Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 72 , Issue 7
Showing 1-30 articles out of 30 articles from the selected issue
  • Masahiko Sisido, Takahiro Hohsaka
    1999 Volume 72 Issue 7 Pages 1409-1425
    Published: 1999
    Released: November 01, 2004
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    Site-specific mutagenesis of proteins was extended to incorporate nonnatural amino acids through in vitro cell-free translation or through in vivo translation in the living cells. To this end, a variety of nonnatural amino acids were synthesized and linked to tRNA by chemical aminoacylation. Further, unique codon/anticodon pairs were derived, such as the 4-base codon/anticodon pairs that are orthogonal to the conventional 3-base codon/anticodon pairs. By the extension of amino acids and the genetic codes, site-directed incorporation of specialty amino acids into a variety of proteins has been achieved. Amino acids that carry large aromatic side groups with straight configurations, such as 2-anthrylalanine and 2-anthraquinonylalanine were successfully introduced into proteins and the CGGG or AGGU 4-base codons were used to assign their positions.
    Amino acids carrying photocleavable side groups, a spin probe, fluorescent probes, and other functional groups have been introduced into proteins. The specialty proteins were shown to be powerful tools for biochemical research and are expected to be novel molecules with designed arrangements of functional groups on the protein framework.
  • Masato Kakihana, Masahiro Yoshimura
    1999 Volume 72 Issue 7 Pages 1427-1443
    Published: 1999
    Released: November 01, 2004
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    This account focuses on the synthesis and characteristics of ceramics prepared by the Pechini-type in-situ polymerizable complex (IPC) method. The current status of the IPC method is reviewed, and the principle and underlying chemistry of the IPC method is illustrated with a special emphasis on its intrinsic advantage over other solution-based technologies. The method has the ability to prepare complex multicomponent oxides with good homogeneity through mixing at the molecular level. The importance of “polymerization” itself in the IPC route is demonstrated by comparing with the non-polymerizable so-called amorphous citrate method, which affords less compositional homogeneity. The use of heterometallic complexes in the IPC processing is shown to be one of the most promising techniques to synthesize ceramics with exceptionally good homogeneity. It is one function of this account to describe how Raman and 13C NMR spectroscopies can be effectively used for characterizing precursors in the IPC processing. Finally, it is demonstrated that another type of polymer complex solution (PCS) method overcomes the serious drawback of the IPC method; i.e. the amount of organics required for the PCS method is less than that required for the IPC method by a factor of about 20.
  • Yoshiyuki Kido, Satoru Yoshimura, Masahiko Yamaguchi, Tadafumi Uchimar ...
    Type: Article
    1999 Volume 72 Issue 7 Pages 1445-1458
    Published: 1999
    Released: November 01, 2004
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    In the presence of GaCl3, silylethyne reacted electrophilically with aromatic hydrocarbons to give β-silylethenylated arenes. The reaction proceeded via cationic species generated by the interaction of GaCl3 and silylethyne. High reactivity of the intermediate was demonstrated by the rapid reaction rate at −78 °C using close to the equimolar amount of the substrates. ipso-Substitution reaction took place with 1,2,3-trimethoxybenzene. Structures and properties of several organogallium compounds involved in the reactions are discussed.
  • Meng-Sheng Liao, Qian-Er Zhang
    1999 Volume 72 Issue 7 Pages 1459-1463
    Published: 1999
    Released: November 01, 2004
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    A theoretical study of the crystal HgCl2 compound has been done using a quasi-relativistic density-functional method. The crystalline environment was simulated by a cut-off type Madelung potential. Bond length, dissociation energy, force constants, and sublimation enthalpy are calculated. The calculated properties are in goon agreement with available experimental data. The calculated difference in bond length between the isolated and crystalline molecule is consistent with the data obtained by the more recent gas-phase electron diffraction and X-ray single crystal measurements. The predicted symmetrical and antisymmetrical force constants (ks, kas) and their trend (kas > ks) are in accordance with the Raman and IR data. The trend is in contrast to the free molecule case, where kas < ks. The sublimation enthalpies of hypothetical HgX2 (X = F, Cl, Br, I) compounds with the XeF2-type structure are evaluated. It is shown that the XeF2-type structures for HgX2are significantly less stable than the actual structures.
