bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Chromotropic Behavior of Nickel(II) Complexes with 1,4-Diazacycloheptane-N,N′-dicarboxylates in Solution
Authors: Fukuda Yutaka , Yamagata Keiko , Kaden Thomas A 
Published: July 2006

Abstract
A new series of nickel(II) complexes containing 1,4-diazacycloheptane-N,N′-dicarboxylates (dachdx, where x=a means the acetate derivative, x=m, e, and p are the α-methyl, α-ethyl, and α-propyl substituents of the carboxyl side chain, respectively) were prepared as solids, Ni(dachdx)Ln (L=H2O or pyridine, n=0, 1, or 2). These complexes can be classified according to their geometry into three types: (1) Octahedral [Ni(dachda)(H2O)2], (2) square planar [Ni(dachdx)](x=m, p, or e) and (3) penta-coordinate [Ni(dachdm)(py)]. In the solid state the strength of the bonds between the metal ion and the carboxylate groups increases in the order: Octahedral&lt;penta-coordinate&lt;square planar. In solution, some of these compounds show chromotropic behavior, e.g. solvatochromism, thermochromism, and inert salt or active salt effects. The stability constants of the Ni2+ complexes were determined by pH-titrations and spectrophotometry. The following equilibria were found:
[Ni(aq)]2++dachdx2−\ightleftharpoons[Ni(dachdx)];
[Ni(dachdx)]+X−\ightleftharpoons[Ni(dachdx)X]−;
where X−=NCS−, Cl−, or Br−. It is shown that the substituent of the carboxylate side chain plays an important steric role, thus determining the value of the stability constant of [Ni(dachdx)].
The Synthesis of Lycoxanthol and Its C-15 Epimer
Authors: Matsumoto Takashi , Imai Sachihiko , Yoshinari Takashi 
Published: July 2006

Abstract
In order to elucidate the absolute configuration of C-15 in natural lycoxanthol, (15R)-11,16-dihydroxy-12-methoxymethoxy-8,11,13-abietatrien-7-one and its (15S)-epimer were transformed into (15R)-12,16-epoxy-6,11,14-trihydroxy-5,8,11,13-abietatetraen-7-one (1a) and its (15S)-epimer, respectively. The synthetic 1a was identical with natural lycoxanthol. Thus, the stereochemistry of C-15 in the natural compound was conclusively assigned as R-configuration.
Practical Method for the Synthesis and Optical Resolution of Axially Dissymmetric 6,6′-Dimethylbiphenyl-2,2′-dicarboxylic Acid
Authors: Kanoh Shigeyoshi , Muramoto Hiroki , Kobayashi Natsumi , Motoi Masatoshi , Suda Hiroshi 
Published: July 2006

Abstract
Racemic 6,6′-dimethylbiphenyl-2,2′-dicarboxylic acid (1) could be conveniently synthesized and efficiently resolved by the recrystallization of the brucine salts in satisfactory yields. Each enantiomer, thus obtained, was confirmed to be optically pure from a high-performance liquid chromatographic (HPLC) analysis on an optically active column.
Synthesis of (−)-8a-epi-Swainsonine, (1S,2R,8R,8aS)-Octahydro-1,2,8-indolizinetriol
Authors: Tadano Kin-ichi , Hotta Yukinori , Morita Masahiro , Suami Tetsuo , Winchester Bryan , Bello Isabello Centi di 
Published: July 2006

Abstract
(−)-8a-epi-Swainsonine (4), one of the stereocongeners of physiologically interesting indolizidine alkaloid (−)-swainsonine (1), has been synthesized starting from known methyl 3-azido-4,6-O-benzylidene-3-deoxy-α-d-altropyranoside. The α-d-mannosidase inhibitory activity of 4 was compared with natural 1.
400 MHz Two-Dimensional NMR Studies of Cyclodextrin Derivatives for 1H and 13C Chemical Shift Determination
Authors: Tabushi Iwao , Nabeshima Tatsuya , Yamamura Kazuo , Fujita Haruo 
Published: July 2006

