of O2.
  • Yukio Sakai, Kanako Ono, Tamotsu Hidaka, Makoto Takagi, Robert W. Cat ...
    2000 年 73 巻 5 号 p. 1165-1169
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The effect of the poly(oxyethylene) (POE) chain length of ionic surfactants, expressed as C12H25-(OCH2CH2)-nOCH2C6H3(OH)(NO2) (n = 2—9), on the extraction of monovalent cations, including alkali metal and tetraalkylammonium (TAA) ions, was investigated. The extraction constants (Kex) with surfactants having a POE chain of n ≥ 6 were almost constant for each alkali metal ion. The Kex sequence was Li+ < Na+ < Cs+ ≤ K+ = Rb+. The extractability and selectivity largely decreased as n in the surfactant decreased (n < 6). The effect of the POE chain length was related to the stability of the alkali metal-POE complex. Unlike an alkali metal ion, the Kex values for all TAA ions were almost constant with surfactants of n = 2—8. These facts indicated that the surfactant extracts alkali metal ions by both complex formation with its POE chain and ion-pair formation with a terminal p-nitrophenolate anion. On the other hand, TAA ions were extracted simply by ion-pair formation with a p-nitrophenolate anion of the surfactant. The proposed structures are discussed from the viewpoint of the spectrum shift of the extracted species.
  • Satoshi Kusakabe
    2000 年 73 巻 5 号 p. 1171-1177
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Chromium(III) ion was extracted from aqueous 1 mol dm-3 NaX (X- = ClO4-, SCN-, NO3-, Br-, and I-) solutions with trioctylphosphine oxide (TOPO) in hexane at 298 K. The extraction was rapidly equilibrated, except from a NaNO3 solution. The number of TOPO molecules solvating to the extracted chromium(III) perchlorate and thiocyanate was 6. That to the bromide and iodide was 5. That to the nitrate was 5 at the beginning of extraction, and changed to 3 within a few hours of two-phase agitation. The hydration number of extracted Cr(ClO4)3·6TOPO was 17.2±0.5. The different solvation number of TOPO among these salts is supposed to be an unstable second hydration sphere of the extracted chromium(III) ion, which may be easily removed by the counter anions.
  • Shan Ji, Tomoki Yabutani, Akihide Itoh, Hiroki Haraguchi
    2000 年 73 巻 5 号 p. 1179-1186
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The coastal seawater sample was filtered with a membrane filter (pore size 0.45 μm), and the filtrate was further filtered with an ultrafiltration filter (molecular weight permeation limit of 10000 Da). Then, major-to-ultratrace elements in the particles which remained on the membrane filter, the membrane-filtered seawater, and the ultrafiltered seawater were determined by ICP-AES (inductively coupled plasma atomic emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry). From these analytical results, the fractional distributions of each element in the particle, large molecule and small molecule fractions of seawater were estimated, where the distributions of the elements in the large molecule fraction were obtained as the differences between the elemental concentrations in membrane-filtered and ultrafiltered seawaters.
    Furthermore, laboratory-made salts (Salts I—III) were prepared from original, membrane-filtered, and ultrafiltered seawaters. The concentrations of major-to-ultratrace elements in laboratory-made salts were also determined by ICP-AES and ICP-MS. It was found that alkali metals, alkaline earth metals, oxoanion-forming elements (V, Mo, W, U) and Cd were mostly contained in the small molecule fraction of seawater, and ca. 95—100% of them in salt, except for V, originated from those in the small molecule fraction. More than 50% of Al, Mn, Fe, Co, Ga, Y, rare earth elements (REEs) and Pb were contained as the particle constituents in seawater, but their intakes into salt were less than 50%. In addition, the fractional distributions of the following elements in the large molecule fraction of seawater were: Al 10%, Mn 4%, Fe 2%, Cu 23%, Zn 7%, Y 5%, REEs 3—15%, and Pb 30%. On the other hand, the intake factors of these elements in salt from the large molecule fraction were: Al 40%, Mn 5%, Fe 28%, Cu 20%, Zn 30%, Y 7%, REEs 5—30%, and Pb 55%. The results obtained in the present experiment suggest that the distributions of the elements in natural salt greatly depend on the chemical forms in seawater.