  • Yoshihiro Sasaki
    1999 Volume 72 Issue 7 Pages 1465-1474
    Published: 1999
    Released: November 01, 2004
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    The response of a sinusoidally perturbed minimal chemical oscillator was simulated over a wide range of perturbation parameters. Under a weakly perturbed condition, the system exhibited entrainment, quasiperiodicity and a Farey tree; under a more strongly perturbed condition, two types of chaos, small-amplitude oscillations and the coexistence of two oscillation modes were found. Phase-shifting of a kicked oscillator was considered in order to understand the entrainment.
  • Mark H. Wall, Jr., Seiji Akimoto, Tomoko Yamazaki, Nobuhiro Ohta, Iwao ...
    1999 Volume 72 Issue 7 Pages 1475-1481
    Published: 1999
    Released: November 01, 2004
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    Ultrafast fluorescence quenching has been examined for 5-pyridyl-10,15,20-triphenylporphinatozinc (ZnP), which is coordinatively linked to ruthenium complex (oxo-acetatobridged-triruthenium ions) (Ru), and for its derivatives having cyanopyridyl groups (Ru1) or 4-(N,N-dimethylamino)pyridyl groups (Ru2). The fluorescence for these peripherally elaborated zinc tetraarylporphyrins are > 99% quenched relative to ZnP. Fluorescence decays were measured in different solvents using the technique of femtosecond fluorescence up-conversion for these three compounds: ZnP–Ru+, ZnP–Ru+–Ru1+, and ZnP–Ru+–Ru2+. The fluorescence lifetime for ZnP* (τf = 1.7—1.8 ns in ZnP monomer) is dramatically decreased by the linkage of ruthenium moieties to the periphery of ZnP; τf = 460—530 fs for ZnP*–Ru+, τf = 380—400 fs for ZnP–Ru+–Ru1+, and τf = 300—380 fs for ZnP–Ru+–Ru2+. This fluorescence quenching behavior is in accord with a semiempirical estimation of the free energy for electron transfer from ZnP* to Ru+. Thus the ultrafast fluorescence quenching process in these molecules is attributed to an intramolecular electron transfer governed by the following equations: ZnP*–Ru+ → ZnP+–Ru0 and ZnP*–Ru+–Ru1+ (or Ru2+) → ZnP+–Ru0–Ru1+ (or Ru2+).
  • Mandeep Singh Bakshi, Ushwinder Kaur
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 7 Pages 1483-1489
    Published: 1999
    Released: November 01, 2004
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    The conductances of tetradecyltrimethylammonium bromide (TTAB) + dodecyltrimethylammonium bromide (DTAB) mixtures over the entire mole fraction range of TTAB (αTTAB) were measured in pure water as well as in the presence of various aqueous ethylene glycol oligomers containing 5 and 10 wt% of each additive in their respective binary mixtures at 30 °C. From the conductivity data, the critical micellar concentrations (cmc) and degrees of micelle ionization (χ) for TTAB + DTAB mixtures were computed. From the slopes of the conductivity curves, the equivalent conductivities of the monomeric (Λm), monomeric in the presence of additive (Λm,a) and the micelle (Λmic) state were calculated, the results are discussed with respect to the glycol-additive effects in the whole mole fraction range of the binary mixture. The micellar parameters of both surfactants and of their mixtures show a significant dependence on the amount in comparison to the number of repeating units of glycol oligomers. These results have been explained on the basis of the medium effects of aqueous additive, which are drastically influenced by the increase in the amount of additive rather than by the increase in the number of repeating units. The non-ideality in TTAB + DTAB mixtures was evaluated by using the regular solution theory and Motomura’s formulation based on the excess thermodynamic quantities. It has been found that the regular solution interaction parameter (β) and micellar mole fraction () remain almost unaffected even in the presence of up to 10 wt% of each additive and molecular weight 4000. These results suggest that there are no significant interactions between the glycol oligomers and the micelles of single and mixed surfactants.
