Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 69 , Issue 8
Showing 1-40 articles out of 40 articles from the selected issue
  • Shigeru Nagase, Kaoru Kobayashi, Takeshi Akasaka
    1996 Volume 69 Issue 8 Pages 2131-2142
    Published: 1996
    Released: June 28, 2006
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    Endohedral metallofullerenes (fullerenes containing metals inside the carbon cage) have long attracted special interest as new spherical molecules with novel properties. Recent important progress has been marked by successful isolation and purification in macroscopic quantities. With the availability of such purified samples, it has been possible to investigate the structures, electronic properties, and chemical reactivities. Very recent progress in the theoretical and experimental studies of endohedral metallofullerenes is summarized to show what are known or still unknown for the future material, catalytic, and biological applications.
  • Eiichi Nakamura, Hidetoshi Tokuyama, Shigeru Yamago, Takashi Shiraki, ...
    1996 Volume 69 Issue 8 Pages 2143-2151
    Published: 1996
    Released: June 28, 2006
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    Two different classes of water-soluble fullerene derivatives, detergent-type and sphere-type, were synthesized. The derivatives were evaluated for their biological activities including cytotoxicity, DNA cleavage, and inhibition of HIV-protease and other enzymes. Both classes of compounds display generally similar behavior except for their cytotoxicity spectra against several cell lines. The fullerene derivatives bearing N-methylpyrrole were found to be photo-inactive with respect to DNA cleaving activity and cytotoxicity. A study on the kinetics for the inhibition of HIV-protease with detergent type derivative revealed that the compound is a potent fullerene-based HIV protease inhibitor, inhibiting the enzyme activity in a reversible and competitive manner with a Ki value of 0.32 μM.
  • Tetsuya Hirade
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2153-2157
    Published: 1996
    Released: June 28, 2006
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    Ole E. Mogensen reported that CS2 was the only liquid which showed large decrease of the Ps intensity with lowering the temperature, even though electron and positron could encounter with each other at low temperatures such as −100 °C. The intensity change by the positron annihilation lifetime was observed at a little lower temperature by the positron annihilation angular correlation. Here I measured the change of intensity and lifetime of the longest lifetime component caused by varying the surface tension, the dielectric constant, and the temperature, to clarify the positron state in CS2. These experimental results confirm the ideas of the “fourth positron state” and the “squeezed positronium state” which were proposed by Ole E. Mogensen.
  • Nozomi Konishi, Kohjiro Hara, Akihiko Kudo, Tadayoshi Sakata
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2159-2162
    Published: 1996
    Released: June 28, 2006
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    The electrochemical reduction of N2O to N2 on gas-diffusion electrodes (GDEs) modified by Pt and Ni electrocatalysts at room temperature was studied. The Faradaic efficiency for the reduction of N2O was 100%, even for a low concentration of N2O gas at a low current density. When 0.6 mmol of N2O was electrolyzed, 99.7% of the N2O was decomposed at a constant current density of 6.4 mA cm−2. The Faradaic efficiency of N2O reduction was increased by using pulse electrolysis.
  • Yukio Yamamoto, Yoichi Yoshida, Seiichi Tagawa
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2163-2166
    Published: 1996
    Released: June 28, 2006
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    Inclusion complexation of 4-biphenylcarboxylate (BPC), 4-biphenylacetate (BPA), and 4-biphenylsulfonate (BPS) with α-cyclodextrin (α-CD) has been investigated by a pulse radiolysis method. The one-electron reduction of BPC and BPS by the hydrated electron was effectively retarded by the 1 : 2 complexation with α-CD as well as by the 1 : 1 complexation with β-CD investigated in our previous study. The retarding effect of α-CD was observed at much higher host concentrations than that of β-CD. No apparent effect of α-CD was observed on the one-electron reduction of BPA, but the effect of β-CD was similar to those for BPC and BPS. The result indicates that the methylene group of BPA sterically inhibits the formation of the 1 : 2 complex. The rate constant for the one-electron reduction of the 1 : 2 complex of BPC with α-CD was 1.0 × 109 dm3 mol−1 s−1, which is smaller than that of the 1 : 1 complex with β-CD, 2.5 × 109 dm3 mol−1 s−1. It is demonstrated that the biphenylyl group of the 1 : 2 complex with α-CD is screened from the attack of the hydrated electron more effectively than that of the 1 : 1 complex with β-CD.
  • Osamu Ito, Yoshiko Sasaki, Akira Watanabe, Kunio Mochida
    1996 Volume 69 Issue 8 Pages 2167-2171
    Published: 1996
    Released: June 28, 2006
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    The electron transfer from cyclic organogermanium compounds to photo-excited C60 in benzonitrile solution has been investigated by the 532 nm-laser flash photolysis with observation of the transient absorption bands in the near-IR region. The transient absorption band of the C60 triplet state (TC60*) appeared at 730 nm immediately after nanosecond laser exposure. With the decay of TC60*, the absorption bands of the radical anion of C60 appeared at 1070 nm, showing that the electron transfer takes place from organogermanium compounds to TC60*. The efficiencies and rates of the electron-transfer reactions vary with ring size of the germanium compounds.
