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  • 1
    ISSN: 1572-8870
    Schlagwort(e): Phosphazenes ; coordination chemistry ; synthesis ; electrochemical behavior ; transition metal ; cinnamonitrile cyclophosphazene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Hexakist 4-formylphenoxy cyclophosphazene (1) reacts with six equivalents of cyanomethylenetriphenylphosphorane to give hexakist 4-cinnamonitrile cyclotriphosphazene bearing 12 functional groups tsix nitriles and six olefins' able to coordinate up to 12 metals. In this way a series of polynuclear phosphazene metal derivatives (8–12) was prepared with different transition metals and in different oxidation states. Pt(0), Pt(II) and Rh(I). The analogous cinnamonitrile derivatives (3–7) were prepared and used as models for the characterization of corresponding phosphazene compounds. The redox properties of the complexes3–5 and8–10 as well as of the free cinnamonitrile2 and the free substituted cyclophosphazene1 have been investigated by cyclic voltammetry (CV) and controlled potential electrolysis (CPE) in aprotic media (THF, CH2Cl2, or NCMe 0.2M [NBu4][BF4]), at Pt electrodes. Cathodic processes have been detected only when the unsaturated C=C bond of the cinnamonitrile group is uncoordinated: hence, for compounds1. 4. and9. they are irreversible occur at potentialsE p red ca. −1.3 to ca. −1.9V vs SCE which are less cathodic than that exhibited by the free cinnamonitrile (2:E p red ca. −2.0 V vs SCE), and are believed to be centered at the electron-acceptor emptyπ * (C=C) orbital of each of the cinnamonitrile groups present in the molecule. Anodic processes are displayed only by complexes3. 5. 8. and10 with at least one Pt(0) site: they are irreversible, conceivably centered at such a metal center, and occur at potentials (E p bv ca. 0.7 1.2 V vs SCE) which are dependent on the electronic effects of the ligands, in particular the strong electron-withdrawing ability of the cyclophosphazene group. Complex10 undergoes dissociation in NCMe to form9 and possibly solvated [Pt(PPh3)2] species which adsorb at the electrode surface. No evidence for any redox process centered at the phosphazene ring has been found.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inorganic and organometallic polymers and materials 5 (1995), S. 123-133 
    ISSN: 1572-8870
    Schlagwort(e): Multifunctional polymer ; cyclolinear polycarbosiloxane ; polyvinyldimethylphenylsilane ; polyvinyldimethylchlorosilane ; replacement ; hydrolytic condensation ; synthesis ; characterization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Controlled synthesis of high molecular weight cyclolinear polycarbosiloxanes (PCCS) is considered, using the following reactions sequence: (1) anionic polymerization of vinyldimethylphenylsilane, (2) replacement of the Ph group in polyvinyldimethylphenylsilane (M n=83.900,M w/M n=1.48) by a Cl group to prepare polyvinyldimethylchlorosilane (PVMCS), and (3) hydrolytic intramolecular condensation of PVMCS. The formation of carbochain polymer with predominantly six-membered carbosiloxane rings is demonstrated (M n=81.400,M w/M n=1.54).
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inorganic and organometallic polymers and materials 8 (1998), S. 167-178 
    ISSN: 1572-8870
    Schlagwort(e): Poly(1,2-phenylenedithiocarbamate) ; poly(1,2-phenylenedithiocarbamate)–metal complexes ; synthesis ; characterization ; structure ; DC electrical conductivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Poly(1,2-phenylenedithiocarbamate) (PPDTC) was prepared by the reaction of 2-aminothiophenol with carbon disulfide followed by condensation through the removal of H2S gas. PPDTC was used as a ligand to prepare four poly(1,2-phenylenedithiocarbamate)–metal complexes of iron(II), cobalt(II), copper(II), and lead(II), by refluxing with the metal salts. The polymer and its metal complexes were investigated by elemental analyses, UV–visible and IR spectroscopy, inherent viscosity, and magnetic susceptibility. The DC electrical conductivity variation with the temperature in the range 298–498 K of PPDTC and its polymeric copper complex was measured. Both polymer and polymer metal complexes showed an increase in electrical conductivity with an increase in temperature: typical semiconductor behavior. The proposed structure of the complexes is (MLX2·mH2O) n .
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis surveys from Japan 3 (1999), S. 119-126 
    ISSN: 1572-8803
    Schlagwort(e): organozeolite ; microporous and mesoporous material ; inorganic-organic composite ; synthesis ; phosphonate ; aluminomethylphosphonate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Attempts in developing organozeolites, namely microporous and mesoporous crystalline inorganic-organic composites with a zeolite-like three-dimensional framework and organic moieties covalently connected to the framework, are briefly reviewed. MCM-41 type mesoporous materials modified by organic functional groups have been prepared by use of organosiloxane as a part of Si sources and by post-modification of the purely inorganic materials using organosiloxane. Also, the incorporation of organic moieties into the zeolite frameworks has been tried. Recently, several novel metal organophosphonates with a three-dimensional framework, which can be regarded as organozeolites, have been prepared. Along with these new attempts, the authors' studies in preparation, structural analysis and gas adsorption properties of microporous aluminomethylphosphonates are introduced.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    BioMetals 9 (1996), S. 377-383 
    ISSN: 1572-8773
    Schlagwort(e): chrysobactin ; Erwinia chrysanthemi ; immunoassay ; siderophore ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Chrysobactin (α-N-(2,3-dihydroxybenzoyl)-d-lysyl-l-serine), a siderophore that is essential for systemic virulence by plant pathogenic Erwinia chrysanthemi, was synthesized with high diastereomeric purity. Chrysobactin was prepared by coupling the N-hydroxysuccinimide ester of α-N-(2,3-dibenzyloxybenzoyl)-ε-N-Cbz-d-lysine with l-serine benzyl ester followed by deprotection via hydrogenolysis. Optically pure chrysobactin was obtained with 98% overall yield. A monoclonal antibody to ferric chrysobactin was developed and characterized as IgM. The antibody reacts with chrysobactin, ferric chrysobactin and less strongly with ferric dihydroxybenzoic acid. The antibody reacts weakly with the siderophores ferrichrome, A, ferric pseudobactin and ferric rhodotorulic acid. This antibody was used in a competitive immunoassay to detect ferric chrysobactin at 10−8 to 10−10 mol. This immunoassay may provide a useful method for the detection of chrysobactin in plant samples.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inorganic and organometallic polymers and materials 7 (1997), S. 1-18 
    ISSN: 1572-8870
    Schlagwort(e): Alternating copolymers ; cis and trans stilbenes and oligomeric dimethylsilylenes ; synthesis ; spectral properties ; photoisomerization and degradation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A series of perfectly alternating copolymers containing oligomeric dimethylsilylene and cis or trans stilbene units has been prepared by the condensation polymerization of silyl ditriflates with the corresponding stilbene dianion. As expected, the spectral characteristics and the polymer processability were very different for the isomeric polymers. Evidence of σ–π interaction was obtained from absorption measurements and the excited state of the Si4 catenates was characteristic of a polar charge transfer state. The polymers are all photoactive and irradiation in the long-wavelength absorption band leads to cis–trans isomerization followed by complete disappearance of the long-wavelength (λ〉300 nm) absorption. The latter was not observed for the monomeric model compounds.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inorganic and organometallic polymers and materials 9 (1999), S. 63-77 
    ISSN: 1572-8870
    Schlagwort(e): Octamethylcyclo-di(meta-silphenylenesiloxane) ; poly(silphenylene-siloxane) ; synthesis ; X-ray structure ; 4-dimethylaminopyridine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Octamethylcyclo-di(meta-silphenylenesiloxane) 1 (cyclic meta-dimer) was synthesized from 1,3-bis(dimethylhydroxysilyl)benzene 7 in a dilute THF solution, in the presence of a catalytic amount of 4-dimethylaminopyridine (DMAP). In contrast, only small amounts of the cyclic meta-dimer 1, cyclic meta-trimer 2, cyclic meta-tetramer, etc. were obtained when the condensation reaction was carried out with the catalyst n-hexylamine 2-ethylhexoate or sodium hydroxide. The major product in these reactions is polymer 8. The structure of compound 1 was confirmed by X-ray crystallography. This cyclic molecule is most likely unstrained since the X-ray structure reveals that the Si–O–Si bond angle is 142.1(1)° which is similar to that in most unstrained siloxane compounds.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Topics in catalysis 4 (1997), S. 249-260 
    ISSN: 1572-9028
    Schlagwort(e): mesoporous materials ; synthesis ; pore size ; activity ; selectivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The development of ordered mesoporous solids is revised. Acid, base, and redox catalytic properties are presented together with their application for a series of organic reactions of fundamental and practical interest. Finally it is explained that it is possible to make use of the high surface and regular porosity of MCM–41 to prepare supported metals, and bifunctional catalysts. The above properties together with the presence of a large number of surface silanol groups allow the grafting of catalytically active transition metal complexes.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1572-8773
    Schlagwort(e): Gram-negative bacteria ; inositol ; mycobacteria ; siderophore analog ; synthesis ; tricatecholate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract A novel 1,3,5-triamino-myo-inositol derivative ispresented as a readily available scaffold for the design oftripodal siderophore mimetics.Based on this scaffold, various hexadentate catecholate-type siderophoreanalogs weresynthesized by attaching the catechols to the inositol scaffold via spacer units of differentstruc-tureand length. The potential to tune the polarity of the inositol containing siderophoreanalogs has also beendemonstrated by varying the protection group strategy. The siderophoreactivity of the prepared siderophoreanalogs was examined by cross-feeding tests withvarious Gram-negative bacteria and mycobacteria.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 38 (1996), S. 245-249 
    ISSN: 1572-879X
    Schlagwort(e): ferri-silicate ; gallo-silicate ; zeolites ; molecular sieves ; synthesis ; mesitylene isomerization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Ferri- and gallo-silicate analogues of NCL-1, a high silica large pore zeolite, have been synthesized and characterized through spectroscopic methods (XRD, IR, ESR and solid state MAS NMR), ion exchange capacity, adsorption (n-hexane, 1,3,5-trimethylbenzene and water), BET surface area and catalytic activity and selectivity in Brønsted acid catalyzed conversion of 1,3,5trimethylbenzene measurements. These data were compared with those exhibited by Al-NCL-1 analogue. During 1,3,5-trimethylbenzene (mesitylene) isomerization into 1,2,4-trimethylbenzene (pseudocumene), the conversion decreased in the order: Al〉 Ga-〉 Fe-NCL-1 (at the same reaction temperature, WHSV and time on stream). However, the selectivity for pseudocumene and isomerization selectivity (vis-á-vis disproportionation) followed the reverse order at comparable conversion level.