  • Hiroto Tachikawa, Akira Shimizu
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 7 Pages 1491-1496
    Published: 1999
    Released: November 01, 2004
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    Direct ab-initio dynamics calculations have been carried out for hydrogen and muonium (Mu) trapped in a C10H16 cluster model in order to elucidate qualitatively the finite temperature effect on f-value ( = |ΦH(0)|2/|Φvac(0)|2, where |Φvac(0)|2 is the contact spin density on H nuclei in vacuum and |ΦH(0)|2 is one in the model cluster). In the dynamics calculations, a split-valence type basis set (31G) was used for the central hydrogen atom and a minimal basis set STO-3G for the cluster model. All atoms were treated as classical particles moving on the ab-initio full dimensional surface including all degrees of freedom calculated at the Hartree–Fock level. Three temperatures, 300, 600, and 1000 K, are chosen as simulation temperatures. The averaged f-values are obtained for each temperature by using MP2/3-21G* level. In addition, the f-value corresponding to 0 K is calculated by the static ab-initio MO calculation (i.e., without dynamics effect). The f-values for 0, 300, 600, and 1000 K were calculated to be 1.224, 1.211, 1.200, and 1.185, respectively, indicating that the f-value linearly decreases with increasing temperature. The f-value was simply expressed by the equation f (T) = f(T = 0 K)[1−0.325 × 10−5 T]. The present calculations indicated that the f-value is slightly affected by the thermal activation, the shift of f-value is small. This work is the first attempt to calculate the finite-temperature effect on the f-value at the ab-initio dynamics level.
  • Shiro Hatakeyama, Takashi Imamura, Nobuaki Washida
    1999 Volume 72 Issue 7 Pages 1497-1500
    Published: 1999
    Released: November 01, 2004
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    The photolysis of chloropicrin in air at 1 atm was performed in a 6-m3 photochemical reaction chamber with a combination of Xe arc lamps and Pyrex filters as a light source. Phosgene was obtained as one of the main products with a yield of unity. No nitrosyl chloride was observed, which supports the C–N scission mechanism for the photolysis. Photochemical ozone formation was enhanced when chloropicrin was added to the propene/NO/air/photoirradiation system after the ozone concentration maximum had been reached. The ozone-formation factor for chloropicrin under the conditions employed was, however, estimated to be 0.25 mole of ozone formed per mole of the decomposed chloropicrin. This implies that the Cl atom, itself, contributes to the destruction of ozone rather than to the formation of ozone under the experimental conditions. NO2 released from chloropicrin is the source of enhanced ozone. If the amount of chloropicrin as a soil fumigant increases, it can cause an increase of the ozone concentration in suburban and/or rural areas.
  • Cheng Zhi Huang, Yuan Fang Li, Shi You Deng, Shu Rong Liu
    Type: Article
    1999 Volume 72 Issue 7 Pages 1501-1508
    Published: 1999
    Released: November 01, 2004
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    The template role of nucleic acids in the long-range assembly of Methylene Blue (MB) was characterized with Resonance Light-Scattering (RLS) measurements, and a determination method of nucleic acids of nanogram was proposed. At the pH range 6.87—8.74 and ionic strength lower than 0.01, the interactions of MB with nucleic acids result in two characteristic RLS peaks at 355.0 and 560.0 nm. Mechanism studies show that these peaks result from the long-range assembly of MB on the molecular surface of nucleic acids. A Scatchard plot was constructed by using the RLS data, yielding an assembly number and assembly constant of 5.67 and 9.22 × 104 mol−1 dm3 for MB assembly on the molecular surface of calf thymus DNA (ctDNA), 5.79 and 4.68 × 104 mol−1 dm3 for MB assembly on that of fish sperm DNA (fsDNA). This assembly could be used for analytical purposes and 0—1.4 μg ml−1 for ctDNA, 0—1.2 μg ml−1 for fsDNA, and 0—0.24 μg ml−1 for yeast RNA could be determined if 3.0 × 10−5 mol dm−3 MB was employed. The limits of determination were 11.0 ng ml−1 for ctDNA, 4.9 ng ml−1 for fsDNA and 8.6 ng ml−1 for yeast RNA, respectively. Four synthetic samples were determined with satisfaction.
