Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 76 , Issue 11
Showing 1-24 articles out of 24 articles from the selected issue
  • Chihiro Kibayashi, Sakae Aoyagi, Hideki Abe
    Type: Accounts
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2059-2074
    Published: 2003
    Released: November 15, 2003
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    The first total synthesis of tricyclic marine alkaloids (±)-fasicularin (2) and (±)-lepadiformine (5) has been accomplished. The key common strategic element for the synthesis is the stereocontrolled intramolecular hetero-Diels–Alder reaction of an N-acylnitroso moiety with an exocyclic diene with or without bromine substitution to control the syn-facial or anti-facial selectivity, respectively. This reaction leads to the trans- or cis-fused decahydroquinoline ring systems 13 or 23 involving the simultaneous introduction of the nitrogenated quaternary center in a single step. On further elaboration of the six-membered or five-membered ring A, the trans-fused adduct 13 provided either (±)-fasicularin (2) or (±)-lepadiformine (5). The hydrochloride salt of synthetic (±)-5 was found to be identical with the isolated natural sample of lepadiformine, however, the tricyclic amino alcohol 4 that has the proposed structure of lepadiformine in a non-zwitterionic form, derived from the cis-fused adduct 23, was found to be different from lepadiformine by spectral comparison. These results thus unambiguously established the relative stereochemistry of lepadiformine, formerly assigned incorrectly, as shown by 5. The synthesis of natural (−)-enantiomer of lepadiformine was then undertaken using a highly efficient protocol involving a new variant of the N-acyliminium ion-initiated intramolecular spirocyclization in which a conjugated diene was exploited as a π nucleophile. Thus, the synthesis is accomplished in nine steps with 31.4% overall yield, making this the most selective and shortest synthesis of lepadiformine to date. Direct comparison of chiral HPLC analysis of synthetic (−)-lepadiformine and the natural product allowed to assign the absolute configuration of natural lepadiformine to be 3R,5S,7aR,11aR.
  • Sergei Victorovich Chapyshev, Hideo Tomioka
    Type: Headline
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2075-2089
    Published: 2003
    Released: November 15, 2003
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    Photochemical transformations of quintet dinitrenes have been studied for the first time by FTIR spectroscopy during the photolysis of 1,3-diazidobenzene and its 2-methyl- and 2,4,6-trimethyl-substituted derivatives in solid argon at 13 K. The reactions involve two competitive processes. In the first one, the intramolecular insertion of the nitrene unit into the 1,6-aromatic bond induces ring-opening, which leads to the formation of aminoacetylenes. The second process involves the intramolecular addition of the nitrene unit to the 1,2-aromatic bond followed by ring-opening to form 4(2H-azirin-2-ylidene)-2-butenenitrile derivatives. Methyl groups in ortho-positions to the nitrene units of quintet dinitrenes efficiently protect their aromatic ring from nitrene attacks, substantially increasing the photochemical stability of such species. However, even quintet 2,4,6-trimethylphenylene-1,3-dinitrene decomposes to ring-opened products on extended irradiation. This indicates that quintet dinitrenes are much more photochemically reactive species than triplet nitrenes. Undesirable photochemical rearrangements of the latter at early stages of the photolysis of 1,3-diazidobenzenes are suppressed on introducing the methyl group in position 2 of these azides.
  • Minoru Ashizawa, Hirofumi Nii, Takehiko Mori, Yohji Misaki, Kazuyoshi ...
    Type: Article
    Subject area: TP
    2003 Volume 76 Issue 11 Pages 2091-2097
    Published: 2003
    Released: November 15, 2003
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    TMET-TTP derivatives in which one or both of the outer 1,3-dithiole rings are replaced by 1,3-diselenole rings (1a1d) have been prepared (TMET-TTP: 2-[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-5-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene). The neutral crystal of 1c has β-type uniform stacks, whereas 1a shows a θ-type molecular arrangement in the neutral crystal. The AsF6 salts of 1a and 1d have a θ-type structure similarly to other TMET-TTP salts. In spite of the relatively small dihedral angle (117°), the conductivity is weakly semiconductive from room temperature. Selenium substitution causes unbalance of the diagonal intermolecular interactions, which may be the origin of a deviation from the universal phase diagram of the θ-phase.
