bluuebunny/crossref_metadata_2025_split huggingface dataset:
MO Analysis of Photocycloaddition Reactions of 2-Pyrones
Authors: Somekawa Kenichi , Shimo Tetsuro , Suishu Takaaki 
Published: July 2006

Abstract
The skeleton of the 2-pyrones (1) is a simple one composed of 2,4-pentadien-5-olides, but has many possibilities for photocycloadditions. To elucidate the peri-, site-, and regioselective photoadditions of the triplet 2-pyrones with some ethylenes, the factors were analyzed by PM3-CI-UHF methods, etc. The regioselective [4+2]cycloadducts (3) and site-selective [2+2]cycloadducts (4) across the C5–C6 double bonds of the 2-pyrones with electron-deficient ethylenes were deduced to be formed by their preferable HSOMO–LUMO interactions and via more stable biradicals by the C6-Cβ bondings. On the other hand, the other kinds of regioselective [4+2] (6) and [2+2]adducts (5) across the C3–C4 double bonds of the 2-pyrones with an electron-donating ethylene were inferred to mainly come from LSOMO–HOMO interactions and via biradicals by C3-Cβ bondings. Selectivities between 3 and 4, and 5 and 6 were also inferred to be caused by SOMOs of the biradicals.
A Practical Synthesis of threo-3-Amino-2-hydroxycarboxylic Acids
Authors: Matsuda Fuyuhiko , Matsumoto Teruyo , Ohsaki Masako , Ito Yoshio , Terashima Shiro 
Published: July 2006

Abstract
An expeditious synthesis of (2R,3S)-3-amino-4-cyclohexyl-2-hydroxybutyric acid (2) and (2S,3R)-3-amino-2-hydroxy-4-phenylbutyric acid (4), the key components of the renin inhibitor (1) and bestatin (3), respectively, have been accomplished by featuring highly diastereoselective formation of cyanohydrin acetates from α-alkoxycarbonylamino aldehydes under phase-transfer conditions.
A Chiral Synthesis of d-myo-Inositol 1-Phosphate Starting from l-Quebrachitol
Authors: Akiyama Takahiko , Takechi Naoto , Ozaki Shoichiro , Shiota Kenji 
Published: July 2006

Abstract
A naturally occurring optically active cyclitol, l-quebrachitol (1l-2-O-methyl-chiro-inositol), was stereoselectively transformed into myo-inositol derivatives via an oxidation-reduction process. The methyl ether was cleaved chemoselectively with AlCl3–NaI in the presence of a cis-cyclohexylidene moiety with d-myo-inositol 1-phosphate being efficiently obtained.
Hydrolytic Metalloenzyme Models. Metal Ion Dependent Site-Selective Acylation of Hydroxyl Groups of Bis-Imidazole Ligands Catalyzed by Zn2+ and Cu2+ in the Reaction with p-Nitrophenyl 2-Pyridinecarboxylate in a Cationic Surfactant Micelle
Authors: Ogino Kenji , Kashihara Nobuyuki , Ueda Toshitomo , Isaka Toshihide , Yoshida Toshiharu , Tagaki Waichiro 
Published: July 2006

Abstract
Co-micelles of hexadecyltrimethylammonium bromide and a lipophilic bis-imidazole ligand, 1-dodecyl-4-hydroxymethyl-α-(1-dodecyl-2-imidazolyl)-2-imidazolemethanol (4) having two primary and secondary hydroxyl groups, together with the co-micelles of the related lipophilic ligands, were investigated for their catalytic activities in the hydrolysis of p-nitrophenyl 2-pyridinecarboxylate (PNPP) in the presence of Zn2+ or Cu2+. The kinetic and product analyses indicated that the reaction proceeds through the transacylation from PNPP to the hydroxyl group of ligand : metal ion complexes and that the active complexes undergoing transacylation are a 2 : 1 and a 1 : 1 complex for Zn2+ and a 1 : 1 complex for Cu2+, respectively. As for the ligand 4, the transacylation was found to be highly site-selective, i.e. it occurred predominantly on the secondary hydroxyl group with Zn2+, while on the primary hydroxyl group with Cu2+, respectively. Such selectivity was discussed in terms of the coordination structures of the active complexes.
Photochromic Properties of 2-Hydroxychalcones in Solution and Polymers
Authors: Matsushima Ryoka , Suzuki Masakazu 
Published: July 2006

