Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 72 , Issue 3
Showing 1-34 articles out of 34 articles from the selected issue
  • Shigeori Takenaka, Makoto Takagi
    Type: Accounts
    1999 Volume 72 Issue 3 Pages 327-337
    Published: 1999
    Released: December 24, 2003
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    Nogalamycin is a threading intercalator and when it binds with double stranded DNA, one of the two sugar substituents goes between adjacent base pairs of DNA to form a stable complex in which the two substituents of nogalamycin are projecting out in each groove of DNA. Since the molecular volume of the substituents of nogalamycin is larger than that of the space created through the motion of DNA strands constituting the double helix, a cleavage of hydrogen bonds in the base pairs of DNA duplex is necessary to form such a complex. The structure of double-stranded DNA is dynamic, and the base pair cleavage (base pair opening) and re-formation (closing) occur frequently at ambient temperature. A wider variety of threading intercalators is obtainable synthetically, and they include several families such as 1,5-disubstituted anthraquinones, 9,10-disubstituted anthracenes, and naphthalene bis(dicarboximide) derivatives. Kinetic study of the complex formation and dissociation of naphthalene bis(dicarboximide) carrying substituents of different size have made one recognize the dynamic character of duplex DNA in intercalation reaction. A cyclic bis-intercalator was also able to form a threading complex of a catenane-like structure. A thorough study of the binding behavior of natural and synthetic threading intercalators with DNA revealed that a proper design of substituents on threading intercalators can produce ligands which specifically bind either to single- or double-stranded DNA. These ligands, synthetic ones in particular, will hopefully serve not only as new DNA structural probes but also as chemotherapeutic agents.
  • Maksudul M. Alam, Osamu Ito
    Type: Article
    Subject area: TP
    1999 Volume 72 Issue 3 Pages 339-345
    Published: 1999
    Released: December 24, 2003
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    The transient absorption bands observed at ca. 400 and 550 nm for 1,3-dihydro-2H-imidazole-2-thione (IT), 1,3-dihydro-1-methyl-2H-imidazole-2-thione (MIT), and 1,3-dihydro-2H-benzimidazole-2-thione (BIT) have been assigned to their triplet states (3IT* ’s) by the quenching and sensitizing experiments using laser flash photolysis technique. Short intrinsic triplet lifetimes and relatively high triplet energies have been evaluated as characteristics of 3IT* ’s. For electron acceptors, photoinduced electron-transfer reaction occurs via 3IT* ’s in the diffusion controlled limit. The nucleophilic character of 3IT* ’s was confirmed by changing the substituents of alkenes on the addition reactions. MO calculations indicate that the lowest electronic configurations of both 3IT* and 3MIT* have 3(n,π*) character, while 3BIT* has 3(π,π*) character. The addition reactivity of 3BIT* is slightly higher than those of 3IT* and 3MIT*, which is opposite to the general tendency.
  • Ryoichi Nakagaki, Masaharu Yamaoka, Kiyoshi Mutai
    Type: Article
    Subject area: TP
    1999 Volume 72 Issue 3 Pages 347-355
    Published: 1999
    Released: December 24, 2003
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    The decay time of biradicals containing a benzophenone ketyl and an anilino-alkyl radical has been examined by nano-second laser photolysis in the presence of external magnetic fields up to 1 T. When sites with high spin densities are labeled with heavy carbon, noticeable magnetic isotope effects are observed on the decay kinetics for biradicals. Small kinetic effects are observed for deuterated species. The obtained results can be interpreted in terms of spin-lattice relaxation due to anisotropic hyperfine and dipole–dipole interactions. Procedures for preparing labeled species are also described.
  • Norihiro Kato, Fujio Takahashi
    Type: Article
    Subject area: TP
    1999 Volume 72 Issue 3 Pages 357-362
    Published: 1999
    Released: December 24, 2003
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    The kinetic parameters of deswelling for conventional and macroporous poly(N-isopropylacrylamide) gels were determined in order to point out the rate-determining step on the deswelling process in a NaCl or KCl solution. The apparent activation energy for the deswelling of the conventional gel in water (130 kJ mol−1) was larger than that of the macroporous gel in water (25 kJ mol−1). The split process of the skin layer, which was formed on the surface of the gel by heating from outside of gel, was considered concerning the rate-determining step in the case of the conventional gel. The activation entropy changes at 313 K (ΔS313’s) of the macroporous gel were determined to be −65 J K−1 mol−1 in 0.1 M NaCl (1 M = 1 mol dm−3), of which the cation exhibits a structure-forming property, and 180 J K−1 mol−1 in 0.1 M KCl, of which the cation exhibits a structure-breaking property. The sign of ΔS313 for the macroporous gel was negative at higher than 0.3 M NaCl or KCl. In order to point out the rate-determining step, the process of the salting-out effect, that of bond formation between the polymer chains, and that of forming water clusters in the presence of the cation inside of the gel are discussed.
  • Kaoru Matsuura, Hirotomo Hase, Shigeyoshi Arai, Yoko Miyatake, Mikio H ...
    Type: Article
    Subject area: TP
    1999 Volume 72 Issue 3 Pages 363-366
    Published: 1999
    Released: December 24, 2003
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    Ethanol and 2-methyltetrahydrofuran (MTHF) solutions of silver perchlorate were irradiated with γ-rays at 77 K. Two kinds of silver atoms (Ag0) and a small amount of dimer cations (Ag2+) were formed in both solids immediately after irradiation. On storing at 77 K, both Ag0 species reacted with Ag+ to form Ag2+ in ethanol, while in MTHF only the minor Ag0 species reacted, resulting in less growth of Ag2+ yield than in ethanol. The mechanism for the formation of Ag2+ has been discussed in terms of thermal diffusion and quantum tunneling.
