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991.
Gold-catalyzed intermolecular reaction leading to dihydronaphthalene derivatives in one pot from two equivalents of ynones with respect to styrene is uncovered. The [4+2] Diels–Alder cycloaddition of ynones and styrenes is catalyzed by a mono-gold(I) complex and the conjugated acid to provide an unstable 3,8a-dihydronaphthalene to subsequently undergo an intermolecular ene-type reaction with the π-activated ynone to afford multi-component coupling dihydronaphthalene products. Linear relationships between chiral ligand-gold complexes and chiral dihydronaphthalene products proves mono-gold catalysis that triggers an asymmetric tandem Diels–Alder and ene reaction sequence. 相似文献
992.
Š. Urban D. Papoušek M. Bester Koichi Yamada G. Winnewisser A. Guarnieri 《Journal of Molecular Spectroscopy》1984,106(1):29-37
The data on the inversion spectrum in the ν2 state of 14ND3 [F. Scappini, A. Guarnieri, and G. DiLonardo, J. Mol. Spectrosc.95, 20–29 (1982)] have been extended by measuring frequencies of 25 new transitions. A simultaneous least-squares analysis of these data with the ground state microwave transition frequencies and the diode laser measurements of the ν2 band has been carried out. Improved sets of molecular parameters have been obtained for 14ND3 and 15ND3, including the ground and ν2 state inversion splittings, ν2 band origins, rotational and centrifugal distortion constants, and the parameters of the Δk = ±3n vibrational-rotational interactions. 相似文献
993.
Satoko Akashi Kazuyoshi Noguchi Reiko Yuji Uno Tagami Kazuo Hirayama Koichi Kato HaHyung Kim Kazuhiro Tokioka Ichio Shimada Yoji Arata 《Journal of the American Society for Mass Spectrometry》1996,7(8):707-721
The amino acid sequences of mouse monoclonal antibodies have been characterized completely by mass spectrometry. Antibodies used in the present study were derived from mouse switch variant cell lines that produce four kinds of immunoglobulin Gs (IgGs). The amino acid sequences of these antibodies had not been estimated from the corresponding DNA sequence, so the sequences of IgGs derived from other strains were used as references in this study. Intra- and interchain disulfide bonds of the IgGs were reduced and carboxymethylated and the products were subjected to proteolytic digestion. The existence of N-linked oligosaccharides also was taken into account. The capabilities and limitations of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and capillary liquid chromatography-electrospray ionization mass spectrometry are discussed in the structural characterization of the antibodies. Based on our results, allotypes of the antibodies examined are discussed. This study shows that amino acid sequences of proteins, such as IgG, can be investigated without information about the corresponding DNA sequence if appropriate reference sequences derived from other strains can be used. 相似文献
994.
Koichi Yamaguchi Yuji Minoura 《Journal of polymer science. Part A, Polymer chemistry》1972,10(10):2875-2885
The reaction of carbon disulfide with one or two equivalents of alkali metal (potassium- or sodium) was carried out, and the deep red reaction mixture obtained only in diethylene glycol dimethyl ether. The polymerization of vinyl monomers with this reaction mixture was studied. The reaction mixtures of mono- and dialkali metal with carbon disulfide induced the polymerization of N-phenylmaleimide, methyl vinyl ketone, and acrylonitrile but did not induce the polymerization of methyl methacrylate and styrene. In the polymerization of acrylonitrile with this reaction mixture of carbon disulfide with monoalkali metal, the polymerization rate was found to be proportional to the initiator concentration and to the square of the monomer concentration. The activation energy was ?1.1 kcal/mole. Similar results were obtained in the case of carbon disulfide with dialkali metal. The polymer yield increased with increasing solvating power of solvents, i.e., diethylene glycol dimethyl ether, dimethyl sulfoxide, hexamethylphosphoramide, dimethylformamide, tetrahydrofuran. In the copolymerization of AN with MMA, the copolymer obtained consisted almost of AN units. 相似文献
995.
Takeo Araki Fumio Nogami Hiroshi Tsukube Koichi Nagata Shuso Iyoshi 《Journal of polymer science. Part A, Polymer chemistry》1978,16(5):1037-1057
The reaction course of 1-(N-phenyl-carbamyl)aziridine with NaI was found to be highly sensitive to the nature of solvent used; e.g., acetone preferentially gives 1-phenyl-2-imidazolidinone, whereas dimethylformamide (DMF) gives 2-anilino-2-oxazoline. Nuclear magnetic resonance (NMR) study of the solvent effect revealed the relation between the site in the aziridine compound, with which the solvents interact, and the reaction products. From the results obtained by these ring-transformation studies, the use of diethyl sulfate, which is expected to solvate simultaneously at the carbonyl oxygen and the carbamyl–nitrogen atoms, resulted in polymerization of the monomer selectively to the oligomer of type—[CH2CH2N(CONHPh)]n—. The diethyl sulfate was shown to play dual roles as a solvating reagent and an initiator. The oligomer obtained includes relatively definite amount (one molecule per ca. four monomer units) of diethyl sulfate in the “washed” state. The absorbed diethyl sulfate can be removed by treating with aqueous NaOH solution or Amberlite-400 column elution without altering the chemical constitution of the backbone in the polymer. Application of the polymerization procedure to several N-alkyl substituted monomers resulted in oligomers of a similar type. The difference in the monomer reactivity depending on the nature of the substituent groups can be due mainly to steric factors. 相似文献
996.