Abstract
Two-dimensional (2D) NMR spectroscopies, proton (400 MHZ)– proton (400 MHz) and carbon (100 MHz)– proton (400 MHz) chemical shift correlation spectroscopy, were developed as a reliable technique for the strict assignment of crowded and complicated NMR absorptions of substituted cyclodextrin derivatives, pentakis[2,6-O-(t-butyldimethylsilyl)]-A,B-bis-[2-O-(t-butyldimethylsilyl)-6-deoxy-6-(methylthio)]-β-cyclodextrin (2) and A,B-bis[6-deoxy-6-(methylthio)]-β-cyclodextrin (1).
The Study of Planarized and Planar Cyclohexane Rings on the Basis of Molecular Mechanics
Authors: Dodziuk Helena 
Published: July 2006

Abstract
Recent rapid development of synthetic and theoretical methods has yielded molecules with unusual stereochemistry on carbon atom. One of the most interesting examples of such earlier unsought of arrangements is provided by planar cyclohexane rings. Few molecules of this kind have been synthesized and two others have been postulated on the basis of molecular mechanics calculations. In the present article a critical review of existing experimental and theoretical results is supplemented with a molecular mechanics study of a series of cyclohexanes fused with up to six 3-, 4-, and 5-membered rings causing the flattening of C6 ring. The existing experimental data and the results of the calculations seem to indicate that the flattening is more pronounced when smaller and/or larger number of rings are fused. The applicability and limitations of molecular mechanics with the MM2 parameterization to the study of the flattening of cyclohexane ring have been critically analyzed. The synthetic efforts in this field seem to indicate that some results calculated for hypothetical molecules will be checked in the near future. Similarly to hypothetical [6]asterane and hexaprismane, the planarity of [6.3]coronane has been postulated.
An Ab Initio Molecular Orbital Study of Lithiopyridines
Authors: Kikuchi Osamu , Togo Hideo , Furukawa Naomichi 
Published: July 2006

Abstract
Ab initio molecular orbital calculations were performed for 2-, 3-, and 4-lithiopyridine monomers, and the molecular and electronic structures of lithiopyridines and their reactivity with electrophiles were examined.
(3E)-Laureatin and (3E)-Isolaureatin, Halogenated C-15 Non-Terpenoid Compounds from the Red Alga Laurencia nipponica Yamada
Authors: Suzuki Minoru , Kurosawa Etsuro 
Published: July 2006

Abstract
(3E)-Laureatin and (3E)-isolaureatin have been isolated as major metabolites from the red alga Laurencia nipponica Yamada, and their structures were confirmed on the basis of spectral and chemical evidence.
Majusculone, a Novel Norchamigrane-Type Metabolite from the Red Alga Laurencia majuscula Harvey
Authors: Suzuki Minoru , Kurosawa Etsuro , Kurata Kazuya 
Published: July 2006

Abstract
The structure of majusculone, a novel norchamigrane-type terpene isolated from the red alga Laurencia majuscula Harvey, was deduced from the spectral data.
The Simple Synthesis of Cordiachrome B, a Terpenoid Benzoquinone from Cordia Millenii
Authors: Watabe Takashi , Hosoda Yasushi , Okada Keiji , Oda Masaji 
Published: July 2006

Abstract
Cordiachrome B, a tricyclic terpenoid p-benzoquinone isolated from Cordia millenii, was synthesized in three steps from 1,2-dihydro-3,6-dimethoxybenzocyclobutene employing a Diels–Alder reaction in a key step.
Neutralization Dialysis for Deionization
Authors: Igawa Manabu , Echizenya Kiyoyuki , Hayashita Takashi , Seno Manabu 
Published: July 2006

Abstract
In neutralization dialysis, cations are exchanged with protons across a cation-exchange membrane, while anions are exchanged with hydroxide ions across an anion-exchange membrane, and the effective deionization and the neutralization occur simultaneously on the base of Donnan equilibrium. The ion-exchange membranes are much more permeable to the electrolytes than the nonelectrolytes and their mutual separation is possible by this method.
Preparations and Structures of 3-Chloro-ONN-4′-methylazoxybenzene and 4-Methoxy-ONN-4′-methylazoxybenzene
Authors: Yamamoto Jiro , Tsuboi Takashi , Sumi Yasunori , Oda Noriyasu , Fukuyama Keiichi 
Published: July 2006