    Materialart: Digitale Medien
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  • 11
    ISSN: 1572-8803
    Schlagwort(e): pyridine bases ; synthesis ; catalyst ; pentasil zeolite ; ZSM-5 ; shape selectivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Pyridine bases are widely used in pharmaceuticals, insecticides, and herbicides due to their high bioactivity. In this paper, in addition to the conventional synthesis methods for pyridine bases, recent advances in the gas phase synthesis of pyridine bases over the shape selective catalysts (ZSM-5) are described.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 11 (1998), S. 155-158 
    ISSN: 1572-9605
    Schlagwort(e): Tl based superconductors ; synthesis ; phase formation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract Polycrystalline (Tl,Bi)(Sr,Ba)2Ca2Cu3Ox (Tl,Bi-1223) samples were synthesized by mixing the precursor with 5wt% micrometer-size LaAlO3 or LSAT particles. These particles appeared to provide suitable surface for epitaxial growth of Tl,Bi-1223 phase. The growth zone is typically 5 - 10 μm thick and several zones can coalesce to form a larger zone. Consequently, there is a dramatic increase in the magnetization signals, indicating the increased superconducting volume fraction. The enhancement is uniform in the external magnetic field. The Tc of the samples was not affected by the additives and the transition remained sharp. The results suggest that a controlled growth of Tl-1223 grain with improved texture can be achieved by adding the growth centers.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 393-401 
    ISSN: 1572-8943
    Schlagwort(e): dinuclear Ni(II) complex ; non-isothermal kinetics ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Crystal of the complex Ni2L (ClO4)2 was obtained by reaction of Ni(ClO4)2 and macrocyclic ligand H2L, where L2− is the dinucleating macrocycle with two 2,6-di(aminomethyl)-4-methyl phenolate entities combined by the same two lateral chains, –(CH2)2–NH–(CH2)2–, at the amino nitrogens. The thermal decomposition processes of the title complex were studied in a dynamic atmosphere of dry argon using TG-DTG. The kinetic analysis of the first and second thermal decomposition steps were performed via the TG-DTG curves, and the kinetic parameters were obtained from analysis of the TG-DTG curves with integral and differential methods. The most probable kinetic function was suggested by comparison of the kinetic parameters.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 785-793 
    ISSN: 1572-8943
    Schlagwort(e): double sulfates ; lanthanides ; synthesis ; thermal studies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract On evaporation at room temperature of an aqueous reaction mixture of Ln(III) sulfate and ethanolammonium sulfate in a molar ratio higher than 1∶16, crystal products with a waxy feel were obtained. They were identified by means of the X-ray powder diffraction patterns and it was concluded that they are isostructural. The results of elemental analysis and the mass losses by TG analysis indicated the formation of double sulfates with general formula: (HOCH2CH2NH3)4Ln2(SO4)5·4.5H2O (Ln=La, Ce, Pr or Nd) Their thermal decompositions in static atmosphere in the temperature range from ambient up to 1173 K took place in a similar way, and mainly Ln2O2SO4 was obtained as final product. The exception was the Ce compound, which decomposed to CeO2. The double sulfates decomposed in many not well-differentiated steps. From the mass losses occurring during thermal decomposition, the mode of thermal decomposition was presumed. The X-ray powder diffraction patterns of Ln2O2SO4 (Ln=La, Pr and Nd) show that they are also isostructural.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 53 (1998), S. 285-296 
    ISSN: 1572-8943
    Schlagwort(e): alanine ; complexes of rare earth bromides ; synthesis ; TG-DTG ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The complexes of rare earth bromides with alanine, REBr3·3Ala·nH2O (RE=Ce, Pr, Sm, Eu, Gd and Tb, n=3; RE=Dy and Y, n=2.5 Ala=alanine), were prepared and characterized by means of chemical analysis, elemental analysis, molar conductivity, thermogravimetry, IR spectra and X-ray diffraction. The thermal decomposition in N2 of these complexes was studied by means of TG-DTG techniques from ambient temperature to 1000°C. During heating, the hydrated complexes of Ce, Pr and Y lose waters in one step, but the hydrated complexes of Sm, Eu, Gd, Tb and Dy lose waters in two steps. Then anhydrous complexes lose 2.5 alanine molecules except the complexes of Eu which lose three alanine molecules. Apparently, only be complex of Eu has an intermediate, EuOBr. All complexes finally decompose to oxides.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 53 (1998), S. 577-584 
    ISSN: 1572-8943
    Schlagwort(e): nicotinamide ; phenazone ; synthesis ; thermal decomposition ; zinc complex
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract New zinc complex compounds of general formula ZnL2,X2 {X=CI, Br; L=phenazone(phen), nicotinamide(nam)} were synthesized. The new compounds were characterized by elemental analysis, IR spectroscopy and DTA, TG/DTG methods. Thermal properties of the new compounds were investigated. It was found that nicotinamide, phenazone and ZnCl2 or ZnBr2 are released during the thermal decomposition of the compounds. Mass spectroscopy has been used for the determination of the thermal decomposition intermediate products.
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  • 17
    ISSN: 1572-8951
    Schlagwort(e): Bichromophoric molecules ; intramolecular energy transfer ; synthesis ; fluorescence ; X-Ray structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The design, structures and spectral properties of a number of bichromophoric molecules are presented. These bichromophoric molecules are composed of an aromatic ring connected by two methylene chains to an α-diketone moiety. Both absorption and emission spectra can be attributed to a superposition of the individual spectra of the separate chromophores. The critical transfer radius for electronic energy transfer from the aromatic (donor) chromophore to the α-diketone (acceptor) chromophore was calculated from the spectral overlap between the fluorescence spectrum of the aromatic moiety and the absorption spectrum of the α-diketone moiety. The results show that this series of molecules is well suited for a mechanistic study of short-range intramolecular electronic energy transfer.
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  • 18
    ISSN: 1572-9001
    Schlagwort(e): X-ray structure ; benzoxazine ; synthesis ; potassium channel modulators
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract With the aim of discovering new molecules with K+ channel modulating properties, we have synthesized analogues of cromakalim, an important molecule which shows specific affinity toward the K+ channels, by replacing the benzopyrane ring with a benzoxazine moiety. As a part of this study, we have synthesized and characterized, in solution and in the solid state as well, the compound ethyl [2,2-dimethyl-6-(Δ2-thiazolin-2-yl)-4H-l,4-benzoxazin-3-one-4-yl]butyrate (V). This compound exhibits in the solid state the following parameters: molecular formula C19H24N2O4S, triclinic, space group $$P\bar 1$$ , Mw = 376.5, a = 12.581(3) Å, b = 5.485(4) Å, c = 14.612(2) Å, α = 91.85(2), β = 108.9(3), γ = 82.04(4), V = 944.7 Å3, Z = 2, d = 1.323 g·cm−3. We describe here the synthesis and discuss the solid-state conformation of this new molecule; when tested on rat aorta ring precontracted with phenylephrine, the compound showed a concentration-dependent relaxation comparable to that measured for cromakalin taken as reference drug.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 515-520 
    ISSN: 1572-8943
    Schlagwort(e): SiO2-aerogel ; synthesis ; thermal stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Aerogels are extremely porous high-tech materials based on inorganic oxides, especially silica. The paper describes synthesis and properties of SiO2-aerogel, and changes occurring during heating of SiO2-aerogel in the temperature range from 20 to 1000°C. Four thermoanalytical methods were used: Thermodilatometry, Differential thermal analysis, Thermogravimetry and Derivative thermogravimetry.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1255-1261 
    ISSN: 1572-8943
    Schlagwort(e): barium cerate ; oxalate coprecipitation ; proton conductor ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The decomposition process of barium, cerium and neodymium oxalates in air was investigated by DTA-TG. Decomposition of an oxalate coprecipitate precursor and formation of barium cerate were examined in air, N2 and CO2 atmospheres, respectively, by employing DTA-TG and XRD. The results showed that, in air, cerium oxalate could easily be decomposed to CeO2 below 350°C and Nd2O3 could be obtained at 670°C, while a high temperature of 〉1400°C was needed to obtain BaO. Although some amount of BaCeO3 was formed at 500°C in air, at 650°C in N2 and at 800°C in CO2, single perovskite phase of BaCeO3 could only be obtained at a much higher temperature.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Molecular and cellular biochemistry 173 (1997), S. 1-5 
    ISSN: 1573-4919
    Schlagwort(e): human ; cytotrophoblast ; syncytiotrophoblast ; culture ; iso-transferrins ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Transferrin (Tf) mRNA was recently demonstrated in rat and mouseplacental tissue. Rat placental cells were shown to secrete transferrin. Thecell type with which Tf mRNA was associated was not investigated. Wetherefore studied the ability of immunopurified human term cytotrophoblastcells in culture to synthesize Tf, by means of pulse-label experiments with35S-methionine and report that these cells do synthesize Tf. Tf mRNA wasdemonstrated in the cell lysates by means of RT-PCR. Tf isolated fromcytotrophoblast and syncytiotrophoblast cells was shown to be different fromboth maternal and fetal serum Tf with respect to the distribution ofisoforms as demonstrated by means of iso-electric focusing. The iso-electricpoints were found at lower pH values (pH 5.0-5.4), compared to theiso-electric points of maternal and fetal serum Tf, suggesting a higherdegree of sialylation and glycan chain complexity.
