bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Chiroptical Properties of Optically Active Tetracyclic Cage-shaped Hydrocarbons; [m.0]Triblattanes and [m.1]Triblattanes
Authors: Naemura Koichiro , Katoh Tohru , Fukunaga Rink\={o} , Chikamatsu Hiroaki , Nakazaki Masao 
Published: July 2006

Abstract
Horse liver alcohol dehydrogenase mediated reduction of tetracyclo[4.3.0.02,5.03,8]nonan-9-one ([1.0]triblattan-9-one) (17) gave (+)-17 and (−)-tetracyclo[4.3.0.02,5.03,8]nonan-9-ol(18). Hydrogenolysis of (+)-17 with 5% rhodium-alumina to (+)-(1R,3R,6R8R)-twist-brendan-9-ol with known absolute rotation allowed us to assign the 1S,2S,3R,5R,6R,8R absolute configuration to (+)-17 and to calculate the absolute rotation of (+)17. Wolff-Kishner reduction of (+)-17 gave (+)-[1.0]triblattane. BF3-Catalyzed diazomethane ring expansion of (+)-17 was followed by Wolff-Kishner reduction to afford optically active [m.0]triblattanes. (+)-Tetracyclo[5.2.12,6.04,8]decan-5-one ([1.1]triblattan-5-one) with known absolute configuration and absolute rotation was transformed to optically active [m.1]triblattanes by diazomethane ring expansion with BF3 etherate followed by Wolff-Kishner reduction. The known optical purities of our starting materials permitted calculation of the absolute molecular rotations of [m.0]triblattanes and [m.1]triblattanes. The chiroptical properties of triblattanes are discussed.
N-Hydroxy Amides. III. Active Esters of Polystyrene-bound 1-Hydroxy-2-pyrrolidinone and Their Use in Peptide Synthesis
Authors: Akiyama Masayasu , Shimizu Kazuyuki , Aiba Seiichi , Katoh Hiroaki 
Published: July 2006

Abstract
A polymer-bond cyclic N-hydroxy amide has been prepared by reaction of aminomethylated copoly(styrene–2% divinylbenzene) with 1-hydroxy-5-oxo-3-pyrrolidinecarboxylic acid using dicyclohexylcarbodiimide (DCC) as a condensing agent. Several N-blocked α-amino acids have been loaded on this resin by use of DCC. The amino acid resin can be utilized for peptide synthesis. Repetitive usage of the resin in the form of esters and facile synthesis of a biologically active pentapeptide, Leu5-enkephalin, show the usefulness of the polymer-bound 1-hydroxy-2-pyrrolidinone.
Preparation of New Nitrogen-bridged Heterocycles. 11. A New Synthetic Method of Pyrazolo[1,5-a]pyridines from the Alkaline Treatment of 1-[(Acylmethylthio)methyleneamino]pyridinium Salts
Authors: Kakehi Akikazu , Ito Suketaka , Ito Masayoshi , Yotsuya Toshiaki , Nagata Kenji 
Published: July 2006

Abstract
Alkaline treatment of 1-[(acylmethylthio)methyleneamino]pyridinium halides gave unexpectedly 3-acyl- or 3-(acylthio)pyrazolo[1,5-a]pyridine derivatives in 35–87% yields. Some 4,4a-dihydropyrido[1,2-d][1,3,4]thiadiazine intermediates involved in these reactions could be detected by their nmr follows and three related 4a,8-dimethyl derivatives were isolated. Substituent effect and possible mechanisms are also discussed.
Stereochemical Control in Electron-transfer Induced Reactions. Cyclic Voltammetry and Cathodic Reduction of Epimeric 3-Halogeno-6-nitro-5-cholestenes
Authors: Sato Takeo , Wada Takahiro , Komeichi Yoshihisa , Kainosho Masatsune 
Published: July 2006