  • Hiroyuki Sato, Yuji Ohashi
    Type: Article
    Subject area: TP
    1999 Volume 72 Issue 3 Pages 367-375
    Published: 1999
    Released: December 24, 2003
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    Three cobaloxime complexes with a chiral 1,2-bis(ethoxycarbonyl)ethyl group bonded to the cobalt atom: [(R)-1,2-bis(ethoxycarbonyl)ethyl]bis(dimethylglyoximato-N,N′)[(S)-1-phenylethylamine]cobalt(III), 1, [(R)-1,2-bis(ethoxycarbonyl)ethyl]bis(dimethylglyoximato-N,N′)(pyridine)cobalt(III), 2, and [(R)-1,2-bis(ethoxycarbonyl)ethyl]bis(dimethylglyoximato-N,N′)(propylamine)cobalt(III), 3, were analyzed by X-rays. The cell dimensions of 2 were remarkably changed when the crystal was irradiated with a xenon lamp. The structure after the irradiation indicated that the chiral 1,2-bis(ethoxycarbonyl)ethyl group was changed to the disordered racemates retaining the single crystal form. The other two crystals showed no change after the irradiation in the same conditions. Comparing the reaction cavities among four crystals analyzed so far, the shape rather than size of the cavity may play an important role in the crystalline-state racemization.
  • Hiroto Oshiman, Takamasa Momose, Tadamasa Shida
    Type: Article
    Subject area: TP
    1999 Volume 72 Issue 3 Pages 377-379
    Published: 1999
    Released: December 24, 2003
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    The fluctuation of physical quantities in multicomponent solutions and its relevance to the light scattering intensity are reexamined. The fluctuation of thermodynamic quantities in solutions is derived without any constraint to the system, such as the assumption of constant volume or constant mass. Based on the mean square correlation among the fluctuation of thermodynamic variables, a general expression for the light scattering intensity is obtained. The present result coincides with that derived by assuming artificial constraints to the volume or the mass of the solutions, the procedure which has been adopted customarily by previous workers. The relation between the fluctuation of density and the mass fraction is also discussed.
  • Hideyoshi Takeshita, Yoshio Suzuki, Yoshinori Nibu, Hiroko Shimada, Ry ...
    Type: Article
    Subject area: TP
    1999 Volume 72 Issue 3 Pages 381-387
    Published: 1999
    Released: December 24, 2003
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    The pressure effect on the phase transitions in hexamethylbenzene and hexa(methyl-d3)benzene crystals was studied compared with the temperature effect on the phase transitions. The transition from phase II to phase III of hexa(methyl-d3)benzene crystal takes place under lower pressure than that for hexamethylbenzene crystal. The change in the spectral structure due to the intermolecular vibrations caused by an increase in the pressure indicates that the marked interaction between the intermolecular rotational vibration and the intramolecular methyl torsional vibration of hexa(methyl-d3)benzene crystal takes place under lower pressure than that for hexamethylbenzene crystal. These facts suggest that the intramolecular methyl torsional vibration plays an important role for the II-to-III phase transition in hexamethylbenzene crystals.
  • Kathaperumal Mohanalingam, Daisuke Yokoyama, Chihiro Kato, Hiro-o Hama ...
    Type: Article
    Subject area: TP
    1999 Volume 72 Issue 3 Pages 389-395
    Published: 1999
    Released: December 24, 2003
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    Ultraviolet absorption and Raman spectra of p-nitroaniline (pNA) have been measured in acetonitrile/CCl4 mixed solvents for seventeen different fractions of acetonitrile. The observed spectral changes were interpreted with the use of a combined singular value decomposition (SVD) analysis, in which the ultraviolet absorption and Raman spectra were combined into one set of spectra. A least-squares fitting analysis was carried out for the SVD decomposed spectra and their amplitudes, using a model in which three distinct species of pNA, the 1 : 0, 1 : 1, and 1 : 2 species, exist in equilibrium. Here, the 1 : 0, 1 : 1, and 1 : 2 species have 0, 1, and 2 acetonitrile molecules associated with pNA. Three intrinsic ultraviolet absorption and Raman spectra have been obtained as a result of the fitting analyses. The three intrinsic spectra show different degrees of charge transfer in the three different solvated forms of pNA. Two equilibrium constants, K1 for the equilibrium between the 1 : 0 and 1 : 1 species and K2 for 1 : 1 and 1 : 2, have been determined. These equilibrium constants give the standard free energy changes for the association of acetonitrile with pNA. A microscopic and quantitative view on the solvation of pNA in acetonitrile/CCl4 mixed solvents has thus been established.
  • Seema Vajhallya, Farid Khan
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 3 Pages 397-402
    Published: 1999
    Released: December 24, 2003
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    Polarography was used to determine the stability constants (log β) of ternary complexes of Zn2+ with L-lysine, L-ornithine, L-threonine, L-serine, L-phenylglycine, L-phenylalanine, L-glutamic acid, and L-aspartic acid as primary ligands and γ-picoline as secondary ligand at pH = 8.50 ± 0.01 and ionic strength μ = 1.0 mol dm−3 NaClO4 at 25 °C. The waves of Zn and its complexes were quasireversible. Zn formed 1 : 1 : 1, 1 : 1 : 2, and 1 : 2 : 1 complexes. The kinetic parameters viz. the standard rate constant (k), degree of irreversibility (λ), and charge transfer coefficient (α) were also determined. The trend of the stability constants of Zn2+complexes with these amino acids and γ-picoline is L-lysine < L-ornithine < L-threonine < L-serine < L-phenylglycine < L-phenylalanine < L-glutamic acid < L-aspartic acid, which is explained on the basis of the sizes and basicities of the primary ligands.
