bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Improved Free-Energy Parameters of RNA Stability to Codon–Anticodon Interactions
Authors: Sugimoto Naoki , Sasaki Muneo 
Published: July 2006

Abstract
Free-energy parameters of the RNA duplex stability have been applied in order to investigate the complex between codon oligomers and anticodon loops in transfer RNA. The results suggested that the very large stability of the complex might be due to the stacking interactions of adjacent bases on the codon–anticodon helix and an additional hydrogen-bond formation of the core helix as well as a conformational change of the nucleic acid.
Reaction Behavior of Propylene Oxide in Various Solvents in the Presence of Boron Trifluoride
Authors: Sugiyama Shigeru , Ôhigashi Shinji , Sato Kiyozumi , Fukunaga Sadao , Hayashi Hiromu 
Published: July 2006

Abstract
The reaction behavior of propylene oxide with boron trifluoride was affected remarkably by solvent. In dioxane, the isomerization to propionaldehyde proceeded smoothly and selectively, while the reaction behavior in heptane, benzene, and tetrahydrofuran was quite different from that in dioxane.
Unequivocal Synthesis of the Four d,l-Pairs of 3-Substituted 2-Aminonorbornane-2-carboxylic Acids
Authors: Avenoza Alberto , Cativiela Carlos , Mayoral Jose A , Roy Miguel A 
Published: July 2006

Abstract
The Diels–Alder reaction between methyl α-cyanocinnamate and cyclopentadiene, as a key step in the synthesis of 2-amino-3-phenylnorbornane-2-carboxylic acids, is studied. The cycloadducts can be easily separated and converted into the amino acids through simple reactions.
Heterocycles Synthesis through Reactions of Nucleophiles with Acrylonitriles. 7. A Novel and Facile One-Step Synthesis of 4H-Thiopyrans
Authors: Abdel-Latif Fathy Fahim 
Published: July 2006

Abstract
Several new 4H-thiopyrans were synthesized via a facile one-step method. Structures and reaction mechanisms are also reported and supported by another synthetic routes.
Synthetic Inorganic Ion-Exchange Materials. LII. Ion-Exchange Selectivities of Crystalline Antimonic Acid for Tervalent Metal Ions
Authors: Abe Mitsuo , Hirata Masao , Tsuji Masamichi 
Published: July 2006

Abstract
The determination of selectivity coefficients for tervalent metal ions/hydrogen ions on cubic crystalline antimonic acid (C-SbA) was carried out for Ga3+, Fe3+, Ce3+, Sm3+, Y3+, Sc3+, and In3+ by batch equilibration at 30, 45, and 60 °C in nitric acid media. The selectivity in microamounts showed: Al3+&lt;Tm3+&lt;Ga3+&lt;Yb3+=Y3+&lt;Er3+&lt;Dy3+&lt;Fe3+&lt;Eu3+&lt;Sm3+&lt;Ce3+&lt;La3+&lt;Sc3+=In3+. The ion-exchange isotherms of the systems of tervalent metal ions/hydrogen ions have also been studied on C-SbA. The selectivity coefficients in logarithm scale vs. equivalent fraction of metal ions in exchanger showed almost straight line, indicating monofunctional site with steric effect. In order to interpret the selectivity in microamounts of metal ions, hypothetical equilibrium constant was determined by extrapolating to zero loading of metal ions in C-SbA. From these values, the hypothetical thermodynamic data were calculated and evaluated.
Thermal Decomposition of Ammonium Copper(II) cyclo-Hexaphosphate Cu2(NH4)2P6O18·8.5H2O and Ammonium Calcium cyclo-Hexaphosphate Ca2(NH4)2P6O18·7H2O
Authors: Takenaka Atsushi , Kobayashi Hironobu , Tsuchie Katsumi , Motooka Itaru , Nariai Hiroyuki 
Published: July 2006