  • Yuichi Shimazaki, Stefan Huth, Shun Hirota, Osamu Yamauchi
    2000 年 73 巻 5 号 p. 1187-1195
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Copper(II) complexes of several new N3O-type tripodal ligands, 2,4-di(t-butyl)-6-{[bis(2-pyridyl)methyl]aminomethyl}phenol (HtbuL), 2,4-di(t-butyl)-6-{[(6-methyl-2-pyridyl)methyl](2-pyridylmethyl)aminomethyl}phenol (HtbuL(Mepy)), 2,4-di(t-butyl)-6-{bis[(6-methyl-2-pyridyl)methyl]aminomethyl}phenol (HtbuL(Mepy)2), and 2,4-di(t-butyl)-6-{[(1-methyl-2-imidazolyl)methyl][(6-methyl-2-pyridyl)methyl]aminomethyl}phenol (HtbuL(im)(Mepy)), were prepared. They were structurally characterized by the X-ray crystallographic method to have a square-pyramidal structure with a weakly coordinating group at an apical position. The phenol moiety of [CuCl(tbuL(Mepy))] (2), [CuCl(tbuL(Mepy)2)] (3), and [CuCl(tbuL(im)(Mepy))] (4) was revealed to be coordinated equatorially; it was converted to the phenoxyl radical upon oxidation with Ce(IV), giving a new absorption peak at 405—420 nm. ESR measurements at low temperatures and resonance Raman spectra established that the radical species has a Cu(II)-phenoxyl radical bond. The cyclic voltammograms exhibited a quasi-reversible redox wave at E1/2 = 0.56—0.61 V (vs. Ag/AgCl) corresponding to the formation of the phenoxyl radical, which displayed a first order decay with a half life of 65 and 62 min at -20 °C for 2 and 4, respectively, while that for 3 was only 9.0 min at -40 °C. The radical stability increased with the donor ability of the equatorial N ligands.
  • Yoshitaka Aoki, Hidetaka Konno, Hiroto Tachikawa, Michio Inagaki
    2000 年 73 巻 5 号 p. 1197-1203
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Single phase LnCrO4 (Ln = La-Nd) compounds were attempted to synthesize by the pyrolysis of precursors prepared from LnIII-CrVI mixed solutions. Only LaCrO4 and NdCrO4 were obtained as a single phase. LaCrO4 was monazite type (monoclinic, P21/n), as reported, and the cell parameters were refined to be a = 0.70369, b = 0.72348, c = 0.66918 nm and β = 104.950° by an X-ray Rietveld method. NdCrO4 was zircon type (tetragonal, I41/amd) and the cell parameters were a = 0.73107 and c = 0.66999 nm. It was found that CrO43- tetrahedra in LaCrO4 have C1 symmetry and the four Cr-O bond lengths are different, whereas those in NdCrO4 have D2d symmetry and all Cr-O bond lengths are 0.1702 nm. Detailed Raman spectra of LaCrO4 and NdCrO4 were measured and assigned to the vibrational modes of the CrO43- tetrahedra. Molecular orbital calculations indicated that the charge density on the chromium ions in the tetrahedra is much less than the nominal 5+ due to the migratory electrons from oxygen atoms, and nearly the same irrespective of the symmetry of tetrahedron, suggesting that the Cr-O bonds are strongly covalent in nature.