  • Toshitaka Hori, Nobuko Taniguchi, Sadayuki Himeno, Ken-ichi Sano, Osam ...
    Type: Article
    1999 Volume 72 Issue 7 Pages 1509-1514
    Published: 1999
    Released: November 01, 2004
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    The structure of [NEt4]6[H4Na2(PH)6Mo12O54]·4H2O (1) has been determined by the single-crystal X-ray method. The crystals are monoclinic, space group of C2/c, with cell parameters a = 23.790(3), b = 16.319(2), c = 28.788(3) Å, β = 114.365(7)°, and Z = 4. The structure model was refined by full-matrix least squares to R = 0.0624 and Rw = 0.0661 for 6798 independent reflections with Fo > 3σ(F) and in 2θ < 50°. The existence of a meso-type heteropolyion [H4Na2(PH)6Mo12O54]6− (2) in the title crystals has been confirmed. It is composed of a pair of enantiomeric moieties of [H2Na(PH)3Mo6O27]3− (3 and 3i, respectively) which are linked by sharing Na+ ions; here, the superscript i denotes the symmetrical operation code of (1/2−x, 1/2−y, −z). The six MoO6-octahedra contained in the respective moieties are arranged to form Plus- and Minus-helices.
  • Toshio Nakashima, Hirohiko Waki, Taichi Tanaka, Gohsuke Sugihara
    1999 Volume 72 Issue 7 Pages 1515-1517
    Published: 1999
    Released: November 01, 2004
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    The stability constants for complexes of a ring oxoanion of phosphorus dodecaoxohexaphosphate(III), with magnesium, calcium, and strontium were evaluated in aqueous solutions at an ionic strength of 0.1. A new spectroscopic equilibrium analysis for a system involving complexes of very high stability was accomplished by introducing EDTA as a complexation-competing agent to the system. The logarithmic stability constant values for the magnesium, calcium, and strontium complexes were found to be 8.4, 8.8, and 7.5, respectively, whose stability order was different from that of a simple one expected from their ionic radii.
  • Ryuichi Arakawa, Tsutomu Abura, Tsuyoshi Fukuo, Hironobu Horiguchi, Ge ...
    Type: Article
    1999 Volume 72 Issue 7 Pages 1519-1523
    Published: 1999
    Released: November 01, 2004
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    An on-line electrospray ionization mass-spectrometric analysis for an electrolysis reaction was developed by the installation of a compact, efficient flow-through cell upstream of an electrospraying needle. The electrode was designed to avoid any reduction of the oxidation products formed during electrolysis. The electrolytic oxidation reaction of a Ru and Os metal complex was carried out to examine the performance of the system. From the electrolysis of [M(bpy)3](PF6)2 (where M = Ru and Os, and bpy = 2,2′-bipyridine) we detected the one-electron oxidation product, [M(bpy)3]3+. The electrolysis of [Ru(bpy)2(en)](ClO4)2 (en = ethylenediamine) formed two complex products along with the elimination of two and four hydrogen atoms from the en ligand. The structure of the two complex products was determined to be a monoimine and diimine complex, based on an electrolysis experiment using a deuterium-labeled complex, [Ru(bpy)2(ed)](ClO4)2 (ed = ethylene-d4-diamine, H2N–CD2–CD2–NH2). The results indicate that electrochemical oxidation occurs at the ethylenediamine ligand and that the monoimine complex is a reaction intermediate for the formation of a diimine complex.
