Acetolysis of polysaccharides

The degradation of cellulose to the compound now known to be -cello-biose octaacetate by acetic anhydride-acetic acid-sulfuric acid was first reported almost ninety years ago. Assignments of structure to the various products from this reaction caused much controversy in the period during which the structure of cellulose and of starch was being established. However, no useful purpose is served by reviewing these controversies in this Series, their place now being in the domain of the chemical historian. 

The great use of acetolysis in polysaccharide chemistry is in degradation of the polysaccharides, imder mild conditions, to oligosaccharide per-acetates. More-drastic conditions afford monosaccharide peracetates, including those of the aldehydo forms of the sugars. The many oligosaccharides obtained from the partial acetolysis of various polysaccharides are excellently documented in a book by Bailey, and the reader searching for particular examples is referred thereto. 

Matsuda and coworkers studied first the acetolysis of isomaltose [a-D-(l— 6)] and nigerose [d-(W3)] the former was completely broken down, but the latter was not degraded. Use of the same conditions on several dextrans permitted them to isolate nigerose, proving the presence of (1— 3)-links, as well as kojiobiose [a-D-(l— 2)]. 

Presumably, the (1— 6)-linkages are split preferentially because of the greater ease of approach to that site than to a secondary-secondary linkage (compare the cleavage of methylene acetals, on p. 12). 

A more subtle specificity of acetolysis was suggested by Smith and Srivastava. From the results of work on the glucomannan of lies mannan, it was suggested that the linkage between two n-mannose residues is split more readily than the linkage between D-glucose and n-mannose residues. No work has since been done on simple systems to test this hypothesis. Experiments on a series of disaccharides could usefully extend our knowledge of acetolysis. 

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Acetolysis of polysaccharides from Smith degradation of carboxyl-reduced Sterculia urens gum ... 

Acetolysis of polysaccharides yields, in addition to acetates of the constituent monosaccharides, various oligosaccharide acetates and particu-... 

Various techniques have been utilized for sequencing the glycosyl residues of polysaccharides and oligosaccharides. These techniques are elaborations of the commonplace procedure of converting polysaccharides, by partial hydrolysis, into structurally analyzable oligosaccharides. This conversion is generally achieved by partial hydrolysis with acid, by acetolysis,131 or by formolysis.62 These reagents may differ in the... 

A. I. Usov and V. V. Barbakadze, Polysaccharides of algae. 27. Partial acetolysis of the sulfated galactan from the red seaweed Grateloupia divaricata Okam, Sow J. Bioorg. Chem., 4 (1978) 814-820(English translation from Bioorg. Khim., 4 (1978) 1107-1115). 

Definitive proof of the location of L-rhamnopyranosyl residues in gum arabic was obtained on acetolysis of the carboxyl-reduced polysaccharide, from which degradation, 4-O-L-rhamnopyranosyl-D-glu-cose (19) and 0-L-rhamnopyranosyl-(l — 4)-0-D-glucopyranosyl-(1 — 6)-D-galactose (20) were identified as products of partial... 

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