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  • 22
    ISSN: 1573-4919
    Schlagwort(e): apolipoprotein B ; synthesis ; secretion ; clearance ; nonsense ; mutation ; mRNA metabolism ; apoB48
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Low levels of cholesterol are protective against development of coronary artery disease. Heterozygous hypobetalipoproteinemic individuals expressing truncated apolipoprotein (apo)B as a result of mutation in the capob gene have low levels of cholesterol and apoB in their plasma. To study the molecular mechanism of low levels of apoB in these individuals, we employed a previously reported knock out mouse model generated by targeted modification of the apob gene. The heterozygous, apoB-100/B-81, mice express full length and truncated apoB, B-81, and have 20 and 35% lower levels of total cholesterol and apoB, respectively, when compared to WT (apoB-100/B-100) mice. The majority of the truncated apoB, B-81, fractionated in the VLDL- density range. The mechanism of low levels of apoB in B-100/B-81 mice was examined. Total hepatic apoB mRNA levels decreased by 15%, primarily due to lower levels of apoB-81 mRNA. Since apoB mRNA transcription rates were similar in B-100/B-100 and B-100/B-81 mice, low levels of mutant apoB-81 mRNA occurred by enhanced degradation of apoB mRNA transcript containing premature translational stop codon. ApoB synthesis measured on isolated hepatocytes decreased in B-100/B-81 mice by 35%, while apoB-48, apoE, and apoAI syntheses remained unchanged. Metabolic studies using whole animal showed a 32% decrease in triglyceride secretion rates, consistent with the apoB secretion rates. Inhibition of receptor-mediated clearance of apoB-81-containing particles resulted in greater relative accumulation of apoB-81 in plasma than apoB-100, suggesting enhanced clearance of apoB-81-containing particles. These results demonstrate that low levels of apoB in heterozygous hypobetalipoproteinemic mice occurs by low rates of apoB secretion, and increased clearance of truncated apoB. Similar mechanisms appear to contribute to low levels of apoB in hypobetalipoproteinemic humans.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Topics in catalysis 9 (1999), S. 13-34 
    ISSN: 1572-9028
    Schlagwort(e): boralites ; synthesis ; characterization ; isomorphous substitution ; boron
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The synthesis, physico-chemical characterization and catalytic activity of boron-containing molecular sieves (boralites) are reviewed and discussed. Incorporation of boron in the silica framework of several phases has been assessed by structural and spectroscopic evidence. Compared with the aluminosilicate parent compounds, boralites display weaker acid strength sufficient, however, for catalyzing several reactions.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Topics in catalysis 9 (1999), S. 59-76 
    ISSN: 1572-9028
    Schlagwort(e): synthesis ; silica zeolites ; framework density ; phase selectivity ; connectivity defects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Recent advances in the synthesis of all-silica and high-silica crystalline molecular sieves in fluoride media, with special regard to low framework density phases, are presented. The fundamental differences between the synthesis in hydroxide and fluoride media with respect to the properties of the materials obtained and the phase selectivity of the crystallization are discussed.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Topics in catalysis 9 (1999), S. 93-103 
    ISSN: 1572-9028
    Schlagwort(e): mixed-bonded ; aluminophosphates ; open-framework ; layered ; synthesis ; structure ; hydrothermal ; solvothermal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The structural features, the synthesis and the role of templates in the synthesis for mixed-bonded open-framework aluminophosphates and related layered materials will be reviewed in this article. These aluminophosphate materials differ from the (4,2)-connected aluminophosphates and zeolites in that they contain TO5 and/or TO6 primary building units or terminal T-O bonds (T stands for Al or P). The extra ligands for the TO5 and TO6 units in the aluminophosphates with framework Al/P = 1 are either bridging OH groups or H2O molecules in most cases whereas the terminal T-O bonds are either P-OH or P=O species with P=O bonds being prevalent in layered aluminophosphates. Most of TO5 or TO6 containing aluminophosphates are prepared using a cyclic amine or a diamine as the structure directing agent (template), and the aluminophosphates with Al/P〈1 or the layered materials tend to form from an alcoholic medium. Both synthetic conditions and templates play a critical role in determining the composition and structural feature of these materials.
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  • 26
    ISSN: 1573-1561
    Schlagwort(e): Eriocrania cicatricella ; Eriocrania sparrmannella ; Eriocraniidae ; Lepidoptera ; sex pheromone ; EAG ; GC-EAD ; mass spectrometry ; synthesis ; evolution ; (Z)-4-hepten-2-one ; (2R)-heptan-2-ol ; (2R)-(Z)-4-hepten-2-ol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Extracts from different body parts of adult femaleEriocrania cicatricella (Zett.) were tested for electrophysiological activity on conspecific male antennae. Extracts from the Vth abdominal segment, containing a pair of exocrine glands, elicited the largest electroantennographic response when compared to extracts of other body parts. Female extracts were analyzed by gas chromatography with simultaneous flame ionization and electroantennographic detection (EAD). The EAD active peaks were identified as (Z)-4-hepten-2-one, (2R)-heptane-2-ol, and (2R)-(Z)-4-hepten-2-ol by coinjection on a gas chromatography and by comparison of mass spectra with those of synthetic standards. In field tests, a blend of these three pheromone components was highly attractive to conspecific males, and a subtractive assay confirmed that the unsaturated alcohol is the major pheromone component, whereas no definite behavioral activity could be assigned to the ketone or the saturated alcohol. A bait containing the two alcohols withS-configuration was attractive to maleE. sparrmannella (Bosc), whereas no males ofE. cicatricella were found in these traps. The sex pheromone compounds inE. cicatricella are chemically similar to pheromones reported in Trichoptera and they are produced in homologous glands.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical ecology 25 (1999), S. 355-368 
    ISSN: 1573-1561
    Schlagwort(e): Calomyrmex sp. males ; mandibular gland secretion ; 3,5,6-trimethyltetrahydropyran-2-ones ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The relative configuration of a δ-lactone isolated from the mandibular gland extracts of Calomyrmex sp. males has been determined to be (3SR,5RS,6SR)-3,5,6-trimethyltetrahydropyran-2H-one after the synthesis of the four possible racemates and comparison of their mass spectra and gas chromatographic properties with those reported in the literature for the natural product.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 8 (1997), S. 831-836 
    ISSN: 1573-4846
    Schlagwort(e): aerogel ; silica-zirconia ; synthesis ; sintering ; pore distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A solution of zirconium propoxide stabilized by methoxyethanol is mixed with silicon ethoxide in ethanol and hydrolyzed by small amounts of neutral, basified or acidified water. The obtained silica-zirconia gel is dried in supercritical conditions, yielding an aerogel. The modifications of the aerogel porous texture as a function of chemical composition and thermal treatment are investigated using adsorption-desorption isotherms analysis, mercury porosimetry, electron-microscopy and X-ray diffraction.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 8 (1997), S. 831-836 
    ISSN: 1573-4846
    Schlagwort(e): aerogel ; silica-zirconia ; synthesis ; sintering ; pore distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A solution of zirconium propoxide stabilized by methoxyethanol is mixed with silicon ethoxide in ethanol and hydrolyzed by small amounts of neutral, basified or acidified water. The obtained silica-zirconia gel is dried in supercritical conditions, yielding an aerogel. The modifications of the aerogel porous texture as a function of chemical composition and thermal treatment are investigated using adsorption-desorption isotherms analysis, mercury porosimetry, electron-microscopy and X-ray diffraction.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 15 (1999), S. 201-209 
    ISSN: 1573-4846
    Schlagwort(e): sol-gel ; synthesis ; protoenstatite ; 29Si-NMR ; freeze-drying
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Three different magnesium silicate sols were prepared from Mg(OMe)2 and TEOS for which hydrolysis with H2O2 and H2O was under stoichiometric, stoichiometric, or over stoichiometric. Xerogels were prepared from the sols by simple evaporation, spray-drying, or freeze-drying. The freeze-dried precursor formed mostly protoenstatite, a high-temperature polymorph of enstatite (MgSiO3) that is generally not stable at room temperature; the other precursors formed mixtures of protoenstatite and clinoenstatite. The three xerogels and their calcined products were studied with XRD, HTXRD, BET, carbon analysis, TG/DTA and29 Si-NMR. Residual carbon was found to be an important factor in the crystallization, and 29Si-NMR spectroscopy was found to be a better tool than XRD to assess the phase purity of protoenstatite.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Molecular diversity 4 (1998), S. 149-153 
    ISSN: 1573-501X
    Schlagwort(e): combinatorial ; cyclic peptides ; cyclization ; dipeptides ; diversity ; macrocycles ; orthogonally protected lysine ; solid phase ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A simple and efficient synthesis of novel 14-membered macrocycles from a resin-bound orthogonally protected lysine residue is described. Reductive alkylation of the lysine α-nitrogen introduces the first diversity element. Acylation of the resultant secondary amine with an Fmoc-amino acid introduces the second diversity element providing a resin-bound protected di-peptide precursor. Removal of the Fmoc-group is followed by acylation with a succinic anhydride to introduce the final diversity elements. Removal of the methyltrityl-group from the amino group followed by macrocyclization provides the desired macrocycles, after TFA cleavage, in excellent yield and purity.
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 2623-2626 
    ISSN: 1573-9171
    Schlagwort(e): stannyl-substituted ; 1-germacyc lope nta- 2,4-diene ; stannyl-substituted 1-germacyclopent-3-ene ; synthesis ; reactivity ; photolysis ; germanium-tin bond cleavage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Previously unknown stannyl-substituted germanium heterocycles, 1, 1 -bis(trimethylstannyl) 2,3,4,5-tetraphenyl-l-germacyclopenta-2,4-dienc and 1,1-bis(trimethylstannyl)-3,4-dimethyl-1-germacyclopent-3-ene were synthesized, and their photolysis and chemical transformations were Studied.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 163-166 
    ISSN: 1573-9171
    Schlagwort(e): palladium ; carbonylphosphine clusters ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Several methods for the synthesis of the Pd38(CO)28L12 cluster (L = PEt3) by treatment of Pd10(CO)12L6 with CF3COOH-Me3NO, CF3COOH-H2O2, Pd(OAc)2-Me3NO, and Pd2(dba)3 mixtures (dba is dibenzylideneacetone) were proposed. The tri-n-butylphosphine analog, Pd38(CO)28(PBu3)12, was synthesized by the reaction of Pd10(CO)14(PBu3)4 with Me3NO. The reaction of Pd4(CO)5L4 with Pd2(dba)3 yields clusters with an icosahedral packing of the metal atoms, Pd34(CO)24L12 and Pd16(CO)13L9.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 1929-1932 
    ISSN: 1573-9171
    Schlagwort(e): long-chain diacetylenic acids ; N-pyridyl andN-pyrimidylamides of alkanediyni cacids ; long-chain derivatives of nitroxyl radicals ; synthesis ; monolayers ; Langmuir-Blodgett films
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Acyl derivatives of 2-aminopyridine, 2-aminopyrimidine, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl were obtained from long-chain diacetylenic acyl chlorides and the corresponding heterocyclic compounds. Spreading isotherms of monolayers on a water surface show that lengthening of the hydrocarbon chain and replacement of the pyridyl groups in these compounds by the more hydrophilic pyrimidyl groups render the films more condensed. Long-chain acyl derivatives of nitroxyl radicals form monolayers possesing a low collapse pressure. ESR spectra of Langmuir-Blodgett films of these radicals before and after photopolymerization were recorded.
