bluuebunny/crossref_metadata_2025_split huggingface dataset:
α,β-Epoxy Sulfoxides as Useful Intermediates in Organic Synthesis. X. An Improved Synthesis of α,β-Unsaturated Carbonyl Compounds from Carbonyl Compounds with Carbon Homologation through α,β-Epoxy Sulfoxides
Authors: Satoh Tsuyoshi , Itoh Masayuki , Ohara Teruhiko , Yamakawa Koji 
Published: July 2006

Abstract
Treatment of the α,β-epoxy sulfoxides derived from ketones and chloromethyl phenyl sulfoxide or 1-chloroalkyl phenyl sulfoxides with lithium perchlorate in the presence of tributylphosphine oxide in toluene at 110 °C for about 1–3 h gave α,β-unsaturated aldehydes or α,β-unsaturated ketones in high yields. In contrast to these results, the α,β-epoxy sulfoxides derived from aldehydes did not give the desired α,β-unsaturated ketones. In this case, a sequential treatment of the α,β-epoxy sulfoxides with benzenethiolate and m-chloroperbenzoic acid afforded α-phenylsulfinylated ketones, which were heated in toluene at 110 °C to give the desired enones in good overall yields. The oxidation of the α,β-unsaturated aldehydes obtained by this method gave α,β-unsaturated carboxylic acids in high yields. These procedures afforded a new method for the synthesis of α,β-unsaturated carbonyl compounds, including α,β-unsaturated esters, from carbonyl compounds with carbon homologation.
Preparation of New Nitrogen-Bridged Heterocycles. 15. Synthesis and Reaction of 1,9a-Dihydropyrido[2,1-c][1,4]thiazines
Authors: Kakehi Akikazu , Ito Suketaka , Yonezu Shingo , Maruta Katsunori , Yuito Kazuhiro , Shiohara Morio , Adachi Kyoko 
Published: July 2006

Abstract
Alkaline treatment of 1-[2-(substituted methylthio)vinyl]pyridinium bromides, readily obtainable from the S-alkylation of pyridinium 1-(thiocarbonyl)methylides with various alkyl bromides such as bromoacetonitrile, ethyl bromoacetate, and some phenacyl bromides, gave smoothly 1,9a-dihydropyrido[2,1-c][1,4]thiazine derivatives as almost isomeric mixtures. These dihydropyridothiazines are very unstable and decomposed rapidly at ordinary temperature, but by treating them with a dehydrogenating agent such as lead tetraacetate (LTA) or 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) at 0 °C the desulfurized and the rearranged aromatic indolizine derivatives were formed in moderate to good yields.
Metal Ion-Catalyzed Reduction of Substituted Nitrosobenzenes by 1-Benzyl-3,5-bis(1-pyrrolidinylcarbonyl)1,4-dihydropyridine in Acetonitrile
Authors: Awano Hiroshi , Takemoto Kazuo , Ohya Hirohisa , Tomio Minaki , Tamagaki Seizo , Tagaki Waichiro 
Published: July 2006

Abstract
Metal ion catalyzed reduction of substituted nitrosobenzenes by 1-benzyl-3,5-bis(1-pyrrolidinylcarbonyl)1,4-dihydropyridine (BPDH) in acetonitrile has been studied for seven bivalent metal ions. The reduction of N-methylacridinium salt (MA) has also been examined. In the former cases, it was found that the metal ions catalyze the reduction by forming a 1:1 complex with BPDH according to a Michaelis–Menten type saturation kinetics which allowed to derive the association constants, KM, for the complexation and the second-order rate constants, k2, for the reduction. A linear relationship was found between logk2 and the ionization potentials of metal ions with a positive slope. A linear Hammett relationship was also observed between logk2 and the Hammett σ constants with a positive ρ value for three metal ions. These results suggest that a bivalent metal ion is sandwiched between the BPDH and the substrate and acts as a Lewis acid to stabilize the incipient N-oxide anion of the substrate which is formed by hydride transfer in the transition state. In the cases of MA, all metal ions inhibited the reduction. Repulsion between the positive charges of the metal ion-BPDH complex and the substrate salt appears to be prevailing.
Atropisomerism of Zinc Tetrakis(o-cyanophenyl)porphyrins. The Crystal Structure of the αβαβ-Isomer and the Atropisomerization Rates
Authors: Hatano Keiichiro , Kawasaki Kyoko , Munakata Sonono , Iitaka Yoichi 
Published: July 2006