  • Shigeo Sasaki, Hiroshi Maeda
    1996 Volume 69 Issue 8 Pages 2173-2178
    Published: 1996
    Released: June 28, 2006
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    A new experimental method to measure the diffusion coefficients of interacting particles in porous silica is described. The diffusion behavior of NaNO3 from a porous silica sphere into a solution of NaCl was found to be very sensitive to the cross diffusion term when the concentration ratio of NaCl to NaNO3 was high. The diffusion behavior of NaCl, KNO3, and KI from the inside to the outside of the sphere was also examined. Theoretical equations to analyze the cross diffusion flows of interacting particles were derived. The cross diffusion coefficient of NaNO3 and NaCl as well as the diffusion coefficients NaNO3, NaCl, KNO3, and KI in porous silica were evaluated from the present experimental results. The obtained diffusion coefficients were found to be about one third of those in solution. The diffusion behavior of NaNO3, NaCl, KNO3, and KI from spherical polyacrylamide gel was also examined for comparison.
  • Masayoshi Maehara, Yoshio Suzuki, Hideki Mizobe, Hiroshi Kawano, Yoshi ...
    1996 Volume 69 Issue 8 Pages 2179-2183
    Published: 1996
    Released: June 28, 2006
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    The Raman active inter- and intramolecular vibrations of tetramethylpyrazine and trihydrated tetramethylpyrazine crystals were studied under various pressures between 1 atm and 5 GPa. The pressure effect on the Raman frequency due to the intermolecular vibrations indicates that a tetramethylpyrazine crystal undergoes phase transitions under about 1.2 and 2.2 GPa and a trihydrated tetramethylpyrazine crystal undergoes phase transition under about 3.5 GPa. The pressure effect on the Raman frequency due to the intramolecular vibrations indicates that the pressure-induced frequency shift for the skeletal vibrations of trihydrated tetramethylpyrazine is larger than the corresponding shift of unhydrated tetramethylpyrazine, while the shift for the characteristic vibrations of the methyl groups of trihydrated tetramethylpyrazine is smaller than the corresponding shift of unhydrated tetramethylpyrazine. These observations suggest that the attractive force induced by the hydration plays a considerable role in the intermolecular interaction under high pressure in the molecular crystal, in addition to the repulsive force. The change of electron distribution, which strengthens the chemical bonds of the pyrazine ring more strongly than the bonds in the methyl groups, takes place with increasing pressure.
  • Hironobu Umemoto, Nobuhiro Ohsako
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2185-2189
    Published: 1996
    Released: June 28, 2006
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    The deactivation processes of Cd(53P1) and Cd(53P0) by H2 and D2 were examined by employing a laser excitation-depletion technique. The concentration of the ground-state Cd(51S0) atoms was measured in both the presence and absence of an intense saturable pump laser beam. In the presence of a pump laser, the concentration decreased in accordance with the production of CdH(CdD). From this decrease, the branching ratios for the production of CdH(CdD) could be determined. The depletion was unaffected when N2 was added. This suggests that the branching ratios are the same for Cd(53P1) and Cd(53P0), although the production of CdH(CdD) is endothermic for Cd(53P0). The branching ratios were 0.81 ± 0.04 for H2 and 0.76 ± 0.06 for D2. The efficient production of CdH(CdD) from not only Cd(53P1), but also Cd(53P0), can be accounted for by correlational considerations.
  • Nobuhiro Saito, Noriyuki Sonoyama, Tadayoshi Sakata
    1996 Volume 69 Issue 8 Pages 2191-2194
    Published: 1996
    Released: June 28, 2006
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    The excitation and emission spectra of CaWO4, MgWO4, PbWO4, ZnWO4, and CaMoO4 were analyzed by a configurational coordination model. The spectral line shapes simulated by a configurational coordination model with a singlet ground state and an excited triplet state well explained the line shape of the luminescence spectra and the line shape at the rising part of the excitation spectra of these salts at room temperature. The energy level of the excited triplet state and the reorganization energies at the ground sate and the triplet state were determined. It was concluded that the potential curve at the excited state becomes shallower than that at the ground state for these systems.
  • Tatsuji Sano, Osamu Matsuoka
    1996 Volume 69 Issue 8 Pages 2195-2199
    Published: 1996
    Released: June 28, 2006
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    A super configuration–interaction method is applied to a direct calculation of orthogonal localized molecular orbitals (LMO). Its iterative procedure converges quadratically, retaining the initial forms of the LMOs. When the basis sets of large sizes are employed for the calculation, Davidson’s diagonalization method can be adopted beneficially, where the time-consuming four-index transformation of LMO integrals is replaced by simpler two-index transformations. Test calculations using double-zeta basis sets are reported in detail for H2CO (formaldehyde). B2H6 (diborane), C3H4(1-propyne [metylacetylene]), and cytosine. The implication of the method concerning macromolecular calculations is discussed.