  • Jaya Sarkar, Saswati Prasad Bag, Amitava Basumallick
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 3 Pages 403-405
    Published: 1999
    Released: December 24, 2003
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    The solvent extraction of uranium has been carried out with chloroform solutions of N-phenylbenzohydroxamic acid (BPHA) and Trioctylphosphine oxide (TOPO). The experiments were statistically planned to quantitatively assess the effect of the concentration of BPHA, the concentration of TOPO and the aqueous-phase pH of the solution on the percentage extraction of uranium. In addition, the interactional influence of the above-mentioned variables was also studied. A regression equation has been developed which successfully predicts the percentage extraction of uranium with the values of the variables lying between the selected range of experiments.
  • Masami Nakamoto, Kenji Fukaishi, Tsuyoshi Tagata, Hide Kambayashi, Koj ...
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 3 Pages 407-414
    Published: 1999
    Released: December 24, 2003
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    A series of [Fe4X4(YAd)4]2− (X, Y = S, Se; Ad = 1-adamantyl) were prepared as a model of high potential iron–sulfur proteins. Hydrolysis of the clusters was effectively depressed in aqueous poly[2-(dimethylamino)hexanamide] (PDAH) solutions due to the enbedding effect in hydrophobic environment and/or inhibition of dissociation of the terminal ligand into the aqueous media. Cyclic voltammetry of those clusters in aqueous PDAH solutions showed pH-dependent redox potentials of not only the [Fe4X4]+/2+ but also the [Fe4X4]2+/3+ (X = S and Se) couples, resulting from redox-linked protonation reactions of three oxidation states of [Fe4X4(YAd)4]n (n = 1—3). pKavalues of the reduced, oxidized, and super-oxidized forms of [Fe4X4(YAd)4]2− were determined by computer simulation of the pH dependent redox potentials. The basicity of the core X (X = S and Se) of three oxidation states of [Fe4X4(YAd)4]n (n = 1, 2, 3) was stronger than the terminal YAd (Y = S and Se) ligands: in the case of the mono-protonated [Fe4X4(YAd)4]3−(H+) and [Fe4X4(YAd)4]2−(H+), basicity of the terminal YAd ligand of [Fe4X4(YAd)4]2−(H+) becomes stronger than that of core X, although the core X of [Fe4X4(YAd)4]3−(H+) still showed a stronger basicity than those of terminal YAd ligands.
  • Yasuhiro Funahashi, Chie Kato, Osamu Yamauchi
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 3 Pages 415-424
    Published: 1999
    Released: December 24, 2003
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    With a view to understanding better the redox reactions between the metal center and the pterin cofactor in phenylalanine hydroxylase (PAH) and the effects of possible sulfur coordination to the metal center, we isolated model copper(II) complexes of 2,2′-bis(2-pyridylmethyl)amine (dpa), S-ethyl-N-(2-pyridylmethyl)aminoethanethiol (pat), and pterin-6-carboxylate (ptc), [Cu(dpa)(ptc)]·H2O·CH3OH (1), [Cu(pat)(Cl)]Cl·H2O (2), and [Cu(pat)(ptc)]·3H2O (3), of which 1 and 3 contained ptc as a cofactor model. These binary and ternary Cu(II) complexes were studied by X-ray diffraction, spectroscopic, and electrochemical methods. Redox reactions between Cu(II) complexes ([Cu(dpa)]2+ or 1) and tetrahydropterins (5,6,7,8-tetrahydro-6,7-dimethylpterin (h4dmp) or 5,6,7,8-tetrahydropterin-6-carboxylate (h4ptc)) were also investigated by time-resolved spectroscopic methods. The molecular structures of 1, 2, and 3 showed that dpa and pat occupy three equatorial positions and that ptc in 1 and 3 is vertically coordinated. Complexes 2 and 3 exhibited relatively high redox potentials due to thioether sulfur coordination (E1/2 = −0.06 and −0.18 V vs. Ag/AgCl, respectively) in contrast to [Cu(dpa)]2+ and 1 (E1/2 = −0.32 and −0.39 V, respectively). Coordination of h4dmp and h4ptc to the Cu(II) center of [Cu(dpa)]2+ and 2 to form ternary complexes was detected by the ESR spectra with the use of the rapid mix-freeze-quenching technique; subsequent redox reactions were concluded from the absorption spectral changes.
  • Takao Sasagawa, Hidetake Seino, Youichi Ishii, Yasushi Mizobe, Masanob ...
