Phenylosazones anhydro derivatives

As in other fields of chemistry, research in the area of carbohydrates has benefited from the advent of such instrumental methods of structure elucidation, as NMR, MS, and X-ray crystallography. The impact of these tools can be realized by considering the time it took chemists to determine the structure of two hydrazine derivatives of about equal complexity, before and after the advent of NMR spectroscopy it took 65 years (from 1887 to 1952) and the efforts of four of the best chemists to prove by classic methods that the anhydro derivative obtained in acid media from what was then called glucosazone was 3,6-anhydro-D-n7 o-hexulose phenylosazone and only a few months in 1990 to determine that the oxidation products obtained from saccharide phenylhydrazones in basic media were in fact A-phenylaldonohydrazono-1,4-lactones (see schemes 52 and 11, respectively). 

L-a 2/lo-Hexose phenylosazone also gave the 3,6-anhydro-L-(2/a o-hexose derivative, and the phenylosazones from lactose and cellobiose yielded 3,6-anhydro-osazones, both with simultaneous Walden inversion on C-3. The D-galactose derivative, on the other hand, gave 3,6-anhydro-n-lyxo-hexose phenylosazone without inversion. 

The sugar osazones are particularly prone to acid-catalyzed dehydration, and form monoanhydro derivatives when their alcoholic solutions are boiled with a trace of acid 69), (See also Chapter VIII.) With the hexose phenylosazones, there is produced a mixture of the epimeric 3,6-anhydro-hexose phenylosazones resulting from dehydration with and without... 

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