Abstract
Ammonium copper(II) and ammonium calcium cyclo-hexaphosphates, Cu2(NH4)2P6O18·8.5H2O and Ca2(NH4)2P6O18·7H2O, were prepared by a wet method. TG-DTA, HPLC-FIA, and X-ray diffraction method were used to investigate the thermal decomposition of the cyclo-hexaphosphates. The effect of humidity on the pyrolysis was also examined by the use of dry N2 gas and humid air. Cu2(NH4)2P6O18·8.5H2O was mainly decomposed to oligophosphates by hydrolysis. Parts of the oligophosphates were changed to poly- (n=1–13) and highpolyphosphates through a condensation. The poly- and the highpolyphosphates were more abundant under the dried conditions. Above 280 °C ammonia was liberated. As the crystalline products, CU2P2O7 was identified at 380 °C, and CU2P4O12 above 430 °C. Ca2(NH4)2P6O18·7H2O lost almost all its water of crystallization by 177 °C. As ammonia was evolved from 270 to 420 °C, accelerated by humidity, amorphous highpolyphosphates were formed. The formation of the highpolyphosphates was considered to proceed through a radical polymerization, since oligophosphates were scarcely detected in the course of the thermal reaction.
Study on the Claisen Rearrangement. VI. Catalytic Effect of Alkali Metal Salts on the Claisen Rearrangement of Allyl o- or p-Hydroxyphenyl Ether
Authors: Hayashi Takatoshi , Okada Yutaka , Inaba Takeshi 
Published: July 2006

Abstract
The Claisen rearrangement of allyl o- or p-hydroxyphenyl ether is catalyzed by alkali metal salts. The mechanism of the catalytic effect is different from that by Lewis acids such as zinc chloride. It is considered that the hydroxyl group is dissociated into phenoxide ion –O− with loss of its proton through attack by the anion residue of an alkali metal salt. Thus, the catalytic effect is attributable to a strong electron-releasing effect of phenoxide ion –O−. Furthermore, for the o-isomer, an intramolecular repulsion between the phenoxide ion –O− and the ethereal oxygen operates.
The Effect of Sodium Hydroxide on the Stereoselectivity of Hydrogenolytic Asymmetric Transaminations between (R)-2-Amino-2-phenylethanol and 2-Keto Acids
Authors: Tamura Minoru , Shiono Shozo , Harada Kaoru 
Published: July 2006

Abstract
Hydrogenolytic asymmetric transaminations between (R)-2-amino-2-phenylethanol and 2-keto acids were carried out over Pd catalyst in the absence or presence of various amount of sodium hydroxide in water or alcohols. The stereoselectivity of the reaction was significantly influenced by the amount of sodium hydroxide in the reaction mixture. When pyruvic acid was used in water the optical purity of alanine was 22% ee (R) and in 1 M (1 M=1 mol dm−3) sodium hydroxide solution it was 62% ee (S). When 2-oxobutyric acid was used in ethanol in the absence and presence of sodium hydroxide (1M), the optical yields of 2-aminobutyric acid were 2% ee (R) and 81% ee (S), respectively. In contrast, the addition of sodium hydroxide had little or no effect on the stereochemistry of the reaction using (S)-α-methylbenzylamine as a chiral source in aqueous or ethanolic solution. The substituent, additive, temperature, and solvent effects on the asymmetric reactions were examined in aqueous or ethanolic alkaline solution. Based on these experimental results, a possible explanation for the change in stereoselectivity by using sodium hydroxide is discussed.
Non-Catalyzed Thermal Reactions of Acylquinones with Allylstannanes
Authors: Maruyama Kazuhiro , Matano Yoshihiro 
Published: July 2006

Abstract
Thermal reactions of acylquinones with allylstannanes in benzene afforded several kinds of product after column chromatography on silica gel; acyl allyl quinones, acyl allyl epoxy quinones, cyclopentanoid compounds including stannyl moiety, allyl hydroxy quinones, acyl hydroquinones, and acyl allyl hydroquinones. The main product comprises cyclopentanoid compounds, which are novel [2+3] cyclo adducts with 1,2-migration of trialkylstannyl moiety. Spectroscopic examinations (1H NMR and Vis-UV) enabled us to confirm the reaction pathways that four types of precursors were initially generated via polarized tight pair and inverted to isolated products during purification by column chromatography. Similar reactions in acetonitrile showed a remarkable difference in the reactivity, that is, acyl allyl quinones and the corresponding hydroquinones are obtained, but the [2+3] cyclo adducts are not produced at all. From 1H NMR examination, it was confirmed that three types of precursor are generated via solvent separated ion pairs at the initial stage. The rather strong reactivity of acylquinones towards allylstannanes will be due to electron withdrawing ability of acyl group.
Linear Tetranuclear Copper(II) Complexes with Bridging Methoxide and a Schiff-Base Ligand: The Preparation and Magnetic Study of the [Cu(salpd-μ-O,O′)(μ-L)Cu(μ-CH3O)2Cu(μ-L)(sapd-μ-O,O′)Cu] Complexes (and L=Acetate or Formate Ions) and the Structure Determination of the Complex with L=Acetate
Authors: Fukuhara Ch\={o}ki , Tsuneyoshi Kazuhiko , Katsura Kosho , Matsumoto Naohide , Kida Sigeo , Mori Masayasu 
Published: July 2006

