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  • Wiley-Blackwell  (9)
  • Molecular Diversity Preservation International
  • 1985-1989  (9)
  • 1
    Electronic Resource
    Electronic Resource
    On the Macrolactonization of β-Hydroxy Acids. Crystal structures of the pentolide and the hexolide from (R)-3-hydroxybutanoic acid. Molecular modeling studies of the tetrolideDedicated to Prof. Dr. Wilhelm Simon on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1704-1717 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The temperature and concentration dependence of the previously reported formation of oligolides from (R)- or (S)-3-hydroxybutanoic acid under Yamaguchi's macrolactonization conditions (2,4,6-trichlorobenzoyl chloride/base) was studied. While the content of hexolide 2 in the product mixture is almost invariably ca. 35%, the amounts of pentolide 1 and of the larger rings strongly depend upon the temperature employed (Fig.1). Cyclic oligomers (5,6) are also obtained from 3-hydroxypentanoic acid. Enantiomerically pure β-butyrolactone can be used for the preparation of pento-, hexo-, and heptolide under Shanzer's macrolactonization conditions (tetra-oxadistannacyclodecane ‘template’). The X-ray crystal structures of the pentolide 1 and of two modifications (space groups C 2 and P 21) of the hexolide 2 were determined (Figs. 2-6 and Tables 1 and 5). No close contacts between substituent atoms and atoms in the rings or between ring atoms are observed in these structures. The hexolide C 2 modification is ‘just a large ring’, while the crystals of the P 21 modification contain folded rings the backbones of which resemble the seam of a tennis ball. A comparison of the torsion angles in the folded hexolide ring of the P 21 modification with those in the helical poly-(R)-3-hydroxybutanoate (PHB) suggests (Table 2) that the same interactions might be responsible for folding in the first and helix formation in the second case. Molecular modeling with force-field energy minimization of the tetrolide from four homochiral β-hydroxybutanoic acid units was undertaken, in order to find possible reasons for the fact that we failed to detect the tetrolide in the reaction mixtures. The calculated conformational energies (per monomer) for some of the tetrolide models (Figs. 7-9 and Tables 3 and 4) are not significantly higher than for the pentolide and hexolide crystal structures. We conclude that thermodynamic instability is an unlikely reason for the lack of tetrolide isolation. This result and failure to observe equilibration of pentolide 1 to a mixture of oligomers under the reaction conditions suggest that product distribution is governed by kinetic control.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720807
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  • 2
    Electronic Resource
    Electronic Resource
    Ringöffnung von N-(Tetraalkylamidinio)pyridinium-Salzen durch Anionen methylenaktiver Verbindungen (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 3276-3296 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ring Opening of N-(Tetraalkylamidinio)pyridinium Salts by Anions of CH-Acidic Methylene CompoundsN-Carbeniopyridinium salts 2, 4, 14, and 18 offer three sites to nucleophilic attack; depending on the reactants, all three modes have been realized. With anions of CH-acidic methylene compounds, α-attack at the pyridinium ring followed by ring opening leads to azahexamethine merocyanines (8, 15, 23). In some cases, kinetically controlled reactions yield 1,4-dihydropyridines which isomerize thermally to give 1,2-dihydropyridines which undergo ring opening spontaneously. Also, nucleophilic attack at the cationic substituent of the N-carbeniopyridinium salts is possible as is indicated by the formation of push-pull olefins 11, 16 and of enol ether 12.
