bluuebunny/crossref_metadata_2025 huggingface dataset:
New Efficient Synthesis of a Biosynthetic Precursor of Lipid A
Authors: Oikawa Masato , Wada Akira , Yoshizaki Hiroaki , Fukase Koichi , Kusumoto Shoichi
Published: June 2006

A biosynthetic precursor of lipid A has been synthesized by an improved efficient method. Two appropriately modified acyl-substituted glucosamine units were synthesized from d-glucosamine using (R)-3-(benzyloxy)tetradecanoic acid and then coupled by the Lewis acid-promoted glycosidation via the corresponding trichloroacetimidate. Glycosyl phosphorylation and hydrogenolytic deprotection, followed by purification by liquid–liquid partition chromatography, afforded the target compound in 2.9% total yield through 13 steps from N-Troc-d-glucosamine.
Effect of Proline Residue in Polypeptides on the Interactions between Polypeptides and DNA
Authors: Uchida Chieko , Wakamatsu Kaori , Oya Masanao
Published: June 2006

The interaction between high molecular-weight synthetic polypeptides containing proline residue and salmon DNA were studied by circular dichroism spectra (CD) in aqueous solution, 1H NMR in D2O solution, and 13C NMR spectra in solid state. The interactions were compared with those of polypeptides containing lysine residue and DNA. The complexes of poly(Pro) and poly(Pro-co-Gly) with DNA were made by lyophilization after dialysis of the mixed solution of the corresponding solutions. These complexes were soluble in water and insoluble in 1 M NaCl, in contrast to the poly(Lys)–DNA complex, which was insoluble in water and soluble in 1 M (mol dm−3) NaCl. The polypeptides containing proline residue (poly(Pro-co-X)) interacted with DNA in the solution, which differed from the interaction of poly(Lys) with DNA. In addition, the interactions of poly(Pro) and poly(Pro-co-Gly) with DNA differed from each other.
Thermodynamic and Structural Aspects on Solvation Steric Effect in Nonaqueous Solution
Authors: Ishiguro Shin-ichi
Published: June 2006

Formation thermodynamics and structure of halogeno and pseudo-halogeno complexes of transition metal(II) and lanthanide(III) ions have been studied in N,N-dimethylacetamide (DMA) and hexamethylphosphoric triamide (HMPA), and compared with those in N,N-dimethylformamide (DMF). Significant differences in the formation thermodynamics and structure among solvents has been explained in terms of a solvation steric effect. A structural survey by EXAFS demonstrates that solvent coordination number of a solvate metal ion is kept unchanged (weak solvation steric effect) or reduced (strong solvation steric effect) when the metal ion is transferred to DMA or HMPA, respectively, from DMF. DMA usually exhibits a weak solvation steric effect. It elucidates that a weak solvation steric effect of DMA is ascribable mainly to a distortion of the M–O–C–N dihedral angle. The solvent effect operates for a complex with a coordination number larger than four in DMF, but it does not for a complex of four-coordination. Lanthanide(III) ions exhibit a specific solvation steric effect, and an outer-sphere bromo complex in DMF changes to an inner-sphere complex in DMA. Besides, the solvent coordination number varies with solvent composition in DMF–DMA mixtures, and the variation manner strongly depends on the metal ion or the ionic radius. HMPA shows a strong solvation steric effect, and halogeno complexation is significantly enhanced in HMPA relative to that in DMF, although HMPA has a stronger electron-pair donating ability. The coordination number is four or five, and the M–O(HMPA) bondlength is significantly shortened.
Structure and Properties of Non-Classical Polymers. XI. Heteroatomic Analogues of Poly(1,3-phenylenemethylene)’s
Authors: Tyutyulkov Nikolai , Dietz Fritz , Müllen Klaus , Kübel Christian
Published: June 2006

The magnetic properties of a new class of high-spin organic 1-D polymers were studied theoretically. The polymers have the same topology as poly(1,3-phenylenemethylene)s (PMP) and are derived from the latter by substitution of the exocyclic radical center –C•R– by –B•−R–, –N•–, –N+•H–, –O+•– or –S+•–. All of these polymers possess a narrow half-filled band (HFB) within the energy gap. The nature of spin-exchange interactions of π-electrons within the HFB has been investigated. The three components of the effective exchange integral, Jeff, in the Heisenberg Hamiltonian representing the potential (direct), kinetic and exchange (due to the spin polarization—indirect exchange) interaction of the π-electrons in the HFB were calculated. In all cases, the potential (Coulomb) exchange was the main contribution to the ferromagnetic (Jeff > 0) exchange interaction.
Ab Initio Molecular Orbital Study of the Benzene–Chlorine Complex
Authors: Matsuzawa Hidenori , Osamura Yoshihiro
Published: June 2006

The geometrical structures and stabilization energies of benzene–chlorine complex were studied theoretically using an ab initio molecular orbital method. Full geometry optimization was carried out for four models ((1) [On Center (C6v symmetry)], (2) [On Atom (Cs symmetry)], (3) [On Bond (Cs symmetry)] and (4a,b) [Resting (Cs symmetry)]) with restricted Hartree–Fock (RHF) and second-order Møller–Plesset perturbation (MP2) methods, MP2 (Frozen), and MP2 (Full), using various basis sets. The RHF method is not good enough to describe the molecular structure and interaction energy of the complex. The geometry obtained with the MP2/DZP + d method has good agreement with the X-ray crystal structure. An unusual basis set superposition error (BSSE) was found when the MP2 method with a frozen-core approximation was applied to evaluate the interaction energy. In the MP2 (Full) method, in which the inner-core wavefunctions was correlated, the reasonable stabilization energy is obtained. The BSSE-corrected interaction energies (ΔE(corr.)) of models(1), (2), and (3) are −6.63, −8.44, and −8.14 kJ mol−1, respectively. The most stable structure of the benzene–chlorine complex was calculated to be model (2). Model (3) lies at only 0.3 kJ mol−1 higher energy than model (2) in the MP2(Full)/DZP + d calculation. The position of chlorine would be very flexible on the benzene ring, and the molecular structure of the complex is easily interchangeable between models (2) and (3).
A Completely Inorganic BZ-Type Oscillator in a Closed Homogeneous System
Authors: Li Hexing , Shen Chun
Published: June 2006