  • Hashem Sharghi, Hossein Naeimi
    1999 Volume 72 Issue 7 Pages 1525-1531
    Published: 1999
    Released: November 01, 2004
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    The ring opening of epoxides with elemental iodine and bromine in the presence of some Schiff-base complexes of the first-row transition metal(II) as new catalysts affords vicinal iodo alcohols and bromo alcohols in high yields. This new procedure occurs regioselectively under mild conditions in various aprotic solvents. The catalysts are easily recovered and can be reused several times.
  • Hidemitsu Uno, Yasuaki Nishihara, Noboru Mizobe, Noboru Ono
    1999 Volume 72 Issue 7 Pages 1533-1539
    Published: 1999
    Released: November 01, 2004
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    In the presence of BF3·OEt2, the reaction of 1-t-butoxycarbonyl-2-t-butyldimethylsiloxypyrrole with aliphatic and aromatic aldehydes in ether occurred stereoselectively to give the corresponding erythro and threo isomers, respectively, while a similar reaction in the presence of SnCl4showed completely opposite selectivity. The transition states leading to the major isomers are discussed.
  • Isao Yamaguchi, Hidetake Ishii, Kohtaro Osakada, Takakazu Yamamoto, Sh ...
    Type: Article
    1999 Volume 72 Issue 7 Pages 1541-1545
    Published: 1999
    Released: November 01, 2004
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    Addition of 1,4-butanediol diglycidyl ether (glycidyl = 2,3-epoxypropyl) to aqueous solutions of α-cyclodextrin (CD) leads to separation of the 2 : 1 complex from the solution. The 13C CP/MAS NMR spectrum of the complex indicates the presence of diastereomeric oxirane groups formed via the complexation. 1,4-Butanediol diglycidyl ether forms the 1 : 1 or 2 : 2 complex with γ-CD similarly from the aqueous reactions of the two compounds. 2,2-Dimethyltrimethylene glycol diglycidyl ether also forms water-insoluble host–guest complexes with α-CD (2 : 1) and with γ-CD (1 : 1 or 2 : 2). Poly(propylene glycol diglycidyl ether) with an Mn of 640 reacts with β-CD to give the 1 : 4 complex. Poly(tetrahydrofuran) terminated with NH2 groups at both ends also forms the 1 : 4 complexes both with α-CD and with γ-CD.
  • Masayasu Kuwahara, Miki Arimitsu, Masahiko Sisido
    1999 Volume 72 Issue 7 Pages 1547-1552
    Published: 1999
    Released: November 01, 2004
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    Nielsen’s-type peptide nucleic acids (PNA) and the oxy-PNA (OPNA), both carrying thymine or adenine bases, were prepared. Hybridizations were observed not only between the complementary pairs of PNA(A12)–DNA(T12) and OPNA(A12)–DNA(T12), but also between the complementary pairs of the artificial nucleic acid analogues, OPNA(A12)–PNA(T12). In the three-component mixture of PNA(T12)–DNA(T12)–OPNA(A12), OPNA(A12) was found to hybridize preferentially with DNA(T12). Addition of DNA(T12) to a preformed duplex of OPNA(A12)–PNA(T12) gave rise to a strand displacement to form a OPNA(A12)–DNA(T12) duplex. No triplex formation was detected in the three-component mixture.
  • Hiroshi Kajiro, Shuichi Mitamura, Atsunori Mori, Tamejiro Hiyama
    Type: Article
    1999 Volume 72 Issue 7 Pages 1553-1560
    Published: 1999
    Released: November 01, 2004
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    Scandium trifluoromethanesulfonate is found to be a Lewis acid catalyst for selective cleavage of esters containing a coordinative group adjacent to an ester moiety. The reaction proceeds under weak acidic conditions at room temperature; the catalyst can be recovered and reused. Even α-acyloxy ketones are deacetylated without racemization. Selective monodeacetylation at C-10 of paclitaxel has been achieved.
