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61.
62.
A novel neutral glycosphingolipid found in Microcosmus sulcatus containing a β-d-Galp(1→4)[α-d-Fucp-(1→3)]β-d-Glcp-(1→)Cer motif was synthesized. Trisaccharide derivatives were synthesized using trimethylsilyltrifluoromethanesulfanate (TMSOTf) and N-iodosuccimide (NIS)/trifluoromethane sulfonic acid (TfOH) as the promoters. Synthesis was achieved with an efficient one-pot glycosylation strategy. This is the first report of a one-pot glycosylation strategy using the procedure of Boons et al. for the synthesis of a natural product. Coupling of trisaccharide derivative 19 and ceramide derivative 20 by TMSOTf afforded the glycosphingolipid derivative 21. The fully protected glycoside was deprotected to give the target glycosphingolipid 2. 相似文献
63.
64.
The formation processes of α-Keggin-type [H2W12O40]6− and [H3W12O40]5− complexes were investigated in aqueous WVI (0.05–0.50 M) solutions. The formation of [H2W12O40]6− was ascertained by the appearance of a 183W NMR line at −117 ppm, but no evidence was found for the existence of [H3W12O40]5− in the solution at the accessible pH range. The addition of (CH3)4N+ (Me4N+) to the WVI solution directly precipitated the (Me4N)6[H2W12O40] salt. On the other hand, the addition of the larger Bu4N+ cation precipitates the (Bu4N)4.5H0.5[H3W12O40] salt, because a naked proton formed during the crystallization process or in the solid state may enter into the Keggin shell to produce [H3W12O40]5−. This explanation is based on the fact that [H2W12O40]6− is not spontaneously converted into [H3W12O40]5− in acidified aqueous solution. On the basis of their voltammetric properties, a simple diagnostic criterion was developed to distinguish between [H2W12O40]6− and [H3W12O40]5−. 相似文献
65.
Sato S Tsunoda M Suzuki M Kutsuna M Takido-uchi K Shindo M Mizuguchi H Obara H Ohya H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,71(5):2030-2039
Various hybrid compounds comprised of two types of nitroxide radicals and either a pentamethine (Cy5) or trimethine cyanine (Cy3) were synthesized. The nitroxide radicals were linked either via an ester-bond to one or two N-alkyl carboxyl-terminated groups of Cy5, or via two amido-bonds (aminocarbonyl or carbonylamino group) to the 5-position of the indolenine moieties of Cy5 and Cy3. Changes in fluorescence and ESR intensities of the hybrid compounds were measured before and after addition of Na ascorbate in PBS (pH 7.0) to reduce the radicals. Among the hybrid compounds synthesized, those that linked the nitroxide radicals via an aminocarbonyl residue at the 5-position of the indolenine moieties on Cy5 and Cy3 exhibited a 1.8- and 5.1-fold increase in fluorescence intensity with the reduction of the nitroxide segment by the addition of Na ascorbate, respectively. In contrast, fluorescence intensity was not enhanced in the other hybrid compounds. Thus, the hybrid compounds which exhibited an increase in fluorescent intensity with radical reduction can be used in the quantitative measurement of reducing species such as Fe(2+) and ascorbic acid, and hydroxyl radicals. Because these hybrid compounds have the advantage of fluorescing at longer wavelengths-661 (Cy5) or 568 (Cy3)nm, respectively, they can be used to measure radical-reducing species or radicals either in solution or in vivo. 相似文献
66.
67.
Kakiuchi N Fukuda K Nishikawa F Nishikawa S Shimotohno K 《Combinatorial chemistry & high throughput screening》2003,6(2):155-160
Hepatitis C virus is one of the causative agents of non-A non-B hepatitis. Since one of viral proteins, NS3, has serine protease activity indispensable for virus maturation. NS3 serine protease is considered to be a suitable target for anti-HCV reagents. We report an assay of HCV NS3 protease in living cells. We designed peptide substrates bearing one of the sequences of HCV NS3 protease cleavage sites sandwiched with fluorescent proteins CFP and YFP. Substrates were expressed and cleaved efficiently in HeLa cells by cotransfection with HCV NS3 protease. The relationship between the progress of cleavage reaction and the change in fluorescence of the substrate emitted from living cells was confirmed. As a group of candidates for inhibitor of HCV NS3 protease, we chose RNA aptamers, nucleic acid ligands selected from a completely random RNA pool by in vitro selection. We found that 3 classes of aptamers, G9-I, II and III, bound NS3 protease specifically and inhibited cleavage in vitro. We studied the effect of RNA aptamers introduced into HeLa cells. The addition of G9-II RNA in the medium at a concentration of 2.5 micro g/ml reduced cleavage by one-third that of control. 相似文献
68.
Hashimoto Y Waki I Yoshinari K Shishika T Terui Y 《Rapid communications in mass spectrometry : RCM》2005,19(2):221-226
We report a new hybrid mass spectrometer, which is a combination of a quadrupole ion trap and an orthogonal time-of-flight (TOF) mass spectrometer. This new configuration consists of a collisional-damping chamber (CDC) inserted between an MSn-capable ion trap and a high-mass-accuracy orthogonal-TOF mass spectrometer. Because the CDC converted an ion packet into an energy-focused and quasi-continuous beam, a high mass resolution of over 10,000 and a high mass accuracy of better than 3 ppm were achieved. Moreover, the ratio of the maximum detectable m/z to the minimum detectable m/z, which is referred to here as the mass window, was improved to more than 10. 相似文献
69.
A heterogenized Pd catalyst, Pd(II)-hydrotalcite (palladium(II) acetate-pyridine complex supported by hydrotalcite) catalyzes the aerobic oxidation in toluene of a variety of primary and secondary alcohols into the corresponding aldehydes and ketones in high yields using atmospheric pressure of air as a sole oxidant under mild conditions. This catalyst is also effective for the oxidation of allylic alcohols, especially such as geraniol and nerol, without any isomerization of an alkenic part. The catalyst can be easily prepared from all commercially available reagents and reused several times. 相似文献
70.
Masao Tomoi Yasunori Hosokawa Hiroshi Kakiuchi 《Journal of polymer science. Part A, Polymer chemistry》1984,22(6):1243-1250
The rate of reaction of alkyl halides with aqueous sodium acetate or cyanide catalyzed by phosphonium salts supported on insoluble polystyrene resins, and rates of ion-exchange of the chloride ion in the catalysts against the acetate ion, were studied as a function of catalyst particle size, the percentage of ring substitution, the morphology of polymer support, and distance between active site and polymer backbone. Rates of 1-bromooctane or benzyl chloride with macroporous, 7–25% ring-substituted catalysts increased with increasing ring substitution. Rates with macroporous catalysts increased as a heptamethylene spacer was introduced between the active site and the polymer backbone. Rates of ion-exchange with macroporous catalysts were facilitated with increasing ring substitution or by the introduction of the spacer chain. A relation between the catalytic activity of macroporous or microporous catalysts and ion-exchange rates under triphase conditions was discussed. 相似文献