Abstract
The title complexes have been synthesized in quantitative yield from [Cu(salpd)] and copper(II) acetate or copper(II) formate , where H2salpd represents N,N′-disalicylidene-1,3-propanediamine. [Cu(salpd-μ-O,O′)(μ-L)Cu(μ-CH3O)2Cu(μ-L)(salpd-μ-O,O′)Cu] crystallizes in the monoclinic space group P21/n with formula=Cu4C40H44N4O10, F.W.=995.0, a=11.826(2) Å, b=17.192(4) Å, c=9.836(2) Å, β=94.08(2)°, V=1994.8(7) Å3 and Z=2 (R=3.83%), where L=CH3COO. The complex forms a centrosymmetric molecule made up of two units of [Cu(salpd-μ-O,O′)(μ-CH3COO)Cu] bound by a pair of methoxo bridges; each terminal copper(II) ion forms four short bonds with N and O atoms of salpd and a slightly longer (2.235(4) Å) axial bond with one of the oxygens of the acetato group, whereas each inner copper(II) ion is also pyramidally coordinated by two methoxo oxygens, one of the acetato oxygens, and one of the bridging salpd oxygens, the distant axial position being occupied (Cu–O=2.323(3) Å) by the remaining bridging salpd oxygen. The magnetic susceptibilities of the complexes in the 86.8–299.0 K range have been analyzed on the basis of a four-spin model for the linear copper(II) complexes, and the values of g and Jij, based on the Heisenberg-type Hamiltonian H=−2ΣJijSi·Sj, have been estimated as g (average)=2.13, J12=−390 cm−1, J13=67 cm−1 and J14=34 cm−1 in the complex with acetate bridges, and as g (average)=2.20, J12=−263 cm−1, and J13=39 cm−1 and J14=J34=0 cm−1 in the complex with formate bridges, where the numbering refers to the 3–1–2–4 arrangement of the Cu2+ ions.
Kinetics and Mechanisms of Oxidations by Metal Ions. X. Oxidation of Phosphinic and Phenylphosphinic Acids by Tris(polypyridyl)iron(III) Complexes
Authors: Sharma Kamla , Prakash Aditya , Mehrotra Raj N 
Published: July 2006

Abstract
A kinetic study on the oxidation of phosphinic(hypophosphorous) and phenylphosphinic acids by trispolypyridyliron(III) complexes using excess of either phosphinic or phenylphosphinic acid has been made in perchloric acid. The pseudo first-order rate constant kobs, with respect to iron(III) complex, is independent of [H+]. The results indicated that phenylphosphinic acid is more reactive than phosphinic acid towards any given iron(III) complex. The formation of an intermediate complex is indicated by the kinetics and supported by the spectrophotometry of the reaction mixture. The differences in the observed thermodynamic parameters of this intermediate complex, probably an outer-sphere complex, and those predicted by the Fuoss equation are discussed. It is suggested that the ‘inactive’ form of either of the acid is reactive towards the iron(III) complexes. It is also shown that the rate of disproportionation of the intermediate complex is not affected by the form of phosphinic or phenylphosphinic acid entering into the complex formation. The values of β2 and k1, the equilibrium constant for the formation of the oxidant-substrate complex and the rate limiting constant for its disproportionation respectively, are reported together with respective thermodynamic and activation parameters.
Crystal Structure and Magnetic Property of Cubane Tetranuclear Copper(II) Complex with Ferromagnetic Coupling
Authors: Matsumoto Naohide , Kondo Takashi , Kodera Masahito , Okawa Hisashi , Kida Sigeo 
Published: July 2006