  • Tadashi Yamaguchi, Naoyuki Imai, Tasuku Ito, Clifford P. Kubiak
    2000 年 73 巻 5 号 p. 1205-1212
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    A pyrazine bridged dimer of triruthenium clusters [{RuIII2RuII(μ3-O)(μ-CH3CO2)6(CO)(abco)}2(μ-pz)] (abco =1-azabicyclo[2,2,2]octane, pz = pyrazine) gives an inter-cluster mixed valence state upon one electron reduction. The splitting of the reduction waves in cyclic voltammetry, ΔE, was 470 mV. This corresponds to a comproportionation constant for formation of the mixed valence state of 9.0 × 107. The IR spectrum of the mixed valence species in the ν(CO) region, measured by reflectance IR spectroelectrochemistry, showed a completely coalesced ν(CO) band. This represents delocalized redox behavior on the infrared vibrational timescale. The rate constant for intramolecular electron transfer was estimated to be 1 × 1012 s-1 at -18 °C by simulating the ν(CO) absorption bandshape. The mixed valence complex showed an intervalence charge transfer (ICT) band at 12500 cm-1. Hush analysis provides a spectroscopic estimate of HAB to be 2490 cm-1. Crystal structures of [{RuIII2RuII(μ3-O)(μ-CH3CO2)6(CO)(abco)}2(μ-pz)]·2CH2Cl2 and its precursor, [RuIII2RuII(μ3-O)(CH3CO2)6(CO)(abco)2]·CH2Cl2, were determined by X-ray crystallography. Trends in Ru-O(oxo) and Ru-O(acetate) distances in these compounds show that the divalent site is localized on the Ru center attached to the carbonyl ligand.
  • Toshinobu Masuda, Takeshi Kaneko, Toshiharu Tanaka, Shujiro Goya, Chiy ...
    2000 年 73 巻 5 号 p. 1213-1217
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Novel fluorogenic coumarin derivatives appending 15-crown-5 ether as more active catalytic site were designed and synthesized for the fluorescence derivatization of carboxylic acids. From the stability constants (Ks) for complexation with metal acetates in methanol, it was found that their catalytic abilities were superior to the corresponding benzo-15-crown-5 ether type reagent. However, the reactivity of these reagents in the derivatization of lauric acid was dependent on not only the catalytic ability of the introduced crown-ether but also on the appending position of that in a reagent molecule. Furthermore, the derivatized products showed remarkably high fluorescence quantum yields of above 0.8 in methanol and acetonitrile. Allowing to hold a certain function such as catalyst in a reagent molecule should serve as a new strategy for the development of excellent analytical reagents.
  • Yasunori Yamada, Yoko Maeda, Yoshitaro Miyashita, Kiyoshi Fujisawa, Ta ...
    2000 年 73 巻 5 号 p. 1219-1220
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The reaction of cis-[CoCl2(R-pn)2]+ (R–pn = (R)–1,2-propanediamine) with [Ni(aet)2] (aet = 2–aminoethanethiolate) in water stereoselectively gave an S-bridged trinuclear complex, [Ni{Co(aet)2(R-pn)}2]4+, accompanied by the ligand-transfer of aet from Ni2+ to Co3+. The ΔΔ isomer of the trinuclear complex was selectively formed. The spectrochemical properties of theΔΔ isomer are also discussed in relation to the stereochemical behavior.
  • Jun Wang, Satoshi Osada, Hiroaki Kodama, Michio Kondo
    2000 年 73 巻 5 号 p. 1221-1226
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The synthesis and conformational analysis of cyclo(Pro-Leu-Aib)2 by means of NMR technique are reported. The cyclohexapeptide was synthesized in the classical high-dilution solution method. Its yield in the cyclization reaction from linear hexapeptide active ester was lower than that of the analogous cyclo(Pro-Leu-Gly)2 previously reported. Two sets of amide proton signals for Leu and Aib in NMR spectra and temperature coefficients indicated an asymmetric conformation which contains both cis and trans Aib-Pro bonds. Here Pro amino acids occupy the positions i+2 of β-turns. The CD spectrum gave two negative bands at 202 and 230 nm, which is considered to be the sum of type II (when Aib-Pro is trans) and type VI (when Aib-Pro is cis) β-turns.