Abstract
A treatment of 3-chloro-NNO-4′-methylazoxybenzene (1β) with CrO3 in acetic acid gave 3-chloro-ONN-4′-methylazoxybenzene (1α) in good yield, whereas 4-methoxy-ONN-4′-methylazoxybenzene (2α) isomerized partially to 4-methoxy-NNO-4′-methylazoxybenzene (2β) under the same conditions. The structures of 1α and 2α have been determined by X-ray analysis.
Excited-State Reactions of Coumarins in Aqueous Solutions. IV. The Fluorescence Quenching of 7-Ethoxycoumarins by Inorganic Ions in Micellar Solutions of Sodium Dodecyl Sulfate
Authors: Moriya Tetsuo 
Published: July 2006

Abstract
The effect of added salts (NaCl, NaBr, CsCl) on the fluorescence behavior of 7-ethoxycoumarin (7EC) and 7-ethoxy-4-methylcoumarin (7E4MC) has been studied in aqueous micellar solutions of sodium dodecyl sulfate (SDS). Data on the fluorescence quenching as a function of the salt concentration are analyzed in terms of a proposed two-reactive-state (aqueous and micellar phases) model. The results are in good accord with the model and permit the evaluation of the quenching-rate constants attributable to Br− and Cs+ respectively in the two phases. Quenching mechanisms influencing the fluorescence yield are discussed on the basis of the electrostatic force among micelles and quenchers, the electron-transfer reaction from anion to fluorescer, and the hydration degree of the quencher ions.
A Simple Model for the Kinetics of Beta Meander Formation of Homopolypeptide Chains
Authors: Maeda Hiroshi 
Published: July 2006

Abstract
A simple kinetic theory is presented concerning the irreversible formation of intramolecularly folded β-structure of homopolypeptide chains through a bend formation. To reduce the number of parameters, the number of strands is limited to be less than five and the growth rate of the third and fourth strands is assumed to be so fast that the final strand length is attained immediately after the bend formation. Numerical calculations were carried out on relevant ranges of rate costants for relatively short chains. It was shown that experimentally found diverse kinetic patterns were all explicable based on the present model.
Potentiometric Study of Equilibria in H+–MoO42−–RAsO3H−(R=OH, C6H5, CH3) Systems
Authors: Yagasaki Atsushi , Takahama Hironobu , Sasaki Yukiyoshi 
Published: July 2006

Abstract
The equilibria pH++qMoO42−+rRAsO3H−\ightleftharpoons(H+)p(MoO42−)q(RAsO3H−)r have been studied in 1 M Na(Cl) (1 M=1 mol dm−3) at 25 °C by potentiometry. Heteropoly species which have q⁄r ratios higher than 5 have been found in the R=CH3 and R=C6H5 systems besides the well known species of q⁄r=3. The species, denoted by (p,q,r) according to the equation above, (10, 7, 1), (11, 7, 1), and (11, 6, 1) are proposed as those high ratio species. The formation constant of each species has been determined. The result showed an apparent correlation with pKa’s of arsenic acid and its organic derivatives. Solution structures of the heteropoly species are also discussed.
The Vapor Saturation Method for Preparing Aqueous Solutions of Solid Aromatic Hydrocarbons
Authors: Akiyoshi Mayumi , Deguchi Toshio , Sanemasa Isao 
Published: July 2006

Abstract
A new method to prepare aqueous solutions saturated with solid aromatic hydrocarbons by making use of solute vapor is presented. Air is bubbled through an organic solvent in which an excess quantity of a solid hydrocarbon to be studied has been added, and the resulting vapor is introduced into water and circulated in a closed system. An aqueous solution saturated with a solid solute can thus be prepared in a short time without any need to remove solute microcrystals. Of benzene, cyclohexane, and 1-octanol used as organic solvents, 1-octanol is most promising for this purpose. Solubilities in water at 25.0 °C of nine aromatic hydrocarbons have been measured: Naphthalene, biphenyl, anthracene, phenanthrene, fluoranthene, (o-, m-, p-)terphenyl, and triphenylene. This method can be used for these solutes except phenanthrene.
Preparation and Reaction of Optically Active Organotransition Metal Complexes. II. Preparation and Photoracemization of Optically Active (1-Cyanoethyl)cobaloxime Complexes Coordinated with Various Axial Ligands
Authors: Baba Shoe , Ohgo Yoshiaki , Takeuchi Seiji 
Published: July 2006