Abstract
A series of substituted 2-hydroxychalcones (HC) were prepared, most of which underwent efficient and clean photochemical conversion into flavylium cations (FV) in acidic solution and polymer film, although strongly dependent on the pH and medium conditions as well as the HC structures. 4′-Methoxy and 4′-dimethylamino derivatives showed relatively high thermal stabilities of the colored mixtures, well-separated absorption bands of the HC and FV forms, almost quantitative conversion from HC to FV in the photostationary-state mixtures, and good photochromic performances in solution and polymer film, without suffering from the dissolved oxygen or moisture. A few of them showed relatively high reversibilities in the HC–FV interconversions under special pH and medium conditions.
Rate of Back-Extraction of Tris(acetylacetonato)- and Tris(trifluoroacetylacetonato)chromium(III) from Carbon Tetrachloride into Aqueous Acid Perchlorate Solutions
Authors: Sekine Tatsuya , Kubo Tsuyoshi , Suzuki Yasuhiro 
Published: July 2006

Abstract
The rate of back-extraction of tris(acetylacetonato)chromium(III) ([Cr(acac)3]), and tris(trifluoroacetylacetonato)chromium(III) ([Cr(tfa)3]), from carbon tetrachloride into aqueous acid perchlorate solutions was measured. The rate of [Cr(acac)3] was much higher and that of [Cr(tfa)3] was also a little higher in the higher acid concentration range. This was concluded to be due to formation of the [Cr(acac)3(H+)2] and the [Cr(tfa)3H+] species which increased the concentration of the tris-complex species in the aqueous phase. With the both complexes, the rate was not affected by the ligand concentration in the aqueous phase. From these results, the controlling reaction was concluded to be the dissociation of the first ligand from the tris-complex or from the proton associate of the triscomplex in the aqueous phase.
Determination of the Molar Absorption Coefficients of c-Type Cytochromes Using Optically Transparent Thin-Layer Electrodes
Authors: Sagara Takamasa , Koide Tomoyuki , Saito Hiroyuki , Akutsu Hideo , Niki Katsumi 
Published: July 2006

Abstract
The simultaneous monitoring of both the absorbance and charge consumed in electrolysis in a precalibrated Optically Transparent Thin-Layer Electrode (OTTLE) cell was demonstrated as a precise method for determining the molar absorption coefficients of electron-transfer proteins. In this method, the procedure for a direct determination of the concentration of the protein could be omitted. The values of the molar absorption coefficients of c-type cytochromes at the α-peaks of reduced forms were determined by this method: 28.4 mM−1 cm−1 (1 M = 1 mol dm−3) at 550 nm for horse heart cytochrome c, 119 mM−1 cm−1 at 552 nm for cytochrome c3 from Desulfovibrio vulgaris, Miyazaki F, and 116 mM−1 cm−1 at 552 nm for cytochrome c3 from Desulfovibrio vulgaris, Hildenborough.
Synthesis of New Serine-Linked Oligosaccharides in Blood-Clotting Factors VII and IX and Protein Z.The Syntheses of O-α-d-Xylopyranosyl-(1→3)-d-glucopyranose, O-α-d-Xylopyranosyl-(1→3)-O-α-d-xylopyranosyl-(1→3)-d-glucopyranose, and Their Conjugates with Serine
Authors: Fukase Koichi , Hase Sumihiro , Ikenaka Tokuji , Kusumoto Shoichi 
Published: July 2006