  • Muhammad Q. Ehsan, Yasunori Ohba, Seigo Yamauchi, Masamoto Iwaizumi
    1996 Volume 69 Issue 8 Pages 2201-2209
    Published: 1996
    Released: June 28, 2006
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    The characteristic features of the electronic structure of some trigonal bipyramidal (tbp) copper complexes of the quadridentate tripodal nitrogen donor ligands, tris(2-aminoethyl)amine (tren) and tris(2-dimethylaminoethyl)amine (trenMe6), with different ligands at the fifth coordination position of tbp were studied in a powder form doped in diamagnetic zinc complexes by EPR and ENDOR. EPR shows that the copper complexes of tren and trenMe6 have a ground state with a dz2 unpaired electron orbital, and that some of the complexes are distorted from a trigonal symmetry to rhombic, to the contrary to expectations from the molecular formula. It is shown that a small structural or ligand-field distortion would give a recognizable spectral deviation from trigonal symmetry. It should be noticed that the hyperfine couplings of all the coordinating nitrogen atoms in each complex were observed by ENDOR, and that they were useful for calrifying the characteristic features of the electronic structures of the tbp complexes. The ligand fields at the fifth coordination position of tbp affects all of the coordination bonds as well as the spin distribution among the ligands. These ligand field effects on the electronic structures are discussed in reference to the ligand field parameters obtained by an EPR analysis. It is also shown that the ENDOR analysis well predicts the sp ratios of the coordinating orbitals of nitrogens, consistent with those obtained from the X-ray structural data on the complexes.
  • Ok-Sang Jung, Du Hwan Jo, Young-A Lee, Hee Kwon Chae, Youn Soo Sohn
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2211-2214
    Published: 1996
    Released: June 28, 2006
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    The preparation and characterization of [Co(μ-bpym)(dbbq)2] and [{Co(dbbq)2}2(μ-bpym)] (bpym = 2,2′-bipyrimidine; dbbq = 3,6-di-t-butyl-1,2-benzoquinone) have been established. The temperature-dependent magnetic moments (100—400 K) and variable-temperature near-infrared (NIR) absorption spectra are presented to show that the title complexes exhibit an equilibrium via a catechol to a cobalt intramolecular electron transfer. At temperatures below 200 K the mononuclear complex [Co(μ-bpym)(dbbq)2] has a charge distribution of [CoIII(μ-bpym)(dbcat)(dbsq)] (dbsq = 3,6-di-t-butyl-1,2-semiquinonato; dbcat = 3,6-di-t-butylcatecholato), whereas at temperatures beyond 290 K the mononuclear complex is predominantly in the [CoII(μ-bpym)(dbsq)2] form. From 200—290 K a mixture of Co(III) and Co(II) redox isomers exists at equilibrium in the solid state. In particular, a thermal analysis of a solid sample of the mononuclear complex discloses that the transition for the Co(III)/Co(II) is accompanied by a change in the heat content of 36 kJ mol−1, which may be closely related to the band at 3878 cm−1, assigned as a dbcat to Co(III) charge transfer. In striking contrast, the dinuclear complex [{Co(dbbq)2}2(μ-bpym)] is locked in a charge distribution of [{CoII(dbsq)2}2(μ-bpym)] when the temperature is 100—400 K.
  • Masashi Hojo, Hiroshi Hasegawa, Zhidong Chen
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2215-2220
    Published: 1996
    Released: June 28, 2006
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    The conductance increased linearly up to the equivalence point in the conductometric titration of diphenyl hydrogenphosphate ((PhO)2PO(OH)) with triethylamine (Et3N) in DMF at 25 °C. However, it was found that the conductometric titration of phenyl dihydrogenphosphate (PhOPO(OH)2, 1.0 × 10−3—1.0 × 10−2 mol dm−3) gave a maximum at the half-equivalence point (CHA : [Et3N] = 1 : 1/2) and not the linear curve to the equivalence point. Phosphoric (PO(OH)3), phenylphosphonic (PhPO(OH)2), and vinylphosphonic (CH2CHPO(OH)2) acids also gave maxima at the half-equivalence points. The appearance of maxima was explained by homoconjugation between the acid (HA) and the conjugate anion (A) upon neutralization with the base (B) in DMF : B + 2 HA BH+···HA2. Dibutyl hydrogenphosphate ((n-BuO)2PO(OH)) of higher concentrations also gave a (small) maximum at the half-equivalence point, while dimethylphosphinic acid ((CH3)2PO(OH)) gave no maximum in DMF. In less basic solvents, acetonitrile and benzonitrile, even diphenyl hydrogenphosphate, gave a maximum. The cause for the appearance of maxima at the half-equivalence point in DMF is discussed from the viewpoint of the basicities of the conjugate anion (A) and the number of hydrogen bondings involved in the homoconjugation reaction. The ion-pair and quadrupole (the dimer of ion pairs) formation constants of the organophosphorus acids in DMF were obtained by conductometry. The equilibrium concentration of the dimer (H2A2) of PhOPO(OH)2 was found to exceed that of the ion pair (HA) at >1.6 × 10−3 mol dm−3 of the acid.