Abstract
Optically active (1-cyanoethyl)cobaloxime complexes coordinated with various pyridines, phosphines and amines etc. as axial ligands were prepared and their photoracemization rates were measured in a solution state. It was found that the steric factor, rather than the electronic, of the axial ligand controlled, predominantly, the rate of Co–C bond homolysis in these alkylcobaloximes.
The Effect of Intramolecular Hydrogen Bonding on the Rotational Barriers about the C–N Bonds of o-Hydroxyarenecarboxamides
Authors: Suezawa Hiroko , Tsuchiya Kin-ya , Tahara Eiji , Hirota Minoru 
Published: July 2006

Abstract
Rotational barriers about the C–N bonds of several o-hydroxyarenecarboxamides were determined in four solvents (namely, chloroform, pyridine, methanol, and dimethyl sulfoxide) by DNMR spectroscopy and compared with those of arenecarboxamides void of ortho-hydroxyl group. The height of the rotational barrier is correlated with the strength of the intramolecular O–H···O=C hydrogen bond. The unusual solvent effect on the rotational barriers of these hydroxy–amides are ascribed to the cleavage of the intramolecularly hydrogen bonded chelate ring which occurs in both hydrogen-donating and -accepting solvents.
NAD(P)+–NAD(P)H Models. 64. The Quantitative Elucidation of the Mechanistic Aspects in the Silica Gel-Catalyzed Reduction of α,β-Unsaturated Carbonyl Compounds by a Model of NAD(P)H
Authors: Yasui Shinro , Fujii Masayuki , Ohno Atsuyoshi 
Published: July 2006

Abstract
Eight α,β-unsaturated carbonyl compounds, 1-(2′- or 4′-substituted phenyl)-3-phenyl-2-propen-1-ones (2′- or 4′-substituted chalcones), were subjected to the reduction by an NAD(P)H model in the presence of silica gel in benzene. All of these afforded quantitatively the corresponding saturated carbonyl compounds, whereas no 1,2-reduction took place. For 2′-methoxy, 4′-methyl, 4′-bromo, and 4′-nitro derivatives as well as the unsubstituted carbonyl compound, the apparent reactivity of the substrate increases with the increase in electronwithdrawing ability of the substituent, whereas the degree of the adsorption onto the surface of silica gel decreases. It is also apparent that the 4′-hydroxy derivative exerts lower reactivity than the 2′-hydroxy derivative in spite of much more efficient adsorption of the former. In order to uniformly interpret the apparent results, the data obtained were quantitatively analyzed in terms of kinetics as well as equilibrium constants for the adsorption of the substrates onto the surface of silica gel. It has been revealed that the silanol group on the surface of silica gel acts as a general-acid catalyst in the reduction.
Chemical Studies on Products Obtained from Verdohemochrome IXα Dimethyl Ester by Treatment with Ammonia under Air
Authors: Saito Setsuo , Tamura Norihiro 
Published: July 2006

Abstract
Verdohemochrome IXα dimethyl ester [bis(pyridine)iron(II) 5-oxaprotoporphyrin IX dimethyl ester] gave 5-azaprotohemin IX dimethyl ester (2) and six tripyrrin derivatives upon treatment with ammonia under air, followed by methylation. The reaction of 2 with coned HCl in acetic acid in the presence of ferrous sulfate, followed by methylation gave demetallated product, 5-azaprotoporphyrin IX dimethyl ester (8), accompanied by products obtained by the hydration and reduction of both or one of the vinyl groups of 8. 8,12-Bis[2-(methoxycarbonyl)ethyl]-3,7,13-trimethyl-1-oxo-2-vinyltripyrrin-14-carbaldehyde, obtained as a major tripyrrin product by an oxidative degradation of 1, gave a pyrromethene derivative, 3,7-bis[2-(methoxycarbonyl)ethyl]-2,8-dimethyl-l-methoxy-5-pyrromethene-9-carbaldehyde by the reaction with Tl(OAc)3 under air. The structures of all products obtained in the present study were determined by spectral measurements.
Utilization of Sulfide, Sulfoxide, and Sulfone Groups as Regiochemical Control Elements in the Diels–Alder Reaction of Naphthoquinones
Authors: Iwao Masatomo , Kuraishi Tsukasa 
Published: July 2006