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 3 Pages 425-432
    Published: 1999
    Released: December 24, 2003
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    Treatment of the pyrrolylimido complexes cis,trans-( [WX2(NNCH=CHCH=CH)(L)(PMe2Ph)2] ) (X = Cl, Br, I; L = PMe2Ph (6), CNBut, CO, PhC≡CH, PhCHO, Br) with LiAlH4or KOH produced pyrrole, 1-aminopyrrole, and ammonia, where both the reaction conditions and the nature of the ligand L showed significant effects on the pyrrole/1-aminopyrrole selectivity. Thus, reduction of cis,trans-( [WBr2(NNCH=CHCH=CH)(CNBut)(PMe2Ph)2] ) with LiAlH4 followed by methanolysis gave pyrrole and ammonia in almost quantitative yields. On the other hand, 1-aminopyrrole was quantitatively produced from the complexes by the reaction of KOH in alcohol when L = CO, PhC≡CH, or PhCHO. While analogous treatment of 6 with KOH in ethanol afforded both pyrrole and 1-aminopyrrole with low selectivity under N2 atmosphere, 1-aminopyrrole was produced from 6 in excellent yield under 1 atm of CO. On the contrary, pyrrole and ammonia were selectively formed from the reaction of 6b (X = Br) with KOH/18-crown-6 ether in THF. Replacement of one of the PMe2Ph ligands in the diazoalkane complex cis,mer-[WBr2(NN=CMeCH2CH2COMe)(PMe2Ph)3] (12) by CO or CNBut facilitated the cyclization of the diazoalkane ligand to provide the (2,5-dimethylpyrrolyl)imido complexes cis,trans-( [WBr2(NNCMe=CHCH=CMe)(L)(PMe2Ph)2] ) (L = CO 14; L = CNBut 15), although complex 12 failed to undergo the ring closure by aqueous HBr. 2,5-Dimethylpyrrole and 1-amino-2,5-dimethylpyrrole were selectively obtained by LiAlH4 reduction of 15 and by treatment of 14 with KOH in EtOH, respectively.
  • Keisuke Umakoshi, Yasuhiro Tsuruma, Chang-Eon Oh, Akira Takasawa, Hana ...
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 3 Pages 433-440
    Published: 1999
    Released: December 24, 2003
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    A series of dinuclear iron(III) complexes with μ-O,O′-bridging amino acids (as zwitter ionic forms) have been prepared: [Fe2(μ-O)(μ-amino acid)(tpa)2](ClO4)4 (tpa = tris(2-pyridylmethyl)amine; amino acid = L-valine (1), L-proline (2), L-alanine (3), L-tyrosine (4), L-tryptophan (5), L-phenylalanine (6), L-alanyl-L-alanine (7)). Among them, 1, 2, and 7 were structurally characterized at 163 K. The non-equivalent ligating mode of the two tpa ligands is common to all the three complexes. The amino acid bridged complexes exhibit irreversible one electron reduction waves with splitting or accompanying shoulders. The bulk electrolysis of these complexes confirmed that the total number of electrons involved in the reduction is one; i.e. Fe2(III, III) → Fe2(II, III). Addition of acid or base leaves positive or negative components, respectively, of the splitting wave. This phenomenon was interpreted as a proton coupled electron transfer where the protonated and deprotonated amino acid bridged species are reduced at different potentials. Magnetic susceptibility measurements in the temperature range, 2—300 K, revealed antiferromagnetic coupling with J = −116, −129, −120, −120, and −129 cm−1 for 1, 2, 4, 6, and 7, respectively (H = −2JS1·S2; S1 = S2 = 5/2).
  • Beata Nowicka, Masayuki Hagiwara, Yasuo Wakatsuki, Horst Kisch
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 3 Pages 441-445
    Published: 1999
    Released: December 24, 2003
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    A series of 1,4,8,11-tetraazacyclotetradecanenickel(II) cyanometalates ([Ni(cyclam)]3[Fe(CN)6]2·11H2O (1), [Ni(cyclam)]2[Mo(CN)8]·3H2O (2), [Ni(cyclam)]2[W(CN)8]·3H2O (3), and [Ni(cyclam)][Pt(CN)4]·3H2O (4) (cyclam = 1,4,8,11-tetraazacyclotetradecane)) was obtained and characterised. Magnetic-susceptibility measurements showed a high-spin configuration (S = 1) of Ni(II) in all compounds, which was attributed to the interaction of cyano ligands with free axial coordination sites on nickel. The presence of bridging cyano groups in 1 was confirmed by IR and visible reflectance spectra. Compound 1 shows a long-range magnetic order below 8 K.
  • Takashiro Akitsu, Seiko Komorita, Yoshihiko Kushi
    Type: Article
    Subject area: AI
    1999 Volume 72 Issue 3 Pages 447-454
    Published: 1999
    Released: December 24, 2003
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    Copper(II) complexes [Cu(succim)2(phen)H2O]·H2O (1) (succim = succinimidate, phen = 1,10-phenanthroline) and [Cu(succim)2(bpy)H2O] (2) (bpy = 2,2′-bipyridine) were prepared and the crystal structures were determined by X-ray crystallography. The coordination geometries are found to be five-coordinated square-based pyramidal [CuN4O] for each complex. Crystal data for complex 1 are monoclinic with space group P21/n; a = 9.602(4), b = 12.003(4), c = 17.618(4) Å; β = 100.38(3)°; V = 1997(1) Å3; Z = 4. Crystal data for complex 2 are monoclinic with space group P21/n; a = 9.616(2), b = 11.616(3), c = 15.871(2) Å; β = 90.61(2)°; V = 1772.8(6) Å3; Z = 4. The axial Cu–O(water) bond distances of the present complexes (2.548(5) Å for 1 and 2.673(4) Å for 2) are appreciable longer than those of other square pyramidal trans-[CuN4O] complexes. The diffuse reflectance spectra showing a broad peak at about 17000 cm−1 were analyzed by means of Gaussian curve fitting and angular overlap model (AOM) calculations with respect to dxy, dyz, and dzx orbitals distributing in the [CuN4] basal plane. According to the analyses, transferability of AOM parameters is valid for succim. The ligand field of bpy can be described by the same parameters as py (py = pyridine). However, it is necessary to set a larger π-bonding AOM parameter for phen than that of py to reproduce the experimental results. The reason for this is out-of-plane lone pairs and π-conjugation of phen. The assignment of the one-electron orbital sequences is presumed to be dx2−y2 > dz2 > dxy > dyz > dzx based on the AOM calculations for each complex.
