bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal Structure and Photochemical Behavior of 2,2,4,6-Tetraphenyldihydro-1,3,5-triazine and Its Inclusion Compounds
Authors: Mori Yukie , Ohashi Yuji , Maeda Koko 
Published: July 2006

Abstract
Crystal structures of 2,2,4,6-tetraphenyldihydro-1,3,5-triazine (1), which shows photocoloration, and its photostable propylamine solvate (2) have been determined. The molecular structure of the dihydrotriazine in 1 and 2 showed that it exists in 2,3-dihydro form in the crystals, but the bond distance of N(3)–C(4) was shorter than a normal C–N single bond, indicating that lone-pair electrons on N(3) interact with the π system of C(4)=N(5)–C(6)=N(1). Comparison of crystal structures of 1, 2, and other inclusion compounds previously determined revealed that the difference in the photochemical behavior of the crystals is attributable to different hydrogen bonding schemes. Photolysis of 1 in the solid state, which was carried out in connection with the structural investigation of the photocolored species, gave 2,4,6-triphenyl-1,3,5-triazine as a main product.
Reactions of Alkenes with Iodine(III) Tris(trifluoroacetate)
Authors: Futami Yasuo , Nishino Hiroshi , Kurosawa Kazu 
Published: July 2006

Abstract
The reactions of 1-arylethene, 1,1-diarylethenes, and 1,1-diarylpropenes with iodine(III) tris(trifluoroacetate) gave 1,2-diaryl-1-alkanones, 1-aryl-2-(4-iodophenyl)-1-alkanones, benzoins, benzils, and iodoethenes. A similar reaction of 1,1,4,4-tetraaryl-1,3-butadiene yielded 1,2,4,4-tetraaryl-3-buten-1-one. The reactions of 1,1,5,5-tetraaryl-1,4-pentadienes and 1,1,6,6-tetraaryl-1,5-hexadienes also gave dicarbonyl compounds. The reaction involves aryl migration. The mechanisms and the utility of the reaction for organic synthesis are discussed.
Studies of the Acidity and Ionic Conductivity of Silica-Supported Heteropoly Compounds. I. The Dehydration of t-Butyl Alcohol over Heteropoly Compound Catalysts
Authors: Ohtsuka Reiji , Morioka Yoshio , Kobayashi Jun-ichi 
Published: July 2006

Abstract
The dehydration of t-butyl alcohol (TBA) using various heteropoly compound (HPC) catalysts has been studied. Taking the adsorption of water on the surface of the catalyst into consideration, it is presumed that the dehydration of liquid TBA is governed by a Langmuir–Hinshelwood-like mechanism. Also, the change in the catalytic activity with the amount of HPC supported on the silica suggests that TBA is dehydrated through a pseudo-liquid mechanism in which a few layers of the HPC supported take part in the catalytic reaction. The layer thickness, regarded as a pseudo-liquid phase, depends markedly on the kind of HPC supported. For the dehydration of gaseous TBA, on the contrary, the reaction is found to be of the zero-order; it proceeds through in outer-surface mechanism in which only the outer layer of HPC is effective.
Selective Preparation of 2,3-Epoxypropanamide and Its Facile Conversion to 2,3-Dihydroxypropanamide with Acidic Resins
Authors: Sugiyama Shigeru , \ {O}higashi Shinji , Sawa Ryûichi , Hayashi Hiromu 
Published: July 2006

Abstract
In the equimolar reaction of acrylonitrile with hydrogen peroxide to 2,3-epoxypropanamide (glycidamide), the selectivity and the yield of the epoxide were improved by adding aq. NaOH solution continuously at a constant rate. The conventional literature procedure, by controlled pH from 7.0 to 7.5, resulted in an unfavorable decomposition of hydrogen peroxide. 2,3-Epoxypropanamide could be easily converted to 2,3-dihydroxypropanamide (glyceramide) by a catalytic amount of commercially available acidic resins.
Acidity Enhanced Pillared Clay Catalysts. Modification of Exchangeable Sites on Fluor-tetrasilicic Mica by the Fixed Interlayer Cations
Authors: Sakurai Hiroaki , Urabe Kazuo , Izumi Yusuke 
Published: July 2006

