Cellobiose conformational analysis

The torsion angles predicted by conformational analysis agree closely with those of crystalline cellobiose as measured by X-ray diffraction, the conformation of which is restricted by two chain-stabilising intramolecular hydrogen bonds between 0(3 )-H and 0(5) and also between 0(2 )-H and 0(6) (Figure 4.3). These are also found in cellulose and they assist in maintaining the highly extended conformation which allows it to function as a structural polymer. 

B. J. Hardy and A. Sarko, J. Comput. Chem., 14, 831 (1993). Conformational Analysis and Molecular Dynamics Simulation of Cellobiose and Larger Cellooligomers. 

The size of the cellulose molecule is normally expressed in terms of their degree polymerization (DP), i.e, the number of anhydroglucose units present in a chain. However, the conformational analysis of cellulose indicates that cellobiose (4-0-a-D-glucopyranosyl-a-D-glucopyranose, Fig. 10.2a) is its basic structural unit [10]. The conformation of the repeating unit of cellulose can be explained if we consider the model proposed for the biosynthesis of glucose [11]. 

Rees D.A. and Skerrett R.J. 1968. Conformational analysis of cellobiose, cellulose and xylan. Carbohydr Res 7 334-348. 

The following disaccharides and derivatives have been subjected to conformational analysis by n.m.r spectroscopy and/or computational methods cellobiose in aqueous solution, methyl P-xylobioside, methyl P-cellobioside, P-gentibiose, all possible monomethyl ethers of methyl p-lactoside, unsaturated, sulfated disaccharides, such as IS, obtained by cleavage of glycosaminoglycans with lyases, ° chondroitin sulfate-related ctmqmunds, such as 16, the uronic... 

Fig, 5. Conformation of cellobiose from X-ray crystal structure analysis as a space filling stereo plot. The reducing end is to the right... 

Cellobiose octaacetate and 1,6-Anhydro-p-cellobiose hexaacetate are compared with respect to their glycosidic conformation [93, 94], For cellobiose octaacetate it was concluded that the conformation in solution is close to that one determined by X-ray crystal structure analysis to cp = 45° and i / = 16° (Fig. 5) whereas the 1,6-anhydro derivative is demonstrated by use of NOEs, relaxation data, and coupling constants 3JC>H to adopt torsional angles of = 25° and ]c = 45° respectively. 

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