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  • Atomic, Molecular and Optical Physics  (20)
  • Organic Chemistry  (8)
  • Physics
  • Wiley-Blackwell  (28)
  • National Academy of Sciences
  • 1995-1999  (28)
  • 1996  (28)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 477-480 
    ISSN: 0899-0042
    Keywords: myocardial drug accumulation ; stereoselectivity ; enantiomers ; thiopental ; volume of distribution ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Myocardial uptake of thiopental enantiomers by an isolated perfused rat heart preparation was examined after perfusion with protein-free perfusate. Outflow perfusate samples were collected at frequent intervals for 20 min during single-pass perfusion with 10 μg/ml racemic thiopental (washin phase) and for another 45 min during perfusion with drug-free perfusate (washout phase). (+)- and (-)-thiopental concentrations were assayed by chiral high-performance liquid chromatography. Heart rate, perfusion pressure, and electrocardiogram were also monitored. During the washin phase, there was no significant difference between the mean values of the equilibration rate constants of (+)- and (-)-thiopental enantiomers (0.44 ± 0.07 min-1 and 0.43 ± 0.09 min-1, respectively, P 〉 0.05). Mean volumes of distribution of (+)- and (-)-thiopental enantiomers were similar (6.34 ± 1.20 and 6.45 ± 1.29 ml/g for the washin phase and 7.22 ± 0.71 and 7.47 ± 0.81 ml/g for the washout phase, respectively, P 〉 0.05). This indicates that tissue accumulation of thiopental enantiomers in the isolated perfused rat heart was not stereoselective. Uptake of thiopental by the heart was perfusion flow rate-limited and independent of capillary permeability. These findings suggest that myocardial tissue concentration of racemic thiopental should be an accurate predictor of myocardial drug effect. © 1996 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 206-213 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Synthesis of Substituted 4-Amino-quinazolines and Their HeteroanalogaN-Chloracetyl-anthranilonitriles react with potassium thiocyanate in the presence of alcohol to the (4-aminoquinazolin-2-yl-thio)-acetic acid ester (5). In the presence of water or primary amine the acetic acid derivative (6) or the acetic acid amide derivatives (7) are obtained. 2,4-Diaminoquinazolines (8) arise if vigorous reaction conditions are employed. With 2-chloracetylamino-cyclopent-1-en-carbonitrile as starting material the pyrimidines (11) are formed from the reaction with potassium thiocyanate. Analogously, (4-pyrimidyl-2-yl-seleno)-acetic acid ester (12) and (thiazolo[4,5-d]pyrimid-2-yl-seleno)-acetic acid derivatives (16) can be prepared with potassium selenocyanate. N-Chloracetyl derivatives of 5-membered heterocycles with enamino-nitrile structure (13, 15, 18, 20) react with potassium thiocyanate to yield thieno[2,3-d]-, thiazolo[4,5-d]-, pyrrolo[2,3-d]-, furo[2,3-d]- and pyrazolo[4,3-d]pyrimidines (14, 16, 19a, 19b, 21).
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 169-171 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Improved Synthesis of 5-Unsubstituted 4H-1,2,4-Triazole-3-carbaldehydes
    Additional Material: 1 Tab.
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  • 4
    ISSN: 0947-3440
    Keywords: Calculations, force field ; Dynamic NMR spectroscopy ; Chiral conformations ; Chiral ion pairs ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 2,3-didehydro[15]crown-5 and -[18]crown-6 derivatives 4a, b with vicinal α-naphthyl groups at the double bonds starting from α-naphthoin (3) is described. The barriers to rotation of the naphthyl groups were probed by MM2 and by dynamic 1H-NMR spectroscopy. An achiral syn and a chiral anti conformation were experimentally observed at -90°C for the free ligands and at -40°C for the complexes. The experimental ΔG≠ and the calculated ΔH≠ values are in fair agreement. The barriers are substantially higher in the alkali metal complexes than in the free ligands. In the presence of racemic and potassium S-(+)-mandelate non-equilibrating ion pairs with 4b were observed by low-temperature 1H-NMR spectroscopy for the anti conformation.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 578-580 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 647-653 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of different classes of 5a-substituted tocopherols is described. These compounds are potent antioxidants and highly interesting as vitamin E carriers. The reaction of the readily available 5a-bromo-α-tocopherol with alcohols and phenols is shown to produce 5a-alkoxy-α-tocopherols (3-5, 8, 9) and 5a-aryloxy-α-tocopherols (6, 7), respectively, with high yields. 5a-α-Tocopheryl esters (10, 11) are prepared by reaction with metal carboxylates. 5a-Bromo-α-tocopherol is used as well to introduce tocopheryl groups into tertiary amines by quaternization, that renders these compounds (13, 14) soluble in water and in common organic solvents. 5a-Bromo-α-tocopherol also reacts as an alkylating agent with sterically hindered phenols in a Friedel-Crafts reaction. Phenols not highly substituted are exclusively alkylated in the para position at room temperature or below, whereas at higher temperature the para-as well as the ortho-alkylated product is observed.
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  • 7
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Investigations into the parameters affecting the enantiomeric separation of an intermediate in the synthesis of a drug targeted for cardiac arrhythmia is presented. The separation was achieved under subcritical fluid chromatography using CO2 modified with methanol and co-modifiers isopropyl amine and methylene chloride. The stationary phase was a cellulose based stationary phase manufactured under the trade name Chiracel OB. The results showed the addition of methylene chloride had a noticeable effect on resolution while the separation factor, α, remained constant. The co-modifier, isopropyl amine, did not considerably influence the resolution, or separation factor. Temperature studies were performed in order to establish the thermodynamic parameters of the interaction between the enantiomers and the stationary phase. Plots of In k′ vs. 1/T proved to be curved, while plots of In α vs. 1/T were linear. © 1996 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 57 (1996), S. 53-61 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The D-dimensional Coulomb system serves as a starting point for generating generalized atomic shells. These shells are ordered according to a generalized Madelung rule in D dimensions. This rule together with an Aufbau Prinzip is applied to produce a D-dimensional periodic table. A model is developed to rationalize the ordering of the shells predicted by the generalized Madelung rule. This model is based on the introduction of a Hamiltonian, invariant under the q-deformed algebra Uq(so(D)), that breaks down the SO(D + 1) dynamical symmetry of the hydrogen atom in D dimensions. The D = 2 case (Flatland) is investigated in some detail. It is shown that the neutral atoms and the (moderately) positive ions correspond to the values q = 0.8 and q = 1, respectively, of the deformation parameter q. © John Wiley & Sons, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 579-592 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Position and momentum space plots are presented for localized molecular orbitals in hydrocarbons, boranes, a carborane, and two octahedral transition metal complexes. The p-space representation proves to be valuable for visualizing such orbitals since it highlights the differences in their character from one molecule to another. Factors influencing the form of the orbitals in p space, including the oscillatory behavior caused by contributions to an orbital from more than one center, are examined in detail. © 1996 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1065-1068 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A discussion is presented for possible diamond-lattice-based structures containing holes that can be filled with metal atoms or ions. To allow the formation of coordinative bonds to the metal, some carbon atoms should be replaced by heteroatoms (with nitrogen preferred, but in some cases oxygen or other heteroatoms may be considered). Two types of holes that may lead to the formation of coordinative bonds are discussed in detail: tetrahedral holes for four such bonds and quasi-octahedral holes for six such bonds. In turn, when suitably arranged in a translationally symmetric manner, these holes may resemble open or closed pores in foams; when they are open, the “channels” may lead to interesting properties with regard to metallic conductivity or superconductivity. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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