Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 77 , Issue 6
Showing 1-26 articles out of 26 articles from the selected issue
Award Accounts
The Chemical Society of Japan Award for Young Chemists for 2002
  • Takahiro Hohsaka
    2004 Volume 77 Issue 6 Pages 1041-1049
    Published: 2004
    Released: June 09, 2004
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    Incorporation of nonnatural amino acids into specific positions of proteins was achieved by using extended codons such as CGGG four-base codon. Aminoacyl-tRNAs having nonnatural amino acids and four-base anticodons were prepared and added to an E. coli in vitro translation system together with mutated genes containing four-base codons. Product analysis of the in vitro translation demonstrates that four-base codons are successfully decoded by the corresponding aminoacyl-tRNAs and, as a consequence, nonnatural amino acids are incorporated into desired positions of proteins. By using two independent four-base codons, incorporation of two nonnatural amino acids into single proteins was achieved for the first time. Five-base codons were also found to be available for the nonnatural amino acid incorporation. Extension of the amino acid repertoire was investigated by using four-base codons, and a wide variety of nonnatural amino acids were incorporated into proteins. According to the information on amino acid selectivity of ribosomes, novel fluorescently labeled nonnatural amino acids were designed and utilized for position-specific fluorescence labeling of proteins. The extended codon strategy will allow scientists to construct novel artificial proteins and biomolecular systems.
The Chemical Society of Japan Award for Young Chemists in Technical Development for 2002
  • Takeshi Araki
    2004 Volume 77 Issue 6 Pages 1051-1061
    Published: 2004
    Released: June 09, 2004
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    Metal organic deposition using trifluoroacetate (TFA-MOD) is one of the most promising approaches to YBa2Cu3O7−x superconductors. In this process, CuO nanocrystallites in calcined film never cause random orientation, which is a major problem in the other solution processes. A “quasi-liquid network” created during the firing process suppresses the influence of the nanocrystallites on the epitaxial structure. Impurities in the coating solution cause Y, Ba, and Cu compounds; a long calcining process leads to CuO grain growth in the YBa2Cu3O7−x film. These compounds deteriorate superconducting properties in two ways. One is a direct physical obstacle and the other is an indirect chemical influence. In the latter mode, non-stoichiometric area, which is induced by the compound, breaks up the quasi-liquid and the quasi-liquid changes into the other phase. Therefore, the actual YBa2Cu3O7−x film is thinner and the superconducting properties degrade. To reduce the influence of CuO nanocrystallites, excess humidity in the firing gas is effective because increased quasi-liquid consumes the nanocrystallites. However, the improvement is imperfect. A combination of highly purified coating solution and optimal calcining process is required to obtain high performance YBa2Cu3O7−x superconductors. With such a combination, YBa2Cu3O7−x films having critical current density of 5–7 MA/cm2 (77 K, 0 T) are routinely obtained.
Accounts
Organic and Biological
  • Kenso Soai, Takanori Shibata, Itaru Sato
    2004 Volume 77 Issue 6 Pages 1063-1073
    Published: 2004
    Released: June 09, 2004
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    Asymmetric autocatalysis occurs when a chiral product operates as an asymmetric catalyst for its own production. We have discovered an asymmetric autocatalytic reaction in the enantioselective addition of dialkylzinc to pyridine-3-carbaldehyde, where the product, 3-pyridyl alkanol, acts as an asymmetric autocatalyst. A diol, ferrocenyl alkanol, 5-pyrimidyl alkanol, and 3-quinolyl alkanol were also found to be asymmetric autocatalysts for the enantioselective isopropylation of the corresponding aldehydes. Of these compounds, 5-(2-alkynyl)pyrimidyl alkanol was the best asymmetric autocatalyst, and the asymmetric autocatalytic isopropylation of the corresponding pyrimidine-5-carbaldehyde proceeded quantitatively ( >99%), affording itself as a near enantiomerically pure ( >99.5% ee) chiral product. When an asymmetric autocatalyst with an extremely low ee was used, the asymmetric autocatalytic reaction proceeded along with amplification of the ee, and a highly enantiomerically enriched product was obtained. When the enantioselective isopropylation of pyrimidine-5-carbaldehydes was examined in the presence of chiral organic compounds with a very low ee acting as chiral initiators, then highly enantiomerically enriched 5-pyrimidyl alkanols were obtained. Their absolute configurations were dependent upon the slight excess of enantiomer in the chiral initiators. Chiral inorganic crystals, such as quartz and sodium chlorate, also act as chiral initiators. In conjunction with asymmetric autocatalysis, the chirality of organic compounds with a high enantiomeric excess has been correlated for the first time with the circularly polarized light and chiral inorganic crystals. Moreover, when an enantioselective isopropylation was examined in the absence of a chiral initiator, asymmetric induction above the detection level was observed in the product, with the ratio of the resulting predominant S- and R-isomers being almost equal. This result fulfills one of the conditions necessary for spontaneous absolute asymmetric synthesis.
