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961.
962.
963.
Fukuhara G Okazaki T Lessi M Nishijima M Yang C Mori T Mele A Bellina F Chiappe C Inoue Y 《Organic & biomolecular chemistry》2011,9(20):7105-7112
Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid (AC-H) and its lithium salt (AC-Li) in chiral ionic liquid (CIL), (R)-1-(2,3-dihydroxypropyl)-3-methylimidazolium acetate {[(R)-GLYMI][AcO]}, gave a mixture of two head-to-tail (HT) and two head-to-head (HH) cyclodimers in HT/HH ratios of 1.3-1.7 (for AC-H) and 2.2-4.3 (for AC-Li) with low enantiomeric excesses (ee) of 0-3% for chiral syn-HT and anti-HH dimers. In contrast, irradiation of AC-H in an aqueous solution, containing cucurbit[8]uril (CB[8]) as a host and [(R)-GLYMI][AcO] or [(R)-GLYMI][Tf(2)N] as a modifier of CB portals, afforded the HH dimers in 91-99% selectivity, although the anti-HH dimer was totally racemic. Interestingly, irradiation of AC-H in a dichloromethane solution, containing [(R)-GLYMI][AcO] as a chiral template, led to the formation of the HH-dimers in 98% selectivity with chiral anti-HH dimer in -14% ee, presumably by the dual ligation of two ACs to a CIL through electrostatic and hydrogen-bonding interactions. 相似文献
964.
Different modes of cyclization in zoanthamine alkaloid system, bisaminal versus spiroketal formation
Nakajima T Yamashita D Suzuki K Nakazaki A Suzuki T Kobayashi S 《Organic letters》2011,13(12):2980-2983
Bisaminal cyclization in the zoanthamine alkaloid system was strongly affected by the stereochemistry of the C4 methyl. While cyclization of the (4S)-methyl precursor gave only a bisaminal compound, cyclization of the (4R)-methyl isomer produced both spiroketal and bisaminal products. 相似文献
965.
Robertson A Matsumoto T Ogo S 《Dalton transactions (Cambridge, England : 2003)》2011,40(40):10304-10310
This review discusses the development of aqueous phase, homogeneous, transfer hydrogenation catalysis. Transfer hydrogenation catalysts, based on Ru, Ir and Rh, reduce organic substrates in water by assisting the transfer of hydrogen from simple donor species. These catalysts are expected to have significant benefits when compared with organic phase catalysts, including greater activity, greater selectivity and smaller environmental impact. They will therefore be expected to make a significant contribution to homogeneous catalysis and 'green chemistry'. Here, we comprehensively examine these catalysts, paying special attention to structural features. 相似文献
966.
Kubo A Ohmura M Wakui M Harada T Kajihara S Ogawa K Suemizu H Nakamura M Setou M Suematsu M 《Analytical and bioanalytical chemistry》2011,400(7):1895-1904
Analyses of energy metabolism in human cancer have been difficult because of rapid turnover of the metabolites and difficulties
in reducing time for collecting clinical samples under surgical procedures. Utilization of xenograft transplantation of human-derived
colon cancer HCT116 cells in spleens of superimmunodeficient NOD/SCID/IL-2Rγnull (NOG) mice led us to establish an experimental model of hepatic micrometastasis of the solid tumor, whereby analyses of the
tissue sections collected by snap-frozen procedures through newly developed microscopic imaging mass spectrometry (MIMS) revealed
distinct spatial distribution of a variety of metabolites. To perform intergroup comparison of the signal intensities of metabolites
among different tissue sections collected from mice in fed states, we combined matrix-assisted laser desorption/ionization
time-of-flight imaging mass spectrometry (MALDI–TOF-IMS) and capillary electrophoresis–mass spectrometry (CE–MS), to determine
the apparent contents of individual metabolites in serial tissue sections. The results indicated significant elevation of
ATP and energy charge in both metastases and the parenchyma of the tumor-bearing livers. To note were significant increases
in UDP-N-acetyl hexosamines, and reduced and oxidized forms of glutathione in the metastatic foci versus the liver parenchyma. These
findings thus provided a potentially important method for characterizing the properties of metabolic systems of human-derived
cancer and the host tissues in vivo. 相似文献
967.