Abstract
By the use of fluor-tetrasilicic mica (TSM) as a starting material, La3+-modified pillared TSM was prepared by calcining La3+-exchanged TSM followed by Al-pillaring. Nonmodified pillared TSM managed only a 0.1% conversion for toluene alkylation with methanol, but the alkylation activity was greatly enhanced by the modification to give more than a 7% conversion, the activity level of which was roughly comparable to that of the conventional pillared montmorillonite. The effect of modification greatly depended on the calcination temperature at the pretreatment of La3+-exchanged TSM prior to a pillaring operation; the optimum calcination temperature was between 300 and 400 °C. Other multivalent cations with large ionic radii, such as Ce3+, Ca2+, and Sr2+, were also useful as modifiers. On the basis of the results of measurements involving X-ray diffraction, cation-exchange capacity and IR spectra of the adsorbed pyridine, it was concluded that a part of the thermally dehydrated La3+ ions lost their exchangeability to be fixed on the cation exchange sites of layers, remained between layers even after Al-pillaring, and took charge of the genesis of acidic sites.
The Sensitive and Selective Determination of Palladium(II) Based on Ternary-Complex Formation with Phloxine and Thiamine
Authors: Fujita Yoshikazu , Mori Itsuo , Toyoda Minako , Nakahashi Yoshihiro , Kato Keiji , Nakamura Masaki 
Published: July 2006

Abstract
A sensitive and selective spectrophotometric determination of palladium(II) based on ternary-complex formation with Phloxine and thiamine was established. The apparent molar absorptivity of the proposed method, which does not require an extraction procedure, was 1.02×105 dm3 mol−1 cm−1 at 565 nm. Only gold(III) in an equimolar ratio of palladium(II) among the metal ion examined interfered. The method was applied to a determination of palladium in palladium carbon and palladium asbestos; the results were in good agreement with those obtained by potassium iodide method, the Michler’s thioketone method and ICP-AES. The sensitivity could be further enhanced by about 20 times over that of spectrophotometry and/or fluorimetry by combining it with a membrane filter preconcentration technique. It was suggested that the collection of an aggregate on a membrane filter depends on the molecular size through observing by an scanning electron microscope.
Solvent and Reversed Phase Extraction Chromatographic Separation of Molybdenum and Tungsten with Quaternary Ammonium Salt Reagent, Aliquat 336
Authors: Das Nitya Ranjan , Chattopadhyay Putul 
Published: July 2006

Abstract
A quaternary ammonium salt reagent, Aliquat 336 has effectively been used for radioanalytical separations of molybdenum and tungsten through the techniques of solvent extraction and reversed phase extraction chromatography (RPEC). Studies on solvent extraction revealed that quantitative separations of the elements in a mixture can be achieved by extracting tungsten with ca. 10−4 mol dm−3 solution of Aliquat 336 in cyclohexane from an aqueous solution of 1 mol dm−3 H3PO4. The efficiency of separation of the elements which form varieties of metal salts of poly- and heteropolyanion species in aqueous solution is very much dependent on the types of acids as well as on the reagent concentration. In RPEC system, both the elements were found to be quantitatively extracted by an Aliquat 336 impregnated column of Kieselguhr from an alkaline solution containing a hydroxy compound like tartaric acid. The extracted species were subsequently separated by eluting molybdenum and tungsten respectively with HCl solutions of 0.05 mol dm−3 and 0.1 mol dm−3 concentrations. The purity of the separated species at various stages of their separations was verified by means of gamma-ray spectrometry.
Prototropic Equilibria in Few β-Hydroxy-Substituted 1-Naphthylamines in the Ground and Excited Singlet States
Authors: S. Sarpal Ranjit , K. Dogra Sneh 
Published: July 2006

Abstract
The longest wavelength transition in the absorption spectra of β-hydroxy-substituted 1-naphthylamines is long axis polarised, whereas the fluorescence occurs from the more polar, short axis polarized state. This is based on the spectral characteristics in different solvents. Five different prototropic species are formed in the ground state and six species are obtained in the S1 state. The ground state precursor for the formation of zwitterion is the monocation. pKa values for the different prototropic reactions have been calculated in the ground and excited singlet states.
Prebiotic Evolution of Oxidoreductases: [Fe(III)(CN)5(L)]n− Complexes as Models
Authors: Kamaluddin  , Mala Nath , Sushama W Deopujari 
Published: July 2006