Theoretical and Physical
  • Ryuichi Ikeda
    2004 Volume 77 Issue 6 Pages 1075-1100
    Published: 2004
    Released: June 09, 2004
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    Magnetic properties characteristic in 1-D systems were investigated in halogen-bridged mixed-valence and averaged-valence metal complexes by applying magnetic resonance techniques. Neutral-solitons and polarons formed from impurity amounts of paramagnetic Pt3+ and Pd3+ sites in 1-D chains were sensitively detected by the NMR relaxation measurement. Their rapid 1-D diffusion comparable to that in trans-polyacetylene was revealed in [MII(en)2][MVIBr2(en)2](ClO4)4 (M: Pt, Pd). From 13C NMR spectra and 1H NMR relaxation studies, [NiIIIX(chxn)2]X2 (X: Cl, Br) was shown to be in an averaged-valence state forming S = 1/2 1-D Heisenberg antiferromagnetic chains. [NiBr(chxn)2]Br2 revealed to have the largest exchange interaction so far reported, was expected to transform into a new state at low-temperatures below 100 K. From studies on thermal motions and phase transitions associated with the 1-D chain-structure in [Pt(en)2][PtX2(en)2](ClO4)4 (X: Cl, Br), the presence of the dynamic disorder of the Pt(en)2 chelate-ring conformation in a highly asymmetric double-well potential undetected by the X-ray diffraction was detected by the NMR relaxation measurement.
Headline Articles
Organic and Biological
Articles
Theoretical and Physical
  • Amir Abbas Rafati, Abdol-Khalegh Bordbar, Husein Gharibi, Mohamad-Kaze ...
    2004 Volume 77 Issue 6 Pages 1111-1116
    Published: 2004
    Released: June 09, 2004
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    The binding of a homologous series of n-alkyltrimethylammonium bromides to bovine serum albumin were measured in 2.7 mM phosphate buffer, pH 7.0, and at various temperatures using surfactant membrane selective electrodes as a fast and accurate method. The obtained binding isotherms have been analyzed and interpreted using the binding capacity concept, Hill equation and Wyman binding potential. The system behaved as a system with two sets of binding sites in all studied situations. The results represent the essential role of hydrophobic interactions in the first binding set. At high cationic surfactant concentrations, the occupation of the second binding set occurred, with an accompanying unfolding and exposure of numerous hydrophobic binding sites. However, this unfolding process occurred for the cationic surfactant at much higher concentrations than was required for sodium dodecyl sulfate. The Gibbs free energy change calculated on the basis of the Wyman binding potential concept decreases in the initial stages of binding and passes through a minimum, followed by occupation of the second binding set. The affinity of binding increased with increasing temperature, indicating an endothermic and essentially entropy driven process.
  • Hideyuki Nakayama, Shin-ichi Ohta, Iji Onozuka, Yuichi Nakahara, Kikuj ...
