The Use of Anhydro Sugars in Synthesis

An anhydro sugar which will probably find extensive synthetic use has been described by Hann and Hudson. This is the tricyclic compound, 3,4 l,6-dianhydro-j8-D-talopyranose (LXXIV) which is prepared by the saponification of the 4-tosyl derivative of mannosan (LXXIII). 

Acetolysis of LXXIV gives, as might be expected, a mixture of the acetates of D-mannose and D-idose and as the dianhydro sugar has a free hydroxyl on C2, it should prove to be a source of 2-substituted D-mannose or D-idose and of 2,4-derivatives of D-mannose and 2,3-derivatives of D-idose. 

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