Abstract
The di- and trisaccharide sequences and their conjugates with serine recently identified in the first epidermal growth factor-like domain of bovine and human blood-clotting factors VII, IX, and protein Z were synthesized in order to elucidate their biological function. The disaccharide α-d-Xylp(1→3)-d-Glcp was prepared from 2,3,4-tri-O-benzyl-α-d-xylopyranosyl fluoride and allyl 2,4,6-tri-O-acetyl-α-d-grucopyranoside (9a) using tin(II) chloride and silver perchlorate as glycosylating reagents. The trisaccharide α-d-Xylp(1→3)-α-d-Xylp(1→3)-d-Glcp was prepared from O-(2,3,4-tri-O-benzyl-α-d-xylopyranosyl)-(1→3)-2,4-di-O-benzyl-α,β-d-xylopyranosyl fluoride and 9a with the same reagents. Their conjugates with serine, α-d-Xylp(1→3)-β-d-Glcp(1→3)-l-Ser and α-d-Xylp(1→3)-α-d-Xylp(1→3)-β-d-Glcp(1→3)-l-Ser, were synthesized by the glycosylation of N-benzyloxycarbonyl-l-serine benzyl ester with the corresponding glycosyl trichloroacetimidates of the above saccharides, followed by removal of the protecting groups. The p-nitrobenzyl group, which was recently devised for temporary protection of hydroxyl functions, was used for the 3-hydroxyl group of glucose.
Reactivities of 2-C- and 3-C-Nitro-α- and β-d-erythro-Hex-2-enopyranoside Derivatives towards Methanol and AM1 Studies upon Their Stereoselectivities
Authors: Sakakibara Tohru , Ohkita Noriaki , Nakagawa Toshio 
Published: July 2006

Abstract
The rates of the reactions of six nitro enosides with methanol-d4 in dimethyl sulfoxide-d6 were determined by 1H NMR spectroscopy. Their reactivities and stereoselectivities were discussed including the results of AM1 calculations of model compounds.
Synthesis of Model Compounds of Safflomin C
Authors: Sato Shingo , Obara Heitaro , Onodera Jun-ichi , Endo Akira , Matsuba Shigeru 
Published: July 2006

Abstract
3-[3,3-Dimethyl- and 3-hydroxy-3-methyl-2,4-dihydroxy-5-(4-hydroxycinnamoyl)-6-oxo-1,4-cyclohexadienyl]- 3-(4-hydroxyphenyl)propanoic acid were synthesized as model compounds of safflomin C. Their spectra closely resembled that of safflomin C.
Tigogenin Hexasaccharides from Camassia cusickii.Structural Elucidation by Modern NMR Techniques
Authors: Mimaki Yoshihiro , Sashida Yutaka , Nikaido Tamotsu , Ohmoto Taichi 
Published: July 2006

Abstract
Two steroidal saponins containing six carbohydrate residues have been isolated from the bulbs of Camassia cusickii. Their structures were determined by modern NMR techniques, 1H–1H COSY, HOHAHA, 1H–13C COSY, and HMBC spectra to be (25 R)-5α-spirostan-3β-yl 4-O-[2-O-[3-O-(α-l-rhamnopyranosyl)-β-d-glucopyranosyl]-3-O-[4-O-(α-l-rhamnopyranosyl)-β-d-glucopyranosyl]-β-d-glucopyranosyl]-β-d-galactopyranoside (1) and (25R)-5α-spirostan-3β-yl 4-O-[2-O-[3-O-(β-d-glucopyranosyl)-β-d-glucopyranosyl]-3-O-[4-O-(α-l-rhamnopyranosyl)-β-d-glucopyranosyl]-β-d-glucopyranosyl]-β-d-galactopyranoside (2), respectively. Compound 1 showed inhibitory activity on cyclic AMP phosphodiesterase.
Preliminary Analysis of the Electronic Absorption Spectrum of a Solute in a Biaxially-Stretched Polymer Film
Authors: Kobayashi Michio , Yuan Xinghai , Sakai Haruo , Hoshi Toshihiko , Okubo Jun , Tanizaki Yoshie 
Published: July 2006

Abstract
A biaxially-stretched film method has been proposed and applied for the analysis of the electronic absorption spectrum of a solute embedded in a biaxially-stretched polymer film to demonstrate its usefulness. The intrinsic absorbance change of the solute on biaxial stretching was measured by a ratio (Rbi) of the molar absorptivity (εb) of the solute in the biaxially-stretched film to that (εi) in the nonstretched isotropic film. This Rbi(= εb⁄εi) spectrum was expressed in terms of three orientation factors for three molecular axes of the solute and three absorption components (three-dimensional reduced spectra) purely polarized along the three molecular axes. Problems inherent in this method are discussed by analyzing the Rbi spectra of spherical, disk-like, and rod-like molecules. An approximate estimate of the three-dimensional reduced spectra of a rod-like molecule (pinacyanol, 1-ethyl-2-[3-(1-ethyl-2(1H)-quinolinylidene)-1-propenyl]quinolinium iodide) was obtained by an analysis of its Rbi spectrum by use of orientation factors with the aid of a uniaxially-stretched film method formulated by the use of an orientational distribution function.
Solvent Extraction of Transition Metal Cations by Calixarene-Based Cyclic Ligands
Authors: Nagasaki Takeshi , Shinkai Seiji 
Published: July 2006

