Glucose rotation

As you can see from their structures, a- and /3-glucose have several chiral carbon atoms. Both isomers are optically active they are not enantiomers (mirror images of one another) because they differ in configuration only at carbon atom 1. As it happens, both a- and /3-glucose rotate the plane of polarized light to the right (clockwise). 

The orientational van Hove self-correlation function corresponding to the relaxation of the backbone (top panel) and side (lower panel) vectors of glucose (see text for definition) at 220 K show that glucose rotation in the glass proceed by big jumps and does not have a continuous diffusion component. The side rotation, which involves the jump of the smaller glucose bead, the "exocyclic" B6, relaxes faster (ts 3 fjs) than the rotation involving the jumps of the big "backbone" beads B4 and B1 (ts 15 /is). 

In our research group, a CP/MAS NMR technique was developed to study glucose rotational mobility in the solid state over a range of and in matrices... 

Commercially, glucose is employed in the manufacture of confections, in the wine industry, and in the canning industry. Since solutions of glucose rotate polarized light to the right, glucose is often called dextrose, especially in industry. 

Sucrose is dextro-rotatory. Fructose shows a laevo-rotation greater in magnitude than the dextro-rotation shown by glucose. Hence as the hydrolysis of sucrose proceeds, the dextro-rotation gradually falls to zero and the solution finally shows a laevo-rotation. This hydrolysis is therefore sometimes called inversion and so the enzyme which catalyses the reaction is known as " invertase. Its more systematic name is, however, sucrase. 

The distribution between the a and p anomenc forms at equilibrium is readily cal culated from the optical rotations of the pure isomers and the final optical rotation of the solution and is determined to be 36% a to 64% p Independent measurements have established that only the pyranose forms of d glucose are present m significant quanti ties at equilibrium... 

Cyclodextrins are macrocyclic compounds comprised of D-glucose bonded through 1,4-a-linkages and produced enzymatically from starch. The greek letter which proceeds the name indicates the number of glucose units incorporated in the CD (eg, a = 6, /5 = 7, 7 = 8, etc). Cyclodextrins are toroidal shaped molecules with a relatively hydrophobic internal cavity (Fig. 6). The exterior is relatively hydrophilic because of the presence of the primary and secondary hydroxyls. The primary C-6 hydroxyls are free to rotate and can partially block the CD cavity from one end. The mouth of the opposite end of the CD cavity is encircled by the C-2 and C-3 secondary hydroxyls. The restricted conformational freedom and orientation of these secondary hydroxyls is thought to be responsible for the chiral recognition inherent in these molecules (77). 

Sucrose, in contrast, is a disaccharide of almost universal appeal and tolerance. Produced by many higher plants and commonly known as table sugar, it is one of the products of photosynthesis and is composed of fructose and glucose. Sucrose has a specific optical rotation, of +66.5°, but an... 

D-Glucose can be crystallized in two different forms, a-glucose and p-glucose . The forms have different melting points, and different specific rotations when dissolved in water. These rotations change upon standing to give a solution whose specific rotation is +52.7°. 

The fermenters are inoculated with 7.5% by volume of a 24-hour old culture of Aspergillus sderotiorum Huber grown at 28°C in 50 ml aliquots of the above described soybean-glucose medium contained in 300 ml Erlenmeyer flasks, placed on a shaker rotating at approximately 230 rpm. The inoculated fermenters are agitated at 1,380 rpm and each aerated with 1 liter of air per minute and at a temperature of 28°C for 47 hours. A silicone antifoam is added when required. At the end of the 47-hour period, the pH of the fermentation broth rose to 6.8 to 6.9. Sulfuric acid is then added with sterile precautions to restore the pH to 6.5. 

The formation of 120 can be explained by attack of chloride ion at C-6 (rather than the more hindred endo side at C-3) as depicted in the intermediate 126, with concomitant migration of the ketal function to the 3,5-position. This procedure provides a convenient route to 6-substituted D-glucose derivatives from the readily accessible 49. Since rotation about the C-5—0 bond is required for the migration of the ketal, the reaction most likely is not of a concerted nature and may proceed via 126a-126b. 

Per-O-acetyl dihexulose dianhydrides l3C NMR spectra, 247 H NMR spectra, 250-251 optical rotations and melting points, 244 Per-O-acetyl fructose glucose, H-NMR spectra, 252... 

---