In a batch reactor, an absolutely homogeneous inorganic Belousov–Zhabotinskii (BZ)-type oscillator has been designed in the system of BrO3−–H2PO2−–Mn2+–Fe(phen)32+–H2SO4. The oscillations of both [Br−] and [Mn3+]/[Mn2+] as well as [Fe(phen)33+]/[Fe(phen)32+] were observed by monitoring the changes of either the potential on a bromide electrode or the absorbance at the maximum absorbance wavelength for Mn3+ and Fe(phen)33+, respectively. Both of those two metallic ions are essential in the present system to give rise to the oscillations; their roles in the oscillation are discussed. It is found that Mn2+ can not be replaced by other substances, while Fe(phen)32+ can be replaced by either N2 flow or acetone. However, it can not be replaced by other metallic ions, including Mn2+ and Ce3+. Those results suggest that Mn2+ is the real oscillating catalyst for an autocatalytic formation of HBrO2 and Fe(phen)32+ is a catalyst for the catalytic reduction of Br2 by H2PO2− to remove any excess Br2 produced during the oscillations.
Pulsed Electric Linear Dichroism of Poly(dA)·Poly(dT)·Poly(dT) and Poly(rA)·Poly(rU)·Poly(rU) in Solutions
Authors: Ojima Noriyuki , Gekko Kunihiko , Yamaoka Kiwamu
Published: June 2006

The dependence of reduced dichroism (Δε/ε) of sonicated rodlike title triplexes with the counterion Mg2+, (dA)n·(dT)n·(dT′)n and (rA)n·(rU)n·(rU′)n, on the wavelength (190—300 nm) and on the applied-field strength (3.8—23.1 kV cm−1) was studied in aqueous ionic solutions at 7 °C. The sonicated samples were fractionated and well-characterized by the gel-permeation chromatography/low-angle laser light-scattering method. The reduced dichroism saturated at infinitely high electric fields ((Δε/ε)s) was estimated to be −1.22 for (dA)n·(dT)n·(dT′)n and −1.09 for (rA)n·(rU)n·(rU′)n, by fitting the observed Δε/ε values at 260 nm to a theoretical orientation function. The electric linear dichroism (ELD) spectra, i.e., the dependence of (Δε/ε)s on the wavelength, of (dA)n·(dT)n·(dT′)n and (rA)n·(rU)n·(rU′)n were determined. The measured ELD spectra were simulated by assigning the appropriate roll (θR) and tilt (θT) angles to the constituent bases. The most probable θR and θT values, determined for each triplex, indicate that the structures of triple helices both belong to an “A-form” family. The constituent bases in base-triple do not lie on a common plane. From an analysis of transient decay signals, the translation per base-triple (h) was estimated for each triplex. The structures of the present high molecular-weight triple-stranded helices in aqueous solution were determined for the first time and the plausible structural models were constructed from the experimentally evaluated sets of θR and θT.
Characterization of Dimeric Copper(II) Trichloroacetate Complexes by Electron Spin Resonance, Infrared, and Electronic Reflectance Spectra. Correlation of Spectral Parameters with Molecular Geometry
Authors: Muto Yoneichiro , Horie Hiroshi , Tokii Tadashi , Nakashima Michio , Koikawa Masayuki , Steward Omar W , Ohba Shigeru , Uekusa Hidehiro , Husebye Steinar , Suzuki Ikuo , Kato Michinobu
Published: June 2006

ESR, IR, and electronic reflectance spectral data are presented for dimeric (trichloroacetato)copper(II) complexes, of which magneto-structural data are available: The larger is the distortion of the coordination geometry from square pyramidal (SP) toward trigonal bipyramidal (TBP), the longer is the Cu···Cu distance in the dimers. The elongation of the Cu···Cu distance is accompanied by a reduction of the zero-field splitting parameter (D), the anisotropic exchange parameter (Dex), and the peak separation of the two peaks in the electronic spectra (). The splitting of the carboxylato stretching frequencies, , increases with the distortion. Good linear correlations have been observed between the values of these parameters and the Cu···Cu distances. The axial ESR spectra with g// > g⊥ and the electronic spectra suggest that the ground state of the Cu atom is essentially dx2 − y2, even in the metal geometry of the greatest distortion toward TBP (the z-axis is along the longest Cu–O bond).
Formation of Di- and Tricarbonylruthenium(O) Species from [RuH2(CO)(PPh3)3] via Decarbonylation of Methyl Benzoates: X-Ray Crystal Structures of [Ru(CO)2(PPh3)3] and [Ru(O2)(CO)2(PPh3)2]
Authors: Hiraki Katsuma , Kira Shu-ichi , Kawano Hiroyuki
Published: June 2006

Dihydridoruthenium(II) complex [RuH2(CO)(PPh3)3] (1) reacts with methyl benzoate in the presence of an olefin at 110 °C to afford some dicarbonylruthenium(O) species [Ru(CO)2(PPh3)3] (2) and “Ru(CO)2(PPh3)2L” (L = the olefin or the ester). A tricarbonylruthenium(O) complex [Ru(CO)3(PPh3)2] (3) is formed at higher reaction temperature. The experiment using 13C-enriched methyl benzoate reveals that the second and the third carbonyl ligands are mainly derived by subtraction of the carbonyl group from the ester. When the reaction is carried out in the presence of triethoxyvinylsilane, a part of the second and the third carbonyl groups is derived from the ethoxy group of the silane, because 1 reacts with the silane at 110 °C in the absence of the ester to afford 2 and 3. The formation ratio of 2 and 3 is affected by the type of olefins used; selective formation of 2 and 3 is achieved when triethoxyvinylsilane is used, whereas allylbenzene or cyclooctene affords merely a mixture of the di- and tricarbonyl species. The reaction mixture containing 2 and “Ru(CO)2(PPh3)2L” is exposed to air to give a peroxo complex [Ru(η2-O2)(CO)2(PPh3)2] (4) smoothly. The molecular structures of 2 and 4 are determined by the single crystal X-ray diffraction method. The complex 2 has a distorted trigonal bipyramidal coordination geometry with two equatorial CO ligands, whereas the complex 4 has a distorted octahedral structure.
Variable-Temperature and -Pressure Nitrogen-14 Magnetic Resonance Studies on Solvent Exchange of Nickel(II), Iron(II), and Manganese(II) Ions in Neat 1,3-Propanediamine and n-Propylamine
Authors: Aizawa Sen-ichi , Iida Shigeo , Matsuda Kayoko , Funahashi Shigenobu
Published: June 2006