  • Jungno Lee, Yoshikiyo Moroi
    Type: Article
    Subject area: TP
    2003 Volume 76 Issue 11 Pages 2099-2102
    Published: 2003
    Released: November 15, 2003
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    An investigation was made into the binding of sodium dodecyl sulfate (SDS) to a cationic polymer of high charge density, the homopolymer of diallyldimethylammonium chloride (PDADMAC), in 1 mM (1 M = 1 mol dm−3) NaCl solution using a potentiometric titration method utilizing a surfactant-selective electrode at 15, 20, 25, 30, 35, and 45 °C. The concentrations of PDADMAC examined were 100, 200, and 400 ppm. SDS ions bound very cooperatively to the PDADMAC polymer. Variation of the polymer concentration had almost no effect on the binding parameters at the same temperature, while increasing the temperature had a large effect on the binding system at the same polymer concentration. The intrinsic binding constant (K) and the critical aggregation concentration (cac) decreased and then increased with increasing temperature, having minimum values of 17.9 × 10−2 mM−1 and 0.19 × 10−2 mM at 25 °C, respectively. However, the cooperativity parameter (u) and the binding affinity (uK) had a maximum value of 20.0 × 102 and 357 at the same temperature, respectively. The polymer-concentration-independence of the binding parameters for the anionic surfactant (SDS) to the cationic polymer (PDADMAC) corresponds to the binding of a cationic surfactant to an anionic polymer, and the maximum in the binding affinity at 25 °C is quite similar to the binding of a cationic surfactant to an anionic polymer, and also to the micellization of ionic surfactants having a minimum cmc value at 25 °C.
  • Kazuhisa Yano, Yoshiaki Fukushima
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2103-2109
    Published: 2003
    Released: November 15, 2003
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    Super-microporous silicas with an ordered hexagonal structure were synthesized under dilute conditions using a conventional alkyltrimethylammonium halide as a template. The d100 of the super-microporous silicas was approximately 23 Å. The pore diameter of one of the obtained samples, determined by an argon adsorption measurement, was 16.7 Å. This material adsorbed water vapor with a P/P0 value higher than 0.29, while desorbing it with a P/P0 value lower than 0.14. It can be inferred that this super-microporous silica is suitable as an adsorbent for an adsorption heat-pump system.
  • Masakazu Moro’oka, Hiroshi Ohki, Koji Yamada, Tsutomu Okuda
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2111-2115
    Published: 2003
    Released: November 15, 2003
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    We found a new ionic conduction phase in CuHgSCl above 373 K and in CuHgSBr above 346 K. The crystal structures of these novel phases have been determined by Rietveld refinement of powder X-ray diffraction patterns. The electric conductivity at 500 K measured by AC impedance method was 1.4 × 10−5 S cm−1 for CuHgSCl and 4.0 × 10−6 S cm−1 for CuHgSBr. The activation enthalpy was determined to be 53 kJ mol−1 for CuHgSCl and 67 kJ mol−1 for CuHgSBr. The ionic transport number measurements indicated that Cu+ ions constitute the majority charge carriers in these samples. The electronic contribution to the conduction process is small in comparison with the Cu+ ionic contribution. The charge density analysis by the maximum entropy method (MEM) combined with Rietveld analysis clearly showed that the Cu+ ionic conduction path was along the crystallographic (100) direction.
  • Reza Ojani, Jahanbakhsh Raoof, Fathemeh Mahdavi
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2117-2121
    Published: 2003
    Released: November 15, 2003
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    A novel analytical method that builds on specific features of non-linear chemical systems far from thermodynamic equilibrium is described. The used oscillating chemical system is the BZ (Belousove–Zhabotinskii) reaction in a non-equilibrium stationary state close to a bifurcation point. The method uses a Pt electrode for monitoring the potential response to a perturbation caused by As(III) ion. A linear response, in which the oscillating amplitude varies versus the logarithm of the As(III) concentration, was found in the range of 1.99 × 10−6–1.27 × 10−4 M. Under optimum conditions, a detection limit of 2 × 10−6 M for As(III) was obtained. The relative standard deviation (%RSD) for As(III) 1.59 × 10−5 M is 7.1 (n = 6).