  • Nasser Iranpoor, Marzieh Shekarriz
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 455-458
    Published: 1999
    Released: December 24, 2003
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    Esterification reactions of alcohols with acetic, chloroacetic, trifluoroacetic, propionic, stearic, and benzoic acids were catalyzed with Ce(OTf)4 in a solvent or under solvent-free conditions with high yields. The formylation and acetylation of primary and secondary alcohols were also easily achieved in ethyl formate and ethyl acetate. A high retention of the configuration was observed in the acetylation and formylation of (−)-menthol.
  • Wataru Satoh, Shuji Masumoto, Masakazu Shimizu, Yohsuke Yamamoto, Kin- ...
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 459-463
    Published: 1999
    Released: December 24, 2003
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    The following nine unsymmetrically axially substituted antimony(V) tetraphenylporphyrins with an antimony–carbon bond or an antimony–fluorine bond were synthesized: [(TPP)Sb(Me)(OEt)]+ClO4 (1-ClO4), [(TPP)Sb(Me)(OC6H4CH3-p)]+ClO4 (2-ClO4), [(TPP)Sb(Me)(SC6H4CH3-p)]+ClO4 (3-ClO4), [(TPP)Sb(Me)(NHC6H4CH3-p)]+ClO4 (4-ClO4), [(TPP)Sb(Me)(NHCH2C6H5)]+ClO4 (5-ClO4), [(TPP)Sb(Me)(OC(=O)C6H4Cl-m)]+PF6 (6-PF6), [(TPP)Sb(Me)(Et)]+PF6 (7-PF6), [(TPP)Sb(Me)(CH2CHMe2)]+PF6 (8-PF6), and [(TPP)Sb(F)(OH)]+ClO4 (9-ClO4). All nine compounds were stable towards atmospheric moisture. X-Ray crystallographic analysis of 6-PF6 revealed that the antimony atom lies at 0.182 Å out-of-plane of the four nitrogens (Δ4N) toward the carbon atom; 6-PF6: space group P21/n, a = 25.49(2), b = 11.27(1), c = 16.58(1) Å, β = 96.74(5)°, R = 0.064.
  • Takayo Moriuchi-Kawakami, Haruo Matsuda, Ikuya Shibata, Masato Miyatak ...
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 465-470
    Published: 1999
    Released: December 24, 2003
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    We have found that halogen-exchange occurs effectively between Sn–F and Li–X (X = I, Br, Cl) in tin hydride reagents. This fact induced a complete change in the regiochemistry in the reductions of α,β-unsaturated ketones 1 with Bu2SnH2–Bu2SnF2 (Reagent A): the use of Reagent A in combination with HMPA performed 1,2-reductions, while the addition of LiI to Reagent A achieved 1,4-reductions. It was demonstrated that the regioselectivity of organotin hydrides greatly depends on the properties of the halogen substituents attached to tin atoms.
  • Mohsen A.-M. Gomaa, Ahmed M. Nour El-Din, Azza A. Mohamed
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 471-476
    Published: 1999
    Released: December 24, 2003
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    1′-Aryl-6′-arylimino-2,2′-dioxospiro[(2,3-dihydro-1H-indole)-3,4′-perhydropyridine]-3′-carbonitriles 5ad together with ethyl 2-amino-4-[1-aryl-2,6-bis(arylamino)-4-hydroxy-1,4-dihydro-4-pyridyl]quinoline-3-carboxylate 9ac were obtained from the reaction of N1,N2-diarylacetamidines 1ad with ethyl 2-oxoindoline-3-ylidenecyanoacetate 3. Acetamidines 1ac also reacted with the benzylidenemalononitriles 10ad to afford the adducts 1,4,5,6-tetrahydropyridines 13af.
  • Yumiko Wada, Masayoshi Yamamoto, Yukio Sudo, Mitsunori Ono
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 477-483
    Published: 1999
    Released: December 24, 2003
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    Monoclonal antibodies were raised against p-nitrophenyl phosphonate to elicit catalytic antibodies capable of hydrolyzing p-nitrophenyl carbonates. Of 34 clones selected, three clones catalyzed the hydrolysis of methyl p-nitrophenyl carbonate. Interestingly, 4A1, an antibody out of those clones, showed a significant rate acceleration against substrates that differ from the given haptenic structure in the carrier-proximal region. The rate acceleration (kcat/kuncat) for one of the specific substrates is 6.4 × 104, 20-fold higher than that of a substrate congruent with the hapten. Kinetic analysis of Km and kcat values, as well as the affinity constant (Kd) values of the corresponding transition-state analogs, indicated that the rate enhancement is associated with a decrease in the activation energy due to stabilization of the transition-state in the cleavage reaction. In addition, the inactivation of 4A1 catalytic antibody upon hydrolysis of a particular substrate was observed. The 600 MHz 13C NMR measurement clearly showed that the 13C-labeled fragment attached covalently to the 4A1 antibody, proving formation of an acyl-antibody. Further kinetic analysis study demonstrated that the 4A1 catalytic antibody uses a multistep kinetic sequence for the hydrolytic reaction.
