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221.
Momiyama N Konno T Furiya Y Iwamoto T Terada M 《Journal of the American Chemical Society》2011,133(48):19294-19297
Chiral bis-phosphoric acid 1 was designed to identify a new class of structural features in chiral Br?nsted acid catalysts. X-ray diffraction analysis revealed the single atropisomer 1, bearing S axial chirality at 3,3'-biaryl substituents on (R)-binaphthyl and intramolecular hydrogen bonding between the two phosphoric acid moieties. The newly designed bis-phosphoric acid 1 was evaluated in the Diels-Alder reaction of α,β-unsaturated aldehydes 4 with 1-N-acylamino-1,3-butadienes 3. After systematic variation of the catalyst substituents, as well as the N-acyl substituents of 1,3-butadiene, the use of an N-Cbz amidodiene 3a in the presence of bis-phosphoric acid 1e with a 2,4,6-tri-isopropylphenyl group was found to be optimal to yield the 1S,6R enantiomeric product 5aa in a Diels-Alder reaction of acrolein (4a). Application of this method to substituted substrates was found to be an efficient approach to the enantioselective synthesis of 3- and 3,6-substituted cyclic formylcarbamates 5. The specific character as well as the utility of 1e was further established by comparing its enantioselectivity, absolute stereochemistry, and catalytic efficiency with those of mono-phosphoric acid 2. 相似文献
222.
A series of star-shaped pyrrole-fused tetrathiafulvalene (TTF) oligomers 1-3 was synthesized via an S(N)Ar reaction of fluorinated benzenes with the pyrrolyl sodium salts. Electrochemical and chemical oxidations of 1-3 revealed that a radical cation moiety on each TTF unit was successfully accumulated in all oligomers. Self-assembled structures of neutral and oxidized species were characterized by SEM and XRD, and their conductive properties of the iodine-doped 1-3 as well as an intermolecular mixed-valence ion radical salt were investigated. 相似文献
223.
224.
Quanling Yang Shuji Fujisawa Tsuguyuki Saito Akira Isogai 《Cellulose (London, England)》2012,19(3):695-703
Mechanical, thermal and oxygen barrier properties of regenerated cellulose films prepared from aqueous cellulose/alkali/urea
solutions can be markedly improved by controlling the drying conditions of the films. By pre-pressing followed by vacuum drying
under compression, the tensile strength, Young’s modulus, coefficient of thermal expansion and oxygen permeability of the
dried films reached 263 MPa, 7.3 GPa, 10.3 ppm K−1 and 0.0007 ml μm m−2 day−1 kPa−1, respectively. Thus, films produced in this way show the highest performance of regenerated cellulose films with no orientation
of cellulose chains reported to date. These improved properties are accompanied by a clear increase in cellulose II crystallinity
from 50 to 62% during pre-pressing/press-vacuum drying process. At the same time, the film density increased from 1.45 to
1.57 g cm−3, and the moisture content under equilibrium conditions decreased from 14.1 to 9.8%. Hence, the aqueous alkali/urea solvent
system has potential applications in producing new and environmentally friendly cellulose films with high performances through
control of the drying conditions. 相似文献
225.
Ikue Homma Hayaka Fukuzumi Tsuguyuki Saito Akira Isogai 《Cellulose (London, England)》2013,20(5):2505-2515
The biodegradation behaviors of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose fibers (TOCs) and TEMPO-oxidized cellulose nanofibril (TOCN) films containing various carboxyl-group counter-ions were studied. Na+, H+, Ca2+, NH4 +, Cu2+, K+, and Cs+ were introduced into the TOCs or TOCN films, by ion-exchange treatment, as the carboxyl-group counter-ions. TOCs suspended in distilled water were treated with a commercial crude cellulase, and the TOCN films were subjected to soil burial tests. The crude-cellulase-treated products obtained from the TOCs were separated into water/ethanol-insoluble and -soluble fractions, i.e., high- and low-molecular-weight fractions, respectively. The degradation behaviors of the TOCs were evaluated from the weight recovery ratios of the water/ethanol-insoluble fractions and their viscosity-average degrees of polymerization. The results showed that the degradation behaviors of the TOCs were greatly influenced by the counter ion, and the counter-ion order of degradability was Na+ ≈ NH4 + ≈ K+ ≈ Cs+ ? Ca2+ > H+ > Cu2+. These degradability differences were influenced by the swelling behavior of the corresponding TOCs in distilled water; the higher the swelling degree of the TOC, the higher the degradation efficiency of the TOC in the reaction with crude cellulase. Similar biodegradation behaviors were observed in soil burial tests for TOCN films containing various carboxyl-group counter-ions in soil burial test; again the counter ion greatly influenced the resultant biodegradability. The biodegradation behaviors of TOCs and TOCN films can therefore be controlled by selecting an appropriate carboxyl-group counter-ion. 相似文献
226.
