bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase-Shift Studies of the Quenching of NH(c1Π) by HN3, NO, CO, and CO2
Authors: Sasaki Shun-ichiro , Tsunashima Shigeru , Sato Shin 
Published: July 2006

Abstract
Absolute cross sections for quenching NH(c1Π) by the use of several inorganic molecules were determined at room temperature by using a phase-shift method. The NH(c1Π) radicals were produced by the photolysis of HN3 using an amplitude-modulated Xe-resonance lamp. The results obtained were as follows: 0.01(He), 12(HN3), 48(NO), 49(CO), and 30(CO2) in units of 10−16 cm2. In the case of NO, the 336 nm emission was enhanced, which suggests that NO quenches NH(c1Π) to NH(A3Π). From the phase difference between the 325 and 336 nm emissions, the quenching cross-section of NO for NH(A3Π) was estimated to be 60×10−16 cm2.
Studies of the Metal Complexes of Cyclohexane Derivatives. IX. The Preparation and Properties of Platinum(II) Complexes Containing Methyl Derivatives of cis-1,2-Cyclohexanediamine
Authors: Saito Reiko , Kidani Yoshinori 
Published: July 2006

Abstract
Four 1,2-diamine ligands, (1RS,2SR)-1-methyl-1,2-cyclohexanediamine(1m-chxn), (1R,2S,3R)-3-methyl-1,2-cyclohexanediamine(R,S,R-3m-chxn), (1S,2R,4R)-4-methyl-1,2-cyclohexanediamine(S,R,R-4m-chxn), and (1R,2S,4R)-4-methyl-1,2-cyclohexanediamine(R,S,R-4m-chxn), were prepared. The mixed-ligand complexes of the [PtXL]2+ type(X=(NH3)2, 1,2-ethanediamine, meso-2,3-butanediamine, and 2,3-dimethyl-2,3-butanediamine, L=each m-chxn) were synthesized and characterized by means of their electronic, circular dichroism, and 13C NMR spectra. The chelate ring formed by S,R,R-4m-chxn was almost conformationally fixed to take a δ conformation, while the chelate rings of 1 m-chxn, R,S,R-3m-chxn, and R,S,R-4m-chxn easily interchange between δ and λ conformations. The stereochemistries of these three complexes are attributable to the conformational requirements for both the cyclohexane ring and the chelate ring, for which synchronous inversions are presumed.
Synthetic Approach toward Antibiotic Ezomycins. I. Synthesis of 5-Amino-5-deoxyoctofuranose-(1,4) Derivatives by Henry Reaction and Their Stereochemistry
Authors: Sakanaka Osamu , Ohmori Takashi , Kozaki Shuji , Suami Tetsuo , Ishii Toshio , Ohba Shigeru , Saito Yoshihiko 
Published: July 2006

Abstract
Ezomycins were discovered in a fermentation beer of Streptomyces species as antibiotics, which consisted of aminoocturonic acid, aminoglucuronic acid and base. As a part of a total synthesis of ezomycins, the title compounds have been synthesized. A KF-catalyzed Henry reaction between a nitropentose and a glyceraldehyde derivative gave a nitro alcohols mixture. Hydrogenation of the intact mixture, followed by N-acetylation afforded three diastereomers. The absolute configurations of the newly-introduced chiral centers were established by chemical methods and a X-ray crystal structure analysis.
Synthesis of 29-Norlanostane Derivatives
Authors: Naora (nee Namikawa) Misuzu , Murae Tatsushi , Tsuyuki Takahiko , Takahashi Takeyoshi 
Published: July 2006

Abstract
As authentic samples for identification of 29-norlanostane derivatives isolated from plant fossil, 29-norlanostan-24-one and -23-one, 29-norlanost-9(11)-en-24-one, -23-one, and -3-one, 29-norlanost-7-en-3-one, and 29-norlanostan-3-one were synthesized from a commercial lanosterol containing dihydrolanosterol.
Transition-Metal Complexes of Pyrrole Pigments. XXII. Photoredox Behavior of Oxo(tetra-p-tolylporphinato)molybdenum(V) Complexes
Authors: Matsuda Yoshihisa , Takaki Toshihiko , Murakami Yukito 
Published: July 2006

