Conformations of Sugars: Proton Dihedral Angles from Gauche Coupling Constants

1974 ◽  
Vol 52 (24) ◽  
pp. 4095-4100 ◽  
Author(s):  
T. P. Forrest
Keyword(s):  
Dihedral Angle ◽  
Coupling Constants ◽  
Dihedral Angles ◽  
General Applicability ◽  
Karplus Equation ◽  
Proton Coupling ◽  
Equatorial Proton ◽  
Derivatives Of ◽  
Equatorial Substituent

Proton coupling constants have been used in calculating dihedral angles of vicinal gauche protons in variety of pyranose derivatives of glucose, mannose, arabinose, xylose, altrose, and galactose. The calculations involve the use of a formula which was derived from a correlation of the coupling constants of ethane derivatives with the electronegativities of substituents and their orientation relative to the coupled protons.The results indicate that the formula has general applicability and gives more reasonable values than a Karplus equation in which the constants have been adjusted to fit some compounds of the series. The calculated dihedral angles indicate that an equatorial substituent generally causes little distortion of dihedral angles, whereas an axial substituent generally causes the equatorial proton on the same carbon to have a smaller than normal dihedral angle with the adjacent axial proton and a larger than normal dihedral angle with the adjacent equatorial proton.

N.M.R. studies of aldonolactones. The 80-MHz proton N.M.R. and 20-MHz proton-coupled 13C N.M.R. of D-Arabinono-1,4-lactone in D2O solutions

1984 ◽  
Vol 37 (2) ◽  
pp. 327 ◽  
Author(s):  
H Wong
Keyword(s):  
Computer Simulations ◽  
Coupling Constants ◽  
Dihedral Angles ◽  
Proton Coupling

The 80-MHz proton n.m.r. spectrum of D-arabinono-1,4-lactone in D2O has been simulated and the results utilized in the assignment of the 20-MHz proton-coupled 13C n.m.r. spectrum. Two-and three-bond carbon-proton coupling constants have been derived from computer simulations and are discussed in terms of the dihedral angles in the preferred conformation.

The synthesis and the nuclear magnetic resonance study of β-lactam derivatives of 1,5-benzothiazepines

1988 ◽  
Vol 66 (2) ◽  
pp. 279-282 ◽  
Author(s):  
Aron Szöllösy ◽  
George Kotovych ◽  
Gábor Tóth ◽  
Albert Lévai
Keyword(s):  
Nuclear Overhauser Effect ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Magnetic Resonance Study ◽  
Proton Proton ◽  
Proton Coupling ◽  
Overhauser Effect ◽  
Vicinal Proton ◽  
Nuclear Overhauser ◽  
Derivatives Of

The synthesis and stereochemistry of seven β-lactam derivatives of 1,5-benzothiazepines are presented. The configurational and conformational analysis is based on nuclear Overhauser effect experiments, together with analysis of the vicinal proton–proton coupling constants. In the preferred conformation, the seven-membered ring is in a half-chair. Only for one compound, 2-aza-4-bromo-4-methyl-5,7-diphenyl-8-thiatricyclo[7.4.0.02,5]trideca-Δ1,9,10,12-trien-3-one, were two diastereomers isolated (compounds 6a and 6b). Six of the compounds have the 4S*, 5R*, 7R* configuration while compound 6b has the 4R*, 5R*,7R* configuration.

The Proton–Proton and Proton–Carbon-13 Spin–Spin Coupling Constants in 1,3-Dioxole and Bis-1,3-dioxolyl. Conformational Dependence

1975 ◽  
Vol 53 (18) ◽  
pp. 2734-2741 ◽  
Author(s):  
Ted Schaefer ◽  
Kalvin Chum ◽  
David McKinnon ◽  
M. S. Chauhan
Keyword(s):  
Double Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Dihedral Angles ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
Karplus Relationship ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The carbon-13 satellite peaks in the proton magnetic resonance spectra of 1,3-dioxole and bis-1,3-dioxolyl are analyzed under single and double resonance conditions to yield the signs and magnitudes of proton–proton coupling constants over three, four, and five bonds, and of proton–carbon-13 coupling constants over one, two, and three bonds. The conformational behavior of bis-1,3-dioxolyl contrasts sharply with that of analogous sym-tetrasubstituted ethane derivatives. It is indicated that the two-bond proton–carbon-13 coupling in the ethanic fragment can be used for conformational analysis in a manner similar to vicinal proton–proton couplings. The vicinal three-bond proton–carbon-13 couplings are given for dihedral angles of 180 and 120° and their relative magnitudes are as expected from a Karplus relationship. The two-bond proton–carbon-13 coupling in the olefinic fragment is, at 20.0 Hz, the largest coupling known for such a bond.

Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

1980 ◽  
Vol 58 (23) ◽  
pp. 2452-2459 ◽  
Author(s):  
Ted Schaefer ◽  
Leonard J. Kruczynski ◽  
Bert Krawchuk ◽  
Rudy Sebastian ◽  
James L. Charlton ◽  
...  
Keyword(s):  
Coupling Constants ◽  
Molecular Orbital Calculations ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
Conformational Preferences ◽  
Carbon Carbon Bonds ◽  
Vicinal Proton ◽  
Derivatives Of ◽  
Low Energy Conformations

The 1H nmr spectra in solution of 1-R-(3,5-dibromophenyl) ethanes (R = CH3, C2H5, n-C3H7 to n-C6H13, OH, F, Br), of 1-amino-2-(3,5-dichlorophenyl) ethane, of 3,5-dichloroallylbenzene, and of 4-(3,5-dibromobenzyl) pyridine are analyzed at 305 K. For the ethane derivatives, the populations of anti and gauche conformers are derived from the vicinal proton–proton coupling constants. The conformation about the C1—Cα bond in both gauche and anti forms is discussed in terms of long-range couplings to the ring protons and some approximate barriers about this bond are suggested for both conformers. Greater rigidity exists in the gauche than in the anti conformations. In some cases the measurements are compared with extensive molecular orbital calculations, for example, for phenethylamine. The low-energy conformations and the barriers about the C1—Cα bond are deduced for the allyl and pyridyl compounds.

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