    2004 Volume 77 Issue 6 Pages 1117-1124
    Published: 2004
    Released: June 09, 2004
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    Many amorphous molecular systems prepared by vacuum deposition onto cold substrates turn into crystals directly without exhibiting glass transition when their temperature is raised. To study the mechanism of the crystallization from amorphous states, we monitored the increase of X-ray Bragg peaks at constant temperatures for fluoro-, chloro-, and bromobenzene samples. Data were analyzed by using the Johnson–Mehl–Avrami equation. It was found that the crystallization from amorphous states of these compounds progresses through the nucleation and crystal-growth processes similar to those observed for fused materials. However, slightly complicated behaviors were observed for molecules with larger substituents. These are considered to arise from the wide distribution of molecular arrangements that are stochastically generated in samples by the vapor deposition at low temperatures.
  • Naomi Takagami, Takayuki Ishida, Takashi Nogami
    2004 Volume 77 Issue 6 Pages 1125-1134
    Published: 2004
    Released: June 09, 2004
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    Low-temperature magnets derived from [M{N(CN)2}2(pm)] (M = FeII, CoII) have guest molecules incorporated in the clearance of the three-dimensional framework, where pm stands for pyrimidine. A pm molecule in [Fe{N(CN)2}2(pm)](pm) (1) was characterized as a guest by means of X-ray crystallographic analysis. The guest molecules as well as the host N(CN)2 skeletons are disordered in [Fe{N(CN)2}2(pm)](guest) (guest = EtOH (2), n-PrOH (3), 1/2 n-BuOH (4)) and also in [Co{N(CN)2}2(pm)](guest) (guest = EtOH (5), n-PrOH (6)). The ac and dc magnetic susceptibility measurements on randomly oriented polycrystalline samples of 16 revealed that they were weak ferromagnets (canted antiferromagnets) below TN. The single-crystal magnetization measurements clarified the TN’s and the cant angles at 2 K as follows: TN = 5.6 K, θ = 1.3°(H || c) for 1; TN = 3.3 K, θ = 16°(H || c) for 2; TN = ca. 2 K, θ = 7.1°(H || b) for 5. The magnetic ground state seems to be related with single-ion anisotropy of the metal ions and the spin canting may take place as a combined result of the axial or in-plane anisotropy and antiferromagnetic interaction. The incorporated guest molecule tunes the single-ion anisotropy of the host metal ions, and consequently the magnetic phase transition phenomena were drastically different depending on the guest molecules.
Analytical and Inorganic
  • Ki Won Cha, Hua Zi Huang
    2004 Volume 77 Issue 6 Pages 1135-1137
    Published: 2004
    Released: June 09, 2004
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    A simple, sensitive, and selective method for the determination of palmitate has been investigated on the basis of the fluorescence enhancement of Eu3+–TTA complex in the form of Eu3+–TTA–palmitate. An emission peak of Eu3+–TTA, which increased linearly with the addition of palmitate, occurs at 610 nm in aqueous solution with excitation at 306 nm. The linear curve of calibration ranges is from 1.0 × 10−6 to 6.0 × 10−6 M, and the detection limit is 5.0 × 10−7 M. The effects of foreign ions were studied. The method was applied to the determination of palmitate content in synthetic and beef fat samples.
  • Hai-Ying Jin, Shinji Ikari, Kimiko Kobayashi, Keisuke Umakoshi, Hideki ...
