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  • 1
    ISSN: 1573-4951
    Keywords: centrosymmetry ; CoMFA-Field fit ; GRID ; HIV-1 protease ; X-ray crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The functional groups of cage dimeric N-alkyl substituted 3,5-bis(hydroxymethyl)-4-(4-methoxyphenyl)-1,4-dihydropyridines are similar to those of cyclic and azacyclic ureas that are potent inhibitors of HIV-1 protease of the dihydroxyethylene- and hydroxyethylene type, respectively. In the following study the conformity of common functional groups is investigated concerning their orientation in space as well as in the enzyme HIV-1 protease. Starting from X-ray crystal data of the centrosymmetric cage dimeric N-benzyl derivative with ester groups, the derivative with hydroxymethylene groups was built and a systematic conformational search was performed for the conformationally important torsion angles considering electrostatic and van der Waals interactions. From the huge number of conformations those comprising centrosymmetrical and C2-symmetrical energy minima were selected and minimized. The three remaining conformers were fitted to the azacyclic urea A-98881 selected from the HIV-1 protease enzyme- inhibitor complex using the centroids of the corresponding aromatic residues and additionally by the field fit option of the Advanced CoMFA module of SYBYL. Interestingly, the energetically most favourable one, which, additionally, possesses C2-symmetry like the active site cavity of HIV-1 protease, showed the best fit. Comparing the electrostatic potential (EP) of the latter with the EP of A-98881 the aromatic residues show excellent accordance. Slight differences in the extent of the EP were found in the areas of the hydroxymethylene groups of the cage dimer and the single hydroxy group as well as the urea carbonyl group of A- 98881, respectively. In order to compare the binding possibilities to the enzyme HIV-1 protease for the cage dimer and A-98881, their interaction fields with certain probes (CH3 for alkyl, NHamide, and carbonyl, O− of COO−), representing the decisive functional groups of the active site, have been calculated using GRID and projected into the enzyme placing the structures according to the position of A-98881 in the enzyme- inhibitor complex. The strongest calculated fields of the O− probe were found near Asp 25 for both structures. Another respective conformity consists in the overlap of the fields for the NHamide probe near Ile 50 and 50′ for the investigated cage dimer and A-98881.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1213-1218 
    ISSN: 1434-193X
    Keywords: Cycloadditions ; Diazatetraasteranes ; Crystal structure ; Solid-state chemistry ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Upon irradiation, crystalline 4-methoxyphenyl-1,4-dihy-dropyridines 1 undergo nearly quantitative [2+2]cyclo-addition to form, via the ring-open intermediates 2, the centrosymmetric, polyfunctionalized 3,9-diazatetraasteranes 3. The centrosymmetric character of 3 was confirmed by 1H NMR spectral data as well as by X-ray crystal structure analysis. The dimerization reactions prove to be topochemically controlled by the nearest distance between potentially reacting double bonds, as well as by the conformationally determined packing restraints. This latter factor is shown by the X-ray crystal structure analysis of one dimerizing and one photostable derivative of the monomers 1.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 245-249 
    ISSN: 1434-193X
    Keywords: Cycloadditions ; Cage compounds ; Dimerizations ; Steric hindrance ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---On irradiation at λ ≥ 270 nm solutions of 4-aryl-1,4-dihydropyridines 1 yield cage dimers 2 as the main products beside small amounts of anti dimers 3. 1H-NMR data and X-ray crystal structure prove centrosymmetrical properties for both dimers with axially orientated 4-aryl substituents. Irradiation with filtered light (λ 〉 313 nm) leads to syn and anti dimers 4 and 3 in nearly equal yields. The poor yields of anti dimers 3 on irradiation with unfiltered light are demonstrated to result from a partial cleavage back to their monomeric starting materials 1.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 37 (1965), S. 1264-1272 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An Düsentrocknern mit großen Austauschflächen werden Wärmeübergangszahlen gemessen, die sich dimensionslos darstellen lassen. Im Vergleich zu Untersuchungen an Einzeldüsen und Düsengruppen mit kleinen Düsenteilungen werden stärkere Abweichungen festgestellt, die auf die gegenseitige Beeinflussung der Düsenstrahlen auf der Austauschfläche und auf die Störungen der Freistrahlen durch die Abluftströmung zurückzuführen sind. Bei konstanter Motorleistung läßt sich die Wärmeübergangszahl in Abhängigkeit von der geometrischen Anordnung der Düsen bestimmen und ein Maximum nachweisen.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 41 (1969), S. 731-735 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Die an großen und kleinen Austauschflächen gemessenen Wärmeübergangszahlen lassen sich dimensionslos darstellen. Für große Düsenfelder wird bei konstanter Motorleistung des Ventilators für die Luftumwälzung der Verlauf der Wärmeübergangszahl in Abhängigkeit von der Düsenfläche bestimmt. Optimierungen werden ausgeführt und Rund- und Schlitzdüsenanordnung miteinander verglichen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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