Heptose 1,6-anhydride

S. J. Angyal and T. Q. Tran, Conformational analysis in carbohydrate chemistry. 5. Formation of glycosidic anhydrides from heptoses, Can. J. Chem., 59 (1981) 379-383. 

Higher sugars also can form the anhydrides in which the anomeric position and the terminal carbon atom are linked via a heterocyclic ring. For example, heptoses can form 1,7-anhydro derivatives although they are very rare. Only a few examples of such derivatives have been desaibed in the literature (O Fig. 5) [3]. 

The dehydration of hexose, heptose, and octose phenylosazones in methanolic sulphuric acid has been studied. Each osazone gave rise to two 3,6-anhydrides epimeric at C-3 except 7-deoxy-D-wa no-heptulose phenylosazone which afforded only the 3,6-anhydro-7-deoxy-L- M/o-heptulose phenylosazone with... 

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