Abstract
The Diels–Alder reactions of 2-phenylthio-, 2-phenylsulfinyl-, and 2-phenylsulfonyl-1,4-naphthoquinones, which were unsymmetrically substituted by methoxyl group on the benzenoid ring, with some vinylketene acetals were studied. The regioselectivity of the reactions was cleanly controlled by each of these sulfur substituents. In addition, the reactivity of the naphthoquinones were greatly enhanced by introduction of the sulfone or sulfoxide group. As a result of this study, several anthraquinones including natural products, such as pachybasin and phomarin 6-methyl ether, and 11-deoxyanthracyclinones were efficiently synthesized.
The Mechanism of the Reaction of (Arylthio)trimethylgermanes with Benzyl Bromides Giving Aryl Benzyl Sulfides. A Kinetic Study
Authors: Kozuka Seizi , Tamura Shoji , Ishibashi Satoshi , Ohya Sadamu , Tagaki Waichiro 
Published: July 2006

Abstract
A kinetic study has been conducted on the reaction of (arylthio)trimethylgermanes with benzyl bromides. The reaction was found to be second order and the rate was largely accelerated in polar solvents. Both ρ values due to substituents on arylthio and benzyl groups revealed nucleophilic attack of the sulfur atom on benzylic carbon atom as the reaction mechanism. Rates of the reactions of trimethyl(p-tolylthio)stannane with substituted benzyl chlorides were also examined to compare the substituent effects. Steric crowd around the sulfur atom has been found as an important factor to control the reaction mechanism.
Enzyme Sensors Based on Coated-Wire Electrode. Use of Carboxyl-Substituted Poly(vinyl chloride) as a Support for Immobilizing Penicillinase
Authors: Anzai Jun-ichi , Shimada Masahiko , Osa Tetsuo , Chen Chien-wu 
Published: July 2006

Abstract
A poly(vinyl chloride) derivative which contained 1.8% carboxyl residue was used to prepare a potentiometric sensor sensitive to penicillin G. A pH-sensitive base electrode was fabricated by covering an Ag wire electrode with the membrane composed of the carboxyl-substituted poly(vinyl chloride), o-nitrophenyl octyl ether, and tridodecylamine. The sensitive layer of the pH-sensitive electrode was modified with penicillinase to make a penicillin-sensitive electrode. Penicillinase was adsorbed to the surface of the polymer membrane by immersing the sensitive layer of the electrode in the penicillinase solution. Treatment of the pH-sensitive electrode with ca. 0.3% penicillinase solution at pH 6.7 (1 mM phosphate buffer) resulted in favorable performance of the penicillin sensor. The long-term stability of the penicillin sensor thus prepared was satisfactorily good.
A New Method for the Determination of Optical Purity of Norleucine Based on Enthalpy of Transition in Solid–Solid Phase Transition
Authors: Matsumoto Masayuki , Yajima Hirofumi , Endo Ryuichi 
Published: July 2006

Abstract
A new method for determining the optical purity based on enthalpy of transition in solid–solid phase transition was introduced. The enthalpy of transition of norleucine recovered by an optical resolution procedure was measured by means of DSC. The magnitude of optical purity based on enthalpy of transition was in agreement with that based on specific rotation.
The Influence of Ureas on the Phase-Transition Behavior of the Dipalmitoylphosphatidylcholine Vesicle Membrane
Authors: Inoue Tohru , Miyakawa Kenji , Shimozawa Ryosuke 
Published: July 2006

Abstract
The gel-to-liquid-crystalline phase transition of the dipalmitoylphosphatidylcholine vesicle membrane was observed in the presence of urea, ethylurea, and butylurea by monitoring the scattered light intensity of the vesicle suspension. Urea showed no significant effect on either the transition temperature, Tm, or the transition width, W, whereas ethylurea and butylurea depressed Tm without affecting W.
Prediction of Mutual Solubility Curve for t-Butyl Alcohol–Water System Utilizing Salting Out Phenomenon
Authors: Qing-zhi Zhang , Jian-ji Wang , Yan Lu , Jin-suo Lu , Kato Tadashi 
Published: July 2006