  • Takeshi Yamamura, Masaya Arai, Tsutomu Yamane, Takeshi Ukai, Masato Us ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2221-2230
    Published: 1996
    Released: June 28, 2006
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    The structure of [(Boc–Cys1–Pro–Leu–Cys4–Gly–Ala–OMe)Hg], 1, in DMF(-d7) and DMSO(-d6) solutions was studied by X-ray absorption fine structure (XAFS), rotating frame nuclear Overhauser effect spectroscopy (ROESY), distance geometry (DG), molecular dynamics (MD), and restrained molecular dynamics (RMD). The XAFS study clarified that the inorganic center of compound 1 adopts a linear coordination with r(HG–S) = 2.33 Å. The NMR experiment revealed 33 atom approximate distances for the 1H-1H pairs of the main chain loop, including the side chains of the cysteinyl residues (ROESY). By a complementary use of DG, plain MD, and RMD for distance information from NMR as well as XAFS, we established that compound 1 adopts a new type of hybridized turn structure. The compound has two hydrogen bonds, Cys1 S-Leu HN and Pro CO-Cys4 HN, among which the former is common to the core sites in proteins, Cysi–X–Y–Cysi+3/M2+ (Zn2+, Fe2+), whereas the latter is common to the mirror image of the γ turn structure in proteins.
  • Abdul Khalegh Bordbar, Ali Akbar Moosavi-Movahedi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2231-2234
    Published: 1996
    Released: June 28, 2006
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    The interaction of dodecyltrimethylammonium bromide, as a cationic surfactant, with bovine hemoglobin, as a biopolymer, has been investigated at different temperatures by an equilibrium dialysis technique. The obtained binding isotherms have been analyzed and interpreted by the Wyman binding potential model and other thermodynamic parameters which have been extracted on the basis of this model. A new method of analysis for evaluating the binding isotherms and estimating the free energy change, ΔGt, per mole of ligand has been proposed.
    The unusual behavior of the Scatchard plot at 300 K was analyzed in terms of two sets of binding sites. The first set of binding sites was considered as electrostatic and the second as hydrophobic. The free energy of interaction () from the Wyman model was also resolved according to electrostatic and hydrophobic binding free energies.
  • Kazuaki Shimada, Minoru Yamaguchi, Tohru Sasaki, Kenji Ohnishi, Yuji T ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2235-2242
    Published: 1996
    Released: June 28, 2006
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    Treatment of dihalomethane derivatives, chloroform, or sodium trichloroacetate with elemental selenium in the presence of NaH and an excess amount of an amine gave the corresponding selenoamides, selenoureas, and bis(selenocarbamoyl) triselenides in modest yields. These products were afforded from reactive intermediates related to “selenocarbonyl halides” and “selenophosgenoids” generated by the reaction of dichloromethanide ions and trichloromethanide ion with N-alkylated aminopolyselenide species (R2N–(Se)n).
  • Kiyoshi Tanaka, Tatsuya Imase, Satoru Iwata
    1996 Volume 69 Issue 8 Pages 2243-2248
    Published: 1996
    Released: June 28, 2006
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    3,4-Dihydroisoquinoline N-oxide (1) cycloadded with methyl 4,4,4-trifluoro-2-butenoate at 20 °C to give a mixture of the cycloadduct with a 1,10b-cis-configuration, methyl (1R*, 2R*, 10bR*)-2-trifluoromethyl-1,5,6,10b-tetrahydro-2 H-isoxazolo[3,2-a]isoquinoline-1-carboxylate, and its stereoisomer with a 1,10b-trans-configuration in a ratio of 3 : 1. Nitrone 1 cycloadded with methyl 2-butenoate to afford the cycloadduct with a 1,10b-cis-configuration exclusively. The stereoselectivity in the cycloadditions was reproduced by calculations of the transition structures by the PM3 method.
  • Ashraf A. Aly, Nasr K. Mohamed, Alaa A. Hassan, Aboul-Fetouh E. Mourad
    1996 Volume 69 Issue 8 Pages 2249-2252
    Published: 1996
    Released: June 28, 2006
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    3,4,5,6-Tetrachloro-1,2-benzoquinone (o-CHL) reacted with N,N′-dicyclohexyl-1,2-ethanediimine 1a to give a transient condensation product, which underwent [4 + 2]cycloaddition reaction with another molecule of 1a. In a different manner, utilizing N,N′ -diaryl-1,2-ethanediimines 1b,c as a dienophile led to an initial production of substituted o-CHL, followed by a [4 + 2]cycloaddition reaction with another molecule of 1b,c. A similar behavior was observed on the reaction of N,N′-di(alkyl/aryl)-p-xylenediimines 1af with the same acceptor.
  • Lionel Glendenning, Tomoji Igarashi, Takeshi Yasumoto
    1996 Volume 69 Issue 8 Pages 2253-2263
    Published: 1996
    Released: June 28, 2006
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    Prymnesins are potent ichthyotoxic and hemolytic glycoside molecules isolated from the red tide alga Prymnesium parvum. Their unique molecular structure is conformationally rich with a number of key torsional bonds which were probed with contemporary conformational searching techniques in order to describe the three-dimensional structure of the prymnesin molecule. Important topological features include a backbone twist of 60° and an elongation length of 39.5 Å from ring “A” to ring “N” for the prymnesin-2 molecule in the nOe preferred conformation. An appreciation of these and other molecular structural and energetic features determined by computational techniques were examined with the aim of understanding how prymnesin-2 exhibits it’s potent biological activity in relation to these inherent structural traits.
