Glucofuranose structure

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. 

The purpose of this study was to explore the introduction of an OZT moiety onto the specific C-3 site of both l,2 5,6-di-0-isopropylidene-a-D-glucofuranose and 1,2 4,5-di-0-isopropylidene-p-D-fructopyranose, taking advantage of the well-defined frame of both carbohydrate structures to generate all possible OZT-isomers. These spiroheterocyclic structures could be constructed according to a simplified sequence based on a key stereoselective approach from uloses via epoxides or aziridines (Scheme 16). 

Norrild and coworkersd showed that this structure is only valid as an initial complex formed under completely non-aqueous conditions. In the presence of water, a rapid rearrangement from the a-D-glucopyranose form to the a-D-glucofuranose occurs. In the latter form, all five free hydroxy groups of glucose are covalently bound to the sensor molecule (Figure B.10.4.2). 

Figure 9.7 Six- and five-membered cyclic ethers. The stable ring structures which are adopted by hexoses and pentoses are five- or six-membered and contain an oxygen atom. They are named as derivatives of furan or pyran, which are the simplest organic compounds with similar ring structures, e.g. glucofuranose or glucopyranose for five-or six-membered ring structures of glucose respectively.

Peat and coworkers187 investigated the reversion products formed by the action of acid on D-glucose and found, by periodate oxidation, that the mixed anhydrides contain 18 to 47% of material having a furanoid structure. Some 1,6-anhydro-0-D-glucofuranose was isolated. Other sugars apparently give only pyranoside reversion products. 

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