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  • 1
    Electronic Resource
    Electronic Resource
    Crystal structures of a pair of diastereomeric 3-(N,N-dimethylammonium)-1,1-diphenyl-1-butanol O,O′-di-p-toloyl hydrogen tartrates (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 545-553 
    Details
    ISSN: 1572-8854
    Keywords: Diastereomeric salts ; O, O′-di-p-toloyl hydrogen tartrates ; crystal packing ; molecular mechanics calculations ; conformational analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of a pair of diastereomeric salts of (−)-(2R, 3R)-O, O′-di-p-toloyl tartaric acid and (−)- and ( + )-3-N,N-dimethylamino-1,1-diphenyl-1-butanol have been determined. Crystal data: 3: (-)-(R)-C18HC24NO+(-)-(2R,3R)-C20H17O- 8 orthorhombic, P212121, a = 7.873(2), b = 15.343(3), c = 28.76(1) Å, V = 3474(2) Å3, Z = 4, and D calc = 1.254 g cm−3. 4: (+)- (S)-C18H24NO+, (-)-(2R,3R)-C20H17O- 8orthorhombic, P212121, a = 7.504(1), b = 17.215(2), c = 26.490(4) Å, V = 3422.0(8) Å3,Z = 4, and D calc = 1.273 g cm−3. The geometries and the conformational energies of the solid state conformations of the cations have been compared with global and local energy minimum conformations determined by molecular mechanics calculations. In the solid state, one conformation with and one without an intramolecular hydrogen bond are observed. The calculated global energy minimum conformation in aqueous solution contains the intramolecular hydrogen bond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023296106521
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  • 2
    Electronic Resource
    Electronic Resource
    Conformational energy penalties of protein-bound ligands (1998)
    Springer
    Journal of computer aided molecular design 12 (1998), S. 383-383 
    Details
    ISSN: 1573-4951
    Keywords: AMBER ; bioactive conformation ; conformational analysis ; GB/SA hydration model ; ligand–protein interactions ; MM3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The conformational energies required for ligands to adopt their bioactive conformations were calculated for 33 ligand–protein complexes including 28 different ligands. In order to monitor the force field dependence of the results, two force fields, MM3 and AMBER, were employed for the calculations. Conformational analyses were performed in vacuo and in aqueous solution by using the generalized Born/solvent accessible surface (GB/SA) solvation model. The protein-bound conformations were relaxed by using flat-bottomed Cartesian constraints. For about 70% of the ligand–protein complexes studied, the conformational energies of the bioactive conformations were calculated to be ≤3 kcal/mol. It is demonstrated that the aqueous conformational ensemble for the unbound ligand must be used as a reference state in this type of calculations. The calculations for the ligand–protein complexes with conformational energy penalties of the ligand calculated to be larger than 3 kcal/mol suffer from uncertainties in the interpretation of the experimental data or limitations of the computational methods. For example, in the case of long-chain flexible ligands (e.g. fatty acids), it is demonstrated that several conformations may be found which are very similar to the conformation determined by X-ray crystallography and which display significantly lower conformational energy penalties for binding than obtained by using the experimental conformation. For strongly polar molecules, e.g. amino acids, the results indicate that further developments of the force fields and of the dielectric continuum solvation model are required for reliable calculations on the conformational properties of this type of compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008007507641
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  • 3
    Electronic Resource
    Electronic Resource
    A pharmacophore model for dopamine D4 receptor antagonists (2000)
    Springer
    Journal of computer aided molecular design 14 (2000), S. 769-786 
    Details
    ISSN: 1573-4951
