ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The molecular and crystal structure of curdlan triacetate, acetylated (1 → 3)β-D-glucan, was analyzed by means of an x-ray diffraction technique with the help of the linked-atom least-squares method. Unit cell dimensions are a = b = 11.00(1), c(fiber axis) = 22.91 (9) Å, and γ = 120°. The space group is P61. The unit cell contains six chemical repeating units related by 6/I-helical symmetry, which is essentially the same as the backbone conformation of one of the modifications (form I) of curdlan. During the refinement calculation, the terminal methyl in every acetyl moiety was elastically restrained to the trans conformation commonly observed in related oligosaccharide structures. The difference Fourier map, the observed and calculated densities, and the thermogravimetric measurement indicated one water molecule per glucose residue. The water oxygen is linked to two carbonyl oxygens in adjacent molecules by hydrogen bonds. The conformation of the primary acetyl moiety is a (skew, -gauche, trans). So far, no skew conformation was observed for the primary acetyl and hydroxyl moieties except in α, β-panose. In both cases, the unusual eclipsed orientation of the primary group is attributed to the hydrogen bond and this conformation is quite different from that of pachyman triacetate. © 1996 John Wiley & Sons, Inc.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
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