Abstract
The cathodic electrolyses and cyclic voltammetric measurements were carried out for epimeric 3-halogeno-6-nitro-5-cholestenes. The stability and the fate of anion radicals were found to be highly dependent on the stereochemistry of homoallylic halogen groups. Half-lives of the anion radical from 3α-chloro- and 3α-bromo derivatives were found to be 12.5 and 1.6 s, respectively, while those of 3β-halogeno derivatives were much shorter. On cathodic reduction 3β-derivatives gave a cyclosteroid, 6β-nitro-3α,5α-cyclo-5α-cholestane in a two-electron process, whereas 3α-derivatives gave a dimer, 6β,6′β-dinitro-3α,3′α-cholesta-4,4′-diene, as the major product via a one-electron process. Detailed CV studies were carried out for 6-nitro-5-cholestene as a model. The stereochemistry of 3,3′-dimer was established by the 1H NMR measurements.
Synthesis and Properties of Gramicidin S Analogs Containing Pro–d-Phe Sequence in Place of d-Phe–Pro Sequence in the β-Turn Part of the Antibiotic
Authors: Tamaki Makoto , Takimoto Michiaki , Muramatsu Ichiro 
Published: July 2006

Abstract
Two analogs of gramicidin S, [l-Pro4, d-Phe5]-gramicidin S and [l-Pro4,4′, d-Phe5,5′]-gramicidin S, were synthesized in order to investigate the relationships among positions of Pro residues, antibiotic activity and CD spectra. [l-Pro4,4′, d-Phe5,5′]-gramicidin S showed little activity. On the other hand, the activity of [l-Pro4, d-Phe5]-gramicidin S against Bacillus subtilis and Micrococcus flavus was the same as that of gramicidin S, and its activity toward other microorganisms tested was 1/2 that of gramicidin S. The CD spectra of these analogs and gramicidin S in an aqueous solution differ from each other, indicating that these peptides have different conformations in aqueous solutions. The CD spectrum of [l-Pro4, d-Phe5]-gramicidin S resembles a graphical average of the CD spectra of gramicidin S and [l-Pro4,4′, d-Phe5,5′]-gramicidin S.
Syntheses and Properties of Oligo-l-leucines Containing α-Aminoisobutyric Acid Residues. The Novel Strategy for Solubility Improvement in Helical Oligopeptides Based on the Restriction of the Values of the Backbone Dihedral Angles φ and ψ of α-Aminoisobutyric Acid Residues
Authors: Narita Mitsuaki , Doi Masamitsu , Sugasawa Hiroki , Ishikawa Kazunori 
Published: July 2006

Abstract
In order to provide a succinct demonstration of the usefulness of a new strategy for solubility improvement in protected peptide fragments included in α-helical regions of proteins, model oligo(Leu)s containing Aib or Ala residues were prepared by stepwise elongation and fragment condensation methods. The peptides prepared were the following: Boc–(Leu3–Aib)n–OBzl, Boc–(Leu4–Aib)n–OBzl, and Boc–(leu3–Ala)nOBzl (n=1–3). Carboxyl component peptides having Aib residues at the C-terminals smoothly reacted with amino component peptides in high yields with no care of racemization due to the absence of chiral centers in Aib residues. As expected, peptides containing Aib residues have high solubility in moderate- and high-polar organic solvents and are easily purified by recrystallization from aqueous ethanol. This is in remarkable contrast with the result that the octa- and dodecapeptides containing Ala residues are barely soluble or insoluble in these solvents. Conformational analyses by IR spectroscopies indicated that Boc–(Leu3–Aib)n–OBzl and Boc–(Leu4–Aib)n–OBzl (n=2 and 3) had helical conformations (310- or α-helices) in dichloromethane, whereas Boc–(Leu3–Ala)n–OBzl (n=2 and 3) had fully developed β-sheet structures in the solid state. The high solubility of the peptides containing Aib residues is explained by the observation that replacement of Cα hydrogen atoms with methyl groups greatly disturbs β-sheet structures, promoting helical folding in peptides. The implications of the new findings for the chemistry of peptides and proteins containing α,α-disubstituted α-amino acid residues is also discussed by building up a CPK model of an α-helical structure.
Retentive Stereospecificity in Deoxygenation of Epoxides with Sn–Al or Si–Al Reagents
Authors: Matsubara Seijiro , Nonaka Tsuyoshi , Okuda Yasuhiro , Kanemoto Shigekazu , Oshima Koichiro , Nozaki Hitosi 
Published: July 2006