Abstract
Photochemical reduction of oxomolybdenum(V) complexes of 5,10,15,20-tetra-p-tolylporphine, [Mov(X)(ttp)], was investigated under irradiation with the visible light in benzene, where X stands for an axial ligand placed trans to the oxo group. Irradiation of [MovO(X)(ttp)] resulted in a homolytic cleavage of the Mo–X bond to afford [MoIVO(ttp)] and a radical species generated from the axial ligand (X). The reduction rate was controlled by the nature of the Mo–X bond, and a complex with less ionic character of the axial bond was more reactive in the homolysis process. The bulkiness of the axial alkoxo ligands may provide two different effects which are opposite to each other on the reactivity: (i) The repulsive interaction between an axial ligand and the equatorial ttp accelerates the homolysis of the Mo–X bond; (ii) the diffusion rate of the radical species, generated by the photochemical cleavage of the axial coordinate bond, from the coordination sphere is progressively retarded as the bulkiness of the alkoxo ligand increases. The second effect seems to be more pronounced for the present photochemical reaction. The photochemical reduction of [MoVO(X)(ttp)] is essentially composed of two sequential steps, photochemical cleavage of the Mo–X bond and diffusion of the radical species from the coordination sphere. Reoxidation of [MoIVO(ttp)] under aerobic irradiation conditions afforded [MoVO(OH)(ttp)] and [(MoVO(ttp))2O] via the postulated intermediate formation of [MoV(OO·)(ttp)].
Flameless Atomic-Absorption Spectrometric and Differential-Pulse Polarographic Determination of Cadmium after Coprecipitation with Hafnium Hydroxide
Authors: Ueda Joichi , Yamazaki Natsuko 
Published: July 2006

Abstract
Using the coprecipitation method with hafnium hydroxide, the flameless atomic-absorption spectrometric and the differential-pulse polarographic determinations of cadmium have been studied. The collecting ability of hafnium hydroxide for cadmium is excellent; from 0.01 to at least 1000 μg of cadmium in 50–400 cm3 of a sample solution is coprecipitated quantitatively. The presence of hafnium hydroxide does not interfere with either method of determining cadmium. Of the diverse ions examined, there are no ions which interfere with the flameless atomic-absorption spectrometric determination, even if they are present in a concentration of at least 5000 times that of cadmium; as for the differential-pulse polarographic determination, only indium interferes when present in small amounts. The linear calibration curves through the point of origin were obtained over the range of 0.4–4 ng cm−3 of cadmium for the former method and 0.04–40 μg cm−3 for the latter method. In the proposed methods, the flameless atomic-absorption spectrometric determination was successfully applied to the analysis for trace amounts of cadmium in river-water samples.
From Penicillin to Penem and Carbapenem. IX. C1-Unit Introduction and the Carbapenam Synthesis from the Penicillin Molecule
Authors: Fujimoto Katsumi , Iwano Yuji , Hirai Koichi 
Published: July 2006

Abstract
An effective method for (R)-1-hydroxyethylation of benzyl bis(phenylseleno)penicillanate is described. The hydroxyethylated product was transformed into the 4-methylsulfonyl- and 4-phenylsulfonyl-2-azetidinone derivatives. These monocyclic compounds were reacted with potassium cyanide under two-phase conditions to give the 4-cyano-2-azetidinone derivative (C1-unit introduction) in high yield. The cyano group was then converted into the iodomethyl group. Using the 4-iodomethyl-2-azetidinone derivative an isopenam derivative was synthesized. Furthermore, carbapenam derivative were also constructed by a novel [3+2] cyclization reaction between 4-iodomethyl-2-azetidinone and dimethyl 2-methylthio- and 2-phenylthiofumarate.
Total Synthesis of (−)-Vitrenal and Its Biological Activity
Authors: Kodama Mitsuaki , Tambunan Usman S F , Tsunoda Tetsuto , Itô Shô 
Published: July 2006

Abstract
(−)-Vitrenal, the enantiomer of the natural sesquiterpene aldehyde isolated from a liverwort, has been synthesized starting from (+)-3-carene, and its activity as a plant-growth regulator has been tested.
Cyclodextrin-Catalyzed Hydrolysis of Enantiomeric Esters Showing Stereoselectivity
Authors: Ihara Yasuji , Nakanishi Eiji , Nango Mamoru , Koga Joichi 
Published: July 2006