  • Ken Tanaka, Minoru Nagasawa, Hideki Sakamura
    2000 年 73 巻 5 号 p. 1227-1231
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    A practical synthesis of (6-chloro-3-pyridyl)methylamine (1), one of the key intermediates of neo-nicotinoid insecticides, by a highly selective hydrogenation of 6-chloro-3-pyridinecarbonitrile (4) is described. The use of an improved Raney nickel catalyst, prepared from an alloy of low nickel content (Ni 38%, Al 62%) and subjected to heat treatment in water (98 °C, 2 h) after leaching of aluminum, was highly effective for the selective hydrogenation of 4. The hydrogenation of 4 using this catalyst was carried out in EtOH-H2O [6 : 1 (v/v)] and NH3 at 50 °C and 1.2—1.4 kg cm-2 hydrogen pressure to give 1 in 86% yield and 3-pyridylmethylamine, a dechlorinated by-product, in 2% yield.
  • Miyoko Kamigauchi, Mayumi Yoshida, Kayoko Saiki, Makiko Sugiura, Jujir ...
    2000 年 73 巻 5 号 p. 1233-1241
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The conformational/physicochemical features of corycavidine (1), 5,7,8,15-tetrahydro-3,4-dimethoxy-6,15-dimethyl-[1,3]benzodioxolo[5,6-e] [2]benzazecin-14(6H)-one, an important protopine-type alkaloid that serves as the key intermetabolite in the biosynthesis of isoquinoline alkaloids, were examined by X-ray crystallography, 1H NMR spectroscopy, as well as thermal analysis and energy calculations. Two stable conformations of 1, as proposed by energy calculations, were also observed in both the crystalline and solution states. Racemization of optically active 1, which was caused by heating of the crystal, was analyzed by differential-scanning calorimetry. By taking advantage of the H-2H replacement reaction at the C13 atom of 1, the rate of racemization in the C2H3O2H/NaO2H solution was measured as a function of the temperature; the energy barrier between both enantiomers was estimated to be 4.7 kcal mol-1. The crystallization of racemic 1 led to two different crystal forms, i.e., the racemic crystal and the conglomerate crystal (1 : 1 mixture of both enantiomeric crystals). This was probably due to the low energy difference between both crystals. These physicochemical behaviors are important for understanding the in vivo nonenzymatic racemization of 1 and its related alkaloids during metabolic processes.
  • Kazuyasu Tani, Kazuo Matsuyama, Shinzi Kato, Kohzaburo Yamada, Hirotak ...
    2000 年 73 巻 5 号 p. 1243-1252
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Stoichiometric reactions of alkali metal thio- and dithiocarboxylates with Ph2PCl, PhPCl2, and PBr3 gave the corresponding acylthio- and thioacylthiophosphines [(RCES)nPPh3-n, E = O, S; n = 1—3] 38 in moderate to good yields. The structures of (4-CH3C6H4COS)nPPh3-n (3d: n = 1, 4d: n = 2, 5d: n = 3) and (4-CH3C6H4CS2)2PPh (7b) were analyzed by X-rays. In the thiocarboxylate derivatives 3d, 4d, and 5d, the intramolecular interactions between the carbonyl oxygen and the central phosphorus atoms are weak and the thiocarboxylato ligands act as monodentates through the sulfur atoms. Similarly, in the dithiocarboxylate derivative 7b, the intramolecular interactions between the thiocarbonyl sulfur and the central phosphorus atoms are weak and the dithiocarboxylato ligands act as monodentates. The covalent phosphorus-sulfur and/or phosphorus-phenyl ipso-carbon bonds are nearly at right angles to one another, forming a distorted tetrahedron with the unshared electron pair orbital at the apex. The 31P NMR spectra of the thiocarboxylic acid derivatives 35 show downfield shifts with an increase in the number of thiocarboxylato ligands, whereas those of the dithiocarboxylic acid derivatives 68 show upfield shifts.
