Chitonic acid

The best known 2,5-anhydro hexose is that which was prepared in 1894 by Fischer and Tiemann4 and named by them chitose. Chitose is a liquid with ill-defined properties and is usually characterized by its oxidation derivatives, chitonic acid and isosaccharic acid. It is prepared by the deamination of the naturally occurring chitosamine (D-glu-cosamine). 

Let us now return to the pioneering work of Fischer and Tiemann.4 Chitonic acid is produced from D-glucosamine by deamination and oxidation, in that order. If the order is reversed, however, i. e., if D-glucos-amine is first oxidized to D-glucosaminic acid (2-amino-D-gIuconic acid) and the latter substance subsequently deaminated, chitonic acid is not the product. Instead an isomeric 2,5-anhydro hexonic acid (chitaric acid) is obtained. These facts may be summarized thus ... 

Walden inversion on C2 has occurred in one of these sequences if in the first, then chitose, chitonic acid and isosaccharic acid have the configuration of D-mannose if in the second, i. e., in the deamination of 2-amino-D-gluconic acid, then chitaric acid and epi-isosaccharic acid are... 

Chitose, a 2,5-anhydro-D-mannose obtained by Fischer by the action of nitrous acid on D-glucosamine, was oxidized with bromine to chitonic acid (2,5-anhydro-D-mannonic acid). 

The hydrofuran ring in chitose and the anhydro sugar acids derived from it involves carbons 2 and 5, since isosaccharic acid when heated in hydrogen chloride gas produces furan-o ,Q -dicarboxylic acid (47) and the acetylation-dehydration of chitonic acid yields 5-acetoxymethylfuroic acid (48). 

Anhydro Derivatives from Glucosamine. Treatment of glucosamine with nitrous acid does not lead to the replacement of an amino by a hydroxyl group instead an anhydro ring is formed 267 279). The anhydro sugar formed, called chitose (I), is a 2,5-anhydro sugar, for oxidation leads to chitonic acid (II), which is converted by the action of acetic anhydride to... 

When the above order of operations is reversed, i.e., when the oxidation precedes the treatment with nitrous acid, chitaric acid is formed. This anhy-droaldonic acid is isomeric with chitonic acid. (For additional details, see Chapter VII). 

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