    2004 Volume 77 Issue 6 Pages 1139-1146
    Published: 2004
    Released: June 09, 2004
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    A pair of seven-coordinate oxorhenium complexes of N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (tpen), [ReIVO(tpen)](ClO4)2 (1) and [ReVO(tpen)](ClO4)3 (2), and its R-1,2-propylenediamine analogue (R-tppn), have been prepared. X-ray structural analyses indicate that the structure of complex cation in 1 is best described as a monocapped trigonal prism with the oxo ligand as a cap. The four pyridylmethyl nitrogen atoms are essentially planar. On the other hand, the structure of complex cation in 2 is approximated as a pentagonal bipyramid, in which the four pyridyl nitrogen atoms take a tetrahedrally distorted arrangement. The structural difference is discussed in terms of different d-electron numbers. The μeff value of 1 at 300 K is 1.99 B.M. which corresponds to S = 1/2, while 2 is diamagnetic. The complexes show a reversible redox wave (Re(IV/V)) at +0.31 V vs Ag/AgCl in 0.1 M (n-C4H9)4NPF6 acetonitrile solution. In acetonitrile–aqueous buffer solution (2 < pH < 12), in addition to a pH independent Re(IV/V) wave at +0.18 V vs Ag/AgCl, a pH-dependent quasi-reversible Re(III/IV) wave with a slope of −0.056 V/pH-unit was observed, indicating that the relevant Re(III) species is [Re(OH)(tpen)]2+. The weak absorption peaks of 1 (in acetonitrile) at 836 and 511 nm and those of 2 (in water) at 800, 633, and 408 nm may be assigned to d–d transitions, while the peaks at 428, 381, and 361 nm of 1 may be of charge transfer origin.
  • Dongri Jin, Hideki Hakamata, Kouji Takahashi, Akira Kotani, Fumiyo Kus ...
    2004 Volume 77 Issue 6 Pages 1147-1152
    Published: 2004
    Released: June 09, 2004
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    A highly sensitive and selective method was developed for the determination of 15 flavonoids by high-performance liquid chromatography with electrochemical detection (HPLC–ECD) using a microbore column. The 15 flavonoids were divided into two groups according to their hydrophobicity and were resolved by two isocratic systems, namely, methanol–water (1:1 and 3:7, v/v) containing 0.5% phosphoric acid. The retention factor (k) of each flavonoid linearly correlated with the logarithmic partition of coefficients between 1-octanol–water (log P) values. The detection limits (S/N = 3) of the flavonoids tested were in the range of 2–25 fmol; that is 600 times more sensitive than conventional HPLC with UV detection. The relative standard deviations (RSD, n = 5) were less than 5% at 1 pmol for the flavonoids tested. By the present method, only 100 μL of bottled Japanese green tea were enough to determine the flavonoid contents.
  • Nallathambi Sengottuvelan, Duraisamy Saravanakumar, Vengidusamy Naraya ...
    2004 Volume 77 Issue 6 Pages 1153-1159
    Published: 2004
    Released: June 09, 2004
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    New trans-disubstituted macrocyclic ligands (L1), trans-1,8-[N,N′-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}]-1,4,8,11-tetraaza-5,5,7,12,12,14-hexamethylcyclotetradecane, and (L2), 1,8-[N,N′-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}]-4,11-dimethyl-1,4,8,11-tetraaza-5,5,7,12,12,14-hexamethylcyclotetradecane, were synthesized. The ligands were characterized by elemental analysis, IR, 1H and 13C NMR spectral analyses. The ligand L1 crystallized as monoclinic in the space group P21/n, and the final R-value was found to be 0.062. Copper(II) and nickel(II) complexes of these ligands were prepared and characterized by elemental analysis, IR, UV–visible, FAB-mass spectral studies. Electrochemical studies of the nickel(II) complexes show one-electron quasireversible reduction around −1.00 to −1.13 V and one-electron quasireversible oxidation around 1.00 to 1.14 V. The copper(II) complexes show one-electron quasireversible reduction around −0.93 to −1.10 V. ESR spectral studies of the copper(II) complexes show hyperfine splitting with a g|| value of 2.31, a g value of around 2.02 and an A value of 160 G. The magnetic moment values (μeff) of the Cu(II) complexes fall in the range of 1.71 to 1.72 B.M. at room temperature (298 K). The rate-constant values of the catalytic hydrolysis of p-nitrophenyl phosphate for the copper(II) complexes were in the range 6.3 × 10−3 to 12.2 × 10−3 min−1 and for the nickel(II) complexes in the range 10 × 10−3 to 14 × 10−3 min−1. The rate-constant values of the catalytic oxidation of catechol to o-quinone were in the range 9.4 × 10−3 to 13.4 × 10−3 min−1 for the copper(II) complexes. The copper(II) and nickel(II) complexes of ligand L2 have higher catalytic activity than that of ligand L1.
