Exocyclic Oxirane Derivatives 5,6-Anhydrohexofuranoses

These compounds have a similar steric arrangement of the oxolane ring as do ordinary derivatives of furanoses. Exocyclic oxirane-ring closure proceeds readily as compared to endocyclic epoxides because the required trans-orientation of the reacting groups is adopted without significant steric hindrance. 

The standard methods detailed in the preceding section are suitable for the preparation of all isomers of 5,6-anhydrohexofuranoses. For example, the first compound of this class to be synthesized, 5,6-anhydro-l,2-0-isopropylidene-a-D-glucofuranose,273,332 was prepared by selective tosyla-tion (sulfonylation) of the parent furanose, followed by treatment with alkali for application of this method, see Refs. 28, 333-335. Alternative 

6-Anhydrohexofuranose derivatives of the following configurations have been described gluco 78,332 manno,333 ido 79,335,337 allo,33S and galacto.153 

Ether-linked oligosaccharides have been prepared from 5,6-anhydro-D-glucose derivatives,345 and 5,6-anhydro sugars have also afforded various polysaccharides.338,346 

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