The solvent exchanges of nickel(II), iron(II), and manganese(II) ions in 1,3-propanediamine (tn) and n-propylamine (pa) have been studied by the 14N NMR line-broadening method. The rate constants of the amine exchanges for the first-row transition metal ions are in the order of ethylenediamine (en) < tn < pa, which is largely affected by the difference in the activation enthalpies. The differences in the rate constants and the activation enthalpies among the three amine solvents become greater along the series from manganese(II) ion to nickel(II) ion. These kinetic results have clarified that the differences in the kinetic chelate strain effect in the transition state and the chelate strain effect in the ground state can be attributed to the difference in the chelate ring sizes and the ion radii.
Valence Isomerization. Synthesis and Characterization of Cobalt and Nickel Complexes with Non-Innocent N2S2 Ligand
Authors: Kawamoto Tatsuya , Kuma Hiro , Kushi Yoshihiko
Published: June 2006

The reactions of 2-phenylbenzothiazoline with [M(CH3COO)2]·4H2O (M = Co(II) and Ni(II)) afford the complexes [M(phbt)2 ] (phbt = 2-(phenylmethyleneamino)benzenethiolato) via a ring opening reaction of 2-phenylbenzothiazoline. Spectroscopic data indicate that the cobalt and nickel atoms occupy a tetrahedral and a square planar N2S2 environment, respectively. The single crystal X-ray structure of [Ni(phbt)2] is redetermined and this complex shows a monohelical geometry. Crystal data: [Ni(phbt)2], monoclinic, C2/c, a = 23.065(4); b = 6.924(2); c = 13.809(2) Å; β = 102.64(1)°; V = 2152.0(9) Å3; Z = 4, R = 0.052 (Rw = 0.050). The toluene solution of [Co(phbt)2] and that of [Ni(phbt)2] lead to the complexes [Co(ddbt)] and [Ni(ddbt)] (ddbt = bis-2,2′-(1,2-diphenylethylenediimine)benzenethiolato) through the carbon–carbon bond formation, respectively. The structural features of [M(ddbt)] (M = Co and Ni) point clearly to the neutral dithiolene-like charge distribution. These complexes [M(ddbt)] have the same chemical compositions as the starting complexes [M(phbt)2], and both can be correlated in a new valence isomerism. Crystal data: [Co(ddbt)], monoclinic, P21/n, a = 8.573(2); b = 24.486(3); c =10.771(1) Å; β = 102.08(2)°; V = 2211.0(9) Å3; Z = 4, R = 0.056 (Rw = 0.048); [Ni(ddbt)], monoclinic, P21/n,a = 8.631(10); b = 24.365(19); c = 10.798(4) Å; β = 102.69(6)°; V = 2215.2(33) Å3; Z = 4, R = 0.078 (Rw = 0.075).
Performance and Characterization of a [PtMo6]/MgO Catalyst: The Catalytic Activity for NO–CO Reactions and Structural Analysis by EXAFS
Authors: Tomishige Keiichi , Nagasawa Yosuke , Lee Uk , Iwasawa Yasuhiro
Published: June 2006

The catalytic property of a [PtMo6]/MgO catalyst prepared by using a [PtMo6O24]8− precursor for NO–CO reactions and a structural analysis by means of Pt L3- and Mo K-edge EXAFS spectroscopy was studied. The catalytic activity of the bimetallic ensemble catalyst appeared due to the incorporation of Pt ions into the MgO surface, where Pt4+ ions substituted Mg2+ ions in the first layer of the MgO surface. It seems that the NO–CO reaction proceeded on the Pt sites embedded in the MgO surface by a redox mechanism, whereas metallic Pt particles on MgO were inactive under the present reaction conditions, characterized by an in-situ EXAFS analysis.
Friedel–Crafts Transannular Alkylation of Benzene with (Z,Z)-1,5-Cyclooctadiene: Reassignment of Two Phenylbicyclooctanes by 13C NMR Spectroscopy and Separate Preparation
Authors: Tateiwa Jun-ichi , Uemura Sakae
Published: June 2006

Our previous structure assignment of two phenylbicyclooctanes obtained in Friedel–Crafts transannular alkylation of benzene with (Z,Z)-1,5-cyclooctadiene has been reinvestigated and partly corrected on the basis of 13C NMR spectral data, a separate preparation of an authentic sample, and MM3 calculation. The compounds assigned previously to exo-3-phenyl-cis-bicyclo[3.3.0]octane and exo-3-phenylbicyclo[3.2.1]octane among six products should be assigned to 1-phenyl-cis-bicyclo[3.3.0]octane and exo-3-phenyl-cis-bicyclo[3.3.0]octane, respectively, showing that almost all products have bicyclo[3.3.0]octane framework. A new preparative method for an authentic 1-phenyl-cis-bicyclo[3.3.0]octane and MM3 calculations of all products are also presented.
Synthesis of Functionalized 4H-Pyrano[3,2-c]pyridines from 4-Hydroxy-6-methyl-2-pyridone and Their Reactions. Unexpected New Routes to 3,3′-Benzylidenebis[4-hydroxy-6-methyl-2(1H)-3-pyridinone]s
Authors: Mekheimer Ramadan Ahmed , Mohamed Nabil Helmi , Sadek Kamal Usef
Published: June 2006