Abstract
The rate constants for hydrolysis of the enantiomers of amino acid nitrophenyl esters have been determined at pH 9.00 and pH 10.0 in the presence of α- or β-cyclodextrin. α- and β-Cyclodextrins cause stereoselective acceleration in the hydrolysis of m-substituted enantiomers. On the other hand, less stereoselectivity is observed in the hydrolysis of p-substituted enantiomers. The stereoselective properties are discussed in the light of cyclodextrin-ester dissociation constants and thermodynamic parameters of the reaction.
Conductivity of Lithium Salts in the Mixed Systems of High Permittivity Solvents and Low Viscosity Solvents
Authors: Matsuda Yoshiharu , Morita Masayuki , Tachihara Fumitsugu 
Published: July 2006

Abstract
Electrolytic conductivities of LiClO4 and LiPF6 have been investigated in the mixed systems of the high permittivity solvents and low viscosity solvents. Propylene carbonate (PC), sulfolane (S), and dimethyl sulfoxide (DMSO) were used as the high permittivity solvents, and 1,2-dimethoxyethane (DME) and tetrahydrofuran (THF) as the low viscosity solvents. The conductivity of 1 mol dm−3 LiClO4 has a miximum in the mixed solvent with 40–80 m/o ether for every system. The conductance improvement by solvent-blending was qualitatively described in terms of a favorable combination of high permittivity and low viscosity of each component. The maximum conductivity of 1 mol dm−3 LiClO4 increased in the order of S&lt;PC&lt;DMSO for the systems containing THF. The difference in the order of maximum conductivity between DME and THF was interpreted by ion-solvent interactions, whose measure is generally expressed by the donor and acceptor properties of the solvent. The LiPF6 solutions had much higher conductance than those of LiClO4, especially in high DME concentration regions.
Fluorescence Lifetimes of 9-Methylanthracene in Supersonic Free Jets. A Level Inversion between S1 and T2 States upon the Phase Change from Solution to Gas
Authors: Tanaka Fujio , Hirayama Satoshi , Yamashita Shigeru , Shobatake Kosuke 
Published: July 2006

Abstract
Fluorescence lifetimes measured for 9-methylanthracene in supersonic free jets confirm the occurrence of nonradiative decay at the vibrationless level of S1 that has been suggested from the measurement of the fluorescence yield. The nonradiative decay constants in the isolated and condensed phases have been compared from the viewpoints of relative positions of S1 and T2 levels and of the magnitude of the energy gap.
The Crystal Structure of a Conformational Isomer of Teucrin P1 from Teucrium Gnaphalodes
Authors: Zheng Zeyong , Yamane Takashi , Ashida Tamaichi , Morita Masaya , Kato Natsuki , Iwashita Takashi , Nakanishi Koji 
Published: July 2006

Abstract
The crystal structure of an isomer of Teucrin P1 isolated from Teucrium gnaphalodes has been determined by the X-ray method. Crystal data: orthorhombic, P212121, a=13.849(4), b=15.545(3), c=7.896(2) Å, Z=4. The final R value is 0.048 for 1247 observed reflections with Fo&gt;2σ(Fo). The structure is disordered, and two kinds of components (molecules) with different conformations coexist in the crystal. The major component exists with a probability of 0.74, while the minor one with 0.26. A tetrahydropyran ring in the former takes a boat form, while the latter a chair form, indicating that in this complex fused-ring system a boat form of the tetrahydropyran ring is more stable than a chair one. The conformation of the major component is the same as that of naturally occurring Teucrin P1, apart from the orientation of a furan ring.
A High-Resolution Solid-State 13C NMR Study of (1→3)-β-d-Glucans from Various Sources. Conformational Characterization as Viewed from the Conformation-Dependent 13C Chemical Shifts and Its Consequence to Gelation Property
Authors: Saitô Hazime , Tabeta Ryoko , Sasaki Takuma , Yoshioka Yûko 
Published: July 2006