  • Hiroshi Imahori, Shinichiro Ozawa, Kiminori Ushida, Masao Takahashi, T ...
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 485-502
    Published: 1999
    Released: December 24, 2003
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    Self-assembled monolayers (SAMs) technique has been applied to porphyrin-linked fullerene systems to mimic supramolecular photoinduced charge-separation (CS) events in photosynthesis. Porphyrin-linked C60 molecules with a sulfide group were designed to self-assemble on a gold surface using S–Au interaction. The structure of the SAMs formed on gold electrodes was investigated by spectroscopic methods including X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)-visible spectroscopic ellipsometry, UV-visible absorption spectroscopy, and Fourier transform infrared (FTIR) spectroscopy as well as electrochemical studies. These results indicate that the SAMs have loosely packed structure; the porphyrin-C60 molecules are tilted and nearly parallel onto the gold surface. Short-circuit photocurrent with a level of sub-μA cm−2 was observed for the photoelectrochemical cell in the presence of methylviologen (MV) under illumination with ca. 4 mW cm−2. The maximum intensity of the photocurrent in free-base porphyrin-C60 system is five times larger than that in the corresponding free-base porphyrin system, indicating that C60 is an effective mediator in multistep electron transfer (ET) processes. A possible mechanism for the photocurrent generation is discussed in terms of the photodynamics of porphyrin-linked fullerenes in solution.
  • Yvette Abd El-Sayed Issac
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 503-509
    Published: 1999
    Released: December 24, 2003
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    The reaction of 2-(substituted amino)pyridine with reactive malonic acid derivatives provided an extremely facile synthesis of the mesoionic compound 4-oxo-4H-pyrido[1,2-a]pyrimidin-1-ium-2-olates. N,N′-Disubstituted amidine reacted with diethyl malonate to afford 4-quinolone in a one-pot cyclization and rearrangement (type A/I) of 4-oxopyridiniumolate 6. The latter compound was isolated via a reaction of acyclic amidine with AME’s. A cycloaddition reaction of the mesoionic pyrimidine 6 with maleic anhydride or N-phenylmaleimide yielded [2+4] cycloadducts. Triphenyl pyrrolopyridinetrione 12 was achieved via a ring transformation of the cycloadduct 4-benzyl-3,5-dioxo-1,2,6-triphenyl-2,6-diazabicyclo[2.2.2]octane-7,8-dicarboxylic anhydride 11d. In contrast, the cycloadduct 4-ethyl derivative 11c and substituted 3,5-dioxo-1,2,6-triphenyl-2,6-diazabicyclo[2.2.2]octane-7,8-dicarboxylic N-phenylimides did not give 12 under the same reaction conditions. The mechanistic pathway for the formation of 12 was studied. Dimethyl acetylenedicarboxylate reacted with 6b,c to furnish 2-oxo-1,2-dihydropyridine-4,5-dicarboxylates.
  • Akira Oku, Toshiyuki Miki, Manabu Abe, Masatoshi Ohira, Tohru Kamada
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 511-517
    Published: 1999
    Released: December 24, 2003
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    Irradiation of 2-[3-(2-methoxy-1-phenyl-2-TBDMSO-cyclopropyl)-propyl]-2-cyclohexen-1-one (5) in the presence of Mg(ClO4)2 (1 mol equiv) and 9,10-dicyanoanthracene (DCA, 0.5 mol equiv) in acetonitrile formed methyl 5-oxo-1-phenyldecahydro-1-naphthaleneacetate (6) in 63% yield. When pyrene was adopted in place of DCA, the yield of 6 was 38%. The results indicate that the photocyclization of 5 induced by the SET can be catalyzed by both donor- and acceptor-type photocatalysts. Irradiation of a similar substrate, 4-(2-methoxy-1-phenyl-2-TBDMSO-cyclopropyl)butyl 2-naphthyl ketone (21), produced methyl 2-hydroxy-2-(2-naphthyl)-1-phenylcyclohexaneacetate (27) in 13% in the presense of p-dicyanobenzene (0.1 mol equiv) and 8% in its absence.
  • Takashi Tsuno, Kunio Sugiyama
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 519-531
    Published: 1999
    Released: December 24, 2003
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    Both the direct and sensitized photolyses of [2-(1,2-propadienyl)-substituted alkylidene]malonates gave mainly intramolecular [2+2] cycloadducts. On the other hand, the direct irradiation of methyl (E)-4,4-dimethyl-2,5,6-heptatrienoate (3a) competitively underwent EZ geometric isomerization and intramolecular [2+2] cycloaddition, though prolonged irradiation led to [2+2] cycloadducts as main products. For methyl (E)-4,4,7-trimethyl-2,5,6-octatrienoate (3b), the intramolecular [2+2] cycloaddition occurred under both direct and sensitized irradiation and the EZ geometric isomerization scarcely occurred. In these allenyl(vinyl)methanes under direct irradiation, the 1,2-propadienyl-substituted esters gave a 1,2-propadienylcyclopropane or (2-ethenylidenecyclopropyl)acetate as a minor product. When 3b was irradiated in the presence of hydrogen selenide in toluene, cyclopentenes were formed. The formation of the cyclopentenes indicated that the biradical intermediate is a cyclopentane-1,3-diyl radical. By MO calculations of the model compounds for the chromophores of the esters, it is suggested that the preferential initial bond for the 1,2-butadienyl- or 3-methyl-1,2-butadienyl-substituted esters is between the C6 (allene center carbon) and C2 (α-carbon), while 1,2-propadienyl-substituted esters can also be bonded between the C5 and C3 (β-carbon).