The reaction of 4-hydroxy-6-methyl-2-pyridone 1 with benzylidenemalononitriles in an ethanolic solution containing a catalytic amount of piperidine and α-cyanoacrylic esters in pyridine affords the corresponding 4H-pyrano[3,2-c]pyridines. However, it’s reaction with 3-(cyanomethylene)-2-indolinones gives either 2-amino-3-quinolinecarbonitriles or ethyl 2-amino-5′,6′-dihydro-7′-methyl-2,5′-dioxospiro-[indoline-3,4′-[4H]-pyrano[3,2-c]pyridine-3′-carboxylate. In contrast, the reaction of 1 with 3-aryl-2-cyano-2-propenethioamides affords 3,3′-benzylidenebis[4-hydroxy-6-methyl-2(1H)-3-pyridinone]s. The reaction of the obtained 4H-pyrano[3,2-c]pyridines with acetic anhydride affords the corresponding fused system.
A New Type of φ, ψ Representation of the Protein Tertiary Structure and the Analysis of the Amino Acid Preferences for Specific Locations at Type-II β-Turn by Using 8000 Possible Kinds of Amino Acid Residues
Authors: Narita Mitsuaki , Sode Koji , Ohuchi Shokichi , Hitomi Mitsuo , Murakawa Yuka
Published: June 2006

φ, ψ Representations of three-dimensional structures of 125 globular proteins were depicted for analyzing conformational details in their secondary and tertiary structures. They can be drawn in the form of a two-dimensional diagram. The new type of representation of the protein tertiary structure can be used as a stereotyped finger printing for 125 protein molecules. It is powerful for a precise comparison of the relationship of the primary, secondary, and tertiary structures of homologous proteins. The precise or broad similarity between the patterns of proteins classified into the same family is obvious. This representation is also useful in readily recognizing all of the secondary structures as one progresses along the chain. Complicated three-dimensional structures of 125 globular proteins are easily recognized to be built up from only four secondary structures: helix, β-strand, β-turn, and unordered structure. A combination of intersegments hydrogen bonds among β-strands was also shown in the diagram. In order to demonstrate the usefulness of the diagram, 195 type-II β-turns were extracted from 125 proteins using the new type of two-dimensional φ, ψ diagrams. Their amino acid sequences were surveyed so as better to understand amino acid preferences previously observed. For their analysis, a normalized preference (NP) value of an amino acid residue at a particular position of the secondary structure is defined as the ratio of the average percentage composition at the position based on average percentage composition at large. The statistical significance of the NP-value used in this study is more simple and clearer than that of the d-test based on a normal distribution, which was used in the previous study. It is clearly shown that a high NP-value (5.0) of a single P residue for the position i + 1 of the type-II β-turn is an average preference of a variety of P residues in the middle of triplets consisting of consecutive amino acid residues. The NP-values of P residues, in the middle of 25 particular triplets are outstandingly high. Out of 400 possible P residues 322 kinds of P residues were found in 125 proteins. A remarkable high NP-value (8.8) of a single G residue for the position i + 2 is also an average preference of G residues in the middle of various triplets.
Side-Chain Liquid-Crystalline Polyoxetanes with a Spacer-Separated Azobenzene Moiety. III. Preparation and Characterization of Polyoxetanes Anchoring the Mesogen Cores of a p-Spacer-Substituted Phenyl 4-(4-Alkoxyphenylazo)benzoate in the Side Chain
Authors: Ogawa Hiroshi , Kanoh Shigeyoshi , Motoi Masatoshi
Published: June 2006

Polyoxetanes anchoring the mesogen cores of p-spacer-substituted phenyl 4-(4-alkoxyphenylazo)benzoates through a pendant spacer, –CH2O(CH2)4O–, were prepared by a BF3-initiated cationic ring-opening polymerization of the corresponding oxetanes, followed by a fractional reprecipitation of the raw polymer products containing oligomer fractions. The polyoxetanes separated from the oligomers had their peak tops at molecular weights of around 10000—23000 in nearly mono- or dimodal molecular-weight dispersity curves determined by gel permeation chromatography, and indicated fan-shaped textures due to a smectic mesophase over a wide temperature range from about 250 °C to room temperature on heating and cooling processes by polarized optical microscopy. The formation of highly ordered assemblies of the pendant mesogens is ascribable to a cohesion of the 4-(4-alkoxyphenylazo)benzoate moiety in the mesogen core, which can form a larger dipole, due to forming a longer conjugated system from the ester carbonyl to the alkoxy tail, than that of the simple 4-alkoxybenzoate moiety of the mesogen core previously reported by us.
Laser-Flash Photolysis in High-Speed Photopolymer Coating Layers Containing Carbonylbiscoumarin Dyes and 2,2′-Bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,1′-bi-1H-imidazole
Authors: Urano Toshiyuki , Nagasaka Hideki , Shimizu Shigeki , Ito Hiroto , Shimizu Makoto , Takahara Shigeru , Yamaoka Tsuguo
Published: June 2006

The sensitization mechanisms of ketocoumarin dyes with a radical-generating reagent (10,10′-carbonylbis[1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one] (KCD-J), 3,3′-carbonyldis[7-(diethylamino)-2H-1-benzopyran-2-one] (KCD-DA)) with 2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,1′-bi-1H-imidazole (BI) in a poly(methyl methacrylate) (PMMA) film have been investigated by laser-flash photolysis using a total-reflection cell. The triplet decay time of the dyes in a PMMA film was quenched by BI with a kqs of 1.3 and 0.60 × 105 mol dm−3 s−1 for KCD-J and KCD-DA. The fluorescence and initial absorption for KCD-DA were not quenched by BI in a PMMA film. The fluorescence was quenched at a quenching distance of 10.0 Å, and the initial triplet absorption was not quenched for KCD-J in a PMMA film.