Abstract
Calix[n]arenes (n = 4 and 6) bearing carboxyl groups (1n), hydroxamate groups (2n), and dimethylamino groups (3n) on the lower rim and their monomeric analogs (11, 21, and 31) were synthesized to estimate selective extraction of transition metal cations from the aqueous phase to the organic (chloroform) phase. 14 and 16 showed the selectivity toward Fe3+, Cu2+, Zn2+, and Pd2+. In particular, 16 showed the unusually high extractability toward Fe3+. 24 and 26 showed the selectivity toward Fe3+, Cu2+, and Pd2+, but only Fe3+ was extracted to a significant extent at pH 2.2, the order of the extractability being 26 &gt; 24 &gt; 21. 34 and 36 showed the selectivity toward Pd2+ and Pt4+. The detailed examination of the extraction mechanism established that the ion-pair extraction mechanism is operative in Pt4+ (i.e., extracted as [PtCl6]2−) whereas both the ion-pair extraction mechanism and the chelatecomplex extraction mechanism are operative in Pd2+ (i.e., extracted as [PdCl4]2− in the ion-pair extraction mechanism). The results indicate that the ligand groups circularly arranged on the lower rim of the calixarene cavity form novel binding sites for transition metal cations.
Reaction of Synthetic Melanins with Redox Reagents. II.ESR Spectra Using Flow Method
Authors: Oniki Takayuki 
Published: July 2006

Abstract
Electron spin resonance (ESR) spectra of synthetic pyrogallol melanin showed a hyperfine structure at pH 13.0 under anaerobic conditions but did not under aerobic conditions. The outer signal defined in a previous paper was observed in the reactions with hexacyanoferrate(III) at pH 11.5 and with NaIO4 at pH 13.0. The reaction with NaIO4 indicated that the outer signal is splitted into two lines with hyperfine coupling constant (hfcc) of 0.41 mT. Another signal which is splitted into two lines with hfcc of 0.65 mT was observed in the reaction with NaBH4 at pH 13.0. Na2S2O4 solution showed ESR signal under anaerobic conditions and this signal disappeared by a large amount of melanins. The broad signal defined in a previous paper disappeared slowly by Na2S2O4 but did not by NaBH4. Time courses of ESR signal in reactions of melanins with redox reagents were shown up to 30 min after mixing.
Pressure-Dependent Intensity Anomalies in the B2Σ+∼4Π Perturbed Rotational Lines of the CN (B2Σ+-X2Σ+) 14-14 Band
Authors: Kanda Kazuhiro , Ito Haruhiko , Suzuki Kaoru , Kondow Tamotsu , Kuchitsu Kozo 
Published: July 2006

Abstract
The CN(B2Σ+–X2Σ+) 14–14 emission band was observed in the reaction of Ar(3P0,2) with BrCN by the use of the flowing afterglow method. The intensity anomalies in the rotational lines at N′ = 7 due to the B2Σ+(ν = 14)∼4Π(ν = 7) perturbation were measured as a function of the pressure of Ar or He introduced as a collision partner in the reaction region, the ambient pressure being varied from 9 to 2000 mTorr (1 Torr = 133.322 Pa). The intensities of the perturbed lines relative to that of the rotational band envelope increased with the ambient pressure in the low pressure region in the cases of both Ar and He. On the other hand, they decreased with pressure in the higher pressure region. The pressure dependence of the intensity anomaly for He followed that for Ar, although higher pressure of He was necessary to attain the same level of the intensity anomaly for Ar. These pressure dependences can be explained semiquantitatively by a model with collisional rotational relaxations in the quartet and doublet manifolds, the former being dominant at low ambient pressure and the latter at higher pressure.
Rotational Isomerism and Crystal Structures of 2-Methyl-2,3,3- trinitrobutane and 2-Methyl-2,3,3-trinitropentane
Authors: Lee Swee Yong , Koh Lip Lin , Lam Yu Lin , Huang Hsing Hua 
Published: July 2006