  • Jun Wang, Satoshi Osada, Hiroaki Kodama, Tetsuo Kato, Michio Kondo
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 533-540
    Published: 1999
    Released: December 24, 2003
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    Two cyclic peptides containing the C-terminal tripeptide sequence of oxytocin, cyclo(Pro–Leu–Gly)2 and cyclo(Pro–Leu–Gly)4, have been synthesized from the corresponding linear hexapeptide active ester under high dilution conditions. Cyclo(Pro–Leu–Gly)4 serves as an example of the synthesis of cyclic peptides from linear peptides containing an even number of amino acid residues through dimerization. These two compounds are characterized by TLC, HPLC, amino acid analysis, NMR, and mass spectra. Cyclo(Pro–Leu–Gly)2 has also been synthesized from the linear tripeptide precursor independently, and its properties have been shown to be identical to that from linear hexapeptide. Circular dichroism indicated that cyclo(Pro–Leu–Gly)2 contains β-turns as expected; in contrast, cyclo(Pro–Leu–Gly)4 exhibited a random structure pattern. The NMR spectra demonstrated that cyclo(Pro–Leu–Gly)2 is fixed in only one conformer in DMSO, while in a CDCl3 solution, several conformations with a rapid interconversion are present. Unlike the cyclohexapeptide, cyclo(Pro–Leu–Gly)4 showed more complicated NMR spectra in the two solvents; two or more conformers are considered to be present.
  • Suhk-mann Kim, Hiroshi Kiyonaga, Hideto Yamaguchi, Hiroto Morozumi, To ...
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 541-548
    Published: 1999
    Released: December 24, 2003
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    Muramyl dipeptide is the minimal and essential structural unit for the immunopotentiating activities of bacterial cell walls. The muramyl dipeptide derivative N-acetyl-6-O-(2-tetradecylhexadecanol)muramyl-L-alanyl-D-isoglutamine (B30-MDP) and its amide derivative (B30-MDPA) are good basic materials for use in artificial liposome vaccines (virosomes). The osmotic stability of muramyl dipeptide-bearing liposomes composed of various binary mixtures was examined to find conditions favoring stable liposome formation. The osmotic properties of B30-MDP-bearing and B30-MDPA-bearing liposomes were significantly different from each other. Nevertheless, a good correlation between osmotic stability and virosome formation was found for both types of liposomes. Furthermore, the dynamic structures and the intermolecular interactions of phospholipids in muramyl dipeptide-bearing liposomes were investigated by solid-state 2H and 31P NMR. The results suggested that molecular miscibility in the liposomes is not an essential factor for osmotic stability. Negative charges on the liposome surface and flexible hydrophilic moieties were found to be the most important factors in keeping isolated liposomes osmotically stable.
  • Takao Okazaki, Kazuhiko Tokunaga, Toshikazu Kitagawa, Ken’ichi T ...
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 549-561
    Published: 1999
    Released: December 24, 2003
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    The title bridgehead olefins, generated by the dehalogenation of 1,2-dihalo-2-R-adamantanes (R = Me, Et, Ph, p-CF3C6H4) with excess t-BuLi, yielded 2-t-butyl-2-R-adamantanes (15), 1-t-butyl-2-R-adamantanes (16), and dimeric products. The ratios of the yields (%) of 16 to 15 were 20 : 3 (R = Me), 32 :< 1 (R = Et), 4 : 60 (R = Ph), and 5 : 57 (R = p-CF3C6H4). 2-Alkyladamantenes predominantly yielded the products t-butylated at C(1), whereas 2-aryladamantenes gave the products t-butylated at C(2). The total yields of the dimers decreased with the bulkiness of substituents at position C(2). The dimerization of 2-methyladamantene gave a head-to-head dimer, 1-(2-methyl-1-adamantyl)-2-methyleneadamantane, as well as a head-to-tail dimer, 1-(2-methyl-2-adamantyl)-2-methyleneadamantane. The [4+2] cycloaddition between two molecules of 2-phenyladamantene, in which the phenyl group participates as a part of the diene, yielded a dimer of the head-to-tail type.
    These results suggest that: i) a substituent at position C(2) can kinetically stabilize 2-R-adamantene and suppress the dimerization, ii) 2-alkyladamantenes might have a biradical nature, and iii) the regioselective [4+2] cycloaddition and t-BuLi addition of 2-phenyladamantene in THF can be explained by assuming a certain contribution of zwitterionic nature in the double bond that may be dependent on the media and nucleophiles.
