Carbohydrates anhydrosugars

R. Blattner and D. M. Page, Radical addition to levoglucosenone, synthesis of anhydrosugar herbicide analogues, J. Carbohydr. Chem. 132 21 (1994). 

L. F. Wiggins, Ethylene oxide-type anhydrosugars, Methods Carbohydr. Chem., 2 (1963) 188-191. 

The reaction of carbohydrates in acid or alkaline solution results in a number of products, many of which have been identified over the past century (L/i). With the exception of anhydrosugars (e.g., l,6-anhydro-/ -D-glucopyranose) and oligosaccharides, which are concentration-dependent and equilibrium components (reversion products) formed in acid solution, all of these products result from reactions associated with the Lobry de Bryn-Alberda Van Ekenstein transformation or intermediates formed from this transformation. 

Both unsubstituted bicyclic monomers and related anhydrosugars polymerize by cationic mechanism [148]. In sugar derivatives, the remaining free hydroxyl groups have to be blocked before polymerization by typical methods known in carbohydrate chemistry. 

There are several classes of compounds formed from rapid pyrolysis of carbohydrates. Besides anhydrosugars, they are carbonyl compounds, furan derivatives, lactones, pyran derivatives, phenols, acids and acid esters, and other compounds. In general, the presence of a substantial quantity of 5-hydroxymethylfuraldehyde in the pyrogram indicates that a hexose is present. Substantial amounts of furaldehyde and the absence of 5-hydroxymethylfuraldehyde in the pyrolysis products indicate the presence of a pentose. However, these markers are not diagnostic for a specific hexose or pentose. 

One approach utilized in carbohydrate pyrolysis is Py-MS. Py-MS using El type ionization does not differentiate well between anhydrosugar stereoisomers, and its utilization to obtain structural information on carbohydrates is rather limited. However, there are reports [10a] where the type of bond between monosaccharide units can be differentiated using Py-EI MS. As an example, the Py-EI MS results are shown for a (1 -> 2)-p-glucan and for a (1 -> 3)-p-glucan (laminaran). 

Liquids obtained by fast pyrolysis of four different woods were analysed. On addition of excess water they separated into water-soluble and water-insoluble fractions. The former which is principally of carbohydrate origin was shown by HPLC analysis to consist of sugars, anhydrosugars and low molecular weight carbonyl compounds. The latter was shown by NMR to be a "pyrolytic lignin". In this way 81% to 92% of the organic content of the liquids has been characterised. 

S. Wiggins, L. F. Ethylene Oxide-type Anhydrosugars. Methods in Carbohydrate Chemistry , 188 (1963). 

For the configuration-conformational properties of simple carbohydrates, as well as their reactivities, comprehensive treatises should be consulted (Pigman and Horton, 1972). It has to be mentioned on closing, that recent achievements in macromolecular science have established the ways to the synthesis of linear homopolysaccharides and copolysaccharides (normally by cationic polymerization) of different suitably protected anhydrosugars (Schuerch, 1981). These syntheses open the route to the availability for our studies of a variety of tailor made carbohydrate polymers. A few synthetic polysaccharides have in fact already been used to investigate immunological and allergic reactions in experimental animals and the interaction of plant lectins with carbohydrates (Schuerch, 1981). 

The properties of anhydrosugars make them useful as protecting groups that, under the appropriate conditions, can enable them to serve as reactive intermediates for the formation of new C-C and C-X bonds. These characteristics have made them useful precursors for the formation of a variety of carbohydrate derivatives and medicinally important compounds. For example, anhydrosugars have been utilized in... 

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