Conformation of Acetate Derivatives of Sugars and Other Cyclic Alcohols. Crystal Structures, NMR Studies, and Molecular Mechanics Calculations of Acetates. When Is the Exocyclic C−O Bond Eclipsed?†

2005 ◽  
Vol 70 (7) ◽  
pp. 2486-2493 ◽  
Author(s):  
Jorge González-Outeiriño ◽  
Rima Nasser ◽  
J. Edgar Anderson
Keyword(s):  
Molecular Mechanics ◽  
Crystal Structures ◽  
Nmr Studies ◽  
Molecular Mechanics Calculations ◽  
Derivatives Of ◽  
Cyclic Alcohols

The conformational preference and barrier to internal rotation of an equatorial 3,5-dichlorophenyl group by the J method. Derivatives of cyclohexane, 1,3-dithiane, 1,3-dioxane, and 1,3-dioxolane

1979 ◽  
Vol 57 (3) ◽  
pp. 355-359 ◽  
Author(s):  
Ted Schaefer ◽  
Walter Niemczura ◽  
Werner Danchura
Keyword(s):  
Magnetic Resonance ◽  
Molecular Mechanics ◽  
Internal Rotation ◽  
Phenyl Ring ◽  
Proton Magnetic Resonance ◽  
Conformational Preference ◽  
Molecular Mechanics Calculations ◽  
X Ray ◽  
Carbon Carbon Bond ◽  
Derivatives Of

We report the preparation and the analysis of the phenyl ring proton magnetic resonance spectra of 3,5-dichlorophenylcyclohexane and of the 2-(3,5-dichlorophenyl) derivatives of 1,3-dioxane, 1,3-dithiane, and 1,3-dioxolane. With the exception of the dioxolanes these compounds exist predominantly as the equatorial isomers. The J method is used to show that the phenyl moiety prefers the conformation in which the α C—H bond lies in the phenyl plane. The predominantly twofold barriers to rotation about the carbon–carbon bond between the two ring systems are 2.0 ± 0.3, 0.4 ± 0.2, 2.2 ± 0.3, 0.85 ± 0.3 kcal/mol for these compounds, in the order given above. The low value for the barrier in the 1,3-dioxane derivative agrees reasonably well with molecular mechanics calculations and with the results of calorimetric and X-ray studies on equatorial 2-phenyl-1,3-dioxane.

Structure and Serotonin 5-HT2C Receptor Activity of ortho- and meta-Substituted Phenylpiperazines

1997 ◽  
Vol 53 (6) ◽  
pp. 976-983 ◽  
Author(s):  
M. L. Verdonk ◽  
J. W. Voogd ◽  
J. A. Kanters ◽  
J. Kroon ◽  
R. den Besten ◽  
...  
Keyword(s):  
Molecular Mechanics ◽  
Crystal Structures ◽  
Phenyl Ring ◽  
Structural Characteristics ◽  
Molecular Mechanics Calculations ◽  
Piperazine Ring ◽  
Energy Profiles ◽  
Nitrogen Bond

The structural characteristics of ortho- and meta-substituted phenylpiperazines have been investigated in order to understand their actions at the serotonin 5-HT2c receptor. The crystal structures of the 4-methylated analogues of two phenylpiperazines that are already known as 5-HT2c ligands, 1-(1-naphthyl)-4-methylpiperazine (1NMP) and 1-[(3-trifluoromethyl)phenyl]-4-methylpiperazine (TFMPMP), and those of two novel 5-HT2c ligands, 1-(2-methoxyphenyl)piperazine (oMPP) and 1-(3-methoxyphenyl)piperazine (mMPP), are determined. Molecular mechanics calculations are performed to calculate the energy profiles of six phenylpiperazines for rotation about the central phenyl–nitrogen bond. The activities of several phenylpiperazines, in combination with their crystal structures and conformational characteristics, lead to the hypothesis that the conformation for which the piperazine ring and the phenyl ring are approximately co-planar should be the 5-HT2c receptor `activating' conformation. This hypothesis is then used to predict the activities of the two novel 5-HT2c ligands oMPP and mMPP. oMPP is predicted to be an antagonist at this receptor, whereas mMPP is predicted to be an agonist. As this prediction was confirmed by in vitro and in vivo tests, the proposed conformation is very likely to be responsible for the activation of the 5-HT2c receptor.

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