  • Kazuo Okumura, Yutaka Nakamura, Chung-gi Shin
    Type: Article
    1999 Volume 72 Issue 7 Pages 1561-1569
    Published: 1999
    Released: November 01, 2004
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    The first total synthesis of a macrocyclic antibiotic, micrococcin P (1), was accomplished. After constructing the central 2,3,6-tristhiazolyl-substituted pyridine skeleton [Fragment A—C segment] (21) from ethyl 2-(2-bromoacetyl-6-dimethoxymethyl-3-pyridyl)thiazole-4-carboxylate (15) in 11 steps, successive fragment condensations of 21 with ethyl 2-[(Z)-1-(O-t-butyldiphenylsilyl-L-threonylamino)-1-propenyl]thiazole-4-carboxylate (29) and (S)-1-(O-methoxymethyl-L-threonylamino)-2-(O-methoxymethyl)-2-propanol (25) [the protected Fragments B and D moieties, respectively] gave the protected Fragment A–B–C–D segment 34. Subsequent deprotection of all the protecting groups of 34 with trifluoroacetic acid and then cyclization by using BOP as condensing agent under high dilution conditions gave the expected micrococcin P (1). The synthetic 1 was identical with the natural 1 with respect to the chemical and physical properties.
  • Zhi-Fu Tao, Xuhong Qian, Mingcai Fan
    1999 Volume 72 Issue 7 Pages 1571-1574
    Published: 1999
    Released: November 01, 2004
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    A variety of naphthopyrone hydroperoxides as novel photochemical DNA cleavers were synthesized and evaluated. Their photochemical DNA-cleaving abilities depend on skeleton arrangement of the naphthopyrone core and are much more efficient than those of the reported 1,8-naphthalenedicarboximide analog. The DNA-cleaving mechanism by these new hydroperoxides probably mainly involves hydroxyl radicals, indicating that naphthopyrone hydroperoxides may be able to serve as a new class of intercalating photo-Fenton reagents.
  • Kenji Arakawa, Hiroki Kano, Tadashi Eguchi, Yayoi Nishiyama, Katsumi K ...
    Type: Article
    1999 Volume 72 Issue 7 Pages 1575-1581
    Published: 1999
    Released: November 01, 2004
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    Described in this paper are the characterizations of the synthetic 72-membered macrocyclic tetraether phospholipids (7, 8) and their acyclic congeners (9, 10), the hydrocarbon chains of which are unbranched straight chains instead of isoprenoid chains such as found in those of archaea. Thermal analyses by differential scanning calorimetry (DSC) clearly showed that the phase transition temperature (Tc) of the cyclic tetraether lipids 7 and 8 was rather lower than those of the corresponding acyclic counterparts 9 and 10. This trend was opposite to that of the diether lipids. The findings from 31P NMR and electron microscopic analyses suggested that the lipid polymorphism of 7 and 8 was quite different from that of 9 and 10. These results revealed that the cyclic structure in 7 and 8 contributed not only to the limitation of motional freedom at the hydrophobic region but also to the change of the lipid polymorphism in comparison with 9 and 10. Furthermore, it was found that these physicochemical as well as polymorphic properties were indistinguishable between the regioisomers 7 and 8 (or 9 and 10).
  • Chiaki Kuroda, Chen Ying Tang, Makoto Tanabe, Masabumi Funakoshi
    Type: Article
    1999 Volume 72 Issue 7 Pages 1583-1587
    Published: 1999
    Released: November 01, 2004
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    Iodolactonization of 4,5-disubstituted 2-(trimethylsilylmethyl)- and 2-methyl-penta-2,4-dienoic acids was studied. The latter afforded the corresponding iodolactone in good yield by treatment with I2 in MeCN. Iodolactone was also obtained by treatment with I2/NaHCO3/CHCl3/H2O in the presence of cerium(IV) salt as an additive. It was found that protolactonization proceeds by the aid of the trimethylsilyl group, while it prevents iodolactonization.