  • Shigeru Sasaki, Yoshihiro Tanabe, Masaaki Yoshifuji
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 563-572
    Published: 1999
    Released: December 24, 2003
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    Sterically hindered 1,4-bis(dimesitylphosphino)-2,3,5,6-tetrafluorobenzene (1) was synthesized by the aromatic nucleophilic substitution of lithium dimesitylphosphide with hexafluorobenzene. Two phosphorus atoms of 1 were oxidized and methylated to give the corresponding bis(phosphoryl)benzene 2 and bis(phosphonio)benzene 32+·2TfO (TfO = trifluoromethanesulfonyl), respectively. On the other hand, reaction of 1 with butyllithium and phenyllithium gave more crowded 2,5-dibutyl-1,4-bis(dimesitylphosphino)-3,6-difluorobenzene (4) and 1,4-bis(dimesitylphosphino)-2,5-difluoro-3,6-diphenylbenzene (5), respectively. Structures of 1, 2, 32+·2TfO, 4, and 5 were confirmed by conventional spectroscopic methods; particularly 19F NMR spectroscopy reflected their crowded structures. Molecular structures of 1, 2, and 32+·2TfO, were further investigated by X-ray crystallography, where unusually large bond angles around phosphorus atoms were observed. Electrochemical measurements were carried out to investigate redox properties of 1, 32+·2TfO, 4, and 5. Although the cyclic voltammogram of diphosphine 1 showed irreversible oxidation waves above 0.8 V, in spite of substitution at all the ortho positions to the phosphorus atoms in 1, displacement of the two fluorine atoms of 1 by the butyl or the phenyl groups lowered the oxidation potential and improved the stability of the corresponding radical cations. Particularly, 5 clearly showed two-step oxidation waves. On the other hand, bis(phosphonium salt) 32+·2TfO showed two steps of quasi-reversible redox waves, which suggested reduction to the cation radical and the neutral species, although their stability was limited.
  • Kazuhiro Nagayama, Futoshi Kawataka, Masato Sakamoto, Isao Shimizu, Ak ...
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 573-580
    Published: 1999
    Released: December 24, 2003
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    Acyclic anhydrides oxidatively added to [Pd(styrene)(PMeR2)2] (R = Me, 2a; Ph, 2b) under mild conditions with C–O bond cleavage to give the corresponding trans-acyl(carboxylato)palladium complexes 3a3h. Cyclic acid anhydrides also added to 2a to yield trans-acyl(carboxylato)palladium complexes 4a4c, while reaction of 2a with phthalic anhydride afforded the palladalactone 4d generated via oxidative addition followed by decarbonylation. The acetyl(acetato)palladium complex 3a reacted with dihydrogen or formic acid to give acetaldehyde and acetic acid. Catalytic hydrogenation of acyclic anhydrides by a palladium complex was achieved to form the corresponding aldehydes and carboxylic acids.
  • Kazuhide Nakata, Mizue Fujio, Masaaki Mishima, Hideyuki Nomura, Yuho T ...
    Type: Article
    Subject area: OB
    1999 Volume 72 Issue 3 Pages 581-590
    Published: 1999
    Released: December 24, 2003
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    Substituent effects on the solvolysis rates of 1,2,2-trimethyl-1-phenylpropyl chlorides in 80% (v/v) aq acetone at 45 °C and 1,2,2-trimethyl-1-(2-methylphenyl)propyl p-nitrobenzoates in 50% (v/v) aq ethanol at 75 °C were correlated with the Yukawa–Tsuno equation to give ρ = −4.28 and r = 0.91, and ρ = −2.78 and r = 0.70, respectively. The reduction in r values from r = 1.00 for full conjugation is ascribed to deviation from coplanarity of the carbocationic center and the benzylic π-system in the transition state. Substituent effects on the gas phase stabilities of 1,2,2-trimethyl-1-phenylpropyl cations and 1,2,2-trimethyl-1-(2-methylphenyl)propyl cations were correlated to give ρ = −9.1 and r = 0.89, and ρ = −6.6 and r = 0.70, respectively. The identical r values were obtained for the transition states and for the intermediates. The experimentally obtained torsion angles for twisting estimated from the relationship r/rmax = cos2 θ are in good agreement with theoretically calculated dihedral angles of the corresponding Becke3LYP/6-31G* optimized carbenium ions. This identity provides convincing evidence for occurrence of steric inhibition of resonance through loss of coplanarity and provides strong support for our characterization of the r value as a resonance demand parameter.
  • Kazunori Matsui, Kazuhiro Nozawa, Tsutomu Yoshida
    Type: Article
    Subject area: AM
    1999 Volume 72 Issue 3 Pages 591-596
    Published: 1999
    Released: December 24, 2003
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    The phosphorescence spectra of benzophenone (BP) were studied in tetramethoxysilane (TMOS) sol–gel systems at 77 K. The phosphorescence spectra ascribed to solvent-free benzophenone (f-BP), aggregated benzophenone (a-BP), and a benzophenone–water complex (w-BP) were observed in these systems. The results showed that the spectra varied with the BP concentration and sol–gel conditions, such as the water/TMOS ratios, catalyst, and the various sol–gel reaction stages. The w-BP phosphorescence lifetimes showed a single-exponential decay of 8 ms in sol systems and a double-exponential decay of 8—12 ms and 31 ms in xerogel systems. The longer lifetime component corresponds to a w-BP complex hydrogen bonded with silanol groups. These changes are discussed in terms of the sol–gel structure and surface adsorption effects.
  • Mamoru Ai, Kyoji Ohdan
    Type: Article
    Subject area: AM
    1999 Volume 72 Issue 3 Pages 597-602
    Published: 1999
    Released: December 24, 2003
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    An iron phosphate having a new crystalline phase was obtained by a partial reduction of iron(III) orthophosphate with a reducing agent, usually oxalic acid, in the presence of oxygen and a large amount of water vapor at a low temperature of 200 to 250 °C. XRD spectra of the new phase (designated as M-phase) are similar to those of clay minerals. The effects of reaction variables, such as reducing agent, reaction period, starting iron phosphate, temperature, and oxygen feed rate, on the formation of M-phase were studied. Some characterizations of this M-phase were also attempted.
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