Altrose composition

The presence of substituents outside the ring usually does not affect the composition. Thus, D-allose 6-phosphate, D-altrose 6-phosphate, and d-manno-heptulose 7-phosphate have practically the same composition as the parent sugars.51... 

We have studied the relative reactivity of cellulose and mixed polysaccharides (III) and (IV) in reactions with aqueous and alcoholic solutions of NaOH. The data on the composition of alkali compounds of polysaccharides are given in Table 6. As seen from the data presented in Table 6, the amount of bound alkali in preparations of alkaline compounds of mixed polysaccharides is le than in alkali cdlulose obtained under the same conditions, the DS with respect to NaOH decreasing with increasing content of altrose units in polysaccharide (III) and of 3,6-anhydroglucose units in polysaccharide (IV). 

Table 6. Effect of number of altrose or 3,6-anhydroglucose units in the macromolecule of a mixed polysaccharide on the composition dl alkaline compounds of polysaccharides (III) (IV)...

Steiger and Reichstein have isolated a compound of m. p. 132° and [a]o —43.0° in acetone (c, 1.7) it had the composition of, and was assumed to be, a methyl isopropylidene-anhydro-D-altroside, and was obtained as a by-product during the preparation of a diisopro-pylidene-D-altrose (see Table I) from a D-altrose sirup. 

Various sugars epimerize at different rates. For example, maimose is converted much slower than glucose or fructose [9] and it is also formed more slowly. Idose reacts very rapidly in the presence of bases, altrose rapidly but allose slowly [23]. The most investigated case is, of course, the glucose-maimose-fruc-tose system. The products are formed in a ratio of approximately 4 1 4. More accurate figures have been quoted but the composition will depend on the nature of the base and of the starting material True equilibrium, as already stated, is probably never obtained [9]. 

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