Abstract
The crystal data on cellobiose octaacetate and cellotriose undecaacetate are compared in an effort to analyze what information available from crystal structures of oligosaccharides can be used to arrive at the three‐dimensional structure of the related polysaccharides. This comparison points out the remarkable behavior of the reducing end of both molecules. The glycosidic torsion angles (ϕ,ψ) around the reducing and the middle residues in the disaccharide and in the trisaccharide have values around 45° and 14°, while the conformational angles about the nonreducing residues in cellotriose acetate are 24° and −20°. The conformations of the primary acetate groups on the two nonreducing residues are similar, but they differ from those observed for the acetate groups belonging to the reducing residues. The possibility of a 2~1~ symmetry axis between contiguous triacetate residues within the oligosaccharide is examined, along with a comparison of the molecular packing found in the oligomer structures. Conformational energy calculations have been performed on two dimeric entities derived from cellotriose acetate. The isoenergy maps show the drastic influence of the relative orientations of the primary acetate groups. It is proposed that the nonreducing dimer, as found in the crystal structure of cellotriose acetate, most nearly expresses the “polymer averaged” interactions for contiguous residues in cellulose triacetate.