  • Shinji Inomata, Keiichi Hitomi, Hiroshi Ogino
    2004 Volume 77 Issue 6 Pages 1161-1164
    Published: 2004
    Released: June 09, 2004
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    The reaction of the mixed-ligand iron–sulfur cluster [Fe4(Cp*)3(Ph2C2S2)(μ3-S)33-S2)] ([3]) (Cp* = C5Me5) with iodomethane gave a methylated cluster, [Fe4(Cp*)3(Ph2C2S2)(μ3-S)33-S2Me)]I ([4]I), in 60% yield. The anion exchange of [4]I with KPF6 gave [4]PF6 as a pure sample. A similar treatment of [3] using iodoethane afforded an ethylated cluster, [Fe4(Cp*)3(Ph2C2S2)(μ3-S)33-S2Et)]I ([5]I), and oxidized parent cluster [3]I. The reaction of [3] with 2-iodopropane did not give an alkylated cluster. An unreacted cluster [3] was recovered with a small amount of oxidized cluster [3]I. The molecular structure of [Fe4(Cp*)3(Ph2C2S2)(μ3-S)33-S2Me)] ([4]), which was obtained by the reduction of [4]PF6 with cobaltocene, was determined by an X-ray diffraction study. Crystallographic data are: Monoclinic, P21/a, a = 21.707(2) Å, b = 21.382(2) Å, c = 11.433(1) Å, β = 98.98(1)°, V = 5241.5(9) Å3, Z = 4, and R = 0.067 for 7412 reflections with |Fo| > 3σ(Fo). The methyl group transferred from MeI is located on the singly ligating sulfur atom in the disulfide ligand of the parent cluster [3]. A cyclic voltammogram of [4]PF6 in 0.1 mol dm−3 tetrabutylammonium tetrafluoroborate–CH3CN showed five reversible one-electron redox waves at E1/2 = +1.42 V, +0.92 V, +0.41 V, −0.38 V, and −1.22 V vs SCE, corresponding to 4+/3+, 3+/2+, 2+/1+, 1+/0, and 0/1− charged cluster couples, respectively. An irreversible two-electron reduction wave was also observed at Epc = −1.97 V vs SCE.
  • Tomohiko Okada, Makoto Ogawa
    2004 Volume 77 Issue 6 Pages 1165-1170
    Published: 2004
    Released: June 09, 2004
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    The ion exchange of p-phenylenediammonium and sodium-smectites (montmorillonite and synthetic saponite) resulted in the formation of p-phenylenediammonium radical cation and its dimer by the electron transfer from p-phenylenediammonium to smectites, as revealed by the color change (from colorless to green) as well as the visible absorption spectra. The p-phenylenediammonium-saponite thus obtained adsorbed phenols from aqueous solutions. The basal spacing of the p-phenylenediammonium-saponite increased upon the uptake of phenols, indicating a change in the microstructure. The uptake of phenols into the p-phenylenediammonium-saponite from aqueous solutions occurred through the formation of indoaniline dyes, as revealed by the color change from green to purple (for phenol) or purple-blue (for 2,4-dichlorophenol) as well as the absorption spectra. On the contrary, phenols were not intercalated into the interlayer space of the p-phenylenediammonium-montmorillonite.
  • Noriharu Nagao, Keita Egashira, Daisuke Mogi
    2004 Volume 77 Issue 6 Pages 1171-1172
    Published: 2004
    Released: June 09, 2004
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    A series of 1:1 adducts between late-lanthanide nitrate and tri(2-pyridyl)amine (tpa), [Ln(NO3)3(EtOH)3]·(tpa)·0.5EtOH (Ln3+ = Er3+, Yb3+, and Lu3+) was synthesized. These 1:1 adducts possess similar crystal structures, in which the tpa molecules interact face-to-face with the triangular base of [Ln(NO3)3(EtOH)3] through three hydrogen bonds.