Abstract
The magnetic susceptibility measurement down to the liquid helium temperature and the single-crystal X-ray analysis of alkoxo-oxygen bridged tetranuclear copper(II) complex [CuL]4 have been performed, where H2L is a tridentate ligand derived from condensation of 3-ethoxymethylene-2,4-pentanedione and 2-aminoethanol. The magnetic data demonstrated that the four unpaired electrons of the four copper(II) ions are ferromagnetically coupled, the ground spin state of the cubane molecule being S=2. The structural analysis has confirmed several structural features, i.e., the distorted Cu4O4 cubane structure, the square pyramidal coordination geometry, nearly perpendicular arrengement between adjacent basal coordination planes, and inequivalent Cu–O bond distances.
Synthesis and Four Isomers of 5-Arylamino-3-isopropyl-6-methyl-6-phenyl-1,2,4-trioxanes
Authors: Yamamoto Hiroshi , Nishio Takehiko , Hirayama Masatoshi , Akutagawa Masamoto , Kashima Choji 
Published: July 2006

Abstract
5-Arylamino-3-isopropyl-6-methyl-6-phenyl-1,2,4-trioxanes were synthesized by autoxidation of imines in the presence of isobutyraldehyde. Their four isomers have been identified and the anomerization of 5-arylamino-1,2,4-trioxanes has been detected by the 13C NMR spectra in chloroform-d.
Reaction of Iminophosphoranes with a Diazonium Salt: Synthesis of Wholly Aromatic Aminophosphonium Salts
Authors: Takeishi Makoto , Shiozawa Naoyuki 
Published: July 2006

Abstract
N-Phenyliminotriphenylphosphorane reacts with benzenediazonium tetrafluoroborate to form wholly aromatic N,N-diphenylaminotriphenylphosphonium tetrafluoroborate. This synthetic method can be applied to prepare a cationic polymer having the aminophosphonium structure.
A New Preparative Method of 4-Hydroxybenzofuran-2-carboxylic Acid Derivatives
Authors: Yamaguchi Seiji , Yamamoto Ken-ichi , Ueda Toshinori , Morikawa Tetsuya , Kawase Yoshiyuki 
Published: July 2006

Abstract
4-Oxo-4,5,6,7-tetrahydrobenzofuran-2-carboxylic acid was prepared from 1,3-cyclohexanedione and ethyl bromopyruvate. Dehydrogenation of this acid or its methyl ester gave 4-hydroxybenzofuran-2-carboxylic acid derivatives.
One-Pot C-Arylmethylation of Active Methylene Compounds with Aromatic Aldehydes Induced by a Me3SiCl–NaI–MeCN Reagent
Authors: Sakai Takashi , Miyata Kazuyoshi , Tsuboi Sadao , Utaka Masanori 
Published: July 2006

Abstract
Reaction of active methylene compounds with aromatic aldehydes in the presence of chlorotrimethylsilane–sodium iodide–acetonitrile reagent gave C-arylmethylated products, the reduced condensation products, although the reaction either with aliphatic primary aldehydes or with isobutyraldehyde afforded alkylidenation products or dihydrofurans.
Synthesis of a 24-Epimeric Mixture of 24-Methyl-19,29-dinorlanost-9(11)-en-3-one
Authors: Makino Tetsuya , Murae Tatsushi , Tsuyuki Takahiko , Takahashi Takeyoshi 
Published: July 2006

Abstract
A 24-epimeric mixture of 24-methyl-19,29-dinorlanost-9(11)-en-3-one was synthesized from 24-methylenecycloartanol. The synthesis comprises acid-cleavage of the cyclopropane ring, 4β-demethylation, the Barton reaction of the 3-nitrile, dehydration of the 11β-hydroxy derivative, and oxidation of the 19-hydroxy derivative followed by photolysis.
Selective Dimerization of Alkyl Crotonates Catalyzed by Iron(0) Complexes Having 1,2-Bis(dimethylphosphino)ethane Ligands
Authors: Komiya Sanshiro , Oyasato Naohiko , Furukawa Tomoyuki 
Published: July 2006