Abstract
High-resolution solid-state 13C NMR spectra of a variety of (1→3)-β-d-glucans in the solid state were recorded by means of cross polarization-magic angle spinning (CP–MAS) NMR spectroscopy. We found that the C-1 and C-3 peak-positions of these glucans are significantly displaced (up to 8 ppm) depending upon variety of samples used. Interestingly, these glucans obtained by lyophilization or spray-drying possess regular secondary structures as detected by displacements of the conformation-dependent 13C chemical shifts. In fact, at least four kinds of molecular conformations were distinguishable by 13C NMR spectroscopy. Gel-forming ability of linear (1→3)-β-d-glucans, however, was related to the presence of a single particular conformation without involving any other form. By contrast, gel-formation was noted for a branched glucan whose conformation is similar to that of a linear glucan without gel-forming ability. Further, conformation of all these linear and branched (1→3)-β-d-glucans turned out to be the same when solid samples were prepared by lyophilization from DMSO solution.
Partial Molar Enthalpy of Solution for Tris(2,4-pentanedionato)cobalt(III) in Mixed Solvents of Water and Dimethyl Sulfoxide
Authors: Yoshimura Yasuki , Sato Nobuyoshi , Kikuchi Makoto 
Published: July 2006

Abstract
The solubility (Xs) of tris(2,4-pentanedionato)cobalt(III) ([Co(acac)3]) in mixed solvents of water and dimethyl sulfoxide (DMSO) with various compositions was determined over the temperature range 20–60 °C. It was found that the experimental values of Xs could be satisfactorily fitted to lnXs=A(1⁄T)+BlnT+C and the partial molar enthalpy of solution (Δ\barHs) at 25 °C for [Co(acac)3] was estimated from slopes of the solubility curves. When Δ\barHs was plotted against the mole fraction of DMSO (XDMSO), a clear maximum was found at about XDMSO=0.3. This composition profile of Δ\barHs is discussed in connection with the internal pressure of a mixture of water and DMSO. A method to estimate an approximate value of the partial molar enthalpy of hydrophobic hydration (Δ\barHh) in an aqueous DMSO mixture of [Co(acac)3] is also presented by using the solubility data in mixtures with a lower XDMSO than 0.14.
Palladium-Catalyzed Reaction of 2-Vinyl-2,3-dihydrobenzofurans and Chroman with Nucleophiles
Authors: Hosokawa Takahiro , Kono Takanori , Uno Toru , Murahashi Shun-Ichi 
Published: July 2006

Abstract
Reaction of 2,3-dihydro-2-vinylbenzofuran with nucleophiles (NaCH(COOEt)2 and PhNHCH3) in the presence of palladium catalysts such as Pd(PPh3)4 and PdCl2(PR3)2 (R=Ph and Et) gives 2-(2-butenyl)phenols (46–76% yields) in which nucleophiles are incorporated into the methyl group of the butenyl moiety. 2-Vinylchroman undergoes the same type of reaction where only the palladium complex bearing PEt3 ligand is effective. The effectiveness of PEt3 ligand is also observed in the reaction of 2,3-dihydro-2-isopropenylbenzofuran with diethyl sodiomalonate leading to 3-ethoxycarbonyl-4-(2-methyl-1-propenyl)-2-chromanone.
A Convenient Synthesis of Ethyl 3-(2,2-Dihaloethenyl)-2,2-dimethylcyclopropanecarboxylates and Its Modifications for cis-Isomer Enrichment
Authors: Matsui Kiyohide , Negishi Akira , Takahatake Yuriko , Sugimoto Kikuo , Fujimoto Tamotsu , Takashima Toshiyuki , Kondo Kiyosi 
Published: July 2006