Abstract
Reaction of epoxides with [n-Bu3SnAlMe3]−Li+ affords β-oxido stannanes which collapse to alkene with overall retention of stereochemistry. The SN2 type ring opening of epoxides by tributylstannyl anion followed by anti elimination of Bu3Sn and OAl−Me3 groups explains the stereochemical results. The method can be successfully applied to hydroxy epoxides derived from (E)-2-nonen-1-ol. The deoxygenation of epoxides with PhMe2SiAlEt2 also provides olefins of the same geometry as epoxides.
Raman Spectra of Compounds under Inversion Motions. IV. N-Methyl-2-pyrrolidone
Authors: Fukushima Kunio , Yamaji Masahiro 
Published: July 2006

Abstract
The Raman spectra of N-methyl-2-pyrrolidone in various states were measured. Remarkable changes in the spectrum of CH2 bending vibrations were found besides a spectrum change of the skeletal vibrations. Normal vibration calculations and measurements regarding band-intensity changes associated with temperature changes suggest that a change of the ring conformation takes place in this molecule by hydrogen bonding to a nitrogen atom.
Solubility of Tris(acetylacetonato)chromium(III) in Aqueous Alcohol Mixtures
Authors: Yamamoto Manabu 
Published: July 2006

Abstract
From the temperature dependence of the solubility of tris(acetylacetonato)chromium(III) in aqueous t-butyl alcohol mixtures and in aqueous methanol mixtures, thermodynamic parameters of the solution were calculated. The solubility and these parameters in aqueous t-butyl alcohol mixtures could be explained qualitatively by the cavity formation terms of the scaled particle theory. It was suggested that tris(acetylacetonato)chromium(III) is in water microphases at XBuOH≤0.04 and in t-butyl alcohol microphases over this region.
Cobalt(III) Complexes with [N6−nXn]-type Ligands. V. The Preparation and Properties of N,N′-Disalicylidene-substituted Quadridentate Amine Cobalt(III) Complexes
Authors: Yamamoto Yoshihisa , Tsukuda Shoko 
Published: July 2006

Abstract
(1,8-N-Disalicylidene-3,6-diazaoctane-1,8-diamine)cobalt(III) chloride hydrate (1a; x,y,z: 2,2,2),
(Remark: Graphics omitted.)
\oindent(1,9-N-disalicylidene-3,7-diazanonane-1,9-diamine)cobalt(III) chloride (2a; x,y,z: 2,3,2), (1,10-N-disalicylidene-4,7-diazadecane-1,10-diamine)cobalt(III) chloride (3a; x,y,z: 3,2,3), and (1,11-N-disalicylidene-4,8-diazaundecane-1,11-diamine)cobalt(III) chloride hydrate (4a; x,y,z: 3,3,3) have been isolated from a reaction mixture of [CoCl2L]Cl·nH2O (L: quadridentate amine), AgOH, and salicylaldehyde or from one of quadridentate amine, salicylaldehyde, CoCl2·6H2O and air, and characterized. The 1H and 13C chemical shifts of their amine protons, methylene protons, and methylene carbons have been assigned. The configurations of 1a and 2a are the trans,cis(mf2m) configuration for the two CH=N– and two phenoxyl groups of the coordinated N,N′-disalicylidene-substituted quadridentate amine ligands. On the other hand, complexes 3a and 4a have the cis,trans(fm2f) configuration.
Chromatographic Study of Optical Resolution. XII. Optical Resolution of Bis(oxalato)(1,10-phenanthroline)cobaltate(III) and Its Related Anion Complexes with Cinchona Alkaloid Cations as Eluent
Authors: Miyoshi Katsuhiko , Natsubori Masahiko , Dohmoto Naoko , Izumoto Shinji , Yoneda Hayami 
Published: July 2006

Abstract
Ion-exchange chromatography was applied to the optical resolution of three anion complexes, [Co(ox)2(phen)]−, [Co(ox)2(bpy)]−, and [Co(ox)2(en)]− (ox=oxalate anion, phen=1,10-phenanthroline, bpy=2,2′-bipyridine, and en=ethylenediamine) using as a chiral eluent aqueous solutions of various cinchona alkaloid cations, i.e., cinchoninium, cinchonidinium, quinidinium, and quininium ions, and their 9-acetoxy and N1-methyl derivatives. Fairly good resolution was achieved for the first two complexes with the 9-acetoxy derivatives as eluent, but no practical resolution was attained for [Co(ox)2(en)]−. Retention volumes VR determined and separation factors α estimated from VR revealed that both of the HO–C(9) and H–N(1)+ groups of each alkaloid participate in the interaction with the complex, and that the α value is increased upon acetylation of the OH group with the elution order reversed. These observations were interpreted in terms of two concomitant interaction modes in which the HO–C(9) and H–N(1)+ groups are hydrogen-bonded to the ox ligand(s) and the quinoline ring is stacked with the phen or bpy ligand of the anion complex.
Hexaamminecobalt(III)–Hydrogen Ion Exchange in α- and θ-Zirconium Phosphates with Various Particle-size Distribution
Authors: Hasegawa Yoshitsugu , Fujita Kunio 
Published: July 2006