  • Masanobu Sugawara, Jun-ichi Yoshida
    2000 年 73 巻 5 号 p. 1253-1257
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The relative magnitude of the β-effect of silicon and the γ-effect of tin was evaluated by intermolecular competition. An acetal was allowed to react with a 1 : 1 mixture of an allylsilane and a homoallylstannane in the presence of TMSOTf (trimethylsilyl trifluoromethanesulfonate); the former was found to be more reactive than does the latter, indicating that the β-silyl group activates the carbon-carbon double bond more effectively than the γ-stannyl group. This is consistent with the results of molecular-orbital calculations which indicate that the HOMO level of the allylsilane is higher than that of the homoallylstannane. The intermolecular competition between a homoallylstannane and a terminal alkene toward electrophilic reactions with an acetal have revealed that the former is more reactive than the latter. This result indicates that the stannyl group at the γ-position definitely activates the carbon-carbon double bond toward electrophiles.
  • Hiroyuki Higuchi, Masatoshi Shinbo, Masanobu Usuki, Makoto Takeuchi, K ...
    2000 年 73 巻 5 号 p. 1259-1275
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Various mixed complexes of vinylene-bridged bis- and tris(octaethylporphyrin)s (bis(OEP)-(M1-M2) and tris(OEP)-(M1-M2-M3)) with d8 transition-metal ions M(II) (M: M1, M2, and M3 = Ni or Pd or Pt) were synthesized by step-by-step and selective metallations of the respective free-bases (FB) with limited amounts of the metallation reagent. Metallation of tris(OEP)-(H2-H2-H2) started in the central OEP ring, with the vinylene linkages of the product retaining the same (E,E)-configuration as those in FB. On the other hand, metallation of (E)-bis(OEP)-(H2-H2) afforded the corresponding (E)-bis(OEP)-(M1-M2) predominantly, while metallation of (Z)-bis(OEP)-(H2-H2) was accompanied by a ready isomerization of the vinylene linkage to afford each pair of (E)- and (Z)-isomeric complexes under the similar conditions. Electronic absorption spectra of tris(OEP)-(M1-M2-M3) proved to be affected especially by the central OEP-M2 ring and by the heavier metals more intensively, resulting in the largest splitting of the Soret band for the Ni-Pd-Pt complex. Examination of the oxidation potential E1 values indicated that the electron-releasing abilities of tris(OEP)-(M1-M2-M3) are intensively reduced for the complex carrying at least two consecutive heavier metal OEP rings. In the case of bis(OEP)-(M1-M2), the (E)-isomeric series exhibited the reduction of the electron-releasing abilities regularly in order of the heavy metal complexes similarly to tris(OEP)-M, while the (Z)-isomeric series exhibited little dependence of the electron-releasing abilities upon the incorporated metals M.
  • Oh Hyeong Kwon, Yukio Imanishi, Yoshihiro Ito
    2000 年 73 巻 5 号 p. 1277-1282
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Alteration of the lyophilization conditions significantly enhanced not only the activity of insoluble native subtilisin Carlsberg but also that of solubilized enzyme in benzene. The catalytic activity (kcat/Km) for the transesterification reaction of N-acetyl-L-phenylalanine ethyl ester with 1-propanol in benzene was enhanced more than 1000 times by the solubilization (100-fold enhancement) and the adjustment of lyophilization conditions (10-fold enhancement). Subtilisin Carlsberg was modified with polyethylene glycol (PEG-Sub) so that it could be solubilized in organic solvents. The effects of pH of the aqueous enzyme solution, of salts, or of a substrate analog in the aqueous solution before the lyophilization process, on the catalytic activity of native subtilisin and PEG-Sub were investigated. The activities of both the native subtilisin and PEG-Sub depended on the pH. The activities of both PEG-Sub and the native subtilisin were enhanced by the presence of salts. The presence of a substrate analog, N-Ac-L-Phe, also enhanced the activity of the native subtilisin and PEG-Sub. These results demonstrated that the organic solvent-solubilized subtilisin was affected by the lyophilization conditions.
  • Kazuo Ogawa, Kenji Aso, Shin Ono, Toshiaki Yoshimura, Seichi Rengakuji ...