These results show that a nonstatic sensitization from the triplet to BI is the predominant process in a photoinitiation system containing KCD-DA, and that both static sensitization from the singlet excited state to BI and nonstatic sensitization from the triplet to BI exist in a photoinitiation system containing KCD-J.
The Direct Iodination of Arenes with Chromium(VI) Oxide as the Oxidant
Authors: Lulinski Piotr , Skulski Lech
Published: June 2006

An easy and cheap laboratory method is presented for the direct mono- and diiodination of a number of activated and deactivated arenes. The main iodination reactions occurred at the temperatures not exceeding 65 °C for 0.5—12 h in the anhydrous, strongly acidic liquid system, I2/AcOH/Ac2O/H2SO4, in the presence of prior dissolved CrO3 used as the oxidant. The yields of the pure iodinated products varied from 31% (for 3,5-diiodobenzoic acid) up to 90% (for 4-iodoanisole). So far, benzonitrile and some oxidizable aromatics, e.g. naphthalene, fluorene, xanthene, and thiophene, have been found to be unsuitable for the effective iodination. Nevertheless, this novel, simple method of direct iodination is worthy to be extended to other appropriate aromatics.
Regioselective Robinson Annulation Realized by the Combined Use of Lithium Enolates and Aluminum Tris(2,6-diphenylphenoxide) (ATPH)
Authors: Saito Susumu , Shimada Itsuro , Takamori Yusuke , Tanaka Michiaki , Maruoka Keiji , Yamamoto Hisashi
Published: June 2006

Michael addition of lithium enolates derived from ketones to a variety of α,β-unsaturated ketones was realized in the presence of aluminum tris(2,6-diphenylphenoxide) (ATPH). In this reaction, ATPH can be used as a carbonyl protector of α,β-unsaturated carbonyl substrates upon complexation, which facilitates the regioselective 1,4-addition of lithium enolates to Michael acceptors. Similarly, dianions of β-dicarbonyl compounds undergo Michael addition smoothly using ATPH as an effective promoter of the reaction. Subsequent regioselective, intramolecular aldol condensation was also demonstrated, leading to bicyclic carbon ring systems. Such systems are difficult to obtain by the Robinson annulation usually performed in protic media.
Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by (S)-2-(N,N-Disubstituted aminomethyl)pyrrolidine
Authors: Asami Masatoshi , Inoue Seiichi
Published: June 2006

The enantioselective addition of diethylzinc to aldehydes in the presence of a catalytic amount of several chiral diamines, (S)-2-(N,N-disubstituted aminomethyl)pyrrolidines, was studied. Relatively high selectivity was achieved in the case of aromatic aldehydes by employing 15 mol% of (S)-2-(1-pyrrolidinylmethyl)pyrrrolidine.
Single-Step Acylation of Polyester Terminals by Enzymatic Ring-Opening Polymerization of 12-Dodecanolide in the Presence of Acyclic Vinyl Esters
Authors: Uyama Hiroshi , Kikuchi Hirofumi , Kobayashi Shiro
Published: June 2006

Enzymatic ring-opening polymerization of a 13-membered lactone, 12-dodecanolide (DDL), was performed in the presence of acyclic esters in bulk by using lipase catalyst. The acyl group was introduced at the terminal by adding a fatty acid vinyl ester. Effects of the chain length and concentration of the vinyl ester on the introduced ratio (functionality) and molecular weight of the polymer have been examined. The quantitative acylation of the terminal was achieved by using lipases derived from Pseudomonas family under appropriate reaction conditions. Methacryl- and ω-alkenyl-type polyester macromonomers were synthesized by the polymerization of DDL in the presence of vinyl methacrylate and vinyl 10-undecenoate, respectively. This process could be extended to single-step synthesis of polyester telechelics. The polymerization in the presence of divinyl sebacate produced a telechelic polymer having a carboxylic acid group at each end. In using a fatty acid ethyl ester or an acetic acid alkyl ester as additive, on the other hand, the quantitative introduction of the corresponding acyl group was not achieved.
One-Pot Synthesis of 4-Amino-1,2-dihydro-3-quinolinecarboxylic Acid Derivatives
Authors: Kobayashi Kazuhiro , Takabatake Harumi , Kitamura Tomohide , Morikawa Osamu , Konishi Hisatoshi
Published: June 2006

When 2-(methylamino)benzonitrile was treated successively with magnesium bis(diisopropylamide), generated in situ from the reaction of ethylmagnesium bromide and diisopropylamine, and α,β-unsaturated carboxylic acid esters in diethyl ether at 0 °C, conjugate addition and enolate–nitrile coupling proceeded sequentially to give the corresponding 4-amino-1,2-dihydro-3-quinolinecarboxylates in isolated yields ranging from 36 to 79%.
Strontium Immobilization by Fibrous Cerium(IV) Bis(monohydrogenphosphate) under Hydrothermal Conditions
Authors: Hayashi Hiromichi , Ebina Takeo , Onodera Yoshio , Iwasaki Takashi
Published: June 2006

The uptake of strontium ions from an aqueous solution by fibrous cerium(IV) bis(monohydrogenphosphate) has been studied from the viewpoints of the immobilization of strontium in radioactive waste by a batchwise operation in the temperature range from 25 to 250 °C. Strontium ions can be exchanged below 100 °C following an ion-exchange reaction between hydrogen ions of the phosphate groups. In contrast, strontium ions can be effectively immobilized under hydrothermal conditions accompanied by a structural change of the exchanger, where divalent strontium ions are incorporated into the monazite-like compound to compensate tetravalent cerium ions in trivalent cerium orthophosphate system. This phenomenon is peculiar to alkaline earth metal ions, since the monazite-like compounds were obtained in the presence of Ca2+ and Ba2+, while this phenomenon was absent in the presence of Cu2+ or Ni2+.
Theoretical Study of Lithium-Doped Polycyclic Aromatic Hydrocarbons
Authors: Ago Hiroki , Nagata Koji , Yoshizawa Kazunari , Tanaka Kazuyoshi , Yamabe Tokio
Published: June 2006