Abstract
The consolute temperatures (Ts) for ternary solutions of water-tetrahydrofuran-salt and water–t-butyl alcohol (TBA)–salt (salt: ammonium chloride or potassium chloride) were measured. From a plot of Ts against the salt concentration, the mutual solubility curve for the water–TBA system was predicted. The critical solution temperature and the critical composition were estimated to be about 200 °C and 0.15–0.2 (mole fraction of TBA), respectively.
Re-extraction Behavior of Nitrosyl Ruthenium Complex in Tributyl Phosphate–Dodecane Solvent System
Authors: Sasahira Akira , Izumida Tatsuo , Kawamura Fumio 
Published: July 2006

Abstract
A re-extraction of the nitrosyl ruthenium complex from a tributyl phosphate-dodecane solvent system to a nitric acid solution was carried out. A longer aging of the organic phase before re-extraction lowered the re-extraction yield, while nitric acid extracted into the organic phase increased it. These results could be explained using a model with two organic species.
Effects of NH3 on 13C-Selective Infrared Multiple Photon Decomposition of CF2HCl by a CO2 Laser
Authors: Sugita Kyoko , Arai Shigeyoshi 
Published: July 2006

Abstract
The effects of NH3 on product yields and 13C enrichment factors have been examined for the IRMPD of CF2HCl using a CO2 TEA laser. The IRMPD of neat CF2HCl yields only C2F4 and HCl as final products. The addition of NH3 resulted in the formation of CF3H and NH4Cl in addition to C2F4, and enhanced significantly the decomposition of CF2HCl. The enrichment factors of 13C in C2F4 and CF3H decreased with increasing NH3, but the decreases were relatively small. The mechanism of the IRMPD in the presence of NH3 is discussed on the basis of the observed results.
Spectroscopic Investigations on 9-(4-Dimethylaminophenyl)-10-cyanoanthracene
Authors: Baumann Wolfram , Schwager Beate , Detzer Norbert , Okada Tadashi , Mataga Noboru 
Published: July 2006

Abstract
Excited state dipole moments of 9-(4-dimethylaminophenyl)-10-cyanoanthracene determined from the electric field effect on solutions in several solvents as well as fluorescence spectra, ground state absorption and Sn–S1 transient absorption spectra show that this molecule most probably fluoresces from two excited states in nonpolar and medium polar solvents, whereas only one highly polar excited state emits in polar solvents.
A High-Resolution Solid-State 13C NMR Study of the Secondary Structure of Linear (1→3)-β-d-Glucans: A Conformational Elucidation of Noncrystalline and Crystalline Forms by Means of Conformation-Dependent 13C Chemical Shifts
Authors: Saitô Hazime , Tabeta Ryoko , Yokoi Motoko , Erata Tomoki 
Published: July 2006

Abstract
The high-resolution solid-state 13C NMR spectra of annealed curdlan, a (1→3)-β-d-glucan, were recorded in order to obtain reference data on the 13C chemical shifts of the triple helix form, which would be useful for the conformational elucidation of two distinct noncrystalline forms, curdlan- and laminaran-types. It was found that the C-3 peak of crystalline annealed glucan is substantially displaced from that of noncrystalline starting powder, reflecting the conformational change. The laminaran-type conformation, which is found in either laminaran or a number of fungal branched glucans, was identical with the triple helix, judging from the similarity in the 13C NMR spectra, although the linewidths of the former are much larger than those of the latter. The curdlan-type form, on the other hand, was ascribed to the single helix form on the basis of the previous data on high-resolution 13C NMR. In addition, the 13C NMR spectra of crystalline paramylon showed a number of additional signals other than the peaks of triple-helical annealed curdlan, in spite of the similarity in the X-ray diffraction patterns.
Syntheses of Steroidal trans-Iodo Acetates
Authors: Horiuchi C Akira , Satoh J Yasuo 
Published: July 2006

Abstract
The reaction of the following steroidal olefins with iodine–copper(II) acetate in acetic acid afforded the corresponding steroidal trans-iodo acetates: 5α-cholest-1-, -2-, and -3-ene; and 5β-cholest-1-, -2-, and -3-ene.