Conformations of Sugars: Proton Dihedral Angles from Gauche Coupling Constants

Abstract

T. P. FORREST. Can. J. Chem. 52, 4095 (1974).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.T. P. FORREST. Can. J. Chem. 52, 4095 (1974).Les constantes de couplage du proton ont Bt B utilisees dans le calcul des angles diedres des protons gauches vicinaux dans une varikte de derives pyranosiques du glucose, mannose, arabinose, xylose, altrose et galactose. Les calculs font appel B l'utilisation d'un formule deduite

Poly-amido-saccharides: Synthesis via Anionic Polymerization of a β-Lactam Sugar Monomer

“…For comparison, the monosaccharide methyl α- d -glucopyranoside, which has a chair conformation in solution, has reported values in D 2 O of J (H 1 –H 2 ) = 3.8 Hz, J (H 2 –H 3 ) = 9.8 Hz, and J (H 3 –H 4 ) = 9.1 Hz . In addition to the dihedral angle between the C–H bonds, coupling constants are affected by other factors such as the electronegativity of substituents, bond lengths, and bond angles, and differences in these variables may account for the larger couplings for P1 versus methyl α- d -glucopyranoside . The spectra of all the polymers show that the stereochemistry of the polymer is not affected by the reductive debenzylation.…”

Conformational Equilibrium Isotope Effects in Glucose by 13C NMR Spectroscopy and Computational Studies

“…In fact, carbohydrates are complicated molecules, and a number of experimental and theoretical techniques have been brought to bear on their total molecular structure and behavior. Raman and infrared spectroscopic studies have been used to assign vibrational bands to specific bond stretches, angle bends, and coupled motions. − NMR studies of glucose have been able to demonstrate differences in extracyclic hydroxymethyl rotamer populations between the α- and β-pyranose anomers, and a variety of chemical shift and coupling constant data have been reported. − Most recently, empirical relationships between homo- and heteronuclear coupling constants and carbohydrate conformation 24,33-38 and several ab initio , and molecular dynamics − studies have been used to explain the relative free energies of glucose anomers and their rotamers.…”

Determination of the Relative Configuration and Conformational Analysis of Five-memberedN-Acyl-Iminosugars by Relevant3JCoupling Constants.

“…Substitution pattern, conformation and vicinal 3 J (H,H) couplings are closely inter‐related in cyclanes or heterocyclic compounds, particularly in six‐membered rings. Substituted cyclohexanes as well as their O ‐ and N ‐heterocyclic congeners usually appear as one major chair conformer characterized by specific values of trans,trans‐diaxial (9–12 Hz) and gauche (0–5 Hz) 3 J (H,H) in sugar series . In the particular case of piperidines, where additional substitution at nitrogen is possible, it has been shown that the presence of a N ‐acyl substituent had a strong directing effect on conformation.…”