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991.
Densities have been measured for the electrolyte (NaCl, NaBr and NaI)‐monosaccharide (D ‐mannose and D‐ribose)‐water solutions at 298.15 K. These data have been used to calculate the apparent molar volumes of the saccharides (VΦ,S) and electrolytes (VΦ,E) in the studied solutions. Infinite dilution apparent molar volumes, VΦ,S0 and VΦ,E0, have been evaluated, together with the standard transfer volumes of the saccharides (ΔtVS0) from water to aqueous electrolyte solutions and those of the electrolytes (ΔtVE0) from water to aqueous saccharide solutions. It was shown that both the ΔtVS0 and ΔtVE0 values are positive and increase with increasing molalities of sodium halides and saccharides, respectively. Overall, the ΔtVS0 and ΔtVE0 values have the order of NaCl > NaBr > NaI except for NaI‐ribose and NaI‐ribose. Volumetric interaction parameters for the electrolyte‐monosaccharide pairs in water were obtained and interpreted by the stereochemistry of the monosaccharide molecules and the structural interaction model. 相似文献
992.
Kang EJ Cho EJ Ji MK Lee YE Shin DM Choi SY Chung YK Kim JS Kim HJ Lee SG Lah MS Lee E 《The Journal of organic chemistry》2005,70(16):6321-6329
(+)-SCH 351448 (Na+ salt A) was synthesized employing ring-closing olefin metathesis reaction of an open diene diester intermediate for construction of the 28-membered macrodiolide structure. The open diene diester was prepared from the monomeric hydroxy carboxylic acid and two different olefin fragments. The monomeric hydroxy acid was synthesized via Julia-Julia coupling reaction of intermediates derived from the same olefinic fragments. Oxane units in these fragments were prepared by radical cyclization reactions of beta-alkoxyacrylates. Analogous SCH 351448 salts incorporating other mono- and divalent cations may be prepared. Under acidic conditions, SCH 351448 (Na+ salt A) was the most stable complex, but SCH 351448 (Ca2+ salt) and (Na+ salt B) appear to be physiologically important species. 相似文献
993.
Mesocellular polymer foams with uniform approximately 17 nm cellular pores were fabricated using mesocellular silica foams as inorganic templates. The mesocellular polymer foams have high surface areas up to approximately 600 m(2)g(-1) and pore volumes of 1.6 cm(3)g(-1). 相似文献
994.
Chai OH Lee HK Lee YC Lee MS Han EH Kim HT Song CH 《Experimental & molecular medicine》2005,37(5):408-417
Trimellitic anhydride (TMA) is widely used industrially to make epoxy and alkyd resins, plasticizers and surfactants. The purpose of this study was to investigate whether contact hypersensitivity (CHS) is induced by repeated TMA challenge and the role of TNF-alpha and IgE in the TMA-induced CHS. The repetition of the challenge enlarged the extent of an early and a late phase of CHS in TNF-alpha+/+ (B6129SF2/J) and Balb/c mice. In the late phase of TMA-induced CHS, the peak of ear swelling responses by single challenge showed at 24 h after challenge, but the peak was observed at 8 h after repeated challenge. In the TNF-alpha knockout TNF-alpha-/- (B6;129S-Tnftm1Gk1) mice, the repetition of the TMA challenges enlarged the extent of the late phase of CHS, but less than those in TNF-alpha+/+ mice. Injection of anti-TNF-alpha antibody into the peritoneal cavity of Balb/c mice significantly decreased the extent of the late phase of CHS. Subcutaneous injection of anti-IgE antibody into Balb/c mice also decreased the extent of the late phase of CHS in dose-dependent manner. Histologically, infiltration of polymorphonuclear leukocytes and eosinophils was more pronounced in repeatedly TMA-challenged TNF-alpha+/+ and Balb/c mice than in the TNF-alpha-/- mice and anti-TNF-alpha or anti-IgE antibodies treated Balb/c mice. These results indicate that mice sensitized by TMA could possibly offer a useful model to study the mechanism of CHS, and TNF-alpha and IgE may act as potential modulators in the late phase of TMA-induced CHS. Neutralization of TNF-alpha and IgE by anti-TNF-alpha or anti-IgE antibodies may provide therapeutic tools for the treatment of TMA-induced CHS. 相似文献
995.