  • Masamichi Umemiya, Ken-ichi Sugiura, Hitoshi Miyasaka, Tomohiko Ishii, ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2123-2127
    Published: 2003
    Released: November 15, 2003
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    A substituted porphyrinatoplatinum(II), meso-tetrakis(4-t-butylphenyl)porphyrinatoplatinum(II), has been spectroscopically and structurally characterized. The 1H NMR signal from the β-protons of the pyrrole ring is observed as a singlet with a full-width at half maximum of 1.6 Hz, contrary to the reported quasi-triplet resonance attributable to the 1H–195Pt long-range coupling. The porphyrin nucleus is nearly planar in the solid state. All macrocycle atoms lie within approximately 0.06 Å of the least squares mean plane with a pseudo-wave core conformation. The intramolecular Pt–N distances are 2.019(3) Å.
  • Takashi Oda, Satoru Nakashima, Tsutomu Okuda
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2129-2134
    Published: 2003
    Released: November 15, 2003
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    The effects of cation symmetry and packing on the mixed-valence state of binuclear ferrocene derivatives are discussed by using chiral isomers and the racemic modification of 1′,1″′-bis(2-phenylbutyl)-1,1″-biferrocenium(1+) triiodide. Although the three chiral isomers showed trapped-valence states at 78 K, only the (R,S) isomer showed a perfect detrapped-valence state at room temperature in the three isomers. The racemic modification consisted of the (R,R) and the (S,S) isomers showed a perfect detrapped-valence state at room temperature. This shows that the packing effect overcomes the effect of cation asymmetry. The electron-transfer rate for each pentaiodide salt was faster than that of the corresponding triiodide salt. A comparison between the (S,S) triiodide and the (S,S) pentaiodide salts reveals an important packing effect. The polymeric pentaiodide skeleton forced the (S,S) cation to have pseudo-inversion center.
  • Keiichi Tsukahara, Mari Nishimine, Yuka Shioyama, Hiroshi Takashima, J ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2135-2142
    Published: 2003
    Released: November 15, 2003
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    Horse heart metmyoglobin (metMb), whose N-terminal Gly1 is linked by an N,N,N′,N″,N″-diethylenetriaminepentaacetatocobaltate(III) ion ([CoIII(dtpa)]) with an amide bond, was prepared and characterized. A one-electron reduced protein, [deoxyMb{CoIII(dtpa)}], was prepared by reduction with a methylviologen-radical cation, which was produced in situ by a photoreduction using a tris(2,2′-bipyridine)ruthenium(II) ion in the presence of disodium dihydrogen ethylenediaminetetraacetate at 25 °C, pH 7.5 (a 0.010 mol dm−3 tris(hydroxymethyl)aminomethane–HCl buffer), and an ionic strength of 0.50 mol dm−3 (NaCl). The reaction of [deoxyMb{CoIII(dtpa)}] to form [metMb{CoII(dtpa)}] obeyed a first-order rate law on the protein concentration. The first-order rate constant was dependent on the concentration of the protein, indicating that both intra- and intermolecular electron-transfer (ET) processes simultaneously occur. The latter is the reaction with excess [metMb{CoIII(dtpa)}] remaining. Both intra- and intermolecular ET rates could be explained by the Marcus theory, including the distance dependence of the rate of the reaction, and might arise mainly from the very large reorganization energy for the Co(III)/Co(II) couple. Zinc-substituted myoglobin, [ZnMb{CoIII(dtpa)}], was also prepared and the photoinduced ET reaction from the excited triplet state of zinc myoglobin to the Co(III) moiety was examined. The observed ET quenching rate constant is reasonably explained by the Marcus theory through the same ET pathway as that for [deoxyMb{CoIII(dtpa)}]. It is suggested that the ET occurs with through-bond and van der Waals interactions from the heme edge to the Co(III) edge via Phe138 and Leu137 over 18.8 Å (1 Å = 1 × 10−10 m) both in deoxy and zinc myoglobins.
