Computation of vicinal coupling constants in tetra- and hexa-alditol peracetates using molecular mechanics. A rational approach to conformational analysis in solution

1986 ◽  
pp. 261-263 ◽  
Author(s):  
Satoru Masamune ◽  
Philip Ma ◽  
Richard E. Moore ◽  
Teruyo Fujiyoshi ◽  
Carlos Jaime ◽  
...  
Keyword(s):  
Conformational Analysis ◽  
Molecular Mechanics ◽  
Coupling Constants ◽  
Rational Approach ◽  
Vicinal Coupling Constants

Conformational Studies on 1,3-Dioxepanes. Part IV. Applications of Geminal Coupling Constants to Conformational Analysis of 1,3-Dioxepanes

1974 ◽  
Vol 52 (24) ◽  
pp. 4062-4071 ◽  
Author(s):  
T. Bruce Grindley ◽  
Walter A. Szarek
Keyword(s):  
Conformational Analysis ◽  
Coupling Constants ◽  
Conformational Studies ◽  
Vicinal Coupling Constants ◽  
Geminal Coupling ◽  
Derivatives Of ◽  
Acetal Carbon

The magnitude of —OCH2O— group geminal H,H coupling contants, the size of the vicinal coupling constants, and the tenets of conformational analysis were used to establish that in solution the conformation of the 1,3-dioxepane rings in derivatives of 1,3:2,5-di-O-methylenemannitol and 2,5-O-methylenemannitol is predominantly the twist-chair in which the C2 axis passes through the acetal carbon.

Conformational analysis of acyclic compounds with oxygen–sulphur interactions. Part VI. Some 1-thioderivatives of 2-propanol and its acetates

1979 ◽  
Vol 57 (18) ◽  
pp. 2426-2433 ◽  
Author(s):  
Felipe Alcudia ◽  
José L. García Ruano ◽  
Jesús Rodríguez ◽  
Félix Sánchez
Keyword(s):  
Conformational Analysis ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Conformational Study ◽  
Conformational Preference ◽  
Methyl Group ◽  
Opposite Charge ◽  
H Nmr ◽  
Vicinal Coupling Constants

A conformational study of 1-X-2-propanol (X = SH, SMe, SOMe, SO2Me, +SMe2) and their O-acetyl derivatives (X = SMe, SOMe, SO2Me, and +SMe2) is reported. From the relative values of the vicinal coupling constants in 1H nmr spectra it has been possible to establish the conformational preference. When a density of opposite charge is supported by heteratoms, polar factors determined a great predominance of that conformation in which the sulphur function has an anti-relationship with respect to the methyl group. In thiol and thioethers the conformational preference is not so marked.

Conformational Analysis with Carbon−Carbon Coupling Constants. A Density Functional and Molecular Mechanics Study

1997 ◽  
Vol 62 (11) ◽  
pp. 3702-3704 ◽  
Author(s):  
Martin Stahl ◽  
Ulrich Schopfer ◽  
Gernot Frenking ◽  
Reinhard W. Hoffmann
Keyword(s):  
Conformational Analysis ◽  
Molecular Mechanics ◽  
Density Functional ◽  
Coupling Constants

Conformational analysis and complete assignment of the proton and carbon NMR spectra of ouabain and ouabagenin

1990 ◽  
Vol 68 (8) ◽  
pp. 1263-1270 ◽  
Author(s):  
Deane D. McIntyre ◽  
Markus W. Germann ◽  
Hans J. Vogel
Keyword(s):  
Conformational Analysis ◽  
Molecular Mechanics ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
X Ray Diffraction ◽  
Proton Proton ◽  
Proton Coupling ◽  
Nmr Techniques ◽  
Phase Sensitive ◽  
C Nmr

The 1H and 13C NMR spectra of the cardenolide ouabain and its aglycon ouabagenin have been completely assigned by two-dimensional NMR techniques, including phase-sensitive COSY and carbon–proton correlation (HETCOR, HMQC, and COLOC) spectra. The major conformer of these two compounds in solution is all-chair as determined from proton–proton coupling constants and is similar to that in the crystal lattice as previously determined by X-ray diffraction. The conformations of the A and D rings of ouabain in water are somewhat different than in DMSO/CDCl3 (2:1). At lower temperatures (−20 °C) signals from two conformers in slow exchange were readily observed in the 13C spectra, with an approximate ratio of 1:7. Molecular mechanics and dynamics calculations indicate that the conformational process responsible for this involves a chair/twist-boat interconversion of the A ring, with the all-chair conformer highly preferred. Keywords: ouabain, conformational analysis, 2-D NMR, molecular mechanics, molecular dynamics.

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