Abstract
Highly selective dimerization of alkyl crotonates has been performed in the presence of a catalytic amount of FeHNp(dmpe)2 or FeH2(dmpe)2/UV irradiation at room temperature.
The Adsorption Equilibria of Organic Vapors on Activated Carbon at High Temperatures
Authors: Hori Hajime , Tanaka Isamu , Akiyama Takashi , Arai Yasuhiko 
Published: July 2006

Abstract
Nitrogen gas containing organic vapor was introduced into a column packed with activated carbon at high temperatures up to 200 °C, and the amounts of the solvents adsorbed were measured. The adsorption equilibrium data for single- and bi-component systems could be correlated by the Freundlich and extended Freundlich isotherms respectively.
Electrical Conduction in Some Ternary Metallo-Organic Solid Complexes of Biological Importance and Compensation Effect
Authors: Mallik Biswanath 
Published: July 2006

Abstract
The electrical conduction in some ternary solid complexes of Cu(II) with 2,2′-bipyridyl/1,10-phenanthroline and several amino acids (e.g., α-alanine, leucine, tryptophan, glycine, and norvaline) is studied as a function of temperature. These materials show semiconductivity. Results suggest that true compensation effect is valid for most of the materials studied. Importance of characteristic temperature (To) in biological process is pointed out.
A New Crystalline Form of Bis(1,2-diphenyl-1,2-ethenedithiolato)nickel: Asymmetric β-Ni(dpedt)2
Authors: Megnamisi-Belombe Michel , Nuber Bernhard 
Published: July 2006

Abstract
The full structure of a new crystalline form of bis(1,2-diphenyl-1,2-ethenedithiolato)nickel, β-Ni(dpedt)2, has been determined by single crystal X-ray diffraction at room temperature. The structure was refined by full matrix least-squares to a final Rw=0.038. Comparison of this triclinic (P\bar1) structure with the monoclinic (P21/n) α-form established previously reveals that the difference between the two structures is basically due to a different conformation of the phenyl rings, which gives rise to dissymmetry in β-Ni(dpedt)2.
Ionization and Dissociation of Picric Acid in 4-Methyl-2-pentanone Solutions at Various Water Concentration
Authors: Sekine Tatsuya , Naganawa Hirochika 
Published: July 2006

Abstract
The spectrum of picric acid in 4-methyl-2-pentanone solutions which contained the acid and water at several concentrations was determined in the wavelength range from 330 to 500 nm and the data were statistically analyzed. It was concluded that picric acid molecules formed ion pairs together with four water molecules in these solutions and the ion pairs thus formed dissociated partially. Both of the ion pairs and dissociated picrate ions in these solutions had strong absorption in the visible range where no absorption was found with the acid molecules but the spectra of these two species were different. The formation and dissociation constants of the ion pairs were also calculated from the data and the role of water in these chemical reactions was considered.
Synthesis and Properties of Copper(II) Halide Complexes with Imino Oximes
Authors: Wan Songping , Mori Wasuke , Yamada Shoichiro , Murahashi Shun-Ichi 
Published: July 2006

Abstract
Two types of imino oxime copper(II) complexes were obtained by the reactions of copper(I) halides CuX (X=Br, I) with imino oximes (3-[2-[(alkylamino)ethyl]imino]-2-butanone oximes or 3-[2-[(dialkylamino)ethyl]imino]-2-butanone oximes, abbreviated as Hdox-enRR′). One type contains the binuclear complexes [Cu2(dox-enRR′)2]2+ and uncoordinated halide anions. The magnetic susceptibilities measured over the temperature range 77–320 K show a strong antiferromagnetic spin coupling interaction through the N–O bridge in these complexes. The magnetic behavior can be explained by using the Bleaney–Bowers equation. It is assumed that the complexes of the other type consist of copper(I) and copper(II) in 2:1 ratio without spin-coupling interaction between the copper ions. The plot of the reciprocal magnetic susceptibilities versus temperatures is linear.
Novel Synthesis of Carbamic Ester from Carbon Dioxide, Amine, and Ortho Ester
Authors: Ishii Shigeru , Nakayama Hidenobu , Yoshida Yasuhiko , Yamashita Tadataka 
Published: July 2006