  • Akira Hanaki, Nobuo Ikota, Jun-ichi Ueda, Toshihiko Ozawa, Akira Odani
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2143-2150
    Published: 2003
    Released: November 15, 2003
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    The transport of Cu(II) complexed with histidine-containing tripeptides (Cu(HiL), L = HisGlyGly (i = 2), GlyHisGly (i = 1), and GlyGlyHis (i = 2)) to cysteine was examined by a stopped-flow spectrophotometric method. The S → Cu(II) charge transfer (LMCT) bands at 335 nm and 390 nm were used as probes for tracing the reaction. Primarily formed was the ternary Cu(H−1L)(Cys) complex. The rate of the Cu(H−1L)(Cys) formation depended on the affinity of Cu(II) for the donor atoms at the fourth binding site of Cu(H−2L). Cu(H−1L)(Cys) subsequently reacted with free Cys to yield a binary complex, Cu(Cys)2. The rate of Cu(H−1L)(Cys) formation was generally faster than that of conversion from Cu(H−1L)(Cys) to Cu(Cys)2. An exception was found in the reaction with Cu(H−2GlyGlyHis), where the relation k1+ < k2+ existed. The ternary complex, Cu(H−1HisGlyGly)(Cys), was too labile to be detect by the conventional stopped-flow methods. Probably, Cu(H−1HisGlyGly)(Cys) upon forming changed spontaneously to Cu(HisGlyGly)(Cys), in which the N-terminal His residue coordinated to the Cu(II) via the amino and imidazole nitrogens, and rapidly changed to Cu(Cys)2.
  • Taro Tsubomura, Masakazu Abe, Michihiro Tarutani, Haruya Yamada, Toshi ...
    Type: Short Articles
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2151-2152
    Published: 2003
    Released: November 15, 2003
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    The quenching of the photoluminescence of [Pt(binap)2] by oxygen has been studied. Generation of singlet oxygen was confirmed by NIR spectroscopy. The usefulness of the Pt complex as a photosensitizer was established using a singlet oxygen scavenger, 1,3-diphenylisobenzofuran (DBF). The mechanism for the generation of singlet oxygen is discussed.
  • Jun Kameda, Kazuko Saruwatari, Hidemi Tanaka
    Type: Short Articles
    Subject area: AI
    2003 Volume 76 Issue 11 Pages 2153-2154
    Published: 2003
    Released: November 15, 2003
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    Hydrogen generation was investigated by grinding quartz powder in pH- and ionic strength-controlled liquid media. The effect of ionic strength on hydrogen generation was negligible, while the decrease of generated hydrogen in the acidic pH region (>5.0) was observed. The mechanism of these mechanochemical reactions was discussed.
  • Yuichi Okazaki, Fumio Ando, Jugo Koketsu
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2155-2165
    Published: 2003
    Released: November 15, 2003
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    The cathodic reduction of sulfonium salts in acetonitrile in the presence and absence of benzaldehyde was carried out. Results were compared with results of the base method. In the presence of benzaldehyde, the electrochemical reduction gave epoxides as a result of the Corey–Chaykovsky reaction, thus confirming ylide formation. The electrochemical reduction of sulfonium salts without benzaldehyde yielded rearrangement products in high yield. On the contrary, upon base treatment of sulfonium salts without benzaldehyde, symmetrical epoxides derived from the benzyl group of the sulfonium salt are obtained as main products as a result of the auto oxidation of the sulfur ylide. The reaction mechanisms were elucidated based on the results obtained by a semi-empirical molecular orbital method.
  • Osamu Takahashi, Ko Saito, Yuji Kohno, Hiroko Suezawa, Shinji Ishihara ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2167-2173
    Published: 2003
    Released: November 15, 2003
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    Ab initio MO calculations were carried out, at the MP2/6-311G(d,p)//MP2/6-31G(d) level, for the conformation of a series of diastereoisomers of 1-alkyl-2-phenylpropan-1-ols CH3CH(C6H5)CH(R)OH and 2-phenylalkanes CH3CH(C6H5)CH2R (R = CH3, C2H5, i-C3H7, t-C4H9). A rotamer where R is gauche to C6H5 and anti to the benzylic methyl group has been found to be the most populated. The distances between the CH and OH hydrogens and the phenyl group in the interacted rotamers have been found to be short. The distribution of the possible rotamers depends on the presence or absence of the OH group and the configuration of the alcohol diastereoisomers. The results are discussed in the context of weak attractive molecular forces; the CH/π, OH/π, and CH/O hydrogen bonds, as well as unfavorable steric effects occurring between R and Me and between vicinal CH groups.
  • Takayoshi Abe, Teizo Yamaji, Tsugio Kitamura
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2175-2178
    Published: 2003
    Released: November 15, 2003
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    Long-chained hypervalent iodine benzyne precursors bearing ethyl, butyl, hexyl, octyl, decyl, dodecyl, and tetradecyl groups were synthesized, respectively. As the alkyl chain of the benzyne precursors is lengthened, the solubility in nonpolar organic solvents and the yield of the benzyne adduct with furan gradually increases.