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  • 35
    ISSN: 1573-9171
    Schlagwort(e): α,β-dehydro-α-amino acids ; Wittig-Horner reaction ; diastereoselectivity ; triethylamine ; (Z)-3-aryl-2-(carbobenzoxyamino)acrylates ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The Wittig—Horner reaction of CbzNHCH(CO2Me)P(O)(OMe)2 (1) with ArCHO (2) in the presence of Et3N as a base affords methyl (Z)-3-aryl-2-(carbobenzoxyamino)acrylates (3) with high degrees of diastereoselectivity (Z)/(E) 〉 10∶∶1. One recrystallization of the crude product is sufficient to obtain isomerically and chemically pure (Z)-3.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 2371-2374 
    ISSN: 1573-9171
    Schlagwort(e): silacyclobutanes ; ferrocenyl-derivatives ; 9-carbazolyl-derivatives ; fluoro-derivatives ; synthesis ; polymerization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The synthesis and polymerization of silacyclobutane derivatives with ferrocenyl, 9-carbazolyl, and pentafluorophenyl fragments in substituents have been carried out. The effect of the replacement of H atoms by F in pendant groups of the polysiltrimethylene main chain on the glass transition temperature has been studied.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 381-383 
    ISSN: 1573-9171
    Schlagwort(e): 2-alkoxyhexafluoropropyl-2-isocyanates ; synthesis ; ureas ; carbamates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A convenient preparative method for the synthesis of 2-alkoxyhexafluoropropyl-2-isocyanates is proposed. The reactions of the isocyanates with amines and alcohols are studied.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 1210-1214 
    ISSN: 1573-9171
    Schlagwort(e): copper carboxylates ; synthesis ; structure ; discotic mesomorphism ; phase transition ; textures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The synthesis, structure, and mesomorphism of a new series of copper carboxylates are described. The influence of periphery of the chelate node on the appearance of discophase is studied. A stacked hexagonal structure of copper erucate is proved. The effect of restructuring of the chelate node in this compound after its isothermic exposure, causing the loss of mesomorphism is revealed.
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  • 39
    ISSN: 1573-9171
    Schlagwort(e): alkylferrocenes ; alkylferrocenium cations ; synthesis ; cyclopalladation ; micellar media ; electrochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Absract Simple methods have been developed for the preparation of a series ofn-alkylferrocenes H(CH2) n Fc (n = 3, 5–8, or 12) based on Friedel-Crafts acylation of ferrocenes followed by reduction of the corresponding ketones with Zn amalgam. The properties of H(CH2) n Fc and the corresponding ferrocenium ions in micellar aqueous solutions and the behavior of water-soluble cations H(CH2) n Fc+ in the absence of micelles were studied by cyclic voltammetry. In all cases, the formal redox potentials of ferrocenes (E o′) increase linearly asn increases up to 8. Whether micelles are present or not, the corresponding correlation equation has the following form:E o′= α + βn, where β = 29 mV in all cases. The synthesis of (±)-1-ethyl-2-methylferrocene from racemic α-dimethylaminoethylferrocene is reported.
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 623-629 
    ISSN: 1573-9171
    Schlagwort(e): (S)-prolinol ; chiral 1-amino-1,3-dienes ; generation andin situ transformation ; chiral cyclohexa-1,3-dienes and hexahydronaphthalenes ; synthesis ; monoalkylidenemalonates ; [4+2] cycloaddition ; stereoselectivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 3-Methyl- and 3-phenylbut-2-enal in the presence of (S)-prolinol (0.1 eq.) in benzene or THF react with the acidic monoesters of alkenylidene, and arylmethylidene-, and alkylidenemalonic acids at −10 to +22 °C to give optically active esters of 4,6-disubstituted cyclohexa-1,3-diene-l-carboxylic acids in moderate (10–43 %) yields. The enantiomeric purity of the products formed from the lint two types of acidic ylidenemalonates varies from 28 to 68 % and is higher than that observed in the case of related alkylidenemalonates. Under similar conditions cyclohexylideneacetaldehyde affords optically active derivatives of 1,5,6,7,8,8a-hexahydronaphthalene as mixtures ofcis andtrans isomers. The enantiomeric purity and absolute configuration of the cyclohexadienes thus obtained were determined using1H NMR spectroscopy in combination with chiral solvating agents.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 654-661 
    ISSN: 1573-9171
    Schlagwort(e): crown ether styryl dyes ; synthesis ; complexation ; anion-“capped” complexes ; [2+2] photocycloaddition ; cyclobutane derivatives ; 1H NMR spectra
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract New crown ether styryl dyes (trans-1c,d) containing the 18-crown-6 ether fragment were synthesized. Interaction oftrans-1c,d dyes, as well as their analogs,trans-1a,b containing the 15-crown-5 ether fragment, with Ca(ClO4)2 in MeCN afforded supramolecular structures (dimeric complexes). Competing reactions,trans-cis-photoisomerization with the formation of anion-“capped” complexes ofcis-1a—d and [2+2] autophotocycloaddition with the formation of cyclobutane derivatives8a—d and9c, were observed on photolysis of solutions of complexes oftrans-1a—d with Ca2+. Preorganization oftrans-isomers in dimeric complexes with Ca2+ determined the regio- and stereoselectivity of each of the two directions of the photocycloaddition and the efficiency of the reaction.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 667-670 
    ISSN: 1573-9171
    Schlagwort(e): long-chain 2-alkadiynylpyridines ; synthesis ; Langmuir-Blodgett films
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Four pathways of synthesis of 1-(2-pyridyl)heptacosa-12,14-diyne, using 10-bromodecan-1-ol and acetylene or tetradec-1-yne and 2-methylbut-3-yn-2-ol along with α-picoline as initial compounds, were studied and compared. It was shown that direct introduction of a completely formed unsaturated hydrocarbon chain into an α-picoline molecule by alkylation of its lithium derivative is the most appropriate method for preparation of long-chain 2-alkadiynylpyridines.
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  • 43
    ISSN: 1573-9171
    Schlagwort(e): ansa-zirconocene dichlorides ; synthesis ; molecular structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A mixture ofrac- andmeso-2,2′-propylidene-bis(η5-indenyl)zirconium dichlorides was obtained in 95% yield. The compounds were separated, and their structures were established by X-ray structural analysis.
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  • 44
    ISSN: 1573-9171
    Schlagwort(e): sodium alkyls ; lithium alkyls ; NMR ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 1H,23Na, and7Li NMR spectra of 2-ethyl hexylsodiurn, 2-ethylhexyllithium, and isobutyllithium obtained in the reaction of the corresponding alkyl chlorides and metals have been recorded. The1H N MR signal for the protons of the CH2Na group is shifted upheld compared with that for the protons of the CH2Li group (doublets at δ -0.88 and δ -0.83, respectively). The composition of the products of reaction of 2-ethylhexyl chloride with sodium depends on the form of the metal reagent employed. The use of sodium balls with diameter up to 2 mm results in the formation of products containing ionic chlorine (30–50 % with respect to Na); the reaction with the dispersion proceeds faster and the reaction product is chlorine-free. The23Na NMR spectra of these substances are also different, which is explained by the formation of 2-ethylhexylsodium complexes with NaCl in the former case.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 901-910 
    ISSN: 1573-9171
    Schlagwort(e): carbofunctional silacyclobutanes ; alcohols ; trimethylsilyl ethers ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A four-step synthesis of 1-(ω-ydroxyalkyl)- and 1-(4-hydroxyphenyl)silacyclobutanes was carried out. The influence of the structure of the initial compounds and the reaction conditions on the ratio of the reaction products formed was studied. The stability of the silacyclobutane alcohols and the hydrolysis of their trimethylsilyl ethers were investigated.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 911-913 
    ISSN: 1573-9171
    Schlagwort(e): carbofunctional silacyclobutanes ; alcohols ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Speier rearrangement was used for the synthesis of l-(ω-hydroxyalkyl)- and l-(4-hydroxyphenyl)silacyclobutanes.
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  • 47
    ISSN: 1573-9171
    Schlagwort(e): 2-nitroethanol ; sodium salt ; 2-oxo-3-hydroxypropionic acid oxime ; sodium salt ; 2-bromo-2-nitropropane-1,3-diol ; 2,2-dinitropropane-1,3-diol ; synthesis ; X-ray analysis ; molecular structure, stereochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A novel reaction of the sodium salt of 2-nitroethanol in aqueous ammonia resulted in the sodium salt of 2-oxo-3-hydroxypropionic acid oxime (1) has been found. Bromination of1 affords 2-bromo-2-nitropropane-1,3-diol (2) with a previously unknown molecular conformation. The formation mechanisms of compounds1 and2 were suggested. X-ray analysis of products1,2 and that of the model compound, 2,2-dinitropropane-1,3-diol, was performed.
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  • 48
    ISSN: 1573-9171
    Schlagwort(e): metallofullerenes ; synthesis ; chirality ; platinum ; cluster ; electronic absorption spectra ; 31P NMR spectra ; X-ray analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A novel optically active exo-metallofullerene derivative, η2-C60Pt[(+)-DIOP] (1) (DIOP is 2,3-o,o'-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphinobutane)), is formed as a result of the cleavage of the chelate metallocycle in Pt[(+)-DIOP]2 and the substitution of the bidentate (+)-DIOP ligand with C60. Cluster 1 was also obtained by replacement of the phosphine ligands in η2-C60Pt(PPh3)2 by (+)-DIOP. Compound 1 was identified by its electronic absorption spectra,31P NMR spectra, and the elemental analysis data. A singlecrystal X-ray study of the 1 cyclooctene solvate, η2-C60Pt[(+)-DIOP] C8H14 was performed. Packing of the fullerene cores in a crystal of 1 · C8H 14 corresponds to the diamond structure subjected to the significant orthorhombic distortions.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 1232-1234 
    ISSN: 1573-9171
    Schlagwort(e): sterically hindered 2-propargyl-1,3-diketones ; aminomethylation ; synthesis ; copper(1) ; catalysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 2-Propargyl-substituted methoxy-1,3-diketones react with alkoxymethylamines or paraform and secondary amines in the presence of CuCl at the acetylene group to afford Mannich bases.
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 1490-1491 
    ISSN: 1573-9171
    Schlagwort(e): carborane-containing ketones and enols ; synthesis ; isoncrization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A carborane-containing stable simple enol — 1-2-isopropyl-o-carboran-I-yl)-1-phenyl2-mesityl-2-lrydroxyctlrylcne — has been synthesized. This enol does not isomerize to the starting ketone or keto-enol mixture even after prolonged heating in benzene in the presence of CF3COOH.