Abstract
Carbon dioxide reacted with aliphatic amines and ortho esters to form carbamic esters in good yields. The influence of different ortho esters on the carbamate synthetic reaction is described. In the case of orthocarbonates, carbamic esters were obtained in high yields. The reaction of carbon dioxide, amines, and ortho esters may involve a competitive reaction between the esterification of carbamic acid produced by a reaction of carbon dioxide with amine, and the alkylation of amine.
Electronic Control of Stereoselectivity in the Metal Hydride Reductions of 1,2,3,4-Tetrahydro-1,4-methanonaphthalen-9-ones
Authors: Okada Keiji , Tomita Seiji , Oda Masaji 
Published: July 2006

Abstract
Stereoselectivity in the metal hydride reduction of a series of substituted 1,2,3,4-tetrahydro-1,4-methanonaphthalen-9-ones was investigated in relation to their homoconjugation character. The observed stereoselectivity sequence was found to be parallel with the homoconjugation sequence: the portion of anti-attack increases as the benzene ring becomes electron-rich. The results are rationalized in terms of the transition state model proposed by Cieplak or of the contribution of the nonclassical carbocation in the transition state.
Stereoselective Syntheses of 2-Deoxy-β-C-arabino- and ribopyranosides: 2-Deoxy-β-arabino- and ribopyranosyl Cyanides
Authors: Tatsuta Kuniaki , Hayakawa Jun , Tatsuzawa Yukio 
Published: July 2006

Abstract
2-Deoxy-β-arabino- and ribopyranosyl cyanides, which should be suitable for the syntheses of biologically active products, were stereoselectively prepared from the reaction of the enones, 1,5-anhydro-2-deoxy-erythro-hex-1-en-3-ulose derivatives, with acetone cyanohydrin, followed by the stereoselective reduction of the producing ketones with NaBH4–CeCl3·7H2O and l-Selectride, respectively.
Manganese(III)-Mediated Formylation of Aromatic Compounds in the Presence of Malonic Acid
Authors: Nishino Hiroshi , Tsunoda Katsunori , Kurosawa Kazu 
Published: July 2006

Abstract
The reaction of naphthalenes with malonic acid in the presence of manganese(III) acetate gives naphthalenecarbaldehydes and naphthalenecarboxylic acids. Similar reactions of anthracene, pyrene, and methoxybenzenes also yield formylated and carboxylated products. It was found that the formyl group introduced to the aromatic ring was not derived from carboxymethyl radical generated directly by the thermolysis of manganese(III) acetate, but from a dicarboxymethyl radical formed by the interaction of malonic acid and manganese(III) acetate. In addition, it was also found that the dicarboxymethyl radicals attacked the position of the highest electron density on the aromatic ring and that this formylation was effective when the ionization potential of the aromatic compound was lower than 7.8 eV.
The Desulfurization of Polynuclear Aromatic Sulfur Compounds with a Raney Nickel
Authors: Nagai Masatoshi , Urimoto Hideo , Uetake Kazuya , Sakikawa Noriyuki , Gonzalez Richard D 
Published: July 2006

Abstract
The mechanism of the desulfurization of the polynuclear thiophene compounds with a Raney nickel was studied in ethanol at atmospheric pressure and from 0 to 78.3 °C. The desulfurization rate was initially fast but reached zero in about 30 minutes. The major products were biphenyl in the desulfurization of dibenzothiophene (1), 1-phenylnaphthalene in the desulfurization of benzo[b]naphtho[1,2-d]thiophene (2), and 2-phenylnaphthalene in the reaction of benzo[b]naphtho[2,3-d]thiophene (3) and benzo[b]naphtho[2,1-d]thiophene (4). The desulfurization extent for the four compounds decreased in this sequence: 3&gt;1&gt;2&gt;4. The extent of the desulfurization of the polynuclear thiophene compound was not related to the reaction indices, Fr(E), Fr(N), and Fr(R), of the sulfur atom of the compounds, which were calculated by using a simple Hückel theory; rather, it was related to both the free valence and the π-electron density. Therefore, the polynuclear thiophene compounds were considered to adsorb on a Raney nickel through the free-electron pair of the sulfur atom; consequently, the adsorption led to the C–S bond scission.