Abstract
The structure of one of the four atropisomers of tetrakis(o-cyanophenyl)porphyrin has been determined as the zinc complex by X-ray crystallographic methods. The five-coordinate zinc porphyrin with pyridine as the axial ligand also has a pyridine solvate in the crystal lattice. The conformation of the o-cyanophenyl rings is αβαβ as predicted previously. The two nitrogen atoms of the CN groups on the same side of the coordinated pyridine have close intramolecular contacts to pyridine at the van der Waals distance. However, the structural parameters, bond distances and angles of this molecule do not indicate distinct steric effects of the CN groups. Thermal atropisomerization among the four zinc porphyrin atropisomers occurs in solution. The quantitative composition of the atropisomers at equilibrium and the rates of the isomerization reaction have been determined with aliquots separated by TLC. A nonstatistical equilibrium distribution of the atropisomers suggests some mutual interactions among the CN groups. The slower isomerization rates of the zinc complexes compared to those of the free base have been discussed in connection with the molecular structure.
Studies of a Peptide Antibiotic “Gratisin”. II
Authors: Tamaki Makoto , Takimoto Michiaki , Muramatsu Ichiro 
Published: July 2006

Abstract
In order to investigate the structure-activity relationship of the “gratisin”-related peptide, cyclo(–Val–Orn–Leu–d-Phe–Pro–d-Tyr–)2 (GR-I), its two analogs, cyclo(–Val–Orn–Leu–d-Ala–Pro–d-Tyr–)2 (6a) and cyclo(–Val–Orn–Leu–d-Phe–Pro–d-Ala–)2 (6b), were synthesized. The CD spectra of these synthetic peptides in an aqueous solution were similar to that of GR-I, indicating that these peptides have similar conformations in an aqueous solution. The activity of 6b was half that of GR-I, whereas 6a did not show any antibiotic activity. These results indicated that the phenyl group of the d-Phe residue preceding the Pro residue is essential for exhibiting the activity, while the p-hydroxyphenyl group of the d-Tyr residue following the Pro residue is not essential.
Synthesis of 4-Amino-2(5H)-furanones through Intra- and Intermolecular Nitrile Addition of Ester Enolates. Construction of Carbon Framework of an Antitumor Antibiotic Basidalin
Authors: Hiyama Tamejiro , Oishi Haruhito , Suetsugu Yukari (nee Kusano) , Nishide Kiyoharu , Saimoto Hiroyuki 
Published: July 2006

Abstract
Two new routes to 4-amino-2(5H)-furanones are disclosed. The one is based on the reaction of a magnesium enolate of t-butyl acetate or propionate with O-protected cyanohydrins followed by acid-treatment which effects hydrolysis of the ester group, deprotection, olefin isomerization and lactonization all in a single operation. The other is base-induced ringclosure of α-acyloxy nitriles. The two methods are applied to construction of the carbon framework of an antitumor antibiotic basidalin.
Resonance Raman and 129I Mössbauer Spectroscopic Study of Phenothiazine–Iodine Complexes
Authors: Sakai Hiroshi , Muraishi Shu-ichi , Maeda Yutaka 
Published: July 2006

Abstract
Resonance Raman and 129I Mössbauer spectroscopy have been applied to the phenothiazine–iodine (PT–In) complexes, which exhibit relatively low electrical resistivities. It is shown from the resonance Raman spectra that the two iodine species in the PT–I3 and PT–I2.6 complexes are present in essentially the same chemical form, consisting of a distorted I3− unit and an I2 unit strongly coordinated to the I3− unit. The 129I Mössbauer spectrum, consistent with the results of the Raman spectra, suggests that the PT–I2.6 complex can be approximately formulated as (PT)53+[(I3)3(I2)2]3−, in which about three electrons per five PT molecules are transferred to the iodine and the transferred electrons are delocalized on the thirteen iodine atoms. The radical salt is recognized as a partially oxidized mixed-valence compound. The formation of the complex is quite similar to that of the perylene–I3 complex, which has a low electrical resistivity.
Racemic Structures of Organic Ammonium Salts of N-Acetyl-Dl-2-aminobutyric Acid and N-Acetyl-Dl-norvaline and Optical Resolution by Preferential Crystallization of Dl-Ammonium Salts
Authors: Shiraiwa Tadashi , Yoshida Hirokazu , Tsuda Makoto , Kurokawa Hidemoto 
Published: July 2006

