Altrose rates

These values indicate that the rate of reaction of D-altrose with D-tartrate is the same as that of L-altrose with L-tartrate and that other rates pair up similarly. Similar data were obtained for some other pairs of enantiomers. Unfortunately no kinetic data are available on these systems. 

Fig. 4.—Rates of Consumption13 of Lead Tetraacetate by Some Aldoses (1) D-Mannose, (2) i.-Rhamnose, (3) D-Altrose, (4) D-Allose, (5) D-Galactose, and (6) D-Glucose (Temp. 0°).

Mycaminose has been found as a component of carbomycin (Magna-mycin)83 and, structurally, it resembles desosamine84 (see Table II). On periodate oxidation, one carbon atom is split out, to yield a seven-carbon amino sugar the results of subsequent reaction with the oxidant indicated the presence of a hydroxyl group at C4. Alkaline deamination of the seven-carbon sugar proceeded at a rate similar to that of 2-amino-2-deoxy-D-glucose, whereas mycaminose itself reacted far more rapidly this indicates the dimethylamino group to be at C3. Mycaminose is believed to be 3,6-dideoxy-3-dimethylamino-/3-D-altrose.84a... 

A study of the rates of hydrolysis of the 4,6-0-benzylidene acetals of several methyl hexosides showed that the trans-iused acetals (of n-glucose, D-mannose, and n-altrose) are hydrolyzed only about three times faster than the cis fused ones (of D-galactose and L-idose). It may be concluded, therefore, that the natiu-e of the ring fusion does not, in these fused, six-membered ring systems, greatly influence the rate. 

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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