  • Seizo Tamagaki, Jun Narikawa, Atsushi Katayama
    1996 Volume 69 Issue 8 Pages 2265-2268
    Published: 1996
    Released: June 28, 2006
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    (2-Mercaptoethyl)amino-attached cyclodextrin provides a highly enantioselective environment during the transformation of phenylglyoxal into (S)-mandelic acid, although simple inclusion into native α-,β-, and γ-cyclodextrins and their 2-hydroxypropyl and methyl variants is not sufficient to cause appreciable asymmetric induction.
  • Yasumasa Fukushima
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2269-2274
    Published: 1996
    Released: June 28, 2006
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    Catalytic activity and enantioselectivity of Poly(Asp–Leu–His–Leu–Ser–Leu) with a β-sheet structure for the hydrolysis of chiral phenylalanine p-nitrophenyl esters were compared with those of the peptide hexamer, under various conditions. The relationship between the β-sheet structure of the polypeptide and the hydrolytic properties was also investigated. Both the activity and the enantioselectivity for the polypeptide were higher than those for the peptide hexamer. The activity increased with pH, but the enantioselectivity was independent of pH. An increase of ethanol content in reaction solution led to a relatively lower rate constant and a higher enantioselectivity. The enantioselectivity decreased with increasing temperature; the activity increased to 25 °C and it reduced above 35 °C. Because the nucleophilicity of the polypeptide and the concentration effect of the substrate reduced by a decrease of the β-sheet content with temperature, the regular secondary structure may play an important role in these hydrolytic reactions. In addition, the efficient hydrolytic activity and the enantioselectivity were derived from activation parameters. The polypeptide may provide a good model for studying the relationship between enzymatic activity and steric structural formation.
  • Tadeusz Marek Krygowski, Marcin Wisiorowski, Kazuhide Nakata, Mizue Fu ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2275-2279
    Published: 1996
    Released: June 28, 2006
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    Analysis of the molecular geometry of the ring in 18 exocyclically substituted benzylic cation derivatives shows that an increase of delocalization of the positive charge over the ring is associated with a considerable decrease of its aromatic character. Separation of the aromatic character into energetic and geometric terms allows one to conclude that the effect of dearomatization due to delocalization of the positive charge in the ring is mostly reflected in the geometric term, i.e. by an increase of the alternation of bond lengths in the ring.
  • Yasunori Moritani, Chiaki Fukushima, Toshikazu Miyagishima, Hiroshi Oh ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2281-2286
    Published: 1996
    Released: June 28, 2006
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    trans-α,β-Dibenzyl-γ-butyrolactone lignans were synthesized by stereoselective reduction of α-benzylidene-β-benzyl-γ-butyrolactones using NaBH4–NiCl2. The reduction is found to proceed via conjugate addition of a hydride to an α-benzylidene-β-benzyl-γ-butyrolactone and the stereoselective protonation of the resulting metal enolate. The stereoselectivity would be brought about by the conformational rigidity of the phenyl moiety of the α-benzyl group induced by 1,3-allylic strain.
  • Teruo Umemoto, Masayuki Nagayoshi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2287-2295
    Published: 1996
    Released: June 28, 2006
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    A series of N,N′-difluoro-1,4-diazoniabicyclo[2.2.2]octane salts were synthesized in a pure form by the fluorination of 1,4-diazabicyclo[2.2.2]octane with F2 diluted with N2 in the presence of a Brønsted acid in fluoro alcohol or acetonitrile or by fluorination followed by a treatment with a different Brønsted or Lewis acid. Their complete structural assignment was made based on spectral and elemental analyses of the isolated crystals. A great through-bond interaction between the two N–F’s of the salt was observed on 19F NMR. An assessment was made of the usefulness of N,N′-difluoro-1,4-diazoniabicyclo[2.2.2]octane bis(triflate), bis(HSO4), bis(BF4), and bis(SbF6) salts for electrophilic fluorination; the bis(BF4) salt was demonstrated to be widely applicable as a highly reactive and easy-to-handle fluorinating agent. Thus, the bis(BF4) salt readily fluorinated activated aromatics, active methylene compounds or their salts, substituted styrenes, and vinyl acetates under mild conditions. It was shown that one N–F of the salt was effective for fluorination and that the other N–F played a role to activate fluorination through the bonds. Thus, the reaction mechanism was discussed, and fluorination followed by an immediate intramolecular one-electron transfer was suggested.
