Saccharide hydrazones structure

The structure of inosose mono(phenylhydrazones) is quite similar to that of acyclic saccharide hydrazones neither possess chelated rings and both exist in the Schiff-base form. Cyclization to hydrazino forms, a common process among many saccharide hydrazones, has not been observed in inosose hydrazones, probably because the resulting bicyclic compounds would be unduly strained or rigid. 

The hydrazones of sugars are capable of existing in various cyclic forms, whose presence is apparent from their nuclear magnetic resonance (NMR) spectra and from the complex mutarotation curves they exhibit110,111117118 (which seldom follow first-order kinetics). The principal structures encountered in saccharide hydrazones are the acyclic, Schiff base-type true hydrazones and the cyclic hydrazino forms, namely glycopyranosyl- and gly-cofuranosylhydrazines. For example, three isomeric forms of D-glucose phenylhydrazone have been isolated.119 The Schiff base derivatives can be... 

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