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  • 51
    ISSN: 1573-9171
    Schlagwort(e): arenecyclopentadienyl complexes of ruthenium ; synthesis ; electrochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A series of are necyc lope ntadienyl complexes,i. e., [Ru(η5-c5R5)(η6- are ne)]+ (1, R= H, arene = C6H6; 2, R = Me, arme = C6H6; 3, R = H, arctic = C6H3Me3; 4, R = Me, arene = C6H3Me3; 5, R = H, arene = C6Me6; 6, R = Me, arene = C6Me6) was studied by cyclic voltammetry. These compounds are capable of both oxidation and reduction. The reduction potential values depend on the number of methyl groups in the complex. Reduction of benzene complexes I and 2 by sodium amalgam in THF leads to the formation of decomplexation products, the addition of hydrogen to benzene, and dimerization of the benzene ligands. Both chemical and electrochemical reductions of mesitylene complexes3 and4 result in dimeric products [(η5-C5R5)Ru(μ-η5;η5-Me3H3C6H3Me3)Ru(η5-C5R5)] (14, R = H; 15, R = Me). The action of sodium amalgam on compound5 gives products of hydrogen addition to both hexamethylbenzene (17) and cyclopentadienyl (18) ligands along with the major product, the dimer [η5-C5H5)Ru(μ-η5; η5-Me6C6C6Me6)Ru(η5-C5H5)] (16). In contrast to5, its permcthylated analog 6 is only capable of adding hydrogen to the hexamethylbenzene ligand.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 1952-1954 
    ISSN: 1573-9171
    Schlagwort(e): reactivity ; synthesis ; (N,N-difluoroamino)dinitroacetonitrile ; 5-[(N,N-difluoroamino)dinitromethylltetrazole
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract High reactivity of the nitrite group in (NN-difluoroamino)dinitroacetonitrile was demonstrated. Based on its reaction with HN3, a new preparative method for the synthesis of 5-[(N,N-difluoroamino)dinitromethylltetrazole was developed; some derivatives of the latter compound have been obtained.
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  • 53
    ISSN: 1573-9171
    Schlagwort(e): tetraphenylantimony hydrogen phthalate ; synthesis ; X-ray structural study ; molecular structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Tetraphenylantimony hydrogen phthalate, Ph4SbOC(O)C6H4000H-o, was prepared by the reaction of pentaphenylantimony with phthalic acid. According to the data of X-ray structural analysis, the resulting compound is a trigonal-bipyramidal complex of antimony with three phenyl groups in equatorial positions; the fourth phenyl group and the carboxyl fragment are in axial positions. The CSbO angle is 177.5(1)° the Sb-C(Ph)eq and Sb-C(Ph)ax distances are 2.099(4)-2.177(4) A and 2.129(4) A, respectively. The H atom of the free carboxyl group and the carbonyl O atom of another carboxylate group form an intramolecular hydrogen bond.
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  • 54
    ISSN: 1573-9171
    Schlagwort(e): trinuclear iron carboxylate complexes ; synthesis ; X-ray structural analysis ; spectroscopy ; cyclic voltammetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Reactions of iron(m) salts with a new bidentate ligand, which is potentially capable of forming binuclear iron complexes upon complexation, were studied. Under various conditions, we succeeded in isolating only the trinuclear cationic complex (FeIII 3(O2CR)6(μ3-)17+ (1), where RCO2 is 2-(pyrid-2-ylmethoxy)benzoic acid protonated at the pyridyl moiety. The structure of 1 was established by spectral, magnetic, and X-ray structural studies. Cyclic voltammetry in McCN in the temperature range from -35 to 20 °C demonstrated that 1 undergoes successive FeIII→FeII reduction in three one-electron stages, which is indicative of the electronic interaction between iron atoms in the complex.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 2018-2019 
    ISSN: 1573-9171
    Schlagwort(e): trimethylarsine ; trimethylaluminum ; synthesis ; ecological safety
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A convenient, highly efficient, and environmentally safe procedure for the preparation of trimethylarsine was proposed. A quantitative yield of this compound in the reaction of As2O3 with AIMe3 was attained for the first time by using mechanochemical activation of the process.
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 1903-1906 
    ISSN: 1573-9171
    Schlagwort(e): (+)-4α-(1-trimethylsilyloxyethen-1-yl)-2-carene ; (+)-4α-acetyl-2-carene ; synthesis ; ozonization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract (+)-4α-(1-Trimethylsilyloxyethen-1-yl)-2-carene was synthesized, and the products of its ozonization were identified.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 1952-1954 
    ISSN: 1573-9171
    Schlagwort(e): synthesis ; hypercoordinated organogold(I) compound ; secondary bonds ; diphenylmethane ; X-ray diffraction analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Cyclic organogold $$| \overline {Au(o - C_6 H_4 )CH_2 (C_6 H_4 - o)Au(\mu - PPh_2 CH_2 CH_2 } \mathop P\limits^| Ph_2 )$$ complex, containing an Au...Au bond, was prepared by reaction of Ph3PAu(o-C6H4)CH2(C6H4-o)AuPPh3 with dppe. The length of the carbon bridge of the diphosphine ligand, optimal for formation of the Au...Au bond, was preliminarily determined using molecular simulation. The structure of the complex obtained was determined by X-ray diffraction analysis and by MS,1H NMR, and31P NMR.
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 1970-1970 
    ISSN: 1573-9171
    Schlagwort(e): tantalocene ; hydride ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Modified method for preparation of Cp2TaH3 by reaction between TaCl5, CpNa, and LiAlH4 in dimethoxyethane is described: The yield of Cp2TaH3 is 25 %.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 305-309 
    ISSN: 1573-9171
    Schlagwort(e): Key words ; (+)-3-carene ; dimethyl ester of (-)-(1R)-cis-homocaronic acid ; dimethyl ester of (+)-(1S)-cis-homocaronic acid ; synthesis ; ozonolysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The syntheses of the dimethyl ester of (-)-(1R)-cis-homocaronic acid (7 steps, overall yield 43 %) and its antipode, the dimethyl ester of (+)-(1S)-cis-homocaronic acid (5 steps, overall yield 27 %), were performed starting from (+)-3-carene and its derivatives, (+)-4α-acetyl-2-carene and (+)-4α-acetoxymethyl-2-carene. Oxidative cleavage in the key stages was carried out by ozonization.
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 1084-1086 
    ISSN: 1573-9171
    Schlagwort(e): pseudocyanines ; N-acryloyloxyethyl andN-alkyl derivatives ; quinolinium salts ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A new method for synthesis of 1-[(2-acryloyloxyethyl)- and 1-[(2-propenyl)-2-(2-(1H)-quinolidene)-methyl]-1-ethylquinolinium iodides was proposed. The structures of the dyes obtained were studied by1H NMR spectroscopy.
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  • 61
    ISSN: 1573-9171
    Schlagwort(e): hydrosilanes ; amines ; N-siloxycarbonylation ; carbon dioxide ; O-silylurethanes ; synthesis ; hexamethyldisilazane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The reaction of hydrosilanes with carbon dioxide and secondary amines or silylamines was studied for the first time. The dependence of the composition and the structure of the products obtained on the nature of the reagents and on the reaction conditions was found. The hydrosilane-carbon dioxide system, unknown previously, can be used as anN-siloxycarbonylating reagent in the synthesis ofO-silylurethanes. A scheme for the formation ofO-silylurethanes was proposed.
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 2196-2198 
    ISSN: 1573-9171
    Schlagwort(e): 4,4′-thiodiphenol ; diamide of phenylphosphonous acid ; crown ethers ; synthesis ; oligothioarylenecyclophosphonites ; structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A new representative of phospho(scIII)crown ethers was obtained based on 4,4′-thiodiphenol and tetraethyldiamide of phenylphosphonous acid. Thiaphospho(III)crown ethers can be prepared by different methods depending on the ratio of the initial reactants and the reaction conditions. The structures of the compounds obtained were confirmed by spectroscopic data and X-ray structural analysis.
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 99-101 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; High temperature open-tubular columns ; Solvent make-up ; Acetophenone oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Acetophnone, a substance stable at room temperature, is readily oxidizes in a high temperature open tubular liquid chromatographic system by the residual oxygen in the mobile phase. The oxidation product is less UV absorptive and detection sensitivity decreases greatly. To prevent the oxidation, through degassing of the mobile phase is necessary.
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  • 64
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Endotoxins ; Lipopolysaccharide ; Aminated poly(γ-methyl L-glutamate) ; Bovine serum albumin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method is described for the selective removal of endotoxins from various protein solutions using columns packed with aminated poly (γ-methyl L-glutamate) (PMLG-NH2) spheres. The PMLG-NH2 adsorbents showed a high adsorbing activity for endotoxins which had an ionic strength of μ=0.05–1.0 and pH 5.0–9.0. The endotoxin-adsorbing capacity per millitre of the wet adsorbent increased from 0.40 to 1.35 mg (E. coli O111: B4 LPS) at μ=0.2 and pH 7.0 while the aminogroup content of the adsorbent increased from 0.8 to 3.5 meq g−1. The PMLG-NH2-3.5 has an amino-group content of 3.5 meq g−1. This column packing selectively adsorbed endotoxins, without loss of the protein, from a γ-globulin or cytochromec solution which contained endotoxins at μ=0.05 and pH 7.0. On the other hand, when bovine serum albumin (BSA) was present in solution with endotoxins, both the endotoxins and the BSA were adsorbed by the column. The BSA-adsorbing activity increased with increasing amino-group content of the adsorbent. However, this undesirable adsorption was suppressed with increasing ionic strength of the buffer. As a result, when the packing which had an amino-group content of 1.5 meg g−1 was used in conditions of μ=0.2 and pH 7.0, the endotoxins were removed from a BSA-containing solution without affecting the recovery of the BSA.
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 51-57 
    ISSN: 1612-1112
    Schlagwort(e): Column electrophoresis ; Column liquid chromatography ; Phenolic lignin degradation compounds ; Sugar degradation products ; Quantitative analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method for the quantitative analysis of phenolic lignin degradation products by capillary electrophoresis (CE) with on-column UV detection has been developed. The liquid biomass solutions contain low molecular hemicellulosic sugars and phenolic lignin degradation products with various degrees of polymerization. Special attention has been paid to the monomeric phenolic components of lignin degradation fragments, e.g. derivatives of phenolic acids, aldehydes, and alcohols. Uncoated fused silica capillaries and borate-phosphate buffer systems at moderate pH conditions were used in order to separate the compounds of interest. To provide validation of the method, the same samples were analyzed independently by HPLC using gradient elution on a RP-C18 column. As sugar degradation fragment, furan-2-carboxylic acid was detected.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 85-90 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Phenolic compounds ; Ion-pair solid phase extraction ; On-line trace enrichment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two packing materials, C18 and PLRP-S, are studied for on-line trace enrichment of phenolic compounds in water. Various precolumns of different internal diameter are also tested and the addition of an ion-pair reagent to increase retention and thus, breakthrough volumes of phenolic compounds, is studied. Best results are obtained when a PLRP-S precolumn is coupled on-line with a C18 analytical column and DAD detector. Addition of TBA considerably increases breakthrough volumes. In contrast, when a C18 precolumn is used, breakthrough volumes are lower and it is impossible to determine TCP and PCP, under the experimental conditions used, because of interference of other nonpolar compounds in the samples. The performance of the system is evaluated with river and tap water and the preconcentration of 10 ml of sample in a PLRP-S precolumn involves a linear range between 1 μg 1−1 and 20 μl−1 and limits of determination between 0.5 μg l−1 and 1 μg l−1 are obtained.