Abstract
The transition state, where primary ligands like CN− partially replaced by biomolecules, has been assumed to be interesting from point of view of chemical evolution of oxidoreductase enzymes. Complexes of type [Fe(III)(CN)5(L)]n− (where n=2, 3 and L=glycine, imidazole, triglycine, and histidine) are proposed as models for peroxidases and catalases. Detailed kinetic investigations of decomposition of hydrogen peroxide catalyzed by [Fe(III)(CN)5(L)]n− complexes at 40 °C over a wide pH range 6.0–11.0 are discussed. The decomposition reaction is highly pH dependent. In alkaline media, initially L− is substituted by −OH in [Fe(III)(CN)5(L)]; subsequently HOO− binds to −OH through weak intramolecular hydrogen bonding, formation of peroxo complexes has been proposed to be an active intermediate responsible for accelerating the reaction. Decomposition of hydrogen peroxide catalyzed by [Fe(III)(CN)5(L)]n− complexes conforms to Michaelis Menten type of kinetics.
Correlation of 13C Shifts with Substituent Parameters in 3,4-Diphenyl-1,2,5-oxadiazole 2-Oxides Substituted at the Para-Positions of Either or Both Phenyl Rings
Authors: Balasubrahmanyam S N , Rajendran N , Singh D K 
Published: July 2006

Abstract
C-1′, C-1″, C-3, and C-4 13C shifts in 3,4-di(4′-or/and 4″-X)phenyl-1,2,5-oxadiazole 2-oxides (3,4-diarylfurazan 2-oxides; three series: X=NMe2, OMe, Me, Cl, H, and NO2) were correlated vs. seven different divided substituent parameter sets. Results have implied that i) the C-3–C-4 bond does not transmit mesomeric effects efficiently; ii) no effects can be specifically attributed to the possibility that the C-3 aryl maintains a higher dihedral angle with respect to the furoxan ring than the C-4 aryl; iii) there appears to be a directionality to the propagation of localized π-polarization due to lesser ability of C=N(O)→O to convey effects compared with C=N(O); and, iv) the furazan N-oxide ring, being generally an electron acceptor, transmits substituent effects nonlinearly.
Aromatic Acetonylation by Using Aryltins with Acetonylium Equivalents under the Palladium Catalysis
Authors: Kosugi Masanori , Miyajima Yoshio , Nakanishi Hideyuki , Sano Hiroshi , Migita Toshihiko 
Published: July 2006

Abstract
Palladium-catalyzed reactions of heteroaromatic tins with 2-ethoxyallyl diethyl phosphate and of nitrophenyltins with 2-methoxymethoxyallyl chloride were found to give the coupling products, which can be hydrolyzed to the corresponding acetonylated aromatics in good yields.
A Convenient Synthesis of Trifluoromethylated Pyrroles and Porphyrins
Authors: Ono Noboru , Kawamura Hisayuki , Maruyama Kazuhiro 
Published: July 2006

Abstract
4-Alkyl-3-trifluoromethyl-2-pyrrolecarboxylic acid esters (2) were conveniently prepared by the reaction of trifluoromethylated β-nitro acetates (1) with ethyl isocyanoacetate. The pyrroles were converted into the corresponding porphyrins via tetramerization of 2-(hydroxymethyl)pyrroles.
Stereoisomerism and Crystal Structure of (1R,2S,5R)-(+)-4-(Benzoyloxymethylene)-2,6,6-trimethylbicyclo[3.1.1]heptan-3-one{(1R,2S,5R)-(+)-4-(Benzoyloxymethylene)-3-pinanone}
Authors: Azani Nasser , Labruyere Francis , Metge Claude , Bertrand Charles , Sotiropoulos Jean , Jaud Joël 
Published: July 2006