Organic and Biological
  • Neeraj Agarwal, Sarada Prasad Mishra, Chen-Hsiung Hung, Anil Kumar, Ma ...
    2004 Volume 77 Issue 6 Pages 1173-1180
    Published: 2004
    Released: June 09, 2004
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    21,23-Dithiaporphyrins and 21-monothiaporphyrins with propane-1,3-diyldioxy and its derivatives at the β-thiophene carbons were synthesized and characterized. The cyclic substituents introduced at the β-thiophene carbons altered the electronic properties of the porphyrins. The X-ray structure for 2,3-bis(2,2-dibenzylpropane-1,3-diyldioxy) substituted 21-monothiaporphyrin showed a more planar structure compared to the saddle shaped structure reported for β-unsubstituted 21-monothiaporphyrins.
  • Naoyuki Ito, Yoshihide Tokuda, Shigeru Ohba, Takeshi Sugai
    2004 Volume 77 Issue 6 Pages 1181-1186
    Published: 2004
    Released: June 09, 2004
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    GalNAc (1) was straightforwardly prepared from GlcNAc (2a) in six steps. Selective protection of the hydroxy groups on the C-1, C-3, and C-6 positions at the same time was performed by the treatment of TBDPS chloride (5.5 eq.) in DMF in 70% yield. The nucleophilic attack with CsOAc or KOBz on the chloromethylsulfonyloxy group at C-4 worked well (69–77% yield), accompanied by an unexpected rearrangement, to give the furanose products (6). The deprotection of all silyl and acyl groups under acidic conditions and the re-acetylation provided GalNAc (1) in 51% yield.
  • Yoshifumi Kanosue, Satoshi Kojima, Yoshikazu Hiraga, Katsuo Ohkata
    2004 Volume 77 Issue 6 Pages 1187-1193
    Published: 2004
    Released: June 09, 2004
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    The enzymatic hydrolysis of dipeptides by carboxypeptidase-Y and carboxypeptidase-A was investigated. In the enzymatic hydrolysis of the dipeptides, a good linear relationship (r = 0.997 and 0.999) was found between the Michaelis–Menten constant (Km) and the hydrophobicity of the substrates evaluated from relative elution volume in reversed-phase HPLC. The correlation suggests that the hydrophobicity of the C-terminal amino acid is a major factor in governing the stability of the enzyme–substrate complex. The difference in the slope of the linear-regression lines seems to reflect the degree of relative hydrophobicity of the binding pockets in carboxypeptidase-Y and carboxypeptidase-A.
  • Atsuya Momotake, Junpei Hayakawa, Ritsuko Nagahata, Tatsuo Arai
    2004 Volume 77 Issue 6 Pages 1195-1200
    Published: 2004
    Released: June 09, 2004
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    The photochemical properties of stilbene dendrimers 13 in THF, as well as the corresponding potassium salts (water-soluble stilbene dendrimers = WSDs) 46 in aqueous solution were studied. Unlike the stilbene dendrimers 13, the environment of the core moiety in WSDs 46 depended on the generation. The first generation WSD 4 suffers from the water atmosphere around the stilbene core, as can be understood by the molecular structure. The largest Stokes shift observed in 4 among WSDs indicated that the dipole moment changed considerably upon photoexcitation. The Stokes shift tended to become smaller in higher generations. This means that the surrounding dendron should block the water molecule from reaching the stilbene core. The core stilbene in G3 WSD 6 may have an environment almost free of water, based on the observation of a similar Stokes shift of that of stilbene dendrimer 3, only soluble in organic solvents in which the core stilbene has a hydrophobic environment. These findings can be extended to the preparation of water soluble organic molecules with hydrophobic interiors with a photoresponsive chromophore at the core as a single molecule. Most interestingly, 6 underwent a photochemical one-way trans-to-cis isomerization. In addition to the photochemical studies of 16, the fluorescence properties of G3 dendrimer 3 were compared to those of the other series of stilbene dendrimer 7, which have no carboxylate groups at the periphery.