The interactions between carbon layers and lithium atoms are described with a semiempirical molecular orbital method in order to clarify the Li storage mechanism in amorphous carbon (a-C) materials used in Li ion rechargeable batteries. The general electronic and geometric structures of Li-doped a-C materials are investigated using ovalene (C32H14) as a model carbon structure. The following results are obtained. (i) The intercalation of Li atoms proceeds preferentially up to the C6Li configuration, followed by the absorption of Li atoms on the surface of the carbon layer. (ii) The adsorption of Li atoms can occur even on the nearest neighbor site and can form Li cation clusters commensurate with the carbon lattice. (iii) Li atoms located at the acene-edge sites are more stable than those at the phenanthrene-edge sites. This result suggests that the acene-edge structure is favorable for carbon anode materials. (iv) Substitution of the carbon skeleton by heteroatoms such as boron and nitrogen is not effective for Li storage.
Bethe Surface of Liquid Water Determined by Inelastic X-Ray Scattering Spectroscopy and Electron Correlation Effects
Authors: Watanabe Noboru , Hayashi Hisashi , Udagawa Yasuo
Published: June 2006

By means of inelastic X-ray scattering spectroscopy, the generalized oscillator strength (GOS) of liquid water has been experimentally determined over a range 0.69 ≤ q ≤ 3.59 a.u., where q is the momentum transfer. The Bethe surface was constructed from the GOS, and the loss function, the dielectric response function, and the static structure factor were deduced. It was found that the GOS of liquid water is dominated by individual molecular properties over the q range studied, and that the static structure factor agrees quite well with a calculation including electron-electron correlation effects.
Analysis of Chemical Phenomena by Solving the Constrained Hartree–Fock Equation. III. Influence of Geometry Change on the Energy of π Electrons in Conjugated Hydrocarbons
Authors: Ichikawa Hiroshi , Kagawa Hirotaka
Published: June 2006

The total energy of a conjugated unsaturated hydrocarbon can formally be partitioned into the energy of π electrons and the frame energy. This type of partitioning has been used to study the role of π electrons; to know the relationship between the π-electronic structure and its energy, the molecular geometry has been varied. This paper examines the influences of such geometry change on the energy of π electrons from a basic point of view. It was found that there are four types of geometrical influences which disguise the relationship between the π-electronic structure and its energy. Contrary to this, the constrained Hartree–Fock method was shown to disclose the relationship between π-electronic structure and its energy clearly.

Application of the constrained Hartree–Fock method to D6h and D3h benzenes showed that in a D6h benzene π electrons favor the symmetrically uniform distribution independently of the bond length and the partitioning method, while in a D3h benzene the uniform distribution of π electrons is destroyed. Analysis of gradients of partitioned energies with respect to the bond order at a D3h-distorted benzene indicated that π electrons favor a more uniform delocalization, but this is opposed by one- and two-electron potentials.
Photochromic, Electrochemical, and Photoelectrochemical Properties of Novel Azopyridinium Derivatives
Authors: Nakagawa Masaru , Rikukawa Masahiro , Watanabe Masayoshi , Sanui Kohei , Ogata Naoya
Published: June 2006

Organic photochrome azopyridiniums were systematically prepared by quaternizing azopyridines with either dimethyl sulfate or 1,3-propanesultone. Photochemical, electrochemical, and photoelectrochemical studies on the azopyridiniums as methyl sulfate, hexafluorophosphate, and zwitterionic compounds were carried out in aprotic solvents and in aqueous solutions. The azopyridiniums, which have 3-located quaternized nitrogens to the azo group, exhibited photochemical activity of trans    cis isomerization. Quaternization of the pyridine moiety decreased the photochemical conversion between the trans and cis forms. The photochromic properties were influenced by an electronic effect of quaternized nitrogens and an electrostatic interaction of counter anions. In electrochemical studies, new redox-active azopyridiniums were found by using cyclic voltammetry and an electrochemical technique coupled with UV-vis spectroscopy. By the quaternization of azopyridines, the formal reduction potentials were shifted to a positive region up to −0.27 V vs. Fc/Fc+. The reversibility of the electrochemical reactions was strongly dependent on the location of quaternized nitrogen. The trans    cis photoisomerization of electroactive azopyridiniums influenced their electrochemical properties. The photochromic molecules exhibited a photoelectric effect, which was a change in the cathodic limiting currents of azopyridiniums, reversibly modulated by ultraviolet light of an external stimulation.
Electrocatalytic Fischer–Tropsch Reactions. Formation of Hydrocarbons and Oxygen-Containing Compounds from CO on a Pt Gas Diffusion Electrode
Authors: Hara Kohjiro , Sonoyama Noriyuki , Sakata Tadayoshi
Published: June 2006

Electrocatalytic reduction of CO under high pressure (< 60 atm) using a gas diffusion electrode containing Pt catalyst (Pt-GDE) has been investigated. Acetic acid was formed at a high faradaic efficiency of 32% as a predominant CO reduction product at a constant current density of 200 mA cm−2 under CO 40 atm. Moreover, methane, ethane, ethylene, formaldehyde, acetaldehyde, ethanol, 1-propanol, and allyl alcohol were produced as CO reduction products. The selectivity of the reduction products depends remarkably on electrolysis conditions such as the current density, pressure of CO, and temperature. C2-compounds such as ethylene, ethanol, and acetic acid were preferentially formed at small current densities and/or high CO pressure conditions, whereas methane was predominantly produced at large current densities and/or low CO pressure conditions.
The Micellar Properties of Ionic Surfactants Consisting of the α,ω-Type Surfactant Ion and the Same Type Counter Ion
Authors: Satake Iwao , Morita Tadakazu , Maeda Tamaki , Hayakawa Katumitu
Published: June 2006