    Notes: Die N-Carbeniopyridinium-Salze 2, 4, 14 und 18 bieten für den Angriff eines Nucleophils drei Möglichkeiten, die sich in Abhängigkeit von den Reaktionspartnern alle realisieren lassen. Mit Anionen methylenaktiver Verbindungen führt der α-Angriff am Pyridinium-Ring unter Ringöffnung zu Azahexamethinneutrocyaninen (8, 15, 23). In einigen Fällen bilden sich kinetisch kontrolliert 1,4-Dihydropyridine, die sich thermisch zu den 1,2-Dihydro-pyridinen bzw. deren ringgeöffneten Folgeprodukten umlagern. Schließlich ist auch der nucleophile Angriff am kationischen Substituenten der N-Carbeniopyridinium-Salze möglich, wie die Bildung der Push-pull-Olefine 11, 16 und des Enolethers 12 zeigt.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861191109
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  • 3
    Electronic Resource
    Electronic Resource
    Azahexamethin-Neutrocyanine mit einem Diaminocyclopropenyliden-Auxochrom (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 1791-1794 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azahexamethine Neutrocyanines with a Diaminocyclopropenylidene AuxochromeBy ring opening of the N-(2,3-diaminocyclopropenylio)pyridinium salt 1 with the anions of malononitrile, dimedone, or Meldrum's acid the protonated polymethines 5a-c are formed, which yield the neutral dyestuffs 6a-c on deprotonation. In solution, 5a, b are transformed slowly into the triafulvenes 3a, b. Analogously, polymethine 10 is obtained from the diaminochlorocyclopropenylium salt 8, pyridine, and malononitrile, although the equilibrium of formation of the presumed intermediary pyridinium salt 9 lies far on the side of the components.
    Notes: Durch Ringöffnung des N-(2,3-Diaminocyclopropenylio)pyridinium-Salzes 1 mit den Anionen von Malononitril, Dimedon oder Meldrums Säure entstehen die protonierten Polymethine 5a-c, die sich zu den neutralen Farbstoffen 6a-c deprotonieren lassen. In Lösung entstehen aus 5a, b langsam die Triafulvene 3a, b. Aus dem Diaminochlorcyclopropenylium-Salz 8, Pyridin und Malononitril bildet sich analog das Polymethin 10, obwohl das intermediär anzunehmende Pyridinium-Salz 9 in Lösung nur in einem weit auf die Seite seiner Komponenten verschobenen Gleichgewicht vorhanden ist.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881211015
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  • 4
    Electronic Resource
    Electronic Resource
    Verwendung von mit Platin beladenen Y-Zeolithen als Katalysatoren für die Hydrierung von flüssigen und niedrig schmelzenden Fetten (1989)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 61 (1989), S. 963-964 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330611210
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  • 5
    Electronic Resource
    Electronic Resource
    Analysis of a mutant expressing temperature-sensitive changes of cell size in Tetrahymena (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 123 (1985), S. 361-368 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A temperature-sensitive mutant of Tetrahymena expresses an increase in cell volume by a factor of 2.5 upon shift to restrictive temperature. Cellular amounts of protein, RNA, and DNA increase at roughly the same proportions. The mutant cell size is attained by cessation of divisions immediately after temperature shift for a period of time which is about equal to one generation time. During this time cell growth and DNA replication continue at virtually unchanged rates. Maintained at the restrictive temperature the mutant cells divide at the same rate as the wild-type cells. Upon return to the permissive temperature, cell size is reduced by the combined effects of an accelerated division rate together with a decelerated growth rate.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041230311
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  • 6
    Electronic Resource
    Electronic Resource
    Dikationether, 11. Ambidoselektive Reaktionen von β-Ketoenolaten mit Dikationethern (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 2123-2141 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Dication Ethers, 11(1). - Ambidoselective Reactions of β-Ketoenolates with Dication EthersWhen the bis(N,N,N′,N′-tetramethylformamidinio) ether salt 5a is treated with the β-ketoenolates 7a - h, j or β-ketonitrile acetonitrile, electrophilic transfer of a tetramethylformamidinio group occurs exclusively at an oxygen atom of the ambident anions, thus yielding uronium salts 8a-j. From the acyclic β-ketoenolates 7a-f, β-acylenol ether salts (E)-8a-f are obtained diastereoselectively. Also, electrophilic attack by the dimidazolinio ether salt 5b and the dipyridinio ether salt 5c, d occurs exclusively at an oxygen atom of the dimedone anion (8k, 15, 18). From 5c and the anion of Meldrum's acid, olefin 16 is formed by C/C bond connection. - An X-ray structure analysis of (E)-8f was performed.