  • Takako Inui, Koichi Nakahara, Masaaki Uchida, Wataru Miki, Kei Unoura, ...
    2004 Volume 77 Issue 6 Pages 1201-1207
    Published: 2004
    Released: June 09, 2004
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    The aerobic oxidation of ethanol to acetaldehyde in water is induced by simple polyphenols, such as pyrogallol or catechol, in the presence of FeSO4–DTPA (N,N,N′,N″,N″-diethylenetriaminepentaacetic acid) catalyst. The amount of acetaldehyde formed becomes an indicator of their “prooxidant” ability in terms of the activation of O2. The “prooxidant” ability of pyrogallol is higher than that of catechol. Electron-withdrawing substituents decrease the ability, whereas electron-donating ones enhance it. The “prooxidant” property is exhibited by the total consequence of two processes: hydroxyl radical (OH) generation from O2 and its capture by phenolic compounds.
  • Yuka Odo, Tetsuro Shimo, Kenji Hori, Kenichi Somekawa
    2004 Volume 77 Issue 6 Pages 1209-1215
    Published: 2004
    Released: June 09, 2004
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    The regiochemical results in [2 + 2]photocycloaddition of 2-cyclohexenone (1) with 1-cycloalkenecarboxylates (24) significantly changed from head-to-head (hh) to head-to-tail (ht) adducts depending on increments of the ring-size, from four to six, of the carboxylates. The root of the drastic regioselective change was inferred from the transition state (TS) analysis of the triplet reactions, including the back-reaction at the PM5 and B3LYP levels. The TS energy of the first step (TS1) is the most important factor for this reaction. The change in TS energies at hh adducts was larger than that at ht adducts. For more detailed analysis, the TS energies of the hh and ht reactions (at the three reactions) were partitioned to the two reactant deformation (Edf) and the interaction (or repulsion, Eint) energies. The Edf and Eint energy changes were found to be dependent on the ring-size of the 1-cycloalkenecarboxylates 24. Thus, since the larger ring of 4 has relatively higher TS1 and deformation energies for giving the hh adduct, they may cause the preferential formation of the ht adduct, and result in the significant changes in the ht/hh ratio owing to the ring-size. The root of the significant hh diminution may be the dipole–dipole repulsion between the enone carbonyl and larger carboxylate (4) moieties. The improved PM5 and B3LYP/6-31+G(d) calculations are effective and economical for disclosing the origin of regioselectivity in [2 + 2]photocycloadditions.
  • Masumi Suzuki, Takeshi Sugai
    2004 Volume 77 Issue 6 Pages 1217-1227
    Published: 2004
    Released: June 09, 2004
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    While the cyclization of N-carbamoylamino alcohols into oxazolidinones via the activation with NO+ underwent smoothly, we found that similar reactions of vicinal diol monocarbamates were very slow. Mechanistic studies by means of time-resolved IR measurements of the former reaction suggested that the initial O-nitrosation was the rate-determining step. Indeed, the introduction of an ethyl group on the nitrogen terminus of diol monocarbamate promoted the desired cyclic carbonate formation. The concomitantly formed ethanediazo hydroxide, the precursor of the protonated form of diazoethane, was evidenced by trapping with p-nitrobenzoic acid as an ethyl ester. The formation of ethyl ester accelerates the reaction in an irreversible manner. Based on an elaboration of the substrates and reaction conditions, 2,3-dimethyl-2,3-butanediol mono-N-ethyl-N-nitrosocarbamate, which is easily prepared in situ from the corresponding ethylcarbamate and t-butyl nitrite, was developed as a new ethylation reagent of various carboxylic acids under mild conditions.