Yamada M Minowa M Sato S Slanina Z Tsuchiya T Maeda Y Nagase S Akasaka T 《Journal of the American Chemical Society》2011,133(11):3796-3799
We describe the regioselective cycloaddition of La(2)@I(h)-C(80) with tetracyanoethylene oxide (TCNEO), which enabled the formation of the corresponding adduct having a tetracyanotetrahydrofuran moiety. X-ray crystallographic analysis revealed that the cycloaddition took place as a [5,6] addition. Along with dynamic swing motion of the metal atoms, the results of this electrochemical study demonstrate that TCNEO addition enhanced the electron-accepting character of La(2)@I(h)-C(80) and that the first reduction potential of the adduct reached -0.21 V versus the ferrocene/ferrocenium couple, which is the lowest value reported for endohedral metallofullerenes and their derivatives to date. 相似文献
968.
Abe R Ohashi H Iijima I Ihara M Takagi H Hohsaka T Ueda H 《Journal of the American Chemical Society》2011,133(43):17386-17394
Here, we describe a novel reagentless fluorescent biosensor strategy based on the antigen-dependent removal of a quenching effect on a fluorophore attached to antibody domains. Using a cell-free translation-mediated position-specific protein labeling system, we found that an antibody single chain variable region (scFv) that had been fluorolabeled at the N-terminal region showed a significant antigen-dependent fluorescence enhancement. Investigation of the enhancement mechanism by mutagenesis of the carboxytetramethylrhodamine (TAMRA)-labeled anti-osteocalcin scFv showed that antigen-dependency was dependent on semiconserved tryptophan residues near the V(H)/V(L) interface. This suggested that the binding of the antigen led to the interruption of a quenching effect caused by the proximity of tryptophan residues to the linker-tagged fluorophore. Using TAMRA-scFv, many targets including peptides, proteins, and haptens including morphine-related drugs could be quantified. Similar or higher sensitivities to those observed in competitive ELISA were obtained, even in human plasma. Because of its versatility, this "quenchbody" is expected to have a range of applications, from in vitro diagnostics, to imaging of various targets in situ. 相似文献
969.
Qureshi AK Mukhtar MR Hirasawa Y Hosoya T Nugroho AE Morita H Shirota O Mohamad K Hadi AH Litaudon M Awang K 《Chemical & pharmaceutical bulletin》2011,59(2):291-293
Two new indole alkaloids, neolamarckines A and B (1, 2) were isolated from the leaves of Neolamarckia cadamba (Rubiaceae). Structural elucidation of 1 and 2 was performed by combination of 2D-NMR and circular dichroism (CD) spectra, and chemical correlations. Neolamarckine A (1) showed inhibition of inducible nitric oxide synthase (iNOS) dose dependently. 相似文献
970.
Takahiro Tsukahara Tomohiro KawaseYasuo Kawaguchi 《International Journal of Heat and Fluid Flow》2011,32(3):529-538
Direct numerical simulations of turbulent viscoelastic-fluid flow in a channel with a rectangular orifice were performed to investigate the influence of viscoelasticity on turbulence statistics and turbulent structures downstream of the orifice. The geometry considered is periodic rectangular orifices with 1:2 expansion. The constitutive equation follows the Giesekus model, valid for polymer (or surfactant) solutions, which are generally capable of reducing the turbulent frictional drag in a smooth channel. The friction Reynolds number and the Weissenberg number were set to 100 and 20-30, respectively. A drag reduction of about 20% was achieved in the viscoelastic flows. The onset Reynolds number for the transition from a symmetric to an asymmetric state was found to be shifted to higher values than that for the Newtonian flow. In the viscoelastic flow, the turbulent kinetic energy was decreased and fewer turbulent eddies were observed, as the Kelvin-Helmholtz vortices were quickly damped. Away from the orifice, quasi-streamwise vortices in the viscoelastic flow were sustained for a longer period, accompanied by energy exchange from elastic energy of the viscoelastic fluid to kinetic energy. 相似文献