Abstract
The hexaamminecobalt(III)–hydrogen ion exchange in zirconium phosphates was studied by means of the batch method, mainly with regard to the particle-size distribution of zirconium phosphates. α-Zirconium phosphates were prepared by the direct-precipitation method. The degree of ion exchange increased with the fineness of the zirconium phosphates used. The ion exchange proceeded to a lesser extent in highly crystalline α-zirconium phosphate. θ-Zirconium phosphate with the interlayer distance of 10.4 Å took up the complex cation selectively and easily. Fifty percent of the protons in the θ-zirconium phosphate were thus replaced with hexaamminecobalt(III), and the interlayer distance was expanded to 11.2 Å.
Generation of Nonstabilized Thiazolium and 2-Methylthiazolium Methylides
Authors: Tsuge Otohiko , Kanemasa Shuji , Kuraoka Satoru 
Published: July 2006

Abstract
Desilylation of 3-(trimethylsilylmethyl)thiazolium triflates including 2-methyl derivatives with CsF generates the corresponding thiazolium methylides which are trapped with acetylenic and olefinic dipolarophiles. This paper presents the first example for the generation of nonstabilized thiazolium methylides including 2-methyl derivatives.
Synthetic Photochemistry. XXX. The Addition Reactions of Cycloheptatriene with Some Aromatic p-Quinones
Authors: Mori Akira , Takeshita Hitoshi 
Published: July 2006

Abstract
The photochemical reactions of cycloheptatriene with p-benzoquinone and 1,4-naphthoquinone yielded the spirocyclic ethers, which had 7-oxabicyclo[4.2.1]nona-2,4-diene structures, by the characteristic (6+2)π cycloaddition process. The latter quinone further produced the carbocyclic (2+2)π and (6+2)π cycloadducts.
Photovoltaic Properties of Coumarin Dye Films
Authors: Iijima Sei-ichiro , Mizutani Fumio , Tanaka Yoshio 
Published: July 2006

Abstract
Al/vacuum-deposited dye/Ag(or Au) photocells prepared by using four kinds of coumarin dyes indicate that a Schottky barrier formed at an Al/dye interface is the origin of their photovoltaic effects. Quantum yields of the short-circuit photocurrent of 0.05–0.77% and the photovoltages of 0.30–0.95 V were obtained under 0.1 mW/cm2 light.
Stereoselectivity in the Reduction of Cyclic Ketones with Sodium Borohydride. Effect of the Ratio of the Components of a Mixed Solvent of Tetrahydrofuran and Methanol
Authors: Soai Kenso , Ohi Kazumi 
Published: July 2006

Abstract
Reduction of relatively conformationally rigid cyclic ketones with sodium borohydride was examined in a mixed solvent of tetrahydrofuran(THF) and methanol(MeOH) with varying the ratio of the components. The highest stereoselectivities of the reductions were observed in the mixed solvent, and not in each individual solvent.
Transition-metal-catalyzed Grignard Reaction of Isoprene Bromohydrin
Authors: Araki Shuki , Ohmura Masayuki , Butsugan Yasuo 
Published: July 2006

Abstract
The coupling reaction of isoprene bromohydrin with aryl and alkyl Grignard reagents catalyzed by tetrakis(triphenylphosphine)palladium(0) selectively gave the vinyl-group-migrated products.
Oxidation of Anthracenols and Anthrone to Anthraquinones with Oxygen Mediated by Copper(II) Ion and Imidazole
Authors: Iwata Masaaki , Kuzuhara Hiroyoshi 
Published: July 2006

