2.5- anhydro properties

Aldonic acids, characterization of, 373 —, 2-amino-2-deoxy-, deamination of, 191 —, 2,5-anhydro-, properties of, 220-229 Aldonolactones, 2-amino-2-deoxy-, deamination of, 189... 

VIII. Tables of Properties of Anhydro Sugars and Their Derivatives. 69... 

It is to be noticed that although the anhydro ring of levoglucosan is stable to alkali (Tanret s preparative method consisted in the heating of aromatic jS-D-glucosides with aqueous alkali), it readily undergoes scission in the presence of acid. An isomeric glucose anhydride prepared in 1912 by E. Fischer showed, however, very different properties. 

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). 

Chloro-6-desoxy-3,5-benzylidene-l,4-anhydro-D-sorbitol (XVI) possesses an unusual property in that the benzylidene group is removed by distillation in alkaline or neutral solution. From the neutral solution it was possible to isolate 6-chloro-6-desoxy-l,4-anhydro-D-sorbitol as its triacetyl derivative. At the same time diacetyl-1,4 3,6-dianhydro-D-sorbitol was also formed. This removal of an acetal residue from a... 

The word cellulosan has the disadvantages that (a) it employs an ending ordinarily used for designating simple anhydro-sugars, and (b) that the name implies a relation with cellulose, whereas in fact no relationship is intended and polysaccharides placed in this class are quite different from cellulose in both composition and properties. Their connection with cellulose seems to be only that they occur with cellulose as constituents of the plant cell wall. 

Deprotonation of the a-position of a carbenium center is one of the most typical properties of carbocations. All the alkyl-substituted heterocyclic ions possess an appreciable CH-acidity [82AHC(S)1] the 3-azapyrylium salts are no exceptions to this rule. The formation of anhydro bases, i.e., methylene-1,3-oxazines (e.g., 69), from methyl-3-azapyrylium salts is well known (72S333). 

For the properties of the methyl derivatives of 3,6-anhydro-L-galactose see Advances in Carbohydrate Chemistry, 2, 77 (1946).)... 

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