  • Chiaki Kuroda, Kunihito Ito
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2297-2303
    Published: 1996
    Released: June 28, 2006
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    Fluoride-promoted intramolecular cyclization of ethyl 6-(2-oxocyclohex-1-yl)-2-(trimethylsilylmethyl)hex-2-enoate afforded ethyl 2-(1-hydroxybicyclo[4.4.0]decan-2-yl)acrylate as the major product, together with tricyclic α-methylene-γ-lactone, a model compound of cadinanolides. The former product was also converted to γ-lactone. The cyclization reaction promoted by TiCl4 gave the hydroxy ester and its dehydrated product. Both Lewis acid- and fluoride-promoted cyclizations gave a trans-decaline system mainly. This stereoselectivity is completely different from that of Reformatsky cyclization observed by Dreiding and co-workers.
  • Takeo Yamaguchi, Yoshiya Miyamoto, Shigeyuki Terada
    1996 Volume 69 Issue 8 Pages 2305-2308
    Published: 1996
    Released: June 28, 2006
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    The effects of 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) on the hemolysis of human erythrocytes were examined. To hemolyze, the erythrocytes were exposed to high pressure (200 MPa), heating (52 °C), or a hypotonic medium. Upon EDC treatment, the hemolysis induced by high pressure or heating was completely suppressed, whereas osmotic hemolysis was enhanced. In EDC-treated erythrocytes, high-molecular-weight aggregates of membrane proteins were formed by cross-linking of the membrane with the cytoskeleton, in addition to that of membrane proteins themselves. In such a cross-linking reaction, however, iron(II) in hemoglobin and thiol groups in membrane proteins remained stable. Although phosphate transport via band 3 was considerably suppressed by EDC, the intracellular K+ concentration was almost constant. These results suggest that high-pressure- or heat-induced hemolysis, compared with osmotic hemolysis, is suppressed by a stabilization of the cytoskeletal network.
  • Kazuo Okumura, Akio Ito, Hiroyuki Saito, Yutaka Nakamura, Chung-gi Shi ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2309-2316
    Published: 1996
    Released: June 28, 2006
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    The practical synthesis of a unique dehydropentapeptide (2), the common main skeleton of thiostrepton macrocyclic peptide antibiotics, A10255G and J, is described. Peptide 2 is constructed from a novel 2-[(Z)-1-amino-1-propen-1-yl]oxazole-4-carboxylic acid, 2-(1-aminomethyl)- and 2-[(S)-1-aminoethyl]thiazole-4-carboxylic acid residues, besides L-threonine and dehydroalanine residues at the N- and C-termini, respectively. First, the general syntheses of various 2-[(Z)-1-amino-1-alken-1-yl]oxazole-4-carboxylic acid derivatives (11) and preparation of N-terminal dehydrodipeptides (17) containing the acid (11a) were done. Subsequent coupling of 17 with the C-terminal tripeptide comprised of the above two 2-(aminoalkyl)thiazole-4-carboxylic acid moieties (22) and (23) and serine moiety (4), and final β-elimination were tried and gave the desired protected 2 [(P)-2].
  • Takashi Mochizuki, Satoshi Hayakawa, Koichi Narasaka
    1996 Volume 69 Issue 8 Pages 2317-2325
    Published: 1996
    Released: June 28, 2006
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    Sodium arenesulfinates are oxidized with manganese(III) 2-pyridinecarboxylate or ammonium cerium(IV) nitrates to generate sulfonyl radicals, which add to olefinic compounds to afford sulfonylated products in good yield. When 1-vinyl cyclic alcohols are used as sulfonyl radical acceptors, sulfonylation proceeds with ring-enlargement. Diphenylphosphinyl radical can also be generated by treating diphenylphosphine oxide with manganese(III) 2-pyridinecarboxylate and reacts with olefinic compounds, giving phosphinylated products.
  • Shigehiro Yamaguchi, Kohei Tamao
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2327-2334
    Published: 1996
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    The purpose of this work is the theoretical elucidation of the origin of the unusually long UV-vis absorption maximum, λmax = 398 nm, of 3,3′,4,4′-tetraphenyl-2,2′-bisilole, which we have observed recently. Several semiempirical and ab initio calculations have been performed for some model compounds, silole and 2,2′-bisilole, in comparison with their carbon analogs, cyclopentadiene and 1,1′-bi-1,3-cyclopentadiene, respectively. The PM3 calculations indicate that the silole ring has a considerably low-lying LUMO, arising from σ*–π* conjugation between a π-symmetry σ* orbital of the exocyclic σ bonds on silicon and a π* orbital of the butadiene skeleton. Ab initio calculations at the CIS/6-31G* level of theory suggest that the experimental large differences in the absorption maximum in the UV-vis spectra between the bisilole and the bicyclopentadiene derivatives are ascribed also to the low-lying LUMO level of the bisilole compared with the bicyclopentadiene. It is further demonstrated that the σ*–π* conjugation is enhanced by the molecular distortions, twisting and folding, of the bisilole skeleton present in the X-ray structure, resulting in the lowering of the LUMO level. The calculated data are supported by the redox potentials of some representative compounds, as determined by cyclic voltammetry measurements. The σ*–π* conjugation and the low-lying LUMO would thus be the origin of the unusual optical properties of bisilole derivatives.