Abstract
Dielectric data show that in benzene and carbon tetrachloride at 25 °C, 2-methyl-2,3,3-trinitrobutane and 2-methyl-2,3,3-trinitropentane exist as “trans” : gauche rotameric mixtures in the approximate ratios of 68 : 32 and 57 : 43 respectively. These experimental results are compared with those predicted by AMPAC (AM1) calculations. X-Ray structure investigations show that in both compounds, the nitro group at C2 is “gauche” with respect to the two nitro groups at C3 in the solid state.
Solid-State Reaction between Zinc Hydroxide and 8-Quinolinol
Authors: Dubey Bharat Lal , Tiwari Neeta 
Published: July 2006

Abstract
Solid-state reaction between zinc hydroxide and 8-quinolinol [8-HQ] has been studied. Reaction product has been characterized to be Zn(OH)2(8-HQ)2 by elemental analysis, quantitative estimation of zinc, thermal decomposition in air, thermogravimetry in nitrogen atmosphere, powder X-ray diffraction patterns, and IR spectra. Kinetics of reaction has been investigated by capillary method at different temperatures. Energy of activation for the reaction has been found to be 45.27 kJ mol−1.
Viscosities and Activation Energies of Viscous Flow of the 1,2-Ethanediol/N,N-Dimethylformamide Binary Solvent System
Authors: Corradini Fulvio , Marcheselli Luigi , Marchetti Andrea , Tagliazucchi Mara , Tassi Lorenzo , Tosi Giuseppe 
Published: July 2006

Abstract
Densities (ρ) and absolute viscosities (η) of pure 1,2-ethanediol, N,N-dimethylformamide and of their nine mixtures were determined at nineteen temperatures ranging between −10 and +80 °C. The above properties were fitted by empirical equations stating their dependence on temperature and composition of the mixtures. The extrathermodynamic excess functions, such as the excess rheochor [RE] and the excess Gibbs energy of activation of viscous flow ΔGE, have been studied. The trend of [RE] vs. composition of the mixtures shows negative deviations from ideality, indicating extensive molecular interactions between the components of the binary solvent system. Furthermore, activation enthalpies and entropies for viscous flow have been obtained and their variations with composition have also been discussed.
Thiolate-Bridged Binuclear Nickel(II) Complexes with a Mixed-Spin State
Authors: Mikuriya Masahiro , Handa Makoto , Shigematsu Shinji , Funaki Shunji , Adachi Fumiya , Okawa Hisashi 
Published: July 2006

Abstract
Thiolate-bridged binuclear nickel(II) complexes with N,N-bis[2-(2-pyridyl)ethyl]-2-aminoethanethiol (HL), [Ni2(L)2](ClO4)2·1/2H2O and [Ni2(L)2](PF6)2, have been synthesized and characterized by elemental analyses, infrared and electronic spectra, and magnetic susceptibilities (80–300 K). The crystal structure of the perchlorate has been determined by the single-crystal X-ray diffraction method. The [Ni2(L)2]2+ cation has a novel binuclear structure where one of the nickel ions is coordinated by a square-planar N2S2 donor set and the other has a distorted square-pyramidal configuration (N3S2 donor set) with the pendant pyridyl nitrogen at the apex. From the above results, it was concluded that the present complexes are novel mixed-spin state containing a low-spin Ni(II) and a high-spin Ni(II) in the molecule.
Kinetics and Mechanism of the Oxidation of Formate and Malonate with (trans-1,2-Cyclohexanediamine-N,N,N′,N′-tetraacetato)manganate(III) in Aqueous Medium
Authors: Gangopadhyay Sumana , Ali Mahammad , Banerjee Pradyot 
Published: July 2006