The micellar properties of N,N,N,N′, N′,N′-hexamethyl-1,20-icosanediyldiammonium, or the corresponding di(1-pyridinium)alkanedioates −OOC(CH2)nCOO− (n = 2—10), were studied by conductivity and pyrene fluorescence measurements. In both systems, the critical micelle concentration (cmc) varied little up to n = 4, but decreased rapidly with a further increase in n. The binding degree (β) of the alkanedioate counter ion was virtually independent of the type of surfactant ion head group and gradually increased from 0.69 at n = 2 to 0.91 at n = 10. The observed n dependences of cmc and β were similar to those of the conventional ionic surfactants with an α,ω-type counter ion, indicating the importance of the hydrophobic interaction between the hydrocarbon part of the counter ion and the micellar core. On the basis of a phase-separation model, the transfer free energy per methylene group of the counter ion from aqueous-to-micellar environments was estimated to be about −1.0 RT. The fluorescence measurements suggest that the surface layer of the micelle becomes progressively loose as n decreases. The micelle aggregation numbers of the bis (trimethylammonium) salts are of the order of 50.
Solvent Extraction and Separation Studies of Platinum Using Bis(2-ethylhexyl) Hydrogen Phosphate
Authors: Sherikar Aniruddha V , Phalke Pradeep N , Dhadke Purushottom M
Published: June 2006

The extraction of platinum(II) from hydrochloric acid solution using bis(2-ethylhexyl) hydrogen phosphate in toluene was studied as a function of several variables, such as hydrochloric acid concentration, reagent concentration, metal ion concentration, temperature, effect of various diluents, and effect of various diverse ions. The proposed method was further applied for the separation of platinum from palladium, gold, and osmium in different ratios and to estimate the amount of platinum present in commercially available samples.
Protonation Behavior and Intramolecular Interactions of α,ω-Alkanediaminepolymethylenepolyphosphonates
Authors: Ichikawa Tomohide , Sawada Kiyoshi
Published: June 2006

The protonation equilibria of two types of aminopolyphosphonates ((CH3)2−p(CH2PO3)pN(CH2)mN(CH2PO3)p′(CH3)2−p′) in aqueous solution were investigated by means of potentiometry and 31P NMR spectroscopy. The protonation behavior of diaminotetramethylenetetraphosphonate (p = p′ = 2) is significantly altered by a change in the number of methylene chains (m = 2, 3, 6). The protonations of the imino fragments of hdtmp, which is connected with a six methylene chain (m = 6), are essentially independent of each other, whereas edtmp, which is connected with a two methylene chain (m = 2), forms a hydrogen bond between both nitrogen atoms (NH+···N) in the mono protonated species. The ethylenediaminepolyphosphonates (m = 2), having an iminodiphosphonate group (p = 2, p′ = 0—2), show a peculiar 31P NMR behavior in which the signal shows a downfield shift at higher protonated species. However, eddmp (N,N′), having one methylenephosphonate group at each imino fragment (p = p′ = 1), does not show such an anomaly. These results indicate the existence of an intramolecular interaction between both fragments, such as a hydrogen bond of a protonated nitrogen atom with unprotonated phosphonates of another imino fragment, where two methylenephosphonate groups in one imino fragment are required to operate such an interaction.
Molecular-Dynamics Study of Aqueous Solution of Trehalose and Maltose: Implication for the Biological Function of Trehalose
Authors: Sakurai Minoru , Murata Masashi , Inoue Yoshio , Hino Akihiro , Kobayashi Syouichi
Published: June 2006

Molecular-dynamics simulation of aqueous solution of trehalose and maltose were performed to reveal any difference in the hydration ability between them, and to obtain information about how trehalose protects biological materials from water stress. Here, in order to examine the spatial distribution of water molecules around the hydroxy oxygen of sugar, a two-dimensional pair distribution function was introduced in addition to the conventional radial-distribution function. Both sugars were found to be extensively hydrogen bonded to solvent molecules. However, in a solution of maltose, defective hydrogen bonding was found at the exocyclic hydroxymethyl group of the reducing residue. Thus, maltose has a smaller value in hydration number than does trehalose. The translational diffusion of water molecules around trehalose has been found to be slightly more restrained than that around maltose. These findings are consistent with available experimental data concerning the solution properties of both sugars. On the basis of these results, the functional mechanism of tolerance is briefly discussed.
Reactions of ap- and sp-1-(9-Fluorenyl)-2-(1-methylethenyl)naphthalene Rotamers with Bromine Chloride or Iodine Chloride and Unusual Populations of the Corresponding 1-(9-Fluorenyl)-2-[(E)-2-halo-1-methylethenyl]naphthalene Rotamers
Authors: Oki Michinori , Hirose Takanori , Maeda Kiyoka , Yanagawa Maki , Kataoka Yasukazu , Kojima Hiroharu , Morita Nobuhiro , Toyota Shinji
Published: June 2006

Reactions of bromine chloride and iodine chloride with the olefinic bond in 1-(9-fluorenyl)-2-(1-methylethenyl)naphthalene rotamers were carried out to examine the product distributions. In the case of the ap-isomer bromine chloride yielded some bromo-olefins in addition to the addition product, whereas the yield of (8R*,14cS*)-8-bromomethyl-8-methyl-8,14c-dihydrodibenzo[a.l]aceanthrylene from the sp-isomer diminished with respect to the case of the reaction between bromine and the sp-isomer. The results are attributed to the low nucleophilicity and high proton affinity of the chloride ion. Iodine chloride afforded more addition product for the ap-isomer than the case of bromine chloride, whereas the sp-isomer reacted with iodine chloride to give a better yield of a cyclized compound, (8R*,14cS*)-8-iodomethyl-8-methyl-8,14c-dihydrodibenzo[a,l]aceanthrylene, than that of the cyclized compound from bromine chloride. Such results are attributed to the better stabilizing effects of an iodo substituent on a β-carbocation than a bromo one. Populations of ap and sp rotamers of 1-(9-fluorenyl)-2-[(E)-2-halo-1-methylethenyl]naphthalenes at equilibrium were unusual in the sense that the ap-isomer of the sterically more crowded iodo compound was favored relative to the less crowded chloro compound. UV absorption spectra were not conclusive for charge transfer interactions but X-ray crystallography of these compounds revealed that the olefinic carbons in the ethenyl group were attracted to the fluorene ring significantly.
Photochemistry of Amino-Linked Bichromophoric Anthracenes. Efficient Cyclomerization of 9-(1-Naphthylmethylaminomethyl)anthracene and Adiabatic Cycloreversion of the Cyclomer
Authors: Mori Yukie , Maeda Koko
Published: June 2006