Abstract
Conjugated esters from (+)-isopinocamphone, with a terpenic skeleton which is easily epimerizable may theoretically exist as four diastereomers (2R,4E; 2R,4Z; 2S,4E; 2S,4Z). X-Ray analysis shows that the reaction leads to a single isomer, namely an isopinocamphone derivative (2S,4E).
α-Iodination of Ketones and Enol Acetates with Poly[styrene-co-(4-vinylpyridinium dichloroiodate(1–))]
Authors: \u{S}ket Boris , Zupet Pavel , Zupan Marko , Dolenc Darko 
Published: July 2006

Abstract
Crosslinked poly[styrene-co(4-vinylpyridinium dichloroiodate(1–))] can be used as a very efficient polymeric reagent for α-iodination of ketones, diketones, and corresponding enol acetates.
The β-Sheet Structure-Disrupting Potential of Electron-Donor and -Acceptor Solvents and Role of Mixed Solvents in Solvation of Peptides
Authors: Narita Mitsuaki , Honda Shinya , Obana Satoshi 
Published: July 2006

Abstract
The β-sheet structure-disrupting potential of hydrogen-donor and -acceptor solvents was in the good relationship with their electron-acceptor and -donor numbers (AN and DN), respectively. As AN and DN of solvents are larger, their β-sheet structure-disrupting potential becomes higher. Based on the results of the β-sheet structure disruption in the three component solvent system, it can also be clarified that combinations of homogeneous solvents are suitable for peptide and protein synthesis, but those of heterogeneous ones are not effective. The results of this study are of quite significance for the search for effective solvents in peptide and protein synthesis.
Interfacial Adsorption of Iron(II)–4,7-Diphenyl-1,10-phenanthroline Complex in Ion-Association Extraction Systems
Authors: Watarai Hitoshi , Shibuya Yoko 
Published: July 2006

Abstract
The interfacial adsorptivity of an iron(II)–4,7-diphenyl-1,10-phenanthroline (DPP) complex in chloroform/aqueous salt solution systems was investigated by means of a high-speed stirring method and interfacial tension measurements. The interfacial spectra observed in the stirred system suggested that the adsorbed species at the interface is the tris-DPP complex. A minor effect of the anion concentration on the adsorptivity suggested that the tris-complex adsorbed as an ion-pair in a 0.1 M anion concentration. The interfacial adsorption of the ion-pair under stirring was analyzed by the Langmuir isotherm. The adsorptivity increased, depending on the counter ions, in the order ClO4−&lt;CCl3COO−\simeqBr−&lt;Cl−&lt;SO42−, i.e. the order of increasing hydration energies of these anions.
Temperature Dependence of Conductivities and Ion-Association Constants of Potassium Sulfate in Water
Authors: Yokoyama Haruhiko , Ohta Tomoko 
Published: July 2006

Abstract
From the temperature dependence of the ion-association constants between K+ and SO42− at 0 to 50 °C, the contact ion-pair formation and short-range interactions are discussed while considering the hydration of the anion. The limiting molar conductivities of SO42− are expressed as a cubic equation of the temperature.
Chromatographic Separation of Rare Earth Pairs by a Chelating Resin Having Bis(carboxymethyl)amino Groups
Authors: Kanesato Masatoshi , Yokoyama Toshiro , M. Suzuki Toshishige 
Published: July 2006

Abstract
Adsorption properties of rare earth elements toward a cross-linked polystyrene resin having bis(carboxymethyl)amino groups (CMA) have been studied. The selectivity sequence of the resin for a series of rare earth metals was in good accordance with that of the corresponding stability constants of diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid (DTPA) complexes. The chromatographic separation of La(III)/Pr(III), Nd(III)/Sm(III), and Y(III)/Gd(III) has been carried out by use of the present resin. The chromatographic conditions were empirically evaluated in terms of resolution (Rs), with varying column length, pH of the eluent, the flow rate and the column temperature.
Binding of Modified Guanine Nucleotides to Ribonuclease T1 as Studied by Absorption Spectroscopy. 8-Aminoguanosine 2′-Phosphate, 8-Methylaminoguanosine 2′-Phosphate, and 8-Dimethylaminoguanosine 2′-Phosphate
Authors: Yoshida Hiroshi , Sugiyama Masazumi , Shibagaki Yoshio 
Published: July 2006