    Keywords: bioactive conformation ; conformational analysis ; dopamine D2 ; dopamine D4 ; D2/D4 selectivity ; enantioselectivity ; pharmacophore model ; solvation energies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A pharmacophore model for dopamine D4 antagonists has been developed on the basis of a previously reported dopamine D2 model. By using exhaustive conformational analyses (MM3* force field and the GB/SA hydration model) and least-squares molecular superimposition studies, a set of eighteen structurally diverse high affinity D4 antagonists have successfully been accommodated in the D4 pharmacophore model. Enantioselectivities may be rationalized by conformational energies required for the enantiomers to adopt their proposed bioactive conformations. The pharmacophore models for antagonists at the D4 and D2 receptor subtypes have been compared in order to get insight into molecular properties of importance for D2/D4 receptor selectivity. It is concluded that the bioactive conformations of antagonists at the two receptor subtypes are essentially identical. Receptor essential volumes previously identified for the D2 receptor are shown to be present also in the D4 receptor. In addition, a novel receptor essential volume in the D4 receptor, not present in the D2 receptor, has been identified. This feature may be exploited for the design of D4 selective antagonists. However, it is concluded that the major determinant for D2/D4 selectivity is the nature of the interactions between the receptor and aromatic ring systems. The effects of the electronic properties of these ring systems on the affinities for the two receptor subtypes differ substantially.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008198026843
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  • 4
    Electronic Resource
    Electronic Resource
    Enantiomers of methyl substituted analogs of (Z)-5-decenyl acetate as probes for the chirality and complementarity of its receptor inAgrotis segetum 1: Synthesis and structure-activity relationships (1993)
    Springer
    Journal of chemical ecology 19 (1993), S. 459-484 
    Details
    ISSN: 1573-1561
    Keywords: Lepidoptera ; Noctuidae ; Agrotis segetum ; (Z)-5-decenyl acetate ; pheromone analog ; methyl substitution ; structure-activity ; single-sensillum recordings ; receptor interaction ; conformational analysis ; molecular mechanics ; enantiomers ; chirality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The enantiomers of analogs of (Z)-5-decenyl acetate, a pheromone component ofAgrotis segetum, substituted by a methyl group in the 2, 3, 4, 7, and 8 positions and dimethyl substituted in the 4,7 positions, have been synthesized and studied by an electrophysiological single-cell technique and by molecular mechanics calculations. The results demonstrate that the electrophysiological activity as well as the ability of the (Z)-5-decenyl acetate receptor to differentiate between enantiomers depends on the position of the methyl substituent. For analogs methyl substituted in the 2, 4, or 8 position, no differences in the activities of the enantiomers could be observed. In contrast, the enantiomers of the 3- and 7-methyl analogs display a significant difference in the activities, theR-enantiomers being more active than theS-enantiomers. From an analysis of the structure-activity results of the enantiomers of the 4,7-dimethyl-substituted analogs, the chiral sense of the alkylchain of the natural pheromone component on binding to its receptor could be deduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00994319
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  • 5
    Electronic Resource
    Electronic Resource
    Introduction of methyl groups to acetate substituted chain of (Z)-5-decenyl acetate, a pheromone component of turnip moth,agrotis segetum: synthesis, single-sensillum recordings, and structure-activity relationships (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 637-657 
    Details
    ISSN: 1573-1561
    Keywords: Lepidoptera ; Noctuidae ; Agrotis segetum ; (Z)-5-decenyl acetate ; pheromone analog ; methyl substitution ; structure-activity ; single-sensillum recordings ; receptor interaction ; conformational analysis ; molecular mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Methyl-substituted analogs of (Z)-5-decenyl acetate, a pheromone component of the turnip moth,Agrotis segetum, have been synthesized and studied by electrophysiological single-sensillum recordings and molecular mechanics calculations [MM2(85)]. The analogs are monomethyl substituted in the 2, 3, 4, and 5 positions and geminally dimethyl substituted in the 2, 3, and 4 positions. The methyl groups have been employed as space probes to study the degree of steric complementarity between the acetate-substituted alkyl chain of the pheromone component and its receptor. The electrophysiological activities, interpreted in terms of a receptor interaction model, indicate significant steric repulsive interactions between the introduced methyl groups and the receptor. This implies a high degree of complementarity between the acetate-substituted alkyl chain of the natural pheromone component and its receptor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00987825
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