Abstract
The kinetics of the reduction of (trans-1,2-cyclohexanediamine-N,N,N′,N′-tetracetato)manganate(III) by formate and malonate have been investigated in the pH regions 3.6–5.25 and 4.5–8.30 respectively at constant ionic strength and temperature. In the oxidation of formate slight initial increase in absorbance was observed, whereas for malonate oxidation no such indication was noted. Both the reactions are overall second-order with first-order on both the oxidant and reductants. A general rate law for the oxidation of formate and malonate can be given as −d[oxidant]/dt = k[oxidant] × [reductant], where k is the electron-transfer rate constant. The reactivity of HCOO− is (3.26 ± 0.16) × 10−5 dm3 mol−1 s−1 (kK′) and that of Hmal− and mal2− are (4.28 ± 0.12) × 10−5 (k1) and (6.05 ± 0.12) × 10−4 (k2) dm3 mol−1 s−1 respectively at 40 °C. A plausible inner-sphere mechanism has been suggested for the formate oxidation, whereas malonate oxidation has been interpreted by an outer-sphere mechanism.
Novel Reduction of Carboxylic Acids and Hydroboration of Olefins by Electrolysis of Sodium Borohydride
Authors: Shundo Ryushi , Matsubara Yoshiharu , Nishiguchi Ikuzo , Hirashima Tsuneaki 
Published: July 2006

Abstract
Electrochemical oxidation of sodium borohydride in diglyme containing aliphatic or aromatic carboxylic acids followed by acid-catalyzed hydrolysis afforded the corresponding primary alcohols in good yields. Furthermore, similar electrochemical oxidation in the presence of a variety of olefins instead of carboxylic acids, followed by treatment with alkaline–hydrogen peroxide, brought about novel electrochemical hydroboration to give the corresponding alcohols regio- and stereoselectively in good yields.
Thermodynamics of Triple-Helix and Double-Helix Formations by Octamers of Deoxyriboadenylic and Deoxyribothymidylic Acids
Authors: Sugimoto Naoki , Shintani Yuki , Tanaka Atsushi , Sasaki Muneo 
Published: July 2006

Abstract
The triple-helix and double-helix formations by octamers of deoxyriboadenylic and deoxyribothymidylic acids, (dA)8 and (dT)8, have been studied energetically and dynamically by UV and CD measurements, a melting analysis, curve-fitting and nearest-neighbor calculations. The UV mixing curves and CD spectra showed that the triple-helix of (dA)8·2(dT)8 mainly existed in 0.05 mol dm−3 MgCl2 buffer at a low temperature range, while the double helix of (dA)8·(dT)8 existed in 1 and 0.1 mol dm−3 NaCl buffers. The thermodynamic parameters for the triplex and duplex formations were obtained with analysis for the UV melting curves. The free-energy changes at 25 °C obtained from the melting temperature vs. oligomer concentration plots in the MgCl2 buffer were −20.7 kJ mol−1 for the triplex formation and −27.3 kJ mol−1 for the duplex formation, respectively, which were consistent with the values obtained from the curve-fitting calculations. The free-energy changes for the duplex formation at 25 °C were −28.5 kJ mol−1 in 1 mol dm−3 NaCl buffer, and −11.6 kJ mol−1 in 0.1 mol dm−3 NaCl bufer, respectively. These values were discussed in comparison with the predicted values by the nearest-neighbor calculation.
On the Mechanism of Organoaluminum-Promoted Claisen Rearrangement of Allylic Vinyl Ethers
Authors: Nonoshita Katsumasa , Maruoka Keiji , Yamamoto Hisashi 
Published: July 2006

Abstract
The organoaluminum-promoted Claisen rearrangement of allylic vinyl ethers has been mechanistically studied by two sets of experiments and the observed Z and E selectivity is best accounted for by two possible chair-like structures with R substituents axial and equatorial, respectively.
The Reaction of a 10-Methylacridinium Salt with Tertiary Amines
Authors: Tamagaki Seizo , Ueno Masanori , Tagaki Waichiro 
Published: July 2006

Abstract
The reaction of 10-methylacridinium perchlorate with a variety of N,N-disubstituted alkylamines or aralkylamines was investigated in the presence or absence of air. In all cases studied, 10-methyl-9,10-dihydroacridine was produced in approximately 50% yield or more. In addition, either 10-methyl-9(10H)-acridinone or 9-(dialkylamino)-10-methylacridinium perchlorate or both were isolated, each yield being greatly dependent on the bulkiness of alkyl groups on the amines. In the blanket of air, significant amounts of aldehyde was detected. The mechanism was discussed.