Abstract
The racemic structures of the ammonium salts (AM salts) and seven organic ammonium salts of N-acetyl-Dl-2-aminobutyric acid (Dl-AcAbu) and N-acetyl-Dl-norvaline (Dl-AcNva) were studied on the basis of thermodynamic analyses to explore the possibility of optical resolution by preferential crystallization. An empirical equation has been derived from thermodynamic data at melting points of ammonium and organic ammonium salts of N-acyl-Dl-amino acids to predict racemic structures around room temperature. The AM salts of Dl-AcAbu and -AcNva exist in conglomerate around room temperature. It is possible to resolve optically these Dl-AM salts by preferential crystallization in ethanol at 10 °C, and the successive preferential crystallization followed by purification gave d- and l-2-aminobutyric acids and -norvalines with optical purities close to 100%.
Aldol Condensation Reaction between Formaldehyde and Acetone over Heat-Treated Synthetic Hydrotalcite and Hydrotalcite-Like Compounds
Authors: Suzuki Eiichi , Ono Yoshio 
Published: July 2006

Abstract
Synthetic hydrotalcite, Mg6Al2(OH)16CO3·4H2O, and its analogues were synthesized, heat-treated at 773 K, and used as catalysts for the title reaction to form methyl vinyl ketone (MVK) at 673 K. MVK was formed over all the catalysts examined, the highest MVK yield (20% on acetone basis) being found over the heat-treated hydrotalcite.
Circular Dichroism Spectra of the Dicobalt(III) Complexes Containing Two Bridging μ-Hydroxo Ligands
Authors: Ama Tomoharu , Kawaguchi Hiroshi , Yasui Takaji 
Published: July 2006

Abstract
Five cobalt(III) complexes, [(gly)2Co(μ-OH)2Co(en)2]2+ (two geometrical isomers), [(edda)Co(μ-OH)2Co(en)2]2+ (two geometrical isomers), and [(nta)Co(μ-OH)2Co(en)2]Cl, were newly prepared and optically resolved. Their structures were assigned on the basis of visible and UV absorption, 1H NMR, and circular dichroism (CD) spectral data. It was found that the CD contributions of the two different cobalt(III) chromophores are additive in the present complex systems. The vicinal CD which is induced on one of the two cobalt chromophores by the other chiral cobalt chromophore was strong (|Δε|: ca. 2). These complexes are stable for several days in aqueous solution.
Studies of the Hydrous Niobium(V) Oxide Ion Exchanger. IV. The Rate of the Isotopic Exchange of Sodium Ions between the Exchanger in the Na+ Form and Aqueous Solutions
Authors: Inoue Yasushi , Yamazaki Hiromichi , Ikeda Mitsuji 
Published: July 2006

Abstract
The rate of the isotopic exchange of sodium ions between the hydrous niobium(V) oxide ion exchanger in the Na+ form and aqueous solutions was determined radiochemically. Since the fractional attainment of equilibrium was independent of the sodium-ion concentration in the solutions (≥0.1 mol dm−3), and inversely proportional to the square of the particle radius, the isotopic exchange rate on the hydrous niobium(V) oxide is controlled by the diffusion of the sodium ions in exchanger particles. The self-diffusion coefficients of sodium ions (D=3.1×10−7 cm2 s−1 at 25 °C) and their activation energy (Ea=27±4 kJ mol−1) were also determined.
Association of Naphthalene and Its Methyl Derivatives with Cyclodextrins in Aqueous Medium
Authors: Fujiki Motohisa , Deguchi Toshio , Sanemasa Isao 
Published: July 2006