  • Toshinori Sato, Hiroyuki Akino, Yoshio Okahata
    1996 Volume 69 Issue 8 Pages 2335-2340
    Published: 1996
    Released: June 28, 2006
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    We newly prepared a polyion complex of DNA with lipoglutamide, N,N′-bis(18-hydroxy-7,10,13,16-tetraoxaoctadecyl)-L-glutamide hydrochloride (abbreviated to 2EO4C6N+). Formation and characterization of the DNA/2EO4C6N+ complex were investigated by elemental analysis, melting temperature, and light-scattering measurements. Compaction of DNA by binding with the cationic 2EO4C6N+ was seen by multi-angle light scattering. Aggregation of the DNA/2EO4C6N+ complex was significantly depressed compared with the DNA complex without tetraethylene glycol. The DNA/2EO4C6N+ complex had low cytotoxicity and efficient internalization into tumor cells compared with native DNA.
  • Chan Sik Cho, Shin-ichi Motofusa, Kouichi Ohe, Sakae Uemura
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2341-2348
    Published: 1996
    Released: June 28, 2006
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    Triarylstibines react with α,β-unsaturated ketones and aldehydes in acetic acid at room temperature in the presence of AgOAc and a catalytic amount of Pd(OAc)2 to afford the conjugate addition products (the formal hydroarylated compounds to an olefinic part) in good yields. In contrast, diarylantimony chlorides, arylantimony dichlorides, and diphenylantimony acetate react with the enones and enals even in the absence of AgOAc to afford the same products in higher yields compared with those from triarylstibines. These are new C–C bond-forming reactions using arylantimony(III) compounds in which the formation of a palladium enolate or a trivalent antimony enolate is proposed as an intermediate.
  • Juzo Nakayama, Atsuko Kimata, Hideki Taniguchi, Fumihiko Takahashi
    1996 Volume 69 Issue 8 Pages 2349-2354
    Published: 1996
    Released: June 28, 2006
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    A sulfur ylide intermediate, produced by a 1,3-dipolar cycloaddition of 1,3-benzodithiole-2-thione (5) with benzyne, was successfully trapped by hydrogen chloride to give a novel tetracyclic sulfonium salt, 9aH-9,10-dithia-4b-thioniaindeno[1,2-a]indene chloride (7), in good yield when benzyne was generated by the thermolysis of 2-carboxybenzenediazonium chloride (4). The reaction of ethylene trithiocarbonate with excess 4 provided a convenient one-pot synthesis of 7 in large quantities. The reduction of 7 with NaBH4 gave a novel ring compound, dibenzo[d,g][1,3,6]trithiocin (15), in 95% yield, while alkaline hydrolysis produced the 12-oxide derivative of 15. The treatment of 7 with t-BuOK gave 6,6′-bi(dibenzo[d,g][1,3,6]trithiocinylidene) in 84% yield. Also described are the reactions of benzyne with related compounds of 5.
  • Yukie Mori, Naho Yamada, Miho Kanazawa, Yumiko Horikoshi, Yuka Watanab ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2355-2359
    Published: 1996
    Released: June 28, 2006
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    On applying pressure with a press in the solid state, the title compounds undergo homolysis of the central C–C bond to give green-colored radicals. X-Ray structure analysis for p-chloro derivative showed that the central C(2)–C(2′) bond was not elongated but had a normal distance (1.576 Å) as a hexa-substituted Csp3–Csp3 bond. The amount of the radical formed by mechanical energy depended on the substituents on the 2-phenyl rings and on the solvent of crystallization. As for the crystals containing no solvent, p-bromo and p-chloro derivatives showed higher reactivity than the unsubstituted compound, probably due to smaller dissociation enthalpy. The radical dissociation was suppressed by the presence of some solvent of crystallization. In the solvated crystals, the excess energy supplied by external mechanical energy would be transferred mainly to vibrational modes of the solvent molecules rather than to the substrate.
  • Jun-ichi Tateiwa, Keiji Hashimoto, Takayoshi Yamauchi, Sakae Uemura
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2361-2368
    Published: 1996
    Released: June 28, 2006
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    The Prins reaction of styrenes with paraformaldehyde or 1,3,5-trioxane in toluene in the presence of cation-exchanged montmorillonite (Mn+-mont), which worked as a Brønsted acid catalyst, at 80 °C produced 4-aryl-1,3-dioxanes selectively in up to 99% isolated yield with a turnover number of up to 5.9 × 102. Among the examined 21 Mn+-monts, Ce3+- and Fe3+-monts were revealed to be quite effective. Regeneration of the catalyst was confirmed with the Ce3+-mont, which could be effectively recycled at least three times. Many lanthanide metal ion-exchanged montmorillonites (Ln3+-monts) were prepared and characterized by X-ray powder diffraction (XRD) and temperature-programmed desorption of ammonia gas (NH3-TPD) methods.