Abstract
The copper(II) chloride-imidazole-ethanol system turned out to oxidize 2-anthracenols to 1,2-anthraquinones and 2-methoxy-9-anthrone to 2-methoxy-9,10-anthraquinone in practical synthetic yield.
Response of Copper(II) and Cadmium(II) Ion-selective Electrodes in Some Nonaqueous Solvents
Authors: Aihara Makoto , Kanetake Sachiko , Fukuda Yuka 
Published: July 2006

Abstract
The response of cadmium(II) and copper(II) ion-selective electrodes was evaluated in methanol, ethanol, acetonitrile solutions and their mixtures with water. The electrodes showed an almost Nernstian behavior in nonaqueous solutions and their mixtures with water except in acetonitrile.
The Crystal and Molecular Structure of Anhydrous Zinc 8-Quinolinolate Complex, [Zn(C9H6NO)2]4
Authors: Kai Yasushi , Morita Masahiro , Yasuoka Noritake , Kasai Nobutami 
Published: July 2006

Abstract
The molecular structure of an anhydrous zinc 8-quinolinolate obtained by sublimation has been determined by means of X-ray diffraction. The complex forms triclinic crystals; a=11.858(1), b=13.019(2), c=10.834(1) Å, α=106.56(1), β=109.00(1), and γ=74.14(1)°, space group P\bar1 (No. 2) with one [Zn(C9H6NO)2]4 molecule. The structure was solved by the heavy atom method and refined by the block-diagonal least-squares procedure to R=0.043 for 3320 non-zero reflections. The molecule is centrosymmetric and tetrameric; four [Zn(C9H6NO)2] units being connected by oxygen atoms of 8-quinolinolate ligands. Two types of bridging oxygen atoms were found. Two crystallographically independent zinc atoms take different geometries, hexa-, and pentacoordinations.
Partial Molal Volumes and Volume Changes for the Complex Formation of Metal Chelate Electrolytes, Na2[M(edta)] and K[M(hedta)(H2O)]
Authors: Yoshitani Kouzou 
Published: July 2006

Abstract
The partial molal volumes, V∞, of [M(edta)]2− and [M(hedta)(H2O)]− (M=Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) and H3hedta=N-(2-hydroxyethyl)ethylenediamine-N,N′,N′ -triacetic acid) and two free ligands, edta4− and hedta3−, have been determined from density measurements at 25 °C. From the results for V∞, the volume changes for the complex formation of [M(edta)]2− and [M(hedta)(H2O)]−, ΔV∞, were estimated. The values of ΔV∞, for [M(edta)]2− (32.8 to 45.8 cm3 mol−1) and for [M(hedta)(H2O)]− (25.2 to 36.5 cm3 mol−1) were large, positive ones, and a linear relationship between ΔV∞ and ΔS was observed for these metal chelate ions.
The Stereoselective Retardation of the Alkaline Hydrolysis of Organic Esters by Binuclear Cu(II) Complexes with Cyclodextrins
Authors: Matsui Yoshihisa , Suemitsu Daisuke 
Published: July 2006

Abstract
The alkaline hydrolysis of p-nitrophenyl acetate (p-NPA) in 1.0mol dm−3 NaOH at 25 °C was almost completely retarded by the addition of a binuclear Cu(II) complex with α-cyclodextrin (Cu2α-CD). The dissociation constant for an inclusion complex of Cu2α-CD with p-NPA was determined to be 0.059 mmol dm−3, which is about one 200th that for an inclusion complex of α-CD with p-NPA. The alkaline hydrolysis of o- and m-nitrophenyl acetates was also retarded by Cu2α-CD, though the extent of retardation was much less than that for p-NPA. A binuclear Cu(II) complex with β-cyclodextrin (Cu2β-CD) also caused a stereoselective deceleration of the alkaline hydrolysis of the esters. However, the stereoselectivity of Cu2β-CD was not so remarkable as that of Cu2α-CD. Dissociation constants for inclusion complexes of Cu2α2-CD with several alcohols and other organic substrates were determined by the kinetic examination of the competitive inhibition effect of the substrates on the association of Cu2α-CD with p-NPA. Cu2α-CD formed stable inclusion complexes with such disk-like molecules as cyclohexanol, cycloheptanol, and p-nitrobenzyl alcohol. The geometry of a Cu2α-CD-p-NPA inclusion complex was presumed on the basis of these results.
Anodic Oxidation of Cyclohexanone on Lead Dioxide Electrode in Aqueous Sulfuric Acid Solution
Authors: Kunai Atsutaka , Hatoh Kazuhito , Hirano Yoshinobu , Harada Junji , Sasaki Kazuo 
Published: July 2006