Abstract
Formation constants of naphthalene and its (1- and 2-)methyl and (1,4-, 1,5-, and 1,8-)dimethyl derivatives with α-, β-, and γ-cyclodextrins (CyD) were determined in the aqueous medium in the presence of excess CyD. The technique used to study associations between host (CyD) and guest(hydrocarbon) is based on the facts that the guest molecules can be driven out to gaseous phase by introducing an inert gas at a constant flow rate into the aqueous solution and that the volatilization rate of guest decreases with increasing association with the host in aqueous solution. The 1:1 and 2:1 (host:guest) formation constants were evaluated at 25 °C. From the formation constant estimated, a host–guest spatial-fitting model for each association complex is presented.
Depletion-Mode Field Effect Semiconductor Sensor with Cation-Sensitive Polymer Membranes
Authors: Okawa Yusuke , Sukigara Mitsunori , Yoshida Shoichiro , Watanabe Tadashi 
Published: July 2006

Abstract
Semiconductor ion sensors based on the surface conductance change due to a variation in the depletion layer thickness have been constructed. An n-SnO2 electrode was coupled with four kinds of cation-sensitive polymer membranes (Fe3+- and Cu2+-exchanged Nafion membranes and poly(vinyl chloride)-supported dioctyl phthalate membranes containing a neutral carrier, valinomycin or nonactin), and its surface conductance was measured under depletion conditions as a function of the cation concentration. The sensor exhibited sensitivity to Fe3+, Cu2+, K+, or NH4+ at levels higher than 10−4 mol dm−3 within 10 s. The sensor response was analyzed in terms of (1) the dependence of the surface conductance on the surface band bending and (2) the potential difference at solution/membrane interfaces. From the analysis, it is confirmed that the membranes show nearly Nernstian behavior and that the semiconductor acts as a potentiometric transducer. The applicability of the depletion-mode semiconductor sensor is discussed.
Infrared Spectroscopic Conformational Analysis of Polystyrene Resin-Bound Human Proinsulin C-Peptide Fragments. β-Sheet Aggregation of Peptide Chains during Solid-Phase Peptide Synthesis
Authors: Narita Mitsuaki , Honda Shinya , Umeyama Hiroshi , Ogura Toshihiko 
Published: July 2006

Abstract
Conformational analysis of human proinsulin C-peptide fragments bound to cross-linked and soluble polystyrene resin matrices was performed using IR absorption spectroscopy. The conformational analysis of octa- and tridecapeptides in the swollen and solid states revealed that both peptides easily interacted with each other through intermolecular hydrogen bonding to form a β-sheet aggregation even at a low loading of peptide chains on the matrices. The high potential of the resin-bound peptides for the β-sheet formation was compatible with that of the corresponding peptides free from macromolecular protecting groups and was predicted using the average coil conformational value, 〈Pc〉, of each peptide. The significance of the results is discussed in connection with solid-phase peptide synthesis. Effects of shear stress on conformational transformations of resin-bound peptides was also examined in the solid state.
One-Pot Ortho Hydroxylations of 2-(1-Hydroxyalkyl)naphthalenes and (1-Hydroxyalkyl)benzenes
Authors: Tanoue Yasuhiro , Terada Akira , Seto Iwao , Umezu Yasuo , Tsuge Otohiko 
Published: July 2006

Abstract
Hydroxylations of 2-(1-hydroxyalkyl)-1,4,5,8(or 1,4,5,6,8)-tetra(or penta)methoxynaphthalenes and 2-(1-hydroxyalkyl)-1,4-dimethoxybenzenes at the 3-position were accomplished by a one-pot procedure. The same procedure has been found to be applicable to 2-(1-hydroxyalkyl)naphthalenes and (1-hydroxyalkyl)benzenes having no methoxyl substituent.
New Application of Solid Acid to Carbon–Carbon Bond Formation Reactions: Clay Montmorillonite-Catalyzed Aldol Reactions of Silyl Enol Ethers with Aldehydes and Acetals
Authors: Kawai Motomitsu , Onaka Makoto , Izumi Yusuke 
Published: July 2006