  • Zhi-Chang Wang, Jin Yu, Yong-Li Yu
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2369-2374
    Published: 1996
    Released: June 28, 2006
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    A comparative study of the mutual separation characteristics and mechanism was made for neighboring rare-earth elements La, Ce, Pr, and Nd from their binary chloride mixtures and oxide mixtures using a chemical vapor-transport reaction under a suitable temperature and pressure gradient. The separation factors, expressed as the atomic ratios for the resulting chlorides, were observed within 6 h up to 21.4 for La : Ce, ≥100 for Pr : Ce, and 1.84 for Pr : Nd from the oxide mixtures; however, they were only 12.3 for La : Ce, 5.79 for Pr : Ce, and 1.32 for Pr : Nd from the chloride mixtures under identical reaction conditions, using AlCl3 as the sole complex former. It was also observed for the mutual separation from the oxide mixtures that the separation factors increased when KCl was added as another complex former, but decreased several times when either without chlorine in the carried gas, or without active carbon in the raw material, or under a poor vapor-transport condition. These results provide evidence that this reaction for the oxide mixtures would mainly be the combination of a carbothermic reduction-chlorination of the oxides, complexation of the chlorides, and transportation of the vapor complexes.
  • Takahiro Seki, Ryo-ichi Fukuda, Makoto Yokoi, Takashi Tamaki, Kunihiro ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2375-2381
    Published: 1996
    Released: June 28, 2006
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    Monolayers of amphiphilic poly(vinyl alcohol)s and related low-molecular-mass compounds containing photochromic azobenzene (Az) were spread on a water surface. Their photomechanical responses induced by photoirradiation of UV (365 nm) and visible (436 nm) light were investigated. Illumination by UV light induced area expansion of Az monolayers up to ca. three times in magnitude, which strongly depended on the material, monitoring surface pressure, and subphase conditions. The expanded film of these molecular films reverted to the original area upon illumination with visible light. Use of a polymeric material was found to be advantageous to attain sufficient mechanical strength for full reproducibility and faster response. At a fixed area, reversible surface pressure changes were observed upon alternate UV and visible light illumination, and at 10—15 mN m−1 with the 6Az10-PVA monolayer the changes could be visualized plainly by watching motions of camphor grains. In the case of an Az amphiphile having the dissociative carboxylic acid head group, the photoresponsiveness was altered by pH changes and addition of Cd2+ ion in the subphase. Variations in the magnitude and response time of the photoinduced deformation were related to the packing state of Az monolayers evaluated by UV-visible absorption spectroscopy at the air–water interface.
  • Satoru Yada, Tomoaki Sasaki, Makoto Hiyamizu, Yuzuru Takagi
    1996 Volume 69 Issue 8 Pages 2383-2386
    Published: 1996
    Released: June 28, 2006
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    Pd metal catalysts were prepared by the reaction of palladium(II) chloride with sodium aluminate at pH 6—10. The Pd catalysts prepared at pH 10 contained only small amounts of Al (0.14 wt%), were the most thermally stable, and kept large specific surface areas and high catalytic activities in the hydrogenation of nitrobenzene even after hydrogen treatment at high temperatures up to 380 °C.
  • Hyun-Min Kim, Fumiaki Miyaji, Tadashi Kokubo, Masahiko Kobayashi, Taka ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2387-2394
    Published: 1996
    Released: June 28, 2006
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    The formation of biologically active bonelike apatite on the surfaces of glasses and glass-ceramics is an essential condition for their bonding living bone. In the present study, apatite formation on the surfaces of M2O–TiO2–SiO2 (M = Na, K) glasses was examined in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma in order to evaluate their bioactivity. While none of the Na2O–TiO2–SiO2 ternary glasses formed the surface apatite, K2O–TiO2–SiO2 glasses, not only as SiO2-rich glasses but also as TiO2-rich glasses, formed the apatite. The alkali ions in the glasses exchanged with H3O+ ions in the fluid. The TiO2-rich or SiO2-rich hydrogel which was formed on the surfaces of the glasses induced apatite nucleation. The increased degree of the supersaturation of the fluid with respect to the apatite due to the increase in pH provided favorable conditions for apatite nucleation. This indicates that alkali titanates as well as alkali silicates can be basic components of bioactive glasses.
  • Hu Yan, Hung-Jen Wang, Sanggono Adisasmito, Naoki Toshima
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 8 Pages 2395-2401
    Published: 1996
    Released: June 28, 2006
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    Poly(o-aminobenzoic acid) and copolymers of o-aminobenzoic acid and aniline were synthesized as excellent candidates for the precursor of polyaniline. The reaction conditions were optimized with emphasis on the isolated yield. The polymers were characterized by a number of techniques including infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, thermal analyses, and scanning electron microscopy. The yield of poly(o-aminobenzoic acid) was remarkably improved by addition of sodium hydroxide (an equivalent mole amount to the monomer) into the reaction system. Spectroscopic results indicate that the polymer has principally an Emeraldine structure. The copolymers were also obtained at high yield by addition of sodium hydroxide (an equivalent mole amount to o-aminobenzoic acid). The polymerization mechanism was briefly discussed on the basis of the pH effect upon the yield and easy elimination of the carboxyl group via a ring structure. The copolymer as well as poly(o-aminobenzoic acid) were found to be the precursors to produce polyaniline with elimination of carbon dioxide by heat treatment.
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