Abstract
A synthesis of the title compounds 5 involves the reaction between 3-methyl-2-buten-1-ol and triethyl orthoacetate to produce ethyl 3,3-dimethyl-4-pentenoate, which is followed by the addition of various carbon tetrahalides to the double bond. The reaction of resulting adducts with a base affords 5 in high yields. Stereoselective preparation of the cis-isomer was achieved by the following two methods: First one involves selective transformation of ethyl 4-bromo-6,6,6-trichloro-3,3-dimethylhexanoate to ethyl 6,6,6-trichloro-3,3-dimethyl-4-hexenoate (8a) with piperidine followed by the selective conversion of 8a to cis-2,2-dichloroethenyl compound (cis-5a). Second one is based on the stereoselective cyclization of ethyl 4,6,6,6-tetrachloro-3,3-dimethylhexanoate (t-BuONa/solvent/HMPA) to ethyl cis-2,2-dimethyl-3-(2,2,2-trichloroethyl)cyclopropanecarboxylate which is transformed into cis-5a without cis-trans isomerization.
Vertical Concentration Distributions of Arsenic in a Reservoir and Its Sediment
Authors: Tamari Yuzo , Nishimura Kimio , Tsuji Haruo , Kusaka Yuzuru 
Published: July 2006

Abstract
Vertical concentration distributions of arsenite and arsenate in a reservoir (depth, ≈31 m) and its bottom sediment (core depth, ≈18 cm) have been investigated. The concentrations of arsenite and arsenate in the water were determined by a spectrophotometric method, and those in the sediment were also determined by the same method after the following leaching-treatments of the sediment. The leaching of arsenic from the sediment was carried out by using three solutions; (1) 0.1 M hydrochloric acid (acid-soluble fraction), (2) 1 M sodium hydroxide solution (alkali-soluble fraction), and (3) hydrofluoric and perchloric acid mixture (silicate fraction). It was found that arsenic was rich in the surface layer of the sediment, and most of it existed as arsenite fixed with iron hydroxide. Based on the analytical and leaching results of arsenic, iron, manganese, zinc, copper, and others in the reservoir and in its sediment respectively, the sedimentation process of arsenic from the reservoir and its dissolution process from the sediment have been discussed.
Racemic Structures and Optical Resolutions by Preferential Crystallization of Organic Ammonium Salts of N-Formyl-Dl-phenylalanine
Authors: Shiraiwa Tadashi , Miyazaki Hideya , Sakamoto Yoshihiro , Kurokawa Hidemoto 
Published: July 2006

Abstract
Racemic structures of the butylammonium salt, pentylammonium salt, benzylammonium salt, dicyclohexylammonium salt(Dl-DCH salt), and 4-methylpiperidinium salt(Dl-4-MP salt) of N-formyl-Dl-phenylalanine were studied to explore the possibility of optical resolution by preferential crystallization. Free energies of formation of racemate (ΔGF) of the Dl-salts and data at eutectic points in binary phase diagrams of melting points indicate that the Dl-salts form racemic compounds in the vicinity of the melting points. However, according to ΔGF of Dl-DCH and 4-MP salts and infrared spectra and solubilities of the Dl- and l-salts, these Dl-salts transform into conglomerates around room temperature. It is possible to resolve Dl-DCH and 4-MP salts by preferential crystallization at 10 °C. Successive preferential crystallization of Dl-4-MP salt at 10 °C in 1-butanol gives the d- and l-salts with optical purities of 95–100%.
Preparation and Complexing Properties of Crown Ether Compounds Incorporating a Ferrocene Unit at 1,2- or 1,3-Positions
Authors: Izumi Taeko , Saitou Katsuo , Matsunaga Shigeki , Kasahara Akira 
Published: July 2006

Abstract
Ten new crown ethers incorporating a ferrocene unit at 1,2- or 1,3-positions are reported. These crown ethers were synthesized by the reaction of 1,2- or 1,3-bis(hydroxymethyl)ferrocene with oligoethylene glycol ditosylate (n=1–5) with potassium t-butoxide by a high-dilution method. These new types of ferrocene crown ethers were examined for complexation behavior with alkali, alkaline earth, and transition-metal cations by solvent extraction. It was found to extract thallium ions most effectively.
Thermal Racemization of Thiaheterohelicenes
Authors: Yamada Koh-ichi , Nakagawa Hiroko , Kawazura Hiroshi 
Published: July 2006