Abstract
The electrolytic behavior of cyclohexanone was examined by potentiometry with rotating disk electrode as well as by product analyses. The reaction was activation controlled and the reaction orders were first with respect to cyclohexanone and zero for proton. Cyclohexanone reacted by approximately 6 electrons to give adipic acid mainly which accumulated proportionally to the electricity consumed. Changes in temperature, proton concentration, and current density resulted in only minor effects on the reaction. In neutral solution, however, the oxidation was suppressed and oxygen evolution dominated. Other electrode materials such as Pt, graphite, RuO2, and PtO2 were inactive. The chemical oxidation with PbO2 itself did not occur. From these facts, reaction mechanism was discussed.
Structure–Taste Relationships of Aspartyl Tetrapeptide Esters
Authors: Ariyoshi Yasuo 
Published: July 2006

Abstract
A series of fourteen analogues of l-α-Asp–Gly–Gly–Gly–OMe has been synthesized in relation to structural features of sweet peptides. The rule in the structure-taste relationships of tripeptides barely applies to the aspartyl tetrapeptide esters. In order for the aspartyl tetrapeptide esters to be sweet, the second amino acid must have a d-configuration and a small, compact alkyl side chain. However, the sweetness was accompanied by a bitter or astringent taste. Moreover, some of the tetrapeptides were not sweet but bitter, though they satisfied the requirements for sweet peptides. With increasing length of a peptide, it becomes difficult to fit the deep receptor pocket.
Formation of Blocking Contacts at p-Type Porphyrin/ITO or Electrolyte Junctions
Authors: Yamashita Kazuo , Harima Yutaka , Matsumura Yuhei 
Published: July 2006

Abstract
Energetics of ITO/p-type porphyrin/electrolyte interfaces are discussed on the basis of photoelectrochemical and photovoltaic measurements. When sensitized by a layer of 5,10,15,20-tetraphenylporphyrinatomagnesium(II)(MgTPP), the indium-tin oxide (ITO) electrode acts as only a photocathode in an aqueous electrolyte solution. However, the ITO electrode modified with a film of ZnTPP, CuTPP or H2TPP having oxidation potential more positive than that of MgTPP acts as not only a photocathode but also a photoanode, depending on the electrode potential and the direction of irradiation on the ITO/porphyrin electrode. The cathodic component in the photocurrents is attributed to the downward band-bending in a space charge layer at the porphyrin/electrolyte (blocking) contact and the anodic component to that at the ITO/porphyrin (blocking) contact. The upward band-bending, on the contrary, is found inefficient in producing charge carriers, because the accumulation layer is conducting (ohmic) for majority carriers (holes). The porphyrin/electrolyte junction shows certain similarities to an ITO or metal/porphyrin (semiconductor) junction. However, it should be noted that a Helmholtz double layer exists at the porphyrin/electrolyte interface. The results are rationalized from the energy levels of the porphyrin films, ITO and the redox couple solutions with due regard to the orientation of water dipoles at the porphyrin surface.
Intermolecular Hydrogen Bonding of Enantiomers of Pantolactone Studied by Infrared and 1H-NMR Spectroscopy
Authors: Nakao Yoshihiko , Sugeta Hiromu , Kyogoku Yoshimasa 
Published: July 2006

Abstract
Intermolecular associations of the enantiomers of pantolactone in carbon tetrachloride solution have been studied by infrared and 1H-NMR spectroscopic methods. The spectroscopic data have been analyzed by the least squares method to obtain the association constants and thermodynamic parameters. It was found that pantolactone takes a cyclic dimer structure by dint of hydrogen bonding. The association constant for homochiral dimerization was obtained to be 8.9 mol−1 dm3 at 26°C and the enthalpy and entropy changes were −35 kJ mol−1 and −97 J K−1 mol−1, respectively. The association constant for heterochiral dimerization is just twice as large as that for homochiral dimerization, that is, no selective association exists between enantiomers.