A new synthetic route for biologically interesting benzochromenes was developed starting from naphthalenols and α,β‐unsaturated aldehydes in the presence of ethylenediamine diacetate. This methodology was applied for the total synthesis of the biologically important natural products lapachenole, dihydrolapachenole, and mollugin with a benzochromene moiety. 相似文献
996.
The reaction between Cr(CO)5[C6H6] and ethyl diazoacetate (EDA) has been studied using the technique of laser flash photolysis. Results indicate that the Cr(CO)5 fragment reacts very rapidly with the EDA ligand. Low temperature spectroscopic studies suggest that in the case of W(CO)5, and by analogy also in the case of Cr(CO)5, the initial adduct between the pentacarbonyl fragment and EDA is one where the oxygen atom of the diazocarbonyl ligand is bound to the metal center. This kinetic product is then converted to a thermodynamically favored complex which is tentatively assigned as the nitrogen bound W(CO)5-EDA complex that appears to be stable at r.t. 相似文献
997.
Mao-Peng Lin Haeng-Boo Kim Tomiki Ikeda Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1992,30(11):2365-2369
Benzyl cation was detected by transient absorption spectroscopy with a spectroscopic multichannel analyzer on pulse excitation (fourth harmonic of Nd:YAG laser, 266 nm; 10 ns fwhm) of benzyl(4-hydroxyphenyl) methylsulfonium hexafluoroantimonate(BSS) in 1,2-dichloroethane (EDC). The benzyl cation was long-lived (lifetime, 59 ms) at room temperature and quenched by a vinyl ether compound. The formation of the benzyl cation as active species on photolysis of BSS is in contrast to the formation of Brønsted acids in other sulfonium salts so far reported. © 1992 John Wiley & Sons, Inc. 相似文献
998.
This paper presents the synthesis of some novel acyclonucleosides containing 2‐pyridinones and 2‐hydroxyethoxymethyl, 2,3‐dihydroxy‐propyl side chain. The tosylate of these nucleosides analogues could be modified to azido derivatives. Also, acyclonucleosides with 1‐ethoxymethyl, 1‐benzyloxymethyl, 1‐methylthiomethy 1 and 2‐hydroxyethyl side chains have been investigated. The O‐alkylated pyridine derivatives were obtained during most reactions. 相似文献
999.
[reaction: see text]. Highly enantioenriched quaternary centers are obtained by the reaction of chiral lithiated intermediates complexed to (-)-sparteine with tetrasubstituted, alpha,alpha-dinitrile activated olefins. Lithiated N-Boc-N-Aryl benzylamine furnishes products with drs from 78:22 to 95:5, with ers exceeding 94:6. Lithiated N-Boc-N-Aryl allylamine reactants provide enecarbamate products with drs from 55:45 to 99:1, with ers ranging from 87:13 to 97:3. 相似文献
1000.
The separation of wide molecular mass (Mr) ranges of macromolecules using frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) has been improved by implementing a combination of field and flow programming. In this first implementation, field strength (governed by the cross flow-rate through the membrane-covered accumulation wall) is decreased with time to obtain faster elution and improved detection of the more strongly retained (high Mr) materials. The channel outlet flow-rate is optionally held constant, increased, or decreased with time. With circulation of the flow exiting the accumulation wall to the inlet frit, the dual programming of cross flow and channel outlet flow could be implemented using just two pumps. With this flow configuration, the channel outlet flow-rate is always equal to the channel inlet flow-rate, and these may be programmed independently of the cross flow-rate through the membrane. FI-AFlFFF retains its operational advantage over conventional asymmetrical flow FFF (AFlFFF). Unlike conventional AFlFFF, FI-AFlFFF does not require time consuming, and experimentally inconvenient, sample focusing and relaxation steps involving valve switching and interruption of sample migration. The advantages of employing dual programming with FI-AFlFFF are demonstrated for sets of polystyrene sulfonate standards in the molecular mass range of 4 to 1000 kDa. It is shown that programmed FI-AFlFFF successfully expands the dynamic separation range of molecular mass. 相似文献