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 631-637 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Trace analysis ; Pesticides in tap water ; Aromatic sulphonates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Methodology and instrumentation are described which allow chromatographic screening of water samples under substantially simplified conditions and at reduced cost. A single column is used to accomplish sample extraction, trace enrichment, and separation. The performance of such a system is demonstrated, and the results compared with conventionally used concepts.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 669-673 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Transchelation ; Zinc pyrithione and related compounds ; Antidandruff formulations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An analytical procedure has been developed for the determination of zinc pyrithione in antidandruff formulations. Zinc pyrithione was converted into a stable copper complex and then analysed by reversed-phase HPLC. The proposed method allows the separation of the analyte from related pyrithiones and therefore is able to verify the compliance of cosmetic preparations with current legislation.
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  • 69
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Benzodiazepines ; Solvent effects ; ACN clusters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two different methods were used to determine the separation factor α at different temperatures and the Gibbs-Helmholtz parameters (Δ(ΔH), Δ(ΔS)) of two adjacent benzodiazepines on a chromatogram were obtained from plots of lnα versus 1/T. We first studied each factor (fraction of water ϕ in the ACN/water mixture and column temperatureT), which controls the retention mechanism, and then we examined the simultaneous variation of all these factors. The changes in Δ(ΔH) and Δ(ΔS) in relation to a volume fraction of water ϕ in an ACN/water mixture were examined. In the ACN/water system, Δ(ΔH) was fairly constant in the acetonitrile region of ϕ≤0.52 and appears to be a roughly linear function of ϕ for ϕ≥0.52. In this system Δ(ΔS) is approximately a parabolic function of ϕ with an optimum at ϕ≅0.52. The retention mechanism of ten benzodiazepines was found to be significantly different in the methanol/water and ACN/water mixtures. The separation optimization of these ten benzodiazepines was then considered. A fraction of water of 0.43 in the ACN/water mixture and a column temperature of 44°C gave the most efficient separation conditions in the ACN/water mixture.
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  • 70
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Polyurethane degradation products ; 2,4- and 2,6-toluendiamine ; Urine analysis ; Breast implants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A reversed-phase HPLC method has been developed for the urinary determination of mutagenic 2,4- and 2,6-toluendiamines. These amines are degradation products of polyurethane, a material used to cover textured silicone breast implants. FMOC-Cl was used as fluorescent derivatising agent in order to obtain a limit of detection of 15 ng/ml in urine. Pre-treatment of urine samples was by liquid/liquid extraction and urine specimens of patients after surgury were analysed.
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 41 (1995), S. 657-660 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Polyphenols ; Flavonoids ; Phenolic acids and aldehydes ; Eucalyptus spp.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Standards of the polyphenols occurring in wood, bark and leaf extracts ofEucalyptus spp. (i.e. flavonoids and phenolic acids and aldehydes) have been analyzed by HPLC using reversed phase columns, gradient elution and diode-array detection. The conditions used are reported.
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  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 657-661 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Reversed phases ; Polyencapsulated silica ; Polyacrylates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary By copolymerization of silica modified with vinyl groups and acrylic acid esters in suspension highly efficient, polymeric-encapsulated stationary-phases can be prepared. The suspending liquid has to be selected such that the monomers are at least partially adsorbed on the surface and the polymer formed does not precipitate. Under these conditions stationary phases capable of speedy mass transfer can be prepared, where the reduced plate heights are between 2 and 3. The silica surface shielding is optimized so that basic and acidic solutes elute with symmetrical peak.
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  • 73
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chiral resolution of amino acids ; Pre-column derivatization ; Fluorescent chiral tagging reagents ; Stereochemical purity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Derivatization of amino acid enantiomers with fluorescent chiral Edman-type reagents, 4-(3-isothiocyanatopyrrolidin-1-yl)-7-nitro-2,1,3-benzoxadiazole [R(−)- and S(+)-NBD-PyNCS] and 4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole [R(−)-and S(+)-DBD-PyNCS], yields corresponding diastereomers separable by reversed-phase HPLC on normal achiral columns. The resolved diastereomers were detected fluorometrically at 530 nm with excitation at 490 nm for the NBD-PyNCS derivatives and at 560 nm with excitation at 450 nm for those derived from DBD-PyNCS reagents. This HPLC-derivatization method was used for evaluation of stereochemical purity for some synthetic commercial peptides. The enantioanalysis was reliable down to 0.05% racemization of the amino acid residues and a quantity of 100 μg peptide sample was usually enough for the analysis. Two acid hydrolysis methods, i.e. the standard procedure with constant-boiling hydrochloric acid (HCl) and a rapid vapor-phase procedure with HCl-trifluoroacetic acid (TFA) mixture, were compared. The later was found to be unsuitable owing to increased racemization of the amino acid residues during the hydrolysis. Judging from the results obtained for proline and leucine residues, most of the tested peptides including biologically active peptides, such as neurotensin, [d-Ala2,d-Leu5]-enkepharin and morphine tolerance peptide, possessed stereochemical purities higher than 98%. Influence of structural features of the peptides on the racemization of the amino acid residues was found to be significant.
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  • 74
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Mass spectrometric detection ; Fast atom bombardment ionization ; Serum bile acid ; Rat bile
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary In order to analyse bile acids in biological matrices, e.g. rat bile and human serum, high performance liquid chromatography (HPLC) was coupled to continuous-flow fast atom bombardment mass spectrometry (CFFAB-MS). A gradient elution system which had already proved to be well suited for the quantitative determination of conjugated bile acids in bile was modified to allow HPLC-CFFAB-MS-coupling. Due to the sensitivity of this coupling method it is possible to obtain more information about the biliary bile acid pattern and species-specific secondary bile acids. Furthermore, we were able to identify obviously unknown bile acid species in rat bile which most likely classify as mono-oxo and di-oxo-taurocholates (MW 513 Da, 511 Da) and mono-oxo-glycocholates (MW 463 Da). In the present study we show that using this system it is possible to determine both conjugated and unconjugated as well as sulfated bile acids, without time consuming group separation and derivatization, from rat bile and human serum. In addition, it is suggested that the method presented here should be considered for use in routine analysis.
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  • 75
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fluorescence enhancement ; Bovine serum albumin ; Dansylamino acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The effects of acetonitrile and bovine serum albumin (BSA) concentrations on the signal intensity and retention behavior of dansylamino acids have been examined by using γ-cyclodextrin-bonded silica gel as the stationary phase in microcolumn liquid chromatography. Fluorescence intensities of dansylamino acids were enhanced by BSA as a mobile phase additive, e.g., detection limits of dansyl derivatives of L-Ala and L-Phe were improved by a factor of 12–18.
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  • 76
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Micellar liquid phases ; Octanol-water partition coefficient ; Benzene and naphthalene derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary It is shown that the logarithm of the capacity factor (log k′) for fifteen benzene and naphthalene derivatives in micellar liquid chromatography with forty nine different mobile phases generally correlates better with the logarithm of the octanol-water partition coefficient (log Pow) than the capacity factor (k′). Optimum conditions are established to obtain the best linear correlations of log k′-log Pow.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 247-252 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Photolysis ; Electrochemical detection ; Drugs with chlorinated aromatic rings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Pharmaceuticals containing a thiazide ring or chlorinated aromatic ring were investigated with respect to enhanced selectivity in determination. Oxidative electrochemical detection coupled with HPLC was used to study the influence of the pH of the mobile phase under conditions of photolysis. To cover a pH range 3.9–12, the employment of a polymer column stable in alkaline media was necessary. The method offers the great advantage of derivatization without chemicals at low operating potentials, thereby providing high selectivity.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 296-302 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Structural isomer separation ; Cyclodextrin ; Polymers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Several β-cyclodextrin (CD)-bonded stationary phases for high performance liquid chromatography (HPLC) were prepared, based on silica beads coated with a poly(alkylamine), [poly(ethyleneimine)(PEI)]. In order to obtain stationary phases with a high content of CD and maximum accessibility of the CD cavity, the functionalization was carried out after the coating, using the mono-tosyl derivative of CD as the intermediate. The ability of these supports to separate ortho, meta and para isomers of some disubstituted benzene derivatives was examined. The contribution of the amino groups of the polymer and of the CD cavity to the separation process is discussed. The resolution is mainly based on the difference in the stability of the complexes of the various isomers with CD. The influence of the amount of CD on the height of the theoretical plate is also studied.
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  • 79
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Reversed phase ; Polystyrene ; Pellicular ; Ultra high molecular mass
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Ultra high molecular mass (〉 7 million dalton) polystyrenes are prone to degradation in size exclusion chromatography. In gradient elution reversed phase HPLC they do not elute visibly on small particle size porous supports. However, large diameter C18 pellicular particles were successfully employed for reversed phase study of ultra high molecular mass (15 million dalton) polystyrenes without polymer degradation during elution. Although retention for the lower molecular mass polystyrenes was lower than on small diameter porous particles, the medium high molecular mass polystyrenes (0.5–1 million dalton) showed similar retention. The addition of small diameter porous particles in small quantities, to the large diameter pellicular particles, increased the amount of retention of the low molecular mass polystyrenes without affecting the higher molecular mass polystyrenes.
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  • 80
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Methyl ethyl ketone in urine ; Derivatization ; 3-Methyl-2-benzothiazolinone hydrazone ; Comparison with GC-MS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A HPLC method for the determination of methyl ethyl ketone (MEK) in urine after derivatization with 3-methyl-2-benzothiazolinone hydrazone is proposed. The calibration curve for the ketone was linear, ranging between 0.23–10 mg/L, with a detection limit of 0.025 mg/L. The results were compared to those obtained by GC-MS, coupled to the headspace technique. MEK derivatization and the derivative purification processes were verified with respect to the main variables such as reaction temperature, reagent concentration, probable interferences and enrichment phase. The method is simple and reliable and shows a good sensitivity.
