title: Crystal and molecular structure of methyl 4-O-methyl-beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranoside.
abstract: The cellulose model compound methyl 4-O-methyl-beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranoside (6) was synthesised in high overall yield from methyl beta-D-cellobioside. The compound was crystallised from methanol to give colourless prisms, and the crystal structure was determined. The monoclinic space group is P2(1) with Z=2 and unit cell parameters a=6.6060 (13), b=14.074 (3), c=9.3180 (19) A, beta=108.95(3) degrees. The structure was solved by direct methods and refined to R=0.0286 for 2528 reflections. Both glucopyranoses occur in the 4C(1) chair conformation with endocyclic bond angles in the range of standard values. The relative orientation of both units described by the interglycosidic torsional angles [phi (O-5' [bond] C-1' [bond] O-4 [bond] C-4) -89.1 degrees, Phi (C-1' [bond] O-4 [bond] C-4 [bond] C-5) -152.0 degrees] is responsible for the very flat shape of the molecule and is similar to those found in other cellodextrins. Different rotamers at the exocyclic hydroxymethyl group for both units are present. The hydroxymethyl group of the terminal glucose moiety displays a gauche-trans orientation, whereas the side chain of the reducing unit occurs in a gauche-gauche conformation. The solid state (13)C NMR spectrum of compound 6 exhibits all 14 carbon resonances. By using different cross polarisation times, the resonances of the two methyl groups and C-6 carbons can easily be distinguished. Distinct differences of the C-1 and C-4 chemical shifts in the solid and liquid states are found.
authors.affiliation: Department of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, UK.
authors.forename: Iain D
authors.initials: ID
authors.lastname: Mackie
authors.forename: Jürgen
authors.initials: J
authors.lastname: Röhrling
authors.forename: Robert O
authors.initials: RO
authors.lastname: Gould
authors.forename: Jutta
authors.initials: J
authors.lastname: Pauli
authors.forename: Christian
authors.initials: C
authors.lastname: Jäger
authors.forename: Malcolm
authors.initials: M
authors.lastname: Walkinshaw
authors.forename: Antje
authors.initials: A
authors.lastname: Potthast
authors.forename: Thomas
authors.initials: T
authors.lastname: Rosenau
authors.forename: Paul
authors.initials: P
authors.lastname: Kosma
mesh_terms: D002475:Cellobiose / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D003460:Crystallization; D004187:Disaccharides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure
chemical_list: D004187:Disaccharides; C456720:methyl 4-O-methyl-glucopyranosyl-(1-4)-glucopyranoside; D002475:Cellobiose; D002482:Cellulose