Chitonic acid 2,5-anhydro

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 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 ... 

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... 

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