Anhydrides Prepared Directly from the Corresponding Osazones

Anhydrides of Osazones and Hydeazones 1. Anhydrides Prepared Directly from the Corresponding Osazones 

Although Fischer described a lactose phenylosazone anhydride in 1887, little attention was paid to substances of this type until 1935 when Diels and Meyer reported the isolation of monoanhydrides of D-glucose phenylosazone, D-galactose phenylosazone, D-xylose phenylosazone, L-arabinose phenylosazone, lactose phenylosazone, and cellobiose phenylosazone, as well as a dianhydride of maltose phenylosazone, by boiling the corresponding osazones in alcoholic solution with a little sulfuric acid. Because of the apparent identity of the D-glucose phenylosazone anhydride with the 3,6-anhydro-D-glucose phenylosazone of Fischer and Zach, Diels and Meyer formulated these compounds as 3,6-anhydrides. 

This formulation was abandoned in a later paper in favor of a pyrazole structure (XV) produced by way of a 4-pyrazolone derivative (XIV), as follows. The authors interpret the production of the same 

D-glucose phenylosazone anhydride from 3,6-anhydro-n-glucose phenyl-osazone (XVI) in the following manner. In support of this view it is 

In addition, it has been shown that Diels D-glucose phenylosazone anhydride is not identical with 3,6-anhydro-D-glucose phenylosazone for although the osazones are very similar, the diacetates have widely different properties. 

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