Abstract
The title nucleotides have been synthesized and their binding to ribonuclease T1 studied by means of absorption spectroscopy. Measurements were made at pH 5.5 and 4.1, where a major portion of the base moiety of the nucleotides was in a neutral form and a cationic form protonated at N7, respectively. At both pH’s, difference absorption spectra were induced upon binding of the nucleotides to the enzyme. A comparison of the difference spectra with that for guanosine 2′-phosphate has led to the conclusion that perturbation in the bound nucleotide is the principal cause for the difference spectra. The difference spectra at pH 5.5 and 4.1 were similar, suggesting that the protonation at N7 of the nucleotides can be ruled out as the cause for the difference spectra. The dissociation constants at pH 5.5 and 4.1 of the enzyme–8-aminoguanosine 2′-phosphate complex were of the same magnitude, indicating that both the neutral and the protonated forms bind tightly to the enzyme. However, the cationic form of 8-methylamino- or 8-dimethylaminoguanosine 2′-phosphate has been shown to interact with the enzyme much more loosely than the neutral form.
Synthesis and Spectroscopic Investigation of Directly Conjugated Polyyne Porphyrins
Authors: Maruyama Kazuhiro , Kawabata Shigeki 
Published: July 2006

Abstract
A series of conjugated polyyne porphyrin, in which porphyrin macrocycle is directly connected with one end of diarylpolyyne through aromatic ring, has been prepared and their spectroscopic behaviors were investigated. Diarylpolyynes consisting of aryl group and conjugated triple bond system have rigid and linear structure, and the two chromophores are held at a fixed geometry and a determined distance. The UV-vis absorption spectra of these compounds showed strong conjugative interaction, showing broadening of their spectra and slightly red shifted porphyrin Soret bands with increasing the number of acetylenic bond. From their fluorescence excitation spectra energy transfer efficiencies from polyyne moiety to porphyrin moiety were estimated. The energy transfer efficiencies were almost unity regardless of their substituted position, geometry, and orientation.
Synthesis of 1,5-Bifunctionalized Optically Active 3-Pentanol as a Reversible Chiral Building Block. Asymmetric Reduction of 4-(1,3-Dithian-2-yl)-3-oxobutanoates with Fermenting Bakers’ Yeast
Authors: Chikashita Hidenori , Ohkawa Kazuhiko , Itoh Kazuyoshi 
Published: July 2006

Abstract
Bakers’ yeast reduction of a homologous series of 4-(1,3-dithian-2-yl)-3-oxobutanoates to the corresponding chiral 4-(1,3-dithian-2-yl)-3-hydroxybutanoates was investigated. A shift in enantiomeric excess, stereochemistry, and chemical yield of the reduction product was observed as the size of the ester alkoxyl group was changed. The kind of bakers’ yeast (raw or dry) and reaction conditions also affected the optical purity and chemical yield of the product. These studies showed that the reduction of methyl 4-(1,3-dithian-2-yl)-3-oxobutanoate with the raw yeast in the absence of additives was most efficient, giving methyl (S)-4-(1,3-dithian-2-yl)-3-hydroxybutanoate with 77% ee in 37% yield.
A Practical Optical Resolution of (Arylsulfinyl)acetones and Its Application to the Synthesis of 2-(Arylsulfinyl)cycloalkanones
Authors: Ogura Katsuyuki , Ishida Michio , Tomori Hiroshi , Fujita Makoto 
Published: July 2006

Abstract
Racemic (arylsulfinyl)acetones (1) were efficiently resolved by formation of their oxazolidine derivatives with (R)- or (S)-2-amino-2-phenylethanol followed by chromatography on Florisil–MgO and the subsequent hydrolysis to give (S)- or (R)-1, respectively. Further, derivation of 1 to optically active 2-(p-tolylsulfinyl)cyclohexanone and 2-(p-tolylsulfinyl)-4-cycloheptenone is described.
2-Methoxyethyl Group for Protection of Reducing Hydroxyl Group of Aldose
Authors: Koto Shinkiti , Morishima Naohiko , Takenaka Kazuhiro , Kanemitsu Kumi , Shimoura Noriko , Kase Miyuki , Kojiro Shizuko , Nakamura Teiko , Kawase Tomoko , Zen Shonosuke 
Published: July 2006