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 382-386 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Sulfonamides in foodstuffs ; Honey ; Milk ; Eggs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A procedure for the simultaneous determination of several sulfonamides in different foods, such as honey, milk and eggs is proposed. The analysis is carried out using reversed phase liquid chromatography with spectrophotometric detection. Optimization of the mobile phase led to good separation and a short analysis time when an initial isocratic step with a 3∶97 acetonitrile: water mixture was used for 5 minutes, followed by a linear gradient up to a 40∶60 mixture over 15 min. The proposed method is suitable for routine quality control analysis to ensure the absence of sulfonamides in foods. Recovery studies yielded good results for all food samples because there were no interferences from the matrices.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 40 (1995), S. 411-416 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Particle beam LC/MS interface ; Capillary columns for LC ; Mycotoxins ; Peanut meal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new method for the analysis of aflatoxins in food extracts, based on liquid chromatography/mass spectrometry interfacing, is presented. The chromatographic separation was performed with a reversed phase packed capillary column coupled with a modified particle beam interface capable of handling microliter per minute flow rates. This system allows higher overall sensitivity and easier operation procedures. The method has proved to be particularly suitable for the analysis of the toxins in very complex matrices. The specificity of electron impact ionization allowed positive identification of the aflatoxins with an excellent response linearity for accurate quantitation.
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  • 83
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Thin-layer chromatography ; Reversed phase ; 2-benzoylbenzoic acids ; Anionic and cationic counter ions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The 2-benzoylbenzoic acid series was investigated by reversed-phase, high-performance, thin-layer and column chromatography using various alkylammonium salts and di(2-ethylhexyl)orthophosphoric acid as polar associating reagents. The effects of the individual substituents on retention were quantified by Δlog k′ and ΔRM values. The compounds investigated differing in molecular structure (hydrophilic and hydrophobic substituents) commonly occurring groups in drugs and biologically active substances provide information on molecular interaction in these ion-pair systems. The combined effects on retention of organic modifier and ion-pair reagent concentration were investigated.
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  • 84
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Two-dimensional separation ; D- and L-amino acids ; Enantioseperation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 μl heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 41 (1995), S. 43-50 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ion pair LC ; Sweeteners, preservatives and antioxidants ; Food additive analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na and acesulfame-K), preservatives (sodium dehydroacetate, sorbic acid, salicyclic acid, benzoic acid, succinic acid, methyl-para-hydroxybenzoic acid, ethylpara-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, isopropyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 mM aqueous α-hydroxy-isobutyric acid solution (pH 4.5) (2.2 ∶ 3.4 or 2.4 ∶ 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a C18 column with a flow rate at 1.0 mL/min and detection at 233 nm were used. This method was found to be very reproducible with detection limits ranged from 0.15 to 3.00 μg. The retention factor (k) of each additive could be affected by concentrations of hexadecyltrimethylammonium bromide and α-hydroxyisobutyric acid, and pH and ratio of mobile phase. The presence of additives in some food samples was determined.
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  • 86
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Limit of detection ; Precision ; Uncertainty prediction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The precision of integration over noisy instrumental output for quantitative analysis is studied. A probability theory is developed to predict the relative standard deviation (RSD) of integration results over an integration domain from one-point integation (peak height measurement) to entire area integration in HPLC. Common integration modes of horizontal zero line and oblique zero line are taken into account, but no peak overlap is assumed. The question of the analytical superiority of peak height measurement or integration for quantitation is answered. In the HPLC apparatus used, the minimum RSD of measurements is found in the integration domain of ca. ±0.5 σ for analytes [peaks are approximated by the Gaussian signal of width, σ (standard deviation)]. The RSD of integration measurements is also shown to depend on the stochastic properties of back-ground noise (uncorrelated noise and correlated 1/f type noise). The theoretical conclusion is verified by Monte Carlo simulation and HPLC experiments for some aromatic compounds.
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  • 87
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ion-pair and GPC separations ; Amoxicillin oligomers ; β-Lactam ring polymers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Polymeric substances formed from concentrated sodium amoxicillin in an aqueous solution have been separated using two high-performance liquid chromatographic methods. We used a C18 reversed-phase column with tetrabutylammonium chloride as an ion-pairing agent with an acetonitrile gradient and a TSKgel G2500PWxl column with water as the solvent for gel permeation chromatography. The separated materials, ranging in size from the monomer to the tetramer, have been characterized by functional-group chemical analysis, while the identification of the piperazine-2,5-dione was done using a pure standard. A greater number of peaks which were also better defined were obtained using the ion-pair reversed-phase method, and open and closed beta-lactam ring polymer forms could be distinguished. Using the gel permeation method, only a few monomer, piperazine-2,5-dione, dimer, trimer and combined amoxicillin trimer and tetramer peaks were obtained with water, although those obtained were quite well defined. The data on the time-course of formation of the oligomers and the amoxicillin degradation product were virtually identical by both methods.
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 41 (1995), S. 148-152 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; On-column fluorimetric detection ; Gradient elution ; Dansyl amino acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Fluorimetric detection in the presence of a stationary phase has been applied to gradient elution of dansyl amino acids in liquid chromatography. A 1.5 mm ID quartz tube packed with the same materials as the separation column was employed for the flow cell. Conventional-size columns were employed. The peak height of analytes increased with increasing retention owing to focusing and environmental effects of the stationary phase, leading to improvements in sensitivity, which was pronounced for analytes eluting late. The lower the gradient, the larger the improvement in sensitivity achieved. Detection limits were improved by a factor of up to 5.1 by fluorimetric detection using the packed flow cell, compared with those achieved using a common empty flow cell.
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  • 89
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; LC-MS ; Cinchona alkaloids ; New column packing materials
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A major problem in the HPLC analysis of alkaloids is the poor peak shape and consequently low resolution, due to the interactions of the basic alkaloids with the residual acidic silanol groups of most reversed phase materials. The performance of new packing materials specially designed for the separation of basic compounds has been studied using mobile phases without the special additives commonly applied in the analysis of alkaloids. Strongly basic Cinchona alkaloids were used as test compounds. Retention characteristics and selectivities of each material were studied, after mobile phase optimisation for the column. The influence of the major factors (nature and content of the organic modifier, pH value, salt concentration) affecting resolution was studied. The mobile phases were chosen so that they could be used in thermospray LC-MS. The addition of salts to the mobile phase improves separation but in general the modification of the mobile phase gave little change in selectivity. The performance of silicabased C18 material proved superior to the polymer materials tested.
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Glycoconjugate journal 16 (1999), S. 197-203 
    ISSN: 1573-4986
    Schlagwort(e): gangliosides ; synthesis ; GM3 ; GD3 ; lactones ; Ganglioside ; glycosphingolipid nomenclature ; LacCer, β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GM3, II3-α-Neu5AcLacCer, α-Neu5Ac-(2-3)-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GD3, II3(-α-Neu5Ac)3LacCer, α-Neu5Ac-(2-8)-α-Neu5Ac-(2-3)-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GM2, II3-α-Neu5AcGg3Cer, β-GalNAc-(1-4)-[α-Neu5Ac-(2-3)]-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; Gg4Cer, β-Gal-(1-3)-β-GalNAc-(1-4)-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GM1, II3-α-Neu5AcGg4Cer, β-Gal-(1-3)-β-GalNAc-(1-4)-[α-Neu5Ac-(2-3)]-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GM1-lactone, β-Gal-(1,3)-β-GalNAc-(1-4)-[α-Neu5Ac-(2-3,1-2)]-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GD1b, II3(-α-Neu5Ac)2 Gg4Cer, β-Gal-(1-3)-β-GalNAc-(1-4)-[α-Neu5Ac-(2-8)-α-Neu5Ac-(2-3)]-β-Gal-(1-4)-β-Glc-(1-1)Cer ; GD1b-dilactone, β-Gal-(1-3)-β-GalNAc-(1-4)-[α-Neu5Ac-(2-8, 1-9)-α-Neu5Ac-(2-3, 1-2)]-β-Gal-(1-4)-β-Glc-(1-1)-Cer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A simple procedure is described for preparing GM3 ganglioside, from a few milligrams to grams, from GM1-lactone (Sonnino et al., (1985) Glycoconjugate J 2: 343–54) [1]. The synthesis was carried out under the following optimal conditions: 30 mM GM1-lactone in 0.25 M H2SO4 in DMSO, 30 min, 70°C, nitrogen atmosphere, strong stirring. The yield of GM3 was 55%. The procedure applied to milligram amounts of GD1b-dilactone gave GD3 ganglioside.
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  • 91
    ISSN: 1573-4986
    Schlagwort(e): glycosaminoglycan ; pentasaccharide serine ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A novel pentaosyl serine; GalNAcα(1–4)GlcAβ(1–3)Galβ(1–3)Galβ(1–4)Xylβ(1–3)Ser (2), a putative intermediate of chondroitin sulfate and/or heparan sulfate biosynthesis, was synthesized.