Abstract
Thermal racemizations of four thiaheterohelicenes (TH) with alternant thiophene and benzene rings were examined and compared with those of carbohelicenes (CH). The racemization rate of [5]TH was very fast at room temperature, and the rates of [7]TH and [9]TH were found to be 1/5 to 1/50 times slower than the corresponding CH having a similar internal angle. The ΔS\eweq values obtained by temperature-variable experiments showed a large difference between [7]TH (−103.9±4.8 JK−1 mol−1) and [9]TH (−66.3±4.0), suggesting different conformations in the transition state. CNDO calculations on the transitional conformations of [5]TH demonstrated that a geometry, such as that distorting the benzene rings, has a lower energy than a geometry such as that twisting the thiophene ring. Based upon these results, the conformations in the transition states for the THs are inferred.
Infrared Absorption Study of Human Proinsulin C-Peptide Fragments in the Solid State
Authors: Narita Mitsuaki , Ogura Toshihiko , Sato Kazuhiro , Honda Shinya 
Published: July 2006

Abstract
In order to evaluate the propriety of the solubility prediction method for peptide intermediates having polar side chains, IR absorption spectroscopic analysis of human proinsulin C-peptide fragments was performed in the solid state. The polar amino acid residues involved in the peptide fragments are in the following: Glu(OBzl), Asp(OBzl), Gin, and Ser(Bzl). All peptide fragments except for ones containing the Pro residue exhibit a high potential for the formation of a β-sheet structure, indicating that, even when the polar side chains of the Glu, Asp, and Ser residues are protected by the Bzl group, the coil conformation parameter Pc for each amino acid residue is useful for estimating the potential for the formation of a β-sheet structure of peptide fragments smaller than critical size for development of α-helical structure in the solid state. As in the case of hydrophobic peptides, the β-sheet aggregation clearly plays an important role in reducing solubility of the peptide fragments having polar side chains. The effect of the Pro residue on the disturbance of the β-sheet structure was also observed. The ability of the short-range (polar side chain-backbone) or intraresidue interactions due to the low flexibility of the pyrrolidine ring of the Pro residue to promote helical folding in peptide fragments in the solid state was not observed for the peptide fragments corresponding to helical regions of human proinsulin.
Stereospecific Desulfinylation of α,β-Epoxy Sulfoxides with Butyllithium. A New Synthesis of Epoxides and Allylic Alcohols from Carbonyl Compounds
Authors: Satoh Tsuyoshi , Kaneko Youhei , Yamakawa Koji 
Published: July 2006

Abstract
Desulfinylation of α,β-epoxy sulfoxides, easily prepared from carbonyl compounds and 1-chloroalkyl phenyl sulfoxide, with 1 equivalent of butyllithium at low temperature gave epoxides in good yields. The similar α,β-epoxy sulfoxides having an arylmethyl group at the α-position gave 3-aryl-allylic alcohols upon treatment with excess butyllithium at −70 °C. These reactions offer a simple and useful approach to the synthesis of epoxides and 3-aryl-allylic alcohols from a carbonyl compound.
Formation and Reaction of Carbonyl Ylides. Production of 2 : 1-Cydoadducts of 2-Benzopyrylium-4-olates with Carbonyl Compounds
Authors: Ibata Toshikazu , Toyoda Jiro 
Published: July 2006

Abstract
The Cu(acac)2-catalyzed decomposition of o-(diazoacetyl)benzoates in the presence of carbonyl compounds such as benzaldehydes, acetophenones, acetone, fluorenone, and anthraquinone gave 2 : 1-adducts of the corresponding 2-benzopyrylium-4-olate (3) and the carbonyl compound, together with 1 : 1-adducts. The 2 : 1-adducts were confirmed to be produced by the cycloaddition of 3 toward the carbonyl group of the 1 : 1-adducts which have bulky aryl groups on exo-direction. The product ratios of the 2 : 1-adducts were explained according to the MNDO calculation.
The Synthesis of Macrocyclic Diaza n-n′-Fulvadiene Derivatives
Authors: Ojima J\={u}ro , Ejiri Emiko , Manaka Sumio , Morita Noboru , Asao Toyonobu 
Published: July 2006

Abstract
The diaza analogs of 7-13-, 7-15-, 7-17-, 13-13-, 13-15-, 15-15-, and 19-19-fulvadiene derivatives were synthesized through the reaction of 2,4,6-cycloheptatrienone and the corresponding bisdehydroannulenones with hydrazine dihydrochloride. The 1H NMR and electronic spectra of these compounds are discussed in connection with tropicity.