  • Shoji Matsumoto, Kazuhisa Kumazawa, Katsuyuki Ogura
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2179-2182
    Published: 2003
    Released: November 15, 2003
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    Under “solvent-free” solid–solid and solid–vapor conditions, 1-aryl-4-(methylthio)-2-(p-tolylsulfonyl)-1,3-butadienes (1) react with iodine to form (p-tolylsulfonyl)naphthalene derivatives (2) in high yield. These conditions make the reaction tolerant to the kind of the aryl so that various derivatives of 2 were produced in high yield. The products (2) can be obtained in a nearly pure form by removing co-existing hydrogen iodide and dimethyl disulfide by evaporation. Thus, this process is environmentally benign, because no solvent and water need to get the pure product.
  • Yoshifumi Nagano, Akihiro Orita, Junzo Otera
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2183-2189
    Published: 2003
    Released: November 15, 2003
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    In contrast to conventional substrate selectivity in Lewis-acid promoted nucleophilic reactions wherein less electrophilic aldehydes react preferentially over the more electrophilic counterparts, addition of tetraallyltin to aldehydes occurs in a reversed sense. The substrate selectivity in Lewis acid-promoted nucleophilic addition is generally dependent on the combinations of substrates, nucleophiles, catalysts, etc. Such diversity leads to two one-pot protocols, parallel recognition and shotgun process wherein different chemical transformations take place directly on the separate reaction sites without recourse to protection–deprotection procedures. These two protocols are tunable by controlling the electronic properties of the substrates.
  • Mohammad Abdur Rahim, Yoshihisa Matsui, Takanori Matsuyama, Yoshio Kos ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2191-2195
    Published: 2003
    Released: November 15, 2003
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    A few novel methods were developed for the regioselective preparation of p-hydroxybenzoic acid (pHBA) and its amino derivative by means of the Kolbe–Schmitt reaction. Thus, the carboxylation of tetraalkylammonium phenoxide at 125 °C under the CO2 pressure of 5.0 MPa in the presence of K2CO3 gave pHBA in a maximum yield of 56% with the regioselectivity of 97–100%. The carboxylation of potassium phenoxide (PhOK) at 230 °C under the CO2 pressure of 0.5 MPa also gave pHBA regioselectively in a 39% yield, together with unaltered phenol (61%). Under such conditions, the potassium salt of salicylic acid (SA) once formed was transformed into pHBA. Heat treatment of the dipotassium salt of 13C labeled SA indicated that the transformation occurs via two pathways, i.e., the intramolecular rearrangement of the salicylate (66%) and the decarboxylation of the salicylate followed by the recarboxylation of the resulting PhOK (34%). Furthermore, the carboxylation of cesium m-aminophenoxide and 5-amino-1-naphthoxide with CO2 gave regioselectively 4-hydroxyanthranilic and 8-amino-4-hydroxy-1-naphthoic acids, respectively, in good yields. This is a simple one-pot reaction giving these industrially useful acids with good yields.
  • Satoko Kezuka, Natsuki Ohtsuki, Tsuyoshi Mita, Youichi Kogami, Tomoko ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2197-2207
    Published: 2003
    Released: November 15, 2003
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    The enantioselective 1,3-dipolar cycloaddition reaction of nitrones with α,β-unsaturated aldehydes was realized using 3-oxobutylideneaminatocobalt complex catalysts. Varieties of the cobalt(II) and cobalt(III) complexes were screened and the cationic cobalt(III) complex with hexafluoroantimonate was found to be the most effective for the catalytic enantioselective 1,3-dipolar cycloaddition reaction. In the presence of the cobalt(III) hexafluoroantimonate complex, the enantioselective 1,3-dipolar cycloaddition reaction of various nitrones with α,β-unsaturated aldehydes afforded the corresponding isoxazolidines in high yields and with high enantioselectivities. The absolute configuration of the optically active products was determined by X-ray analysis. Reasonable explanations for the enantioselection in the present 1,3-dipolar cycloaddition reaction catalyzed by the 3-oxobutylideneaminatocobalt complex were proposed.