  • Ping-Jyun Sung, Mei-Ru Lin, Wei-Chen Chen, Lee-Shing Fang, Chung-Kuang ...
    2004 Volume 77 Issue 6 Pages 1229-1230
    Published: 2004
    Released: June 09, 2004
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    A novel briarane-type diterpenoid, fragilide A (1), has been isolated from the Taiwanese gorgonian coral Junceella fragilis. The structure, including the relative configuration of this new metabolite, was elucidated by spectroscopic methods.
Applied and Materials
  • Ichiro Matsubara, Kouta Hosono, Norimitsu Murayama, Woosuck Shin, Nori ...
    2004 Volume 77 Issue 6 Pages 1231-1237
    Published: 2004
    Released: June 09, 2004
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    Intercalative hybrid materials, comprised of polypyrrole (PPy) chains interleaved with the layers of MoO3, have been synthesized using concomitant ion exchange reaction. The (PPy)xMoO3-pressed pellets show a semiconducting-like transport with an activation energy of 0.2 eV. The MoO3 host layers play a dominant role in the determination of the transport properties of (PPy)xMoO3. The (PPy)xMoO3-pressed pellets show a distinct response to volatile organic compounds (VOCs) by increasing their electrical resistivity, which could be induced by the incorporation of VOC molecules into the interlayers of (PPy)xMoO3. (PPy)xMoO3 exhibits higher sensitivities to polar analytes such as formaldehyde and acetaldehyde, whereas it shows almost no response to toluene and benzene.
  • Tsukasa Tamai, Koji Inazu, Ken-ichi Aika
    2004 Volume 77 Issue 6 Pages 1239-1247
    Published: 2004
    Released: June 09, 2004
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    CCl2F2 decomposition with simultaneous halogen absorption by partially fluorinated MgO (MgF2–MgO) was studied, focusing on the effects of the acidity of the surface. CCl2F2 decomposition by MgF2–MgO was greatly promoted by fluorination of MgO at 10 mol% or higher. CCl2F2 decomposition was not a catalytic process over MgF2–MgO but basically a selective fluorine absorption reaction with MgO to form MgF2. Chlorine was released in the form of CCl4 regardless of reaction temperature and degree of fluorination of MgO due to low reactivity to CCl4. NH3-TPD and pyridine adsorption experiments were carried out to characterize the acid sites on MgF2–MgO samples. The amount of acid sites became maximum for 10% MgF2–MgO and the strength of acid sites increased as fluorination proceeded. CCl2F2 decomposition was revealed to be initiated by Lewis acid sites on MgF2–MgO formed by CCl2F2 decomposition as well as by fluorination with hydrofluoric acid aqueous solution. Thus, formation of the Lewis acid sites was considered to be the key step for efficient CCl2F2 decomposition with selective fluorine absorption.
  • Satoshi Inagaki, Kohei Kamino, Masahiro Hoshino, Eiichi Kikuchi, Masah ...
    2004 Volume 77 Issue 6 Pages 1249-1254
    Published: 2004
    Released: June 09, 2004
    JOURNALS RESTRICTED ACCESS
    MCM-22 zeolite crystallized by the vapor-phase transport (VPT) method showed a higher shape-selectivity to p-xylene in the alkylation of toluene with methanol, compared with MCM-22 crystallized by the hydrothermally synthetic (HTS) method, because VPT-MCM-22 has a smaller external surface area and a smaller number of acid sites thereon than HTS-MCM-22. Such textural properties of VPT-MCM-22 are caused by the fact that the spherical particles of VPT-MCM-22 are composed of hexagonal plates as thin as 55 nm; they are larger than those of HTS-MCM-22, which are 30 nm thick. The acidic properties, characterized by NH3-TPD and FT-IR using a pyridine adsorption technique, showed no significant difference between VPT- and HTS-MCM-22, except for the acidity on the external surface.
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