Abstract
A new attempt of utilizing solid acid to the cross aldol reaction of silyl enol ethers with aldehydes or acetals has been investigated. Among solid acids employed, the reaction is promoted most effectively by a catalytic amount of aluminium ion-exchanged montmorillonite (Al-Mont). Simple diastereoselection is significantly sensitive to the nature of the reaction solvent used in the Al-Mont-catalyzed reaction. When the aluminium ions in Al-Mont were replaced by protons or titanium ions in order to investigate the cation effect, almost the same results were observed on simple diastereoselectivity and diastereofacial selectivity. This fact suggests that the metal cations in montmorillonite do not work as Lewis acid in the present aldol reaction. The acid catalysis of montmorillonite in the present aldol reaction is discussed in comparison with the catalytic behavior of some homogeneous acids.
Practical Syntheses of Immunologically Relevant β-Glycosides of 2-Acetamido-2-deoxy-d-mannopyranose. Methyl N-Acetyl-β-d-mannosaminide, N-Acetyl-β-d-mannosaminyl-(1→6)-d-galactose, and Methyl N-Acetyl-β-d-mannosaminyl-(1→4)-α-d-glucopyranoside
Authors: Kaji Eisuke , Lichtenthaler Frieder W , Nishino Takashi , Yamane Aya , Zen Shonosuke 
Published: July 2006

Abstract
Highly stereoselective, expedient syntheses are described for three immunologically relevant β-glycosides of N-acetyl-d-mannosamine, i.e. β-d-ManpNAc-1-OMe (8), β-d-ManpNAc-(1→6)-d-Gal (15), and β-d-ManpNAc-(1→4)-α-d-Glcp-1-OMe (23). Basic mannosamine progenitor in each case is 3,4,6-tri-O-benzoyl-2-(benzoyloxyimino)-2-deoxy-α-d-arabino-hexopyranosyl bromide (1a), which via the three step-sequence β-selective glycosidation → hydroboration → deblocking is converted to 8, 15, and 23 in overall yields of 61, 56, and 39% for the glycosyl acceptors methanol, 1,2:3,4-di-O-isopropylidene-α-d-galactose, and methyl 2,3,6-tri-O-benzyl-α-d-glucopyranoside, respectively.
Condensation and Cyclization Reactions of 2-Hydrazinobenzimidazole, -benzoxazole, and -benzothiazole
Authors: Badr M Z A , Mahmoud A M , Mahgoub S A , Hozien Z A 
Published: July 2006

Abstract
2-Hydrazinobenzoxazole (1), -benzimidazole (2), and benzothiazole (3) were condensed with ethyl chloroformate and/or diethyl oxalate to produce, 1,2,4-triazolo- and 1,2,4-triazino-fused ketones of the title azoles respectively. Condensation of 1 and 2 with aromatic aldehydes and/or acetic anhydride produced, 3-aryl- and 3-methyl-substituted 1,2,4-triazolo-fused azoles respectively. The hydrazines 1 and 2 cyclized with acetylacetone to produce the corresponding 2-(1-pyrazolyl) derivatives. 2-Acetylthiazolobenzimidazole reacted with hydroxylamine and/or alkylamines, to produce the corresponding condensation products. Also it condensed with aromatic aldehydes to give the chalcones. When reacted with benzenediazonium salt, it gave the corresponding 2-arylazo-substituted compounds.
The Crystal Structure of the β′1 Form of Optically Active α-Monostearin
Authors: Goto Midori , Kozawa Kozo , Uchida Tokiko 
Published: July 2006

Abstract
The crystal structure of the β′1 form of (R)-α-monostearin has been determined. The space group is P212121, with a=4.943(1), b=8.858(2), c=101.05(1)Å, and Z=8. The two independent molecules in the title compound have different conformations.
The Crystal Structure and Intramolecular Electron Transfer of 1′,1'″-Diethylbiferrocenium Triiodide at 298 and 140 K
Authors: Konno Michiko , Sano Hirotoshi 
Published: July 2006

Abstract
The crystal structure of 1′,1'″-diethylbiferrocenium triiodide, (EtFcFcEt)+ I3−, was determined by means of X-ray diffraction. The crystals at 298 and 140 K are found to be monoclinic, with the P21⁄c space group and with Z=2. At 298 K, a=9.7557(10), b=9.9772(12), c=13.8216(13) Å, β=107.625(9)°, and U=1282.18(23) Å3, while at 140 K, a=9.6931(17), b=9.8065(22), c=13.7373(19) Å, β=107.642(15)°, and U=1244.4(4) Å3. The structures are refined to R=0.049 at 298 K and R=0.036 at 140 K. The (EtFcFcEt)+ cations and I3− anions sit on a crystallographic center of symmetry both at 298 and at 140 K, and the two ferrocenyl(Fc) units are crystallographically equivalent. The ethyl group in each ethylcyclopentadienyl(EtCp) group is not parallel to the fulvalene moiety, but the terminal CH3 group moves away with the 60° inclination from the Cp plane. An appreciable interaction seems to exist between the Cp ring of the cation and the I3− anion along the a+c⁄2 direction, but the interaction among the cations along the a axis seems to be so weak as to be negligible.
S-Bridged Polynuclear Complexes. II. Formation and Some Properties of [M{Co(l-cys-N,S)3}2]-Type Complexes (M=Fe(III), Co(III), and Ni(II); l-cys=l-cysteinate)
Authors: Aizawa Sen-ichi , Okamoto Ken-ichi , Einaga Hisahiko , Hidaka Jinsai 
Published: July 2006