    2000 年 73 巻 5 号 p. 1283-1284
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The suppressive effects of noncyclic cyanamides (guanidine hydrochloride, urea, and thiourea) on the retrogradation of waxy corn starch (WCS) gel were examined using differential scanning calorimetry and X-ray powder diffraction. We demonstrated that thiourea, guanidine hydrochloride, and urea effectively suppressed the retrogradation of the WCS gel in this order.
  • Thundi Madathil Jyothi, Kurungot Sreekumar, Mahadev B. Talawar, Anagh ...
    2000 年 73 巻 5 号 p. 1285-1290
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Rare earth-promoted (10%) sulfated SnO2 catalysts were prepared by different methods and have been characterized by employing XRD, SEM, Mercury porosimetry, BET surface-area analysis, TG-DTA, and IR spectroscopy. The strength of generated acid sites depends on the preparation method. A thermogravimetric analysis revealed that the removing the sulfate species from the catalyst surface took place at temperatures > 1193 K. The adsorption of butylamine and acetic acid was used to probe the acid-base properties of the catalysts. The catalytic activity of these materials in the oxidative dehydrogenation of ethylbenzene was tested at different temperatures. It was found that rare earth-modified sulfated tin oxide catalysts are more active when compared to the corresponding mixed-oxide systems and sulfated tin oxide. The combined effect of rare earth oxide and the sulfate anion leads to a enhanced oxidation activity. The existence of strong acid sites generated as a result of a sulfate treatment is involved in the activation of ethylbenzene; the addition of rare earth oxides brings about an enhancement of the reaction between the adsorbed oxygen atoms and the adsorbed ethylbenzene.
  • Etsu Yamada, Mitsuo Kimura, Kenichi Tomozawa, Yasuro Fuse, Takeshi Yam ...
    2000 年 73 巻 5 号 p. 1291-1297
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    The behavior and origin of atmospheric NO2, SO2, and O3 in mountains around the Kyoto basin were investigated by using passive samplers. Since these samplers are compact and need no batteries or pumps, they are appropriate for the measurement of atmospheric NO2, SO2, and O3 at low-level concentrations in mountains or forests. The sampling sites were Mt. Hiei, Mt. Daimonji, and 7 other mountains around the Kyoto basin, and 4 clean sites (Seryu, Kuroda, Sasari, Ashu) located about 20—30 km north of the Kyoto basin. The concentrations of atmospheric NO2, SO2, and O3 in mountains on three sides of the Kyoto basin were almost the same at the same altitude in the same season. The source of atmospheric NO2 in mountains around the Kyoto basin may be anthropogenic emission from automobiles or industrial areas, and NO2 concentration at clean sites far away from the Kyoto basin may become lower due to the diffusion of NO2. O3 concentration was higher as the altitude increased. Atmospheric O3 at mountains around the Kyoto basin has its origin in both stratospheric input and O3 production by photochemical reactions.
  • Fei Cheng, Yoshiyuki Sugahara, Kazuyuki Kuroda
    2000 年 73 巻 5 号 p. 1299-1305
    発行日: 2000年
    公開日: 2001/02/28
    ジャーナル 認証あり
    Synthesis and pyrolysis of a soluble precursor possessing an Nb-N backbone structure were investigated. The precursor was prepared by aminolysis reaction of tetrakis(diethylamido)niobium with isopropylamine. The precursor was soluble in benzene, and had a polymeric structure possessing Nb-N-Nb imido-bridges. The precursor was pyrolyzed under NH3-N2 (at 600 °C for 2 h under NH3 and subsequently at 1350 °C for 8 h under N2) and Ar (at 1500 °C for 2 h) atmospheres. δ-NbN was obtained as a main crystalline phase after the pyrolysis of the precursor under NH3-N2, whereas pyrolysis of the precursor under Ar led to the formation of NbC as the only crystalline phase. More than 90% of niobium which was present in the precursor remained in both of the pyrolyzed products.
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