  • Koichi Mitsukura, Hiroko Choraku, San Thi Da, Toshiyuki Itoh
    1999 Volume 72 Issue 7 Pages 1589-1595
    Published: 1999
    Released: November 01, 2004
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    The additive effect on diastereoselectivity towards the lipase-catalyzed hydrolysis of acetates of 3-hydroxy-2-methyl- or 3-hydroxy-2-ethylalkanenitriles has been investigated. Diastereoselectivity was not influenced by thiocrown ether additives, although a significant modification of enantioselectivity was observed. Origin of the diastereoselectivity of the lipase-catalyzed reaction was thus evidently different from that of enantioselectivity. Based on these results, an easy preparation of optically active 3-hydroxy-2-methylpentanenitrile and 3-hydroxy-2-methylbutanenitrile have been demonstrated through lipase-catalyzed reaction by a double enzymatic reaction strategy.
  • Tomoshige Kobayashi, Takeo Tsuzuki, Mayu Saitoh
    1999 Volume 72 Issue 7 Pages 1597-1605
    Published: 1999
    Released: November 01, 2004
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    The electrophilic addition reactions of norbornadiene-fused furans, pyrroles, and thiophenes with bromine, arenesulfenyl chlorides, or a triazoledione generally afforded skeletally rearranged adducts except for a dibenzoyl-substituted thiophene. The formations of the adducts are attributable to the neighboring group participation by five-membered heteroaromatic rings, accompanied by the formations of bridged heteroarenium ions and the subsequent Wagner–Meewein type skeletal rearrangement.
  • Shinji Otoishi, Yoshihiro Tange
    1999 Volume 72 Issue 7 Pages 1607-1613
    Published: 1999
    Released: November 01, 2004
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    The effect of a catalyst, nickel ferrite, on the formation of SiC whiskers from porous bodies containing polycarbosilane and milled carbon fibers was studied. SiC whiskers were deposited at above 1373 K from porous bodies having a catalyst, while noodle-like SiC products were obtained at above 1473 K from porous bodies having no catalyst. A scanning electron-microscopic analysis and an energy-dispersive X-ray analysis revealed that SiC whiskers were formed via a vapor–liquid–solid process. An X-ray diffraction measurement revealed that the whiskers consisted of β-SiC, and that their crystallinity was significantly high in spite of the heating temperature (1373 to 1623 K). Based on changes in the infrared absorption spectra and gas-evolution curves during the heating process, it was presumed that the pyrolyzing process of polycarbosilane in the two kinds of porous bodies, one with a catalyst, and the other without a catalyst, remarkably resembled each other. SiC whiskers were proved to grow remarkably with decreasing the Si–O bondings by infrared spectroscopy and a chemical analysis. It could therefore be presumed that the formation mechanism of the SiC whiskers was analogous to that of silica–carbothermal reduction.
  • Norihiko Takeda, Tsukasa Torimoto, Hiroshi Yoneyama
    1999 Volume 72 Issue 7 Pages 1615-1621
    Published: 1999
    Released: November 01, 2004
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    Effects of mordenite as a support material for TiO2 on photodegradation rates of gaseous propionaldehyde, acetone, and propane were investigated using TiO2 (50 wt%)-loaded mordenite as a photocatalyst in reference to unsupported TiO2. The supported photocatalyst allowed adsorption of all the substrates several times greater than the unsupported photocatalyst, resulting in higher photooxidation rates for them. Detailed analysis suggests that the enhancement of the decomposition rate caused by the use of mordenite support is more remarkable for lower amounts of adsorption of the substrates on the support. The concentration of oxygen was found to have little influence on the photodegradation rates, suggesting that the rate of degradation of the organic substrates was not decided by photogenerated electron transfer processes but by the consumption of photogenerated holes by adsorbed organic substrates.
