Glucofuranose derivatives conformation

In a study related to the original work on 1,2-O-isopropylidenealdo-furanoses, the conformations of a number of l,2 3,5-di-0-ben-zylidene-a-D-glucofuranose derivatives (37) in solution were investi-... 

This free-energy difference between the anomers, which can be estimated by the ratios observed in glycosidation and anomerization equilibria, is larger in derivatives of 4 than in those of D-glucofuranose. This result can be attributed to the lessened conformational flexibility of bicyclic structures. 

Interesting conformational effects are possible with the six-membered 0-isopropylidene ring. It has been found that formation of 6-deoxy-1,2 3,5-di-0-isopropylidene-6-nitro-a-n-glucofuranose (XLVIII) occurs much much less readily than formation of the corresponding derivative (XLIX) of L-idofuranose when the 1,2-0-isopropylidene derivatives are... 

The polymerization of 1,6-anhydro sugars have been studied most thoroughly. Many 1,6-anhydro glucopyranoses derivatives polymerize easily in the presence of Lewis acids however, some 1,6-anhydro glucofuranoses may adopt strainless conformations which reduces their tendency for polymerization. Thus, monomer (8-15) polymerizes very reluctantly 14) (Ar = benzyl) ... 

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