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  • 92
    ISSN: 1573-4986
    Schlagwort(e): Glycoside ; synthesis ; cancer ; hexamethylmelamine ; methylol ; formaldehyde ; modelling ; deacetylation ; triazine ; N-hydroxymethyl
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The synthesis of analogues of the anti-tumour drug 2-[N-(hydroxymethyl)methylamino]-4,6-bis (dimethylamino)-1,3,5-triazine (HMPMM) in which the OH or a dimethylamino group is replaced by a carbohydrate has been explored. Triazinyl β-glycosides were readily prepared by reaction of sugars with trimethyl-triazinylammonium salts. These were made with one or two methylamino groups on the triazine for reaction with formaldehyde to give the cytotoxic NMeCH2OH group. However, reaction of the triazinyl glycosides with formaldehyde gave complex intractable mixtures. When the carbohydrate portion was changed to the fully protected 2,3,4,6-tetra-O-acetyl glucose a good yield of the 2-[N-(hydroxymethyl)methylamino]-4-(dimethylamino)-1,3,5-triazin-2-yl tetra-O-acetyl β-glucoside was obtained. However, de-acetylation using sodium methoxide also removed the N–CH2OH group. We are investigating protection of the base-sensitive N–CH2OH group as trialkylsilyl and benzyl ethers and are looking at de-acetylation methods that are more selective. We have prepared glycosides in which the sugar is joined through the oxygen of the NMeCH2OH group. Coupling of acetobromoglucose with HMPMM catalysed by silver salts was not successful. Although methyl and cyclohexyl derivatives of HMPMM may be produced in high yields by reaction of HMPMM with methyl and cyclohexyl alcohols under acidic catalysis, production of glycosides in this way gave poor yields. MNDO calculations on reactions of HMPMM helped us devise improved reaction conditions for the condensation of 2,3,4,6-tetra-O-acetyl glucose with HMPMM and its derivatives. The best procedure to generate one of the target glycosides is to react 2,3,4,6-tetra-O-acetyl glucose and formaldehyde with 2-methylamino- 4,6-bis(dimethylamino)-1,3,5-triazine. The β-glycoside product was de-acetylated using potassium carbonate in dry methanol. Abbreviations: HMM, hexamethylmelamine (2) or 2,4,6-tris(dimethylamino)-1,3,5-triazine; HMPMM, hydroxymethylpentamethylmelamine or 2-[N-(hydroxymethyl)-methylamino]-4,6-bis(dimethylamino)-1,3,5-triazine; PMM, Pentamethylmelamine or 2-methylamino-4,6-bis(dimethylamino)-1,3,5-triazine; TBMS, t-Butyldimethylsilyl; p-TSA, p-Toluenesulphonic acid
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  • 93
    ISSN: 1573-4854
    Schlagwort(e): mesoporous silica ; hexagonal phase ; synthesis ; room temperature ; inorganic silicate sources ; acidic medium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The room-temperature synthesis of mesoporous silica was investigated by using cationic surfactants and inorganic Si sources, like sodium silicate and colloidal silica. Mesoporous silica analogous to the hexagonal MCM-41 could be obtained over a wide range of pH below ca. 11 within short synthesis time (3 h), when the Q4-state Si was absent in the Si source solution prior to mixing with an aqueous solution of cationic surfactants. It was suggested that the strongly acidic conditions (pH 〈 1) were favorable to give mesoporous silica materials with higher surface area and larger mesopore volume.
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  • 94
    ISSN: 1573-4986
    Schlagwort(e): E-selectin ; P-selectin ; sialyl dimeric Lex ; glycolipid ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The first total synthesis of glycononaosyl ceramide with a sialyl dimeric Lex sequence 1 is described. Regio- and stereo-selective glycosylations of sialyl donors 6,7,8 with the suitably protected Lex trisaccharide acceptors 9,10β were performed to give the expected tetrasaccharides 15 and 21, which were converted into the corresponding donors 20 and 22. Boron trifluoride etherate-promoted glycosylation of 20 with pentasaccharide acceptor 11 afforded regioselectively the expected nonasaccharide 23. After replacing benzyl groups of 23 by acetyl groups, the anomeric acetate was transformed into the α-trichloroacetimidate 27. The crucial coupling between 27 and (2S, 3R, 4E-3-O-benzoyl-2-N-tetracosanoylsphingenine 3 was executed to afford completely protected β-glycoside 28. Finally, selective cleavage of the methyl ester and N,O-deprotection of 28 gave the target ganglioside 1.
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  • 95
    ISSN: 1573-4986
    Schlagwort(e): glycopeptide ; synthesis ; T cell ; immune response
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The 2-bromoethyl β-glycosides of the disaccharide galabiose [Gal(α1-4)Gal] and the trisaccharides globotriose [Gal(α1-4)Gal(β1-4)Glc] and 3′-sialyllactose [Neu5Ac(α2-3)Gal(β1-4)Glc] have been prepared by improved routes. The 2-bromoethyl glycosides were then used in cesium carbonate promoted alkylations of the sulfhydryl groups of cysteine and homocysteine residues in T cell stimulating peptides. This convergent and general approach was used to prepare 16 neoglycopeptides which were obtained in 52–95% yields after purification by HPLC. 1H NMR spectroscopy revealed that β-elimination and epimerization of neoglycopeptide stereocentres did not occur during the synthesis.
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  • 96
    ISSN: 1573-4986
    Schlagwort(e): heparin biosynthesis ; carbohydrates ; sulfated disaccharides ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The synthesis of the disaccharides methyl 4-O-(2′/3′-O-sulfo-β-d-glucopyranosyluronic acid)-2-amino-2-deoxy-α-d-glucopyranoside3 and4 as, disodium salts is described. Allyl 4,6-O-benzylidene-α-d-glucopyranoside6 was converted to trichloroacetimidate20 Glycosylation of20 with5 promoted by BF3·OEt2 gave disaccharide21. Deacetylation of21 followed by monoacetylation of the resultant diol22 afforded the two monoacetylated disaccharides23 and24. Sulfation and deprotection of each disaccharide gave the desired sulfated compounds3 and4.
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Glycoconjugate journal 15 (1998), S. 345-354 
    ISSN: 1573-4986
    Schlagwort(e): CMP-Neu5Ac analogues ; synthesis ; sialyltransferase inhibitors ; sialyltransferase assay ; α(2-6)-sialyltransferase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Quinic acid (4) was transformed into phosphitamides 6, 14, and 15, which could be readily linked to 5′-O-unprotected cytidine derivative 7; ensuing oxidation of the obtained phosphite triesters with tert-butylhydroperoxide furnished the corresponding phosphate triesters 8, 16, and 17, respectively. Hydrogenolytic debenzylation of the phosphate moiety, base catalysed removal of acetyl protective groups, and basic hydrolysis of the methylester of the quinic acid moiety furnished CMP-Neu5Ac analogues 1-3. In order to measure their inhibition of sialyltransferases, a nonradioactive sialyltransferase assay [employed for α(2-6)-sialyltransferase from rat liver (EC 2.4.99.1)] based on reversed-phase HPLC separation of UV-abelled acceptor 20 (p-nitrophenyl glycoside of N-acetyllactosamine) from the UV-labelled product 21 (p-nitrophenyl glycoside of sialyl α(2-6′)-N-acetyllactosamine) and p-nitrophenylalanine as internal standard was developed. The assay reproduced the reported KM values for CMP-Neu5Ac and N-acetyllactosamine and the Ki values for CDP. 1 and 2 turned out to be potent sialyltransferase inhibitors. © 1998 Rapid Science Ltd
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  • 98
    ISSN: 1573-4986
    Schlagwort(e): enzymic sialylation ; glycosphingolipid ; GM3 ; GM3 analog ; lyso-GM3 ; lyso-GM3 analog ; modified polyacrylamide ; photolysis ; polymer support ; sialyltransferase ; synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Two water-soluble polymers, carrying 0.24 meq g−1 of lactosyl-β(1-1)-sphingosine (7) and 0.13 meq g−1 of lactosyl-β(1-3)-sphingosine (8) were prepared. The polymers served as acceptors in the α-(2-3)-sialyltransferase reaction (up to 55.3 and 38.5% transfer yields, respectively). Subsequent photolysis, released compounds 11 (lyso-GM3) and 12 (lyso-GM3 analog), respectively; acylation and chromatography afforded (5-acetamido-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonic acid)-(2-3)-β-D-galactopyranosyl-(1-4)-β-D-glucopyranosyl-(1-1)-(2S, 3R, 4E)-2-octadecanoylamino-4-octadecene-1,3-diol (13, GM3) and (5-acetamido-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonic acid)-(2-3)-β-D-galactopyranosyl-(1-4)-β-D-glucopyranosyl-(1-3)-(2S, 3R, 4E)-2-octadecanoylamino-4-octadecene-1,3-diol (14, GM3 analogue), respectively, thus presenting a route to glycosphingolipids possessing the unusual glycosyl-β(1-3)-spingosine linkage.
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Journal of dynamical and control systems 3 (1997), S. 165-203 
    ISSN: 1573-8698
    Schlagwort(e): 49J15 ; 57N80 ; 93B06 ; 93C10 ; 93C95 ; Optimal trajectory ; cut-locus ; synthesis ; exceptional ; stratification ; generic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract In previous papers, we gave in dimension 2 and 3 a classification of generic synthesis of analytic systems $$\dot v(t) = X(v(t)) + u(t)Y(v(t))$$ with a terminal submanifoldN of codimension one when the trajectories are not tangent toN. We complete here this classification in all generic cases in dimension 3, giving a topological classification and a model in each case. We prove also that in dimensionn≥3, out of a subvariety ofN of codimension there, we have described all the local synthesis.
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  • 100
    ISSN: 1573-1561
    Schlagwort(e): Eriocrania semipurpurella ; Eriocrania sangii ; Eriocraniidae ; Lepidoptera ; sex pheromone ; GC-EAD ; chiral gas chromatography ; mass spectrometry ; synthesis ; field trapping ; nonan-2-one ; (Z)-6-nonen-2-one ; (2S,6Z)-nonen-2-ol ; (2R,6Z)-nonen-2-ol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The fifth abdominal segment of femaleEriocrania semipurpurella (Stephens) andE. sangii (Wood) contains a pair of exocrine glands. Hexane extracts of this segment were prepared from both species and analyzed by gas chromatography with simultaneous flame ionization and electroantennographic detection (EAD). For both species, the EAD active peaks were identified as nonan-2-one, (Z)-6-nonen-2-one, and (Z)-6-nonen-2-ol by means of mass spectrometry and comparison of retention indices with those of synthetic standards. Enantiomeric separation of chiral alcohols from the female extracts was achieved by gas chromatographic analysis on a cyclodextrin column. InE. semipurpurella, a mixture of (2S,6Z)-nonen-2-ol and (2R,6Z)-nonen-2-ol (2: I) was found, whereas inE. sangii (2S,6Z)-nonen-2-ol was the predominant enantiomer and only traces of theR enantiomer were indicated by the antennal response. In field tests, a blend of the three compounds was not attractive to conspecific males. A subtractive assay showed that the alcohol in various enantiomeric mixtures was the only attractive compound, whereas addition of (Z)-6-nonen-2-one to the alcohol completely inhibited the attraction of both species. A trapping experiment including a wide range of ratios between theR andS enantiomers showed that baits containing 95–100% of theS enantiomer were attractive to maleE. sangii, whereas males ofE. semipurpurella were attracted to all tested ratios of the enantiomers. However, the response profiles of maleE. semipurpurella differed between populations from southern Sweden, south Finland, and the Kola Peninsula in Russia. In south Sweden males were maximally attracted to a racemic mixture of the alcohols. At the Kola PeninsulaE. semipurpurella was attracted to baits containing 95–100% of theR enantiomer. In south Finland all tested ratios between 0 and 100%R enantiomer trappedE. semipurpurella, but the trap catches appeared to be bimodally distributed with peaks around 15 and 70%R enantiomer. The trapping results suggest the existence of pheromone races or sibling species among the specimens identified asE. semipurpurella.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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