  • Tadatsugu Yamaguchi, Hiroyuki Nakazumi, Masahiro Irie
    Type: Article
    1999 Volume 72 Issue 7 Pages 1623-1627
    Published: 1999
    Released: November 01, 2004
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    A chiral cyclohexane containing two photochromic azobenzene units, (1R,2R)-N,N′-bis[4-(phenylazo)benzylidene]-1,2-cyclohexanediamine, was synthesized in an attempt to construct a molecule which shows a large optical rotation change due to photoirradiation. The CD spectrum dramatically changed depending on the configuration of the two azobenzene units. The specific rotations of (E,E)-, (E,Z)- and (Z,Z)-isomers were −1400°, −940°, and −670°, respectivly, while that of the monosubstituted chiral cyclohexane, (1R, 2R)-N-[(4-phenylazo)benzylidene]-N′-benzylidene-1,2-cyclohexanediamine ((E)-isomer), was only −470°. There was no difference in the photoisomerization rates of the azobenzene chromophores attached to chiral and nonchiral cyclohexanes.
  • Yasuharu Murakami, Takakazu Yamamoto
    Type: Article
    1999 Volume 72 Issue 7 Pages 1629-1635
    Published: 1999
    Released: November 01, 2004
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    Reactions of 3,5-dichloropyrazoles and 3,3′-dichloro-5,5′-bipyrazoles with zerovalent nickel complex, Ni(0)Lm, have been studied. In cases of 3,5-dichloro-1,4-dimethylpyrazole and 3,5-dichloro-4-methoxycarbonyl-1-methylpyrazole, only the C(5)–Cl bond of the two C–Cl bonds reacts with Ni(0)Lm to afford novel bis(pyrazolyl)nickel(II) complexes with the intact C(3)–Cl bond in moderate yields. Treatment of the bis(pyrazolyl)nickel(II) complexes with H2SO4 gives the new dichloro monomers: 3,3′-dichloro-1,1′,4,4′-tetramethyl-5,5′-bipyrazole and its 4,4′-bis(methoxycarbonyl) analogue. These undergo dehalogenative polycondensation to give poly(1,1′,4,4′-tetramethyl-5,5′-bipyrazole-3,3′-diyl) (6) and its 4,4′-bis(methoxycarbonyl) analogue (7), respectively. Polymer 6 is soluble in formic acid, and gives an intrinsic viscosity of 39 cm3 g−1 in formic acid, whereas polymer 7 is soluble in various organic solvents and has an Mn value of 8800 (Mw/Mn = 1.56) as estimated from GPC. They show photoluminescent peaks at the onset position of the respective π–π* absorption bands.
  • Meili Duan, Hiroaki Okamoto, Vladimir F. Petrov, Shunsuke Takenaka
    1999 Volume 72 Issue 7 Pages 1637-1642
    Published: 1999
    Released: November 01, 2004
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    This paper describes the thermal properties of some homologs of 4- and 3-[2-(perfluoroalkyl)ethoxy]-substituted nitrobenzenes and benzonitriles. Many of the homologs show notable smectic properties involving smectic A and B phases. The smectic structures were characterized by an X-ray diffraction examination. The smectic A phase has a partially interdigitated bilayer arrangement where the layer spacing is 1.2—1.8 times the calculated molecular length. Interestingly, some homologs show a smectic B phase with a layer spacing of 2 times the calculated molecular length. Both fluorophilic and polar interactions are supposed to play important roles for the molecular arrangements.
  • Ho-Sung Kim, Matsuhiko Nisizawa, Takashi Itoh, Isamu Uchida
    Type: Article
    1999 Volume 72 Issue 7 Pages 1643-1646
    Published: 1999
    Released: November 01, 2004
    JOURNALS RESTRICTED ACCESS
    The effects of surface treatments on the hydrogen storage properties of a Mg2Ni alloy particle were investigated by the microvoltammetric technique, in which a carbon-filament microelectrode was manipulated to make electrical contact with the particle placed in a KOH aqueous solution. It was found that the hydrogen storage properties of Mg2Ni at room temperature were improved by the surface treatments with a nickel plating solution. The sodium salts (sodium phosphinate and sodium dihydrogen citrate) contained in the nickel plating solution made the alloy form an amorphous-like state, resulting in an improved hydrogen absorption/desorption capacity at room temperature as high as about 150 mA h g−1 from the original value of 17 mA h g−1.
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