The spectral and photochemical properties of the title compound 1 and bis(9-anthrylmethyl)amine (2) have been investigated. The fluorescence spectrum of 1 in methylcyclohexane showed an emission from the locally excited state of the anthracene part and a weak broad emission at 410—550 nm from the intramolecular exciplex. The fluorescence quantum yields of 1 and 2 decreased along with an increase in the solvent polarity. Both 1 and 2 underwent intramolecular [4+4] cycloaddition. The quantum yield of the cyclomerization of 1 was 0.24 in acidic methanol, while in MeCN the reaction was completely quenched by an intramolecular electron transfer from the amino group to the excited anthracene moiety. Excitation of the cyclomer from 1 at 285 nm brought about fluorescene from both the locally excited anthracene and the exciplex state, indicating that adiabatic cycloreversion took place on the S1 potential surface. To investigate the conformations, the crystal structures of 1 and 2 were determined and PM3 calculations were performed for 1–H+. The calculations indicate that a conformer in which the two chromophores are located close to each other has a higher energy then other stable conformers.
Methyltrioxorhenium-Catalyzed Oxidation of Secondary and Primary Amines with Hydrogen Peroxide
Authors: Yamazaki Shigekazu
Published: June 2006

The methyltrioxorhenium-catalyzed oxidation of secondary amines and primary amines with hydrogen peroxide has been carried out. The oxidation of secondary amines afforded nitrones in good-to-excellent yield. Benzylamines were selectively oxidized to oximes, while general primary alkylamines possessing the α-C–H bond gave mixtures of oximes, nitroso dimers, and azoxy compounds.
Relationship between the Cyclization and Conformation of Pentapeptide Active Esters Related to Gramicidin S Having No Protecting Group on the Side Chain of the Ornithine Residue
Authors: Tamaki Makoto , Komiya Seiji , Akabori Sadatoshi , Muramatsu Ichiro
Published: June 2006

To investigate the contribution of the d-Phe–Pro–Val sequence in the direct formation of gramicidin S (GS) by the dimerization–cyclization of pentapeptide-active esters having no protecting group on the side chain of the Orn residue, the cyclization of four H–X–Pro–Y–Orn–Leu–ONSu’s (X = l- or d-Phe, Y = l- or d-Val, –ONSu = succinimide ester) was examined. Only H–d-Phe–Pro–Val–Orn–Leu–ONSu gave semi-GS (cyclic monomer) and GS (cyclic dimer) in yields of 15 and 38%, respectively. The active ester with a d-Phe–Pro–d-Val sequence produced exclusively [d-Val]–semi-GS in 58% yield. On the other hand, the active esters having Phe–Pro–Val and Phe–Pro–d-Val sequences did not yield any amount of cyclic monomer and cyclic dimer. The change in the configurations of the Phe and Val residues around the Pro residue greatly affected the CD spectra in ethanol and the 1H NMR spectra in DMSO-d6 of the pentapeptide ethyl esters corresponding to four H–X–Pro–Y–Orn–Leu–ONSu’s. A good correlation among the CD spectra, NMR spectra of the pentapeptide ethyl esters, and the main products in the cyclization of the active esters was found.
A Halide-Free Method for Olefin Epoxidation with 30% Hydrogen Peroxide
Authors: Sato Kazuhiko , Aoki Masao , Ogawa Masami , Hashimoto Tadashi , Panyella David , Noyori Ryoji
Published: June 2006

A catalytic system consisting of sodium tungstate dihydrate, (aminomethyl)phosphonic acid, and methyltrioctylammonium hydrogensulfate, effects the epoxidation of olefins using 30% hydrogen peroxide with a substrate-to-catalyst molar ratio of 50—500. The reaction proceeds in high yield without solvents, or, alternatively, with added toluene under entirely halide-free conditions. Lipophilic ammonium hydrogensulfate, which replaces the conventional chloride, and an (α-aminoalkyl)phosphonic acid are crucial for the high reactivity. This method is operationally simple, environmentally benign, and much more economical than the oxidation with m-chloroperbenzoic acid, allowing for a large-scale preparation of epoxides. Various substrates including terminal olefins, 1,1- and 1,2-disubstituted olefins, cyclic olefins, and tri- and tetrasubstituted olefins as well as allylic alcohols, esters, α,β-unsaturated ketones, and ethers can be epoxidized in high yield. The scope and limitations of this new reaction system are discussed.
Resonance Effects in the Solvolysis of α-t-Butyl-α-neopentylbenzyl and α-t-Butyl-α-isopropylbenzyl p-Nitrobenzoates
Authors: Fujio Mizue , Ohe Makoto , Nakata Kazuhide , Tsuji Yutaka , Mishima Masaaki , Tsuno Yuho
Published: June 2006

Substituent effects on the solvolysis rates of α-t-butyl-α-neopentylbenzyl and α-t-butyl-α-isopropylbenzyl p-nitrobenzoates in 50% (v/v) aqueous EtOH at 75 °C were correlated with the Yukawa–Tsuno equation to give ρ = −3.37 and r = 0.78, and ρ = −3.09 and r = 0.68, respectively. The reduction in r values from r = 1.00 characteristic of full conjugation is ascribed to deviation from coplanarity of the carbocationic center and the benzylic π-system in the transition state. The torsion angles for twisting out of coplanarity were estimated from the relationship r/rmax = cos2  θ for a series of sterically hindered tertiary dialkylbenzylic solvolyses. The torsion angles assigned for these twisted benzylic systems are in good agreement with theoretically calculated dihedral angles of the corresponding 6-31G*optimized carbenium ions. This identity provides convincing evidence for occurrence of steric inhibition of resonance through loss of coplanarity, and, in turn, provides strong support for our characterization of the r value as a resonance demand parameter reflecting the degree of resonance (π-delocalization) interaction between an aryl group and the reaction site.