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  • 1
    Electronic Resource
    Electronic Resource
    Towards a new classification of intracellular particle movements based on quantitative analyses (1986)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 128-135 
    Details
    ISSN: 0886-1544
    Keywords: motion analysis ; axonal transport ; cytoplasmic transport ; Brownian motion ; AVEC-DIC microscopy ; saltatory particle motion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A survey study of organelle movements in a variety of cell types of plant and animal origin was made with the aid of video-enhanced contrast, differential interference contrast (AVEC-DIC) microscopy followed by fine analysis of the motile behavior of the individual organelles. We found that there exists besides Brownian motion a wide spectrum of active motions in cells, i.e. motion that is directionally biased through the expenditure of metabolic energy. The types of active motion seen range from a continuous motion (sometimes appearing as streaming) in plant cells and neurons to various types of less ordered and less well directed motion. We did not see any clear-cut qualitative difference between plant and animal cells or between systems presumed to be actin- and microtubule-based. A preliminary classification of the types of active motion is presented. The ongoing research activities, which aim at a more precise definition of the different types of motion by a set of quantitative parameters, are described, and the progress made so far is reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970060210
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  • 2
    Electronic Resource
    Electronic Resource
    Photochemical and Thermal Cycloaddition Reactions of 3-Thioxoandrosta-1,4-dien-17-one with Electron-Deficient Alkynes (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2347-2349 
    Details
    ISSN: 0947-3440
    Keywords: 3-Thioxoandrosta-1,4-dien-17-one ; Cycloaddition reactions ; Steroids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-Thioxoandrosta-1,4-dien-17-one (4) reacts with acetylene dicarboxylic acid esters to form novel spiro compounds of the thiine type (6a, 6b), whereas with free acids, such as acetylene dicarboxylic acid and propiolic acid, the spirocyclic O,S-acetals 7a and 7b are obtained. This study demonstrates that the cycloaddition reaction is promoted by photochemical and also thermal activation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971124
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  • 3
    Electronic Resource
    Electronic Resource
    Regioselective Olefination of Cross-Conjugated 3-Thioxosteroids by [3+2] Cycloaddition (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 613-615 
    Details
    ISSN: 0947-3440
    Keywords: Cycloadditions ; Olefinations ; Steroids ; 3-Thioxoandrosta-1,4-dien-17-one ; Diazo compounds ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 3-thioxoandrosta-1,4-dien-17-one (1) with the diazo compounds 2a-i affords 4′-substituted spiro[17-oxoandrosta-1,4-diene-3,2′-[1,3,4]thiadiazolines], which undergo a two-step ring contraction with extrusion of nitrogen and sulfur, leading to the substituted 3-methylen- and 3-propylidenandrosta-1,4-dien-17-ones 3a-i in good yields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970324
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  • 4
    Electronic Resource
    Electronic Resource
    Cycloaddition Reactions of 2H-Benzo[b]thiete and Thiocarbonyl Compounds (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1603-1605 
    Details
    ISSN: 0947-3440
    Keywords: 4H-1,3-Benzodithianes ; Heterodienes ; Heterodienophiles ; Spiro compounds ; Heterocycles ; Cycloaddition ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2H-Benzo[b]thiete (1) reacts in the o-quinoid form 1′ with the cyclic trithiocarbonates 4 and 6a, b and with the thioketones 8, 10 and 12 in [8π + 2π] cycloaddition reactions to the spiro compounds 5, 7a, b, 9, 11a, b. Irrespective of the presence of C=C double bonds, chemoselective and regioselective addition processes at the C=S double bonds take place that lead to 4H-1,3-benzodithianes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970743
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  • 5
    Electronic Resource
    Electronic Resource
    Umlagerung von 3-Thioxo-Δ1,4-steroiden, ein neuer Zugang zu Steroidthiolen (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1397-1399 
    Details
    ISSN: 0947-3440
    Keywords: 3-Thioxoandrosta-1,4-dien-17-one, rearrangement of ; Thioestratriene ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rearrangement of 3-Thioxo-Δ1,4-steroids, a New Approach of Steroid Thiols3-Thioxoandrosta-1,4-dien-17-one (1) is subjected to a dienthion-thiophenol rearrangement in aprotic and protic solvents in the presence of an acid catalyst resulting in the formation of 1-(acetylthio)-4-methylestra-1,3,5(10)-trien-17-one (2). 1-mercapto-4-methylestra-1,3,5(10)-trien-17-one (3), and the dimer 1,1′-(dithio)bis[4-methylestra-1,3,5(10)-trien-17-one] (4) as the reaction products. The mercapto compound 3 tends to be autoxidized to the sulfide 4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199507189
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  • 6
    Electronic Resource
    Electronic Resource
    Regioselektive Reaktionen an der 17-Oxogruppe von Androsta-1,4-dien-3,17-dion nach in-situ-Schutz mit Titantetrakis(dimethylamid) (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1279-1285 
    Details
    ISSN: 0170-2041
    Keywords: Steroids ; Titanium amides ; Ester enolates ; Dienone-benzene rearrangement ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Regioselective Reactions at the 17-Oxo Group of Androsta-1,4-dine-3,17-dione after in situ Protection with Titaniumtetrakis(dimethylamide)After in situ protection of androsta-1,4-diene-3,17-dione (1) with titaniumtetrakis(dimethylamide) (10) at -20°C to -30°C, the lithium enolates of methyl methoxyacetate (2a) and ethyl acetate (2b) react regio- and stereoselectively at the 17-position to give the 17-hydroxy-17α-pregnanes 12 and 6. Dehydration of 12 and 6 furnishes the 17(20)-olefins 13 and 14, intermediates for the synthesis of corticoids and gestagens. The reaction of 1 with 10 and 2a at -60°C gives byproducts of a dienone-benzene rearrangement of the A-ring. The reactions of 1 with 2a and 2b without titaniumtetrakis-(dimethylamide) (10) proceed regioselectively at the 3-position or nonregioselectively at the 3- and 17-positions, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301209
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  • 7
    Electronic Resource
    Electronic Resource
    Zur Regioselektivität SH-haltiger Nucleophile gegenüber Androsta-1,4-dien-3,17-dion, einem Vorläufer für biologisch aktive Steroide (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 11-15 
    Details
    ISSN: 0170-2041
    Keywords: Androsta-1,4-diene-3,17-dione ; Thioketals ; Hemithioketals ; Steroids ; Michael addition, double ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Regioselectivity of SH-Containing Nucleophiles towards Androsta-1,4-diene-3,17-dione, a Precursor for Biologically Active SteroidsThioketals have been prepared from androsta-1,4-diene-3,17-dione (1) and SH-containing compounds in the presence of different catalysts. The thioketals 4 are obtained by using the aromatic thiols 3d, 3e, and 3g, whereas the aliphatic thiols 3a and 3c yield a mixture of regioisomeric products 4-6. A higher selectivity with regard to the 17-oxo group was observed by using the thiol 3b leading to 5b. With the araliphatic thiol 3f compound 5f is selectively formed. In contrast to the described thioketal formation, the thiol 3d yields in addition to 4d a double Michael addition product 7, which was predominantly obtained by using other catalysts and/or a higher reaction temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930104
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