JS-D-glucose

Acylation of jS-D-glucose with azolides yields preferentially esterification in the 1-position of which for example, with R = C6H5 60% and with R=Ci7H35 71% yield are obtained. Azolides of sterically crowded acids [R = (C6H5)2CH or (CH3)3C] give poorer yields ( 28%).[193]... 

The stereochemical isomerization or structural rearrangement resulting in the interconversion of epimers. For example, the conversion of jS-D-glucose to jS-D-galac-tose involves epimerization at the C-4 carbon atom, and the epimerization at the C-2 of jS-D-glucose results in the synthesis of jS-D-mannose. 

It is of interest to contrast the above-described mechanism (for the alkali-catalyzed transformation of phenyl /S-D-glu copyranoside to 1,6-anhydro-jS-D-glucopyranose) to the mechanism proposed by Lemieux and Brice38 for the acid-catalyzed transformation of 1,2,3,4-tetra-O-acetyl-jS-D-glucose (XXXI) to tri-0-acetyl-l,6-anhyd ro-/S-D-glu copy ran ose (XXXIII). Evidence was obtained showing that, in the presence of stan-... 

The mechanism generally accepted for mutarotation involves conversion to the open-chain form for example, XXXVI —> XL, for the acid-catalyzed mutarotation of a- and jS-D-glucose. 

More precise studies of monosaccharide carbonates began in 1915, when Zempl6n and Ldszl6 obtained, from the action of methyl chloroformate (and ethyl chloroformate) on jS-D-glucose in pyridine at 0°, crystalline compounds which appeared to be the appropriate penta-0-(alkyloxycarbonyl) derivatives II. Important contributions were made from 1924 onward by Haworth and his collaborators, - who carried out an extensive series of... 

In the earlier literature, jS-D-glucose (3) was considered to be an intermediate compound which, on subsequent dehydration, provides levoglucosan. Experimental evidence against this theory has been adduced by Golova and associates, who obtained small yields of levoglucosan from jS-D-glucose and from cellobiose, as compared to a 54—60% yield from cellulose. 

Actually, this enzyme shows almost complete specificity for jS-D-glucose, ct-D-Glucose reacts at a rate of 0.64 relative to 100 for the )8 form. In the latter form, all the hydrogens are axial and the hydroxyl groups are equatorial, allowing... 

We have seen that jS-D-glucose is more stable than a-o-glucose because there is more room for a substituent in the equatorial position. The relative amounts of j8-D-glucose and a-D-glucose are only 2 1, however, so the preference of the OH group for the equatorial position is surprisingly small (Section 22.10). Contrast this to the preference of the OH group for the equatorial position in cyclohexane, which is 5.4 1 (Table 2.10 on p. 99). 

Key A = 2,3,4,6-tetrarO-acetyl-jS-D-glucose B = 2,3,4,6-tetrarO-acetyl-a-D-glucosyl bromide. Equilibrium mixture of a and fi anomers. 

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