Abstract
The crystal structure of methyl β-cellotrioside (methyl
O-β-
d-glucopyranosyl-(1 → 4)
-O-β-
d-glucopyranosyl-(1 → 4)-β-
d-glucopyranoside
) complexed with water and ethanol, C
19H
34O
16 · H
2O · 0.25[C
2H
6O] was determined by combining Cu
K
α X-ray and synchrotron data collected at room temperature. The crystals have the monoclinic space group
P2
1 with
Z = 8 and unit cell parameters
a = 7.9978(11), b = 76.38(4), c = 8.9908(6)
A
̊
and
β = 116.40(1)°. The structure, which was solved by direct methods and refined to a final
R-factor of 0.067, contains four independent molecules of methyl β-cellotrioside with an extended conformation. They are arranged parallel to the long
b axis of the unit cell, and organized in two pairs of antiparallel molecules. Each β-
d-glucopyranosyl residue of the four independent molecules is in the
4
C
1 pyranose conformation, and each (O-6) primary hydroxyl group has the
gt conformation. The crystal structure of methyl β-cellotrioside has many points in common with that of cellotetraose hemihydrate as well as with the structure of cellulose II. Thus, it is likely that the precise atomic coordinates obtained in this study can be directly transposed to give an improved structure for cellulose II where, in particular, only the
gt conformation would be present at the primary hydroxyl groups of both polysaccharide chains.