title: Synthesis and conformational analysis of 6-C-methyl-substituted 2-acetamido-2-deoxy-beta-D-glucopyranosyl mono- and disaccharides.
abstract: Several 6-C-substituted 2-acetamido-2-deoxy-beta-D-glucopyranosides (beta-D-GlcNAc monosaccharides 1a-3a and 1,4-linked disaccharides 1b-3b) were studied by solution NMR spectroscopy. Conformational analysis of the (6S)- and (6R)-C-methyl-substituted beta-d-GlcNAc monosaccharides indicates that the stereodefined methyl groups impose predictable conformational biases on the exocyclic C-5-C-6 bond, as determined by (1)H-(1)H and (13)C-(1)H coupling constants. Variable-temperature NMR experiments in methanol-d(4) were performed to determine DeltaDeltaH and DeltaDeltaS values derived from the two lowest energy conformers. These indicate that while the influence of 6-C-methyl substitution on conformational enthalpy is in accord with the classic principles of steric interactions, conformational preference in solution can also be strongly affected by other factors such as solvent-solute interactions and solvent reorganization.
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA.
authors.forename: Jihane
authors.initials: J
authors.lastname: Achkar
authors.forename: Isabel
authors.initials: I
authors.lastname: Sanchez-Larraza
authors.forename: Carol A
authors.initials: CA
authors.lastname: Johnson
authors.forename: Alexander
authors.initials: A
authors.lastname: Wei
mesh_terms: D000465:Algorithms; D002236:Carbohydrate Conformation; D020650:Combinatorial Chemistry Techniques; D004187:Disaccharides / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D013237:Stereoisomerism
chemical_list: D004187:Disaccharides