  • Jun Terao, Hiroyasu Watabe, Masako Miyamoto, Nobuaki Kambe
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2209-2214
    Published: 2003
    Released: November 15, 2003
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    Aryl-substituted alkenes (ArHC=CH2) react with alkyl halides (R–X, X = Br or Cl) in the presence of a catalytic amount of [Cp2TiCl2] and nBuMgCl in Et2O to give alkylated alkenes (ArHC=CHR). This reaction proceeds regio- and stereoselectively under mild conditions to afford E-olefins. Primary and secondary alkyl bromides and secondary alkyl chlorides can be used as suitable alkylating reagents. The reactions of aliphatic alkenes, such as 1-octene and internal alkenes, were sluggish. When t-alkyl halides are employed, alkylative dimerization of alkenes proceeds exclusively to give symmetrical vic-diarylalkanes. These reactions involve addition of alkyl radicals to arylalkenes to form benzyl radicals as a carbon–carbon bond-forming step. Dimerization of thus formed benzyl radicals affords symmetrical alkanes and β-hydrogen elimination from benzyltitanocene intermediates gives alkylated alkenes. A possibility that titanocene activates alkenes as radical accepters was also proposed.
  • Masao Kawai, Kouji Hosoda, Yoshimasa Omori, Hatsuo Yamamura, Yoshihisa ...
    Type: Short Articles
    Subject area: OB
    2003 Volume 76 Issue 11 Pages 2215-2216
    Published: 2003
    Released: November 15, 2003
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    X-ray crysal structures of two α-alkoxyglycine derivatives, Cbz–Gly(OR)–OR (R = Me and Pri), were determined. The structural and chemical characteristics of Gly(OR) residues as unique β-oxa analogs of α-amino acids are discussed.
  • Takahiro Seki, Takashi Fukuchi, Toru Kobayashi, Kunihiro Ichimura
    Type: Article
    Subject area: AM
    2003 Volume 76 Issue 11 Pages 2217-2223
    Published: 2003
    Released: November 15, 2003
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    The multilayers of three homologous azobenzene (Az)-containing urea derivatives, having two, one and no hydrogen atom(s) at the terminal nitrogen atom in the urea moiety, and a simple long chain urea (hexadecylurea) were prepared by the Langmuir–Schaefer method. X-ray reflectometry, contact angle measurements of water, and Fourier transform infrared (FTIR) spectroscopy were undertaken to evaluate the layer structure and properties of these multilayered films. Of the four compounds, only the Az amphiphile, having no hydrogen atom at the terminus nitrogen atom, provided a different type of multilayers in terms of the molecular orientation, flexibility of the packing state, and characteristics of the intermolecular hydrogen bonding. The obtained data strongly support the formation of bifurcated hydrogen bonds for compounds having one or two hydrogen atom(s) at the terminus nitrogen of urea. The aspects obtained in this structural study can be exactly correlated with the properties of the Langmuir monolayers floating on water (Seki et al., Langmuir, 18, 5462 (2002).). Based on the X-ray and IR spectroscopic data, plausible models of the packed structure of the urea compounds in the multilayers are proposed.
  • Toshiyuki Yokoi, Takashi Tatsumi, Hideaki Yoshitake
    Type: Article
    Subject area: AM
    2003 Volume 76 Issue 11 Pages 2225-2232
    Published: 2003
    Released: November 15, 2003
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    A large distribution coefficient and large sorption capacity were observed during selenate adsorption by cation (Fe3+, Cu2+, and H+)-anchored diamino-functionalized MCM-41. Moreover, these synthetic adsorption media showed excellent selectivity for selenate sorption in the presence of other anions. In a pure potassium selenate solution, the distribution coefficients, Kd, exceeded 200000 when [selenate] < 25 mg in 1 g of these adsorbents (i.e., when the coverage of selenate < 0.4). The adsorption capacities of these three adsorption media were 117, 83.0, and 123 mg (g-adsorbent)−1, respectively, with the Fe and Cu centers having the capacity to bind 1.5 and 1.1 selenate anions on average. Tests on mono- (N-), di- (NN-), and triamino- (NNN-) functionalized MCM-41 showed that the diamino-functionalized varieties exhibited the largest value for Kd when cationated by Fe3+ and Cu2+. In the case of Fe/NN-MCM-41, diamino-functionalized MCM-41 cationated by Fe3+, the degree of inhibition caused by coexisting SO42− was much lower than the value reported for aluminum oxide. Cu/NN-MCM-41 showed the largest resistance to inhibition by Cl. For the adsorbents that we tested, the effects of coexisting nitrate were smallest for these three anions. The local structure of the adsorption center in Fe/NN-MCM-41 was analyzed by EXAFS spectroscopy.
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