Abstract
A variety of benzylated 1-OH derivatives, having an acetyl or an allyl group, of d-glucose, d-galactose, d-mannose, d-xylose, l-arabinose, l-fucose, and l-rhamnose, were synthesized from the corresponding protected 2-methoxyethyl glycosides through a brief treatment with TiCl4 in dichloromethane and a subsequent hydrolysis of the intermediary 1-Cl derivatives on a silica-gel column.
The β-Sheet Structure-Stabilizing Potential of Twenty Kinds of Amino Acid Residues in Protected Peptides
Authors: Narita Mitsuaki , Kojima Yoshihisa 
Published: July 2006

Abstract
A host–guest approach was devised to investigate the β-sheet structure-stabilizing potential of the 20 common amino acid residues in protected peptides where functional groups in side chains were protected by suitable groups commonly used in peptide synthesis. The potential was evaluated using solvent-titration curves for the disruption of the β-sheet structure of cross-linked polystyrene resin-bound host–guest hexa- and octapeptides in CH2Cl2 by HFIP. The β-sheet structure of host–guest hexapeptides, Boc–Val–Ile–X2–Val–Ile-NHCH2–resins, in which X stands for guest amino acid residues, was disrupted in CH2Cl2 by adding increasing amounts of HFIP; the disrupted behaviors were strongly dependent on the nature of guest amino acid residues. A scale for the β-sheet structure-stabilizing potential of the 20 kinds of amino acid residues in CH2Cl2 could be derived at 0.25 M of HFIP concentration as follows: Ile, Val&gt;&gt;Asn&gt;His(Tos) or His, Gln, Cys(Bzl), Tyr(Bzl)&gt;Phe, Gly, Lys(Z), Arg(Tos), Leu&gt;Thr(Bzl), Ala, Met(O), Glu(OBzl), Trp(CHO)&gt;&gt;Ser(Bzl), Asp(OBzl)&gt;&gt;Pro. To confirm the scale, their β-sheet structure-stabilizing potential was further examined using host–guest octapeptides, Boc–X2–Val–Ile–X2–Val–Ile–NHCH2–resins. The disrupted behaviors of the octapeptides having Gly, Ala, and Thr(Bzl) residues as guests were remarkably different from those of the corresponding hexapeptides; the β-sheet structure-stabilizing potential of the Gly, Ala, and Thr(Bzl) residues became significantly high with an increase in their ratios to host residues. The potential of the Gly, Ala, and Thr(Bzl) residues appears to reflect the ratios of guest amino acid residues to hosts, the repeated sequence, and/or neighbor interactions in the sequence. The significance of the present study in the design of synthetic routes for peptides and proteins is briefly discussed.
Peptide Segment Separation by Tertiary Peptide Bonds. Synthesis and Conformational Analysis of Cross-Linked Polystyrene Resin-Bound Human Proinsulin C-Peptide Fragments
Authors: Narita Mitsuaki , Umeyama Hiroshi , Yoshida Toshihiko 
Published: July 2006

Abstract
In order to clarify the role of tertiary peptide bonds in the conformational development of protected peptides in organic solvents, cross-linked polystyrene resin-bound human proinsulin C-peptide fragments were prepared by a fragment condensation method. For the purpose of clarifying the role of tertiary peptide bonds, it is indispensable to force coupling reactions to completion; the addition of HFIP in coupling reactions in CH2Cl2 was significantly effective for their completion when they did not proceed smoothly. The conformational behavior of resin-bound human proinsulin C-peptide fragments in CH2Cl2 was successively investigated using IR absorption spectroscopy. Two Pro residues forming tertiary peptide bonds played the role of stopping the development of helix and β-sheet structures in peptides, and the structure of N- and C-terminiand side-chain-protected human proinsulin C-peptide could be regarded as being assembled with peptide segment structures separated by the two Pro residues. When a peptide segment had a high helix-forming potential, a Pro residue in an N-terminal part of the peptide segment promoted its helix formation. β-Sheet structures formed by peptide segments in CH2Cl2 were easily disrupted by a strong electron-acceptor solvent of HFIP, suggesting that the β-sheet structure disruption of resin-bound peptides is important in achieving efficient coupling reactions.