Dr. Ryu Yamasaki Dr. Masato Ohashi Kyotaro Maeda Takuya Kitamura Minami Nakagawa Korehito Kato Tetsushi Fujita Ryohei Kamura Kazuto Kinoshita Dr. Hyuma Masu Prof. Dr. Isao Azumaya Prof. Dr. Sensuke Ogoshi Prof. Dr. Shinichi Saito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(10):3415-3425
A detailed study of the Ni‐catalyzed [4+3+2] cycloaddition reaction between ethyl cyclopropylideneacetate and dienynes has been conducted, resulting in the development of a new method for the synthesis of compounds containing nine‐membered rings. We studied the reactivity of various dienynes, together with their substituent and conformational effects. The mechanism of the reaction was probed by examining the stoichiometric reactions of the Ni complexes and dienynes. 相似文献
227.
Polysubstituted anilines were prepared by the palladium-catalyzed cross-benzannulation of conjugated aminoenynes 1-4 with diynes 8. The reaction proceeded in a highly regioselective manner under mild conditions, and the anilines were obtained as single regioisomers. Our method complements the well-known precedures for the preparation of polysubstituted anilines which are widely used in organic synthesis. 相似文献
228.
Sogawa K Watanabe M Sato K Segawa S Ishii C Miyabe A Murata S Saito T Nomura F 《Analytical and bioanalytical chemistry》2011,400(7):1905-1911
In a clinical diagnosis microbiology laboratory, the current method of identifying bacterial isolates is based mainly on phenotypic
characteristics, for example growth pattern on different media, colony morphology, Gram stain, and various biochemical reactions.
These techniques collectively enable great accuracy in identifying most bacterial isolates, but are costly and time-consuming.
In our clinical microbiology laboratory, we prospectively assessed the ability of matrix-assisted laser desorption ionization–time
of flight mass spectrometry (MALDI–TOF MS) to identify bacterial strains that were routinely isolated from clinical samples.
Bacterial colonies obtained from a total of 468 strains of 92 bacterial species isolated at the Department of Clinical Laboratory
at Chiba University were directly placed on target MALDI plates followed by addition of CHCA matrix solution. The plates were
then subjected to MALDI–TOF MS measurement and the microorganisms were identified by pattern matching with the libraries in
the BioTyper 2.0 software. Identification success at the species and genus levels was 91.7% (429/468) and 97.0% (454/468),
respectively. MALDI–TOF MS is a rapid, simple, and high-throughput proteomic technique for identification of a variety of
bacterial species. Because colony-to-colony differences and effects of culture duration on the results are minimal, it can
be implemented in a conventional laboratory setting. Although for some pathogens, preanalytical processes should be refined,
and the current database should be improved to obtain more accurate results, the MALDI–TOF MS based method performs, in general,
as well as conventional methods and is a promising technology in clinical laboratories. 相似文献
229.
Nishiyama Y Kaneda M Saito R Mori T Wada T Inoue Y 《Journal of the American Chemical Society》2004,126(21):6568-6569
In the enantiodifferentiating photoaddition of ROH (R = Me, Et, i-Pr) to 1,1-diphenylpropene sensitized by fructosyl 1,4-naphthalenedicarboxylate in supercritical carbon dioxide, the enantiomeric excess of photoadduct increased with increasing bulkiness of the alcohol at all pressures used, with an accompanying sudden jump at the critical density, for which the enhanced clustering of alcohol, particularly in the subcritical pressure region, was revealed to be responsible from the fluorescence spectral examinations. 相似文献
230.
Infrared and nuclear magnetic resonance (NMR) spectroscopies have been applied for quantitative comparison on unsaturated bonds in tetrafluoroethylene (TFE)-propylene (P)-vinylidene fluoride (VdF) terpolymers. These spectroscopies have led to consistent results while they are based on completely different principles. It is shown that the absolute concentration can be evaluated from NMR measurements. The behavior of unsaturation has been discussed in terms of after-treatment such as wet and dry treatments. The result obtained here can give the important information to improve the performance of fluoroelastomer based on TFE-P-VdF terpolymers. 相似文献