Koichi Yamada 《Journal of Molecular Spectroscopy》1980,79(2):323-344
The pure rotational spectra of HNCO and DNCO were measured in the far-infrared region from 80 to 350 cm?1 by a Fourier transform spectrometer with a resolution of 0.1 cm?1. The rRK branches were measured and assigned for HNCO from K = 1 to 6, and for DNCO from K = 3 to 8. The measured transition wavenumbers were analyzed together with the microwave and millimeter wave data reported by Hocking, Gerry, and Winnewisser [Can. J. Phys.53, 1869–1901 (1975)] and with the far-infrared data of Krakow, Lord, and Neely [J. Mol. Spectrosc.27, 148–176 (1968)] in the low-wavenumber region. The microwave and millimeter wave data of H15NCO, HN13CO, and HNC18O reported by Hocking et al. were reanalyzed assuming several centrifugal distortion constants to be identical with those of the normal species. The molecular structure of HNCO was reevaluated using a modified substitution method from the rotational constants obtained in this work. The molecule has a bent structure in a trans configuration with , , , ∠HNC = 123.9°, and ∠NCO = 172.6°. 相似文献
997.
Paradigm Shift from Alkaline (Earth) Metals to Early Transition Metals in Fluoroorganometal Chemistry: Perfluoroalkyl Titanocene(III) Reagents Prepared via Not Titanocene(II) but Titanocene(III) Species 下载免费PDF全文
Motohiro Fujiu Ryota Hashimoto Yuzo Nakamura Prof. Dr. Kohsuke Aikawa Prof. Dr. Shigekazu Ito Prof. Dr. Koichi Mikami 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(8):2382-2386
Perfluoroalkyl (RF) titanocene reagents [Cp2TiIIIRF] synthesized via [Cp2TiIIICl] rather than [Cp2TiII] show new types of perfluoroalkylation reactions. The [Cp2TiIIIRF] reagents exhibit a wide variety of reactivity with carbonyl compounds including esters and nitriles, and selectivities far higher than those reported for conventional RFLi and RFMgX reagents. 相似文献
998.
Dr. Yoshiyuki Manabe Hiroki Shomura Naoya Minamoto Dr. Masahiro Nagasaki Yohei Takakura Prof. Katsunori Tanaka Prof. Alba Silipo Prof. Antonio Molinaro Prof. Koichi Fukase 《化学:亚洲杂志》2018,13(12):1544-1551
The chemical synthesis of a bisecting N‐acetylglucosamine (GlcNAc)‐containing N‐glycan was achieved by a convergent synthetic route through [4+2] and [6+2] glycosylations. This synthetic route reduced the number of reaction steps, although the key glycosylations were challenging in terms of yields and selectivities owing to steric hindrance at the glycosylation site and a lack of neighboring group participation. The yields of these glycosylations were enhanced by stabilizing the oxocarbenium ion intermediate through ether coordination. Glycosyl donor protecting groups were explored in an effort to realize perfect α selectivity by manipulating remote participation. The simultaneous glycosylations of a tetrasaccharide with two disaccharides was investigated to efficiently construct a bisecting GlcNAc‐containing N‐glycan. 相似文献
999.
A fitting method of the sixth-order potential energy function is proposed, where ab initio potential energy data for the fitting are sampled in directions containing maximal anharmonic downward distortions detected by the scaled hypersphere search (SHS) method. This technique has been applied to H2O, HCHO, HCOOH, C2H4, CH3OH, CH3CHO, CH3NH2, B2H6, (H2O)2, and (H2O)3, where, without using the symmetry, 176, 904, 1432, 2992, 2520, 2760, 3608, 6232, 768, and 1456 times single-point energy calculations, respectively, were required for obtaining anharmonic terms. Experimental IR peak positions of not only fundamentals but also overtones and combinations in the excitation energy range of 1000-4000 cm(-1) could be reproduced very accurately by the post-vibrational self-consistent field theory employing potential functions obtained by the present SHS based polynomial fitting method. 相似文献
1000.
Togashi T Naka T Asahina S Sato K Takami S Adschiri T 《Dalton transactions (Cambridge, England : 2003)》2011,40(5):1073-1078
Magnetic nanoparticles (MNPs) have many potential biomedical applications. Improvements in their magnetic properties and solubility are necessary for these applications to realize their full potential. In this study, MNPs in the form of raspberry-like magnetite (Fe(3)O(4)) nanoparticle clusters, consisting of tiny Fe(3)O(4) particles with a diameter of approximately 20 nm, were prepared under hydrothermal conditions at 200 °C in the presence of 3,4-dihydroxyhydroxysinnamic acid (DHCA). The primary particles were connected by DHCA molecules to form the clusters, which were well dispersed in water media because a COOH group from DHCA appeared on their surfaces. The cluster size could be tuned from 50 to 400 nm without changing the primary particle size by controlling the reaction time. Therefore, all prepared clusters displayed superparamagnetic properties at room temperature. In addition, the sensitivity of Fe(3)O(4) to an external magnetic field could also be controlled by the cluster size. 相似文献