Glucose, rearrangement

In the presence of dilute base, D-glucose rearranges to a mixture containing the anomers of D-glucose (—64%), D-fructose (—31%), and D-mannose (3%). This interconversion undoubtedly involves enolization of the hexoses by way... 

Glucose is an example of a monosaccharide, a carbohydrate that cannot be broken down into simpler carbohydrates. Monosaccharides such as glucose rearrange in aqueous solution to form ring structures (T Figure 19.2). 

To this point, the pathway has generated a pool of pentose phosphates. The AG° for each of the last two reactions is small, and the three pentose-5-phosphates coexist at equilibrium. The pathway has also produced two molecules of N/ DPH for each glucose-6-P converted to pentose-5-phosphate. The next three steps rearrange the five-carbon skeletons of the pentoses to produce three-, four-, six-, and seven-carbon units, which can be used for various metabolic purposes. Why should the cell do this Very often, the cellular need for... 

Kuzuhara and his coworkers synthesized (+)-205 by hydroxylation of the alkene 304, which was prepared from the chiral azidocyclohexene derivative (303) derived from D-glucose, in which a novel rearrangement of the C - C double bond accompanying reduction of the azido group with lithium aluminum hydride was observed. 

The use of the glucose chiral auxiliary by Lubineau et al. led to moderate asymmetric induction in the Claisen rearrangement (20% de) (Eq. 12.75).159 Since it could be removed easily, glucose functioned here as a chiral auxiliary. After separation of the diastereomers, enan-tiomerically pure substances could be obtained. 

Figure 1.37 A reducing sugar may modify protein amine groups through Schiff base formation followed by an Amadori rearrangement to give a stable ketoamine product. Glucose is a common in vivo modifier of blood proteins through this process.

A similar interpretation is possible for the Lobry de Bruyn rearrangement of glucose to fructose ... 

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). 

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