Abstract
Three trinuclear complexes with ΔLll- and/or ΛLll-fac(S)-[Co(l-cys-N,S)3] terminals, and ΔLllΔLll-,ΔLllΛLll-, and ΛLllΛLll-[Fe{Co(l-cys-N,S)3}2]3−, ΔLllΛLll-[Co{Co(l-cys-N,S)3}2]3− and ΔLllΔLll-[Ni{Co(l-cys-N,S)3}2]4−, were newly prepared. These complexes were characterized from their electronic absorption, CD, and 13C NMR spectra. Each reaction of ΔLll-fac(S)-[Co(l-cys-N,S)3]3− with Fe(II) and Co(II) was accompanied by the inversion of the absolute configuration of the one or both terminals to give the ΔLllΛLll and ΛLllΛLll isomers, while the reaction with Fe(III), Co(III), or Ni(II) proceeded with the retention of the terminal to give the ΔLllΔLll isomer. The voltammetric study revealed that the formal potential of ΔLllΔLll-[Fe{Co(l-cys-N,S)3}2]3− (−0.16 V) is more anodic than that of ΔLllΔLll-[Co{Co(l-cys-N,S)3}2]3− (−0.43 V). These redox potentials are discussed in relation to the formation ratios of the isomers for the trinuclear complexes.
A Facile Synthesis of Oxetane Derivatives for Preparing Cross-Linked Polyoxetane Resins Bearing the Bromide at the Spacer End
Authors: Motoi Masatoshi , Suda Hiroshi , Shimamura Katsuhiko , Nagahara Shinsuke , Takei Mitsuru , Kanoh Shigeyoshi 
Published: July 2006

Abstract
3-(6-Bromo-2-oxahexyl and 8-bromo-2-oxaoctyl)-3-methyloxetanes, and 1,8- and 1,10-bis(3-methyl-3-oxetanyl)-2,7-dioxaoctane and -2,9-dioxadecane were readily prepared in fairly good yields by the reaction of 3-hydroxymethyl-3-methyloxetane (1) with tetra- and hexamethylene dibromides in the presence of a phase-transfer catalyst. The formation of the mono- and disubstituted products depends upon the molar ratios of the dibromide to 1. The optimum reaction conditions for the etherification of 1 with tetramethylene dibromide were searched. The (ω-bromo-2-oxaalkyl)oxetanes were polymerized to give soluble polyoxetanes (\barMn 3500–5500) by cationic ring-opening polymerization. The use of the bisoxetanes, a new cross-linking agent, as a comonomer gave insoluble elastic polyoxetane resins having a pendant bromide at the spacer end.
Synthesis and X-Ray Crystal Structure of [54](1,2,3,4)Ferrocenophane
Authors: Hisatome Masao , Yamashita Rin-ichi , Watanabe Jun , Yamakawa Koji , Iitaka Yoichi 
Published: July 2006

Abstract
The title compound bridged with four pentamethylene chains has been synthesized by stepwise construction of a pentamethylene bridge via formation of a three-carbon bridge followed by insertion of two carbon units. Crystal structure of the phane has been determined by X-ray diffraction. The compound crystallizes in the monoclinic system, space group P21⁄n with unit cell parameters a=16.691(10), b=9.858(5), c=15.237(8) Å, β=112.43(6)°, and z=4. The structure parameters of the ferrocene moiety fall in normal ranges. Characteristic features are noted in the methylene bridges. The γ-methylene carbons undergo large thermal vibration, and apparent shortening of the bond lengths by oscillatory motions of atoms is seen.