    Notes: Die elektrophile Übertragung einer Tetramethylformamidinum-Gruppe aus dem Bis-(N,N,N′,N′-tetramethylformamidinio)ether-Salz 5a auf die ambidenten β-Ketoenolate 7a-h, j und das β-Ketonitril-Anion 7i erfolgt in Acetonitril ausschileßlich am Enolatsauerstoff, wobei man die Uronium-Salze 8a-j erhält. Aus den acyclischen β-Ketoenolaten 7a - f entstehen diastereoselektiv die β-Acylenolether-Salze (E)-8a-f. Das Diimidazolinioether-Salz 5b und die Dipyridinioether-Salze 5c, d reagieren mit dem Anion von Dimedon ebenfalls ausschließlich am Sauerstoff (8k, 15, 18). Aus 5c und dem Anion von Meldrumsäure erhält man unter C/C-Verknüpfung das Olefin 16. - Eine Röntgenstrukturanalyse von (E)-8f wurde ausgeführt.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619861207
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  • 7
    Electronic Resource
    Electronic Resource
    Berechnetes leben. Carl Wilhelm von Nägeli und die Wurzeln Mathematischer Modellsimulation in der Biologie (1988)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 18 (1988), S. 116-121 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19880180405
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  • 8
    Electronic Resource
    Electronic Resource
    Metallderivate von Molekülverbindungen. II. Darstellung und Struktur des β-Kaliumsilanids (1989)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 572 (1989), S. 75-88 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metal Derivatives of Molecular Compounds. II. Preparation and Structure of β-Potassium SilanideAt -5°C potassium silanide crystallizes from 1,2-dimethoxyethane/n-pentane in a to date unknown low temperature modification {β-form: orthorhombic, Pnma, Z = 4; a = 880.0(2), b = 541.6(1), c = 682.3(1) pm at -110 ± 3°C}. An x-ray structure determination shows the compound to be built up from isolated potassium cations and pyramidal silanide anions without perceptible disorder. Seven counterions make up the coordination sphere of either particle (K⃛Si 356 to 386 pm), two anion-anion contacts (Si⃛Si 355 pm) are observed in addition. The packing of ions represents a defect variant of the barite type, but there are also relationships to the high temperature modification (α-form, rock salt type) and to cesium trihydrogengermanide (thallium iodide type).
    Notes: Kaliumsilanid kristallisiert bei -5°C aus 1,2-Dimethoxyethan/n-Pentan in einer bisher unbekannten Tieftemperatur-Modifikation {β-Form: orthorhombisch, Pnma, Z = 4; a = 880,0(2), b = 541,6(1), c = 682,3(1) pm bei -110 ± 3°C}. Nach den Ergebnissen der Röntgenstrukturanalyse (R = 0,032) baut sich die Verbindung ohne erkennbare Fehlordnung aus isolierten Kalium-Kationen und pyramidalen Silanid-Anionen auf. Zur Koordinationssphäre beider Teilchen gehören sieben Gegenionen (K⃛Si 356 bis 386 pm); beim Anion kommen zwei zusätzliche Kontakte zu gleichnamigen Nachbarn (Si⃛Si 355 pm) hinzu. Die Kristallstruktur stellt eine Defektvariante des Baryt-Typs dar, Verwandtschaft besteht aber auch zur Hochtemperatur-Modifikation (α-Form, Steinsalz-Typ) und zum Caesium-trihydrogengermanidWährend der Name Kaliumsilanid unseres Erachtens eindeutig ist, sollte die homologe Germanium-Verbindung zur Unterscheidung von den binären Phasen Caesium-trihydrogengermanid genannt werden. (Thalliumiodid-Typ).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19895720109
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  • 9
    Electronic Resource
    Electronic Resource
    Soft ionization of biomolecules: A comparison of ten ionization methods for corrins and vitamin B12Devoted to Professor Dr. H. D. Beckey on occasion of his 65th birthday. (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Mass Spectrometry Reviews 5 (1986), S. 249-311 
    Details
    ISSN: 0277-7037
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 43 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mas.1280050303
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