Hexose aqueous solution

A third, and more promising, route is currently under investigation. Bromine oxidation of an aqueous solution of 2-deoxy-D-nbo-hexose gave the hitherto unreported 2-deoxy-D-nbo-hexono-l,4-lactone, which was benzoylated to yield 3,5,6-tri-0-benzoyl-2-deoxy-D-nbo-hexono-l,4-lactone. Studies are in progress to effect a reduction of the benzoylated... 

Deoxy-D-jcylo hexose 6-(dihydrogen phosphate) (21) has also been synthesized (2) the reaction sequence makes use of 3-deoxy l 2,5 6-di-O-isopropylidene D-galactofuranose (16), a compound that can be easily prepared from D-glucose (2, 60). The mono-isopropylidene derivative (17) formed by partial hydrolysis of the di-ketal is converted into the 6-tosylate (18) by reaction with one molar equivalent of p-toluenesulfonyl chloride. From this the epoxide (19) is formed by reaction with sodium methoxide. Treatment of the anhydro sugar with an aqueous solution of disodium hydrogen phosphate (26) leads to the 6-phosphate (20)... 

The products arising from such condensations of the hexoses readily lose the elements of water in a way similar to the dehydration of 7-hydroxy acids, when heated in aqueous solution the hydroxyl groups corresponding to those at C3 and C6 of the original sugar are involved, and a substituted tetrahydrofuran ring results. 

The equilibrium compositions of aqueous solutions of some aldoheptoses are listed in Table III. Because the additional carbon atom in the side chain does not introduce additional steric interactions, the composition of solutions of heptoses is similar to that of the homomorphous hexoses, with only one exception, namely, n-glycero-n-ido-heptose, 92 a-D-Idopyranose in solution is a mixture of the 4Ci and 1C4 conformant) S. J. Angyal and R. J. Beveridge, Carbohydr. Res., 65 (1978) 229-234. 

It has been noted92 that, in aqueous solutions of the D-glycero-L-hep-toses, the a- to y -pyranose ratio is somewhat higher than that for the homomorphous hexoses, whereas, for the D-gh/cero-D-heptoses the ratio is the same, or even slightly lower. No explanation is apparent for this observation. 

Monomers and polymers of carbohydrates, (a) The most common carbohydrates are the simple six-carbon (hexose) and five-carbon (pentose) sugars. In aqueous solution, these sugar monomers form ring structures, (b) Polysaccharides are usually composed of hexose monosaccharides covalently linked together by glycosidic bonds to form long straight-chain or branched-chain structures. 

In cultured fish cells assay, it is an aqueous solution of nutrients and buffering agents, such as Leibovitz s L-15, that contains a hexose, bulk ions, trace elements, amino acids, and vitamins. Volume 1(15). 

Very few reports have been published on the use of X-rays for modification of starch, although the formation of deoxy compounds on irradiation of solid potato starch with 5 X 106 rads under nitrogen has been described. The amount of deoxy compounds formed is related almost linearly to the irradiation dose, and formation of 2-deoxy-D-arabi no-hexose is the major process there are almost no side-pro-cesses. Similar qualitative, but not quantitative, behavior is shown by 1% aqueous solutions of D-glucose, D-xylose, L-arabinose, D-ribose, sucrose, and cellulose powder (Fig. 14). Starch is the most resistant to irradiation among carbohydrates tested.74... 

The finding that the furanone is produced from an Amadori compound was interesting in that it permitted us to test, for the first time, the effect of pH on the products of the reaction. This is not possible using a hexose- derived Amadori compound, because the end products are not stable. The product of 1,2-enolization (3-deoxyosone intermediate) is HMF, which is stable, but the product derived from 2,3 enolization (1-deoxyosone intermediate), maltol and isomaltol are not stable in aqueous solution and thus cannot be detected and measured accurately. In our experiment (Scheme 6), we prepared 1-deoxy-dibenzylamino (13), and -benzylamino (12) D-fructuronic acids, as well as... 

Four major carboxylic acids, acetic, formic, glyceric, and lactic, are formed under mild alkaline oxidation conditions from xylose (Rahardja et al, 1994). At 40-60°C, lactic acid is formed from dilute aqueous solutions of xylose in the largest mass yield, about 50%, under continuous oxidation conditions. This is about 83% of the maximum theoretical yield of 60%. Under batch conditions, the yield of lactic acid from xylose is about 23%, while the yield from glucose is about 41%. These data indicate a commercial alkaline oxidation process for lactic acid from pentoses and hexoses is feasible, but it should be realized that the recovery of carboxylic acids having high water solubilities from dilute aqueous solutions can add signihcantly to production cost (Busche, 1984). 

Table 1.2 displays the tautomeric composition of pentoses and hexoses in aqueous solution as well as 1-deoxy fructose 1.20, and fructofuranose-l,6-diphosphate 1.21. The predominance of pyranoses is observed. The galactofuranoses 1.22 are relatively more stable than the glucofuranoses 1.23, perhaps due to the trans arrangement of the hydroxyl at C-3 and the side chain in the former. We also see that there are ten times as many jS- as there are a-pyranoses in the fructose solutions. At this point we are jumping ahead to Chapter 2, which is devoted to problems of conformation. We can draw /To-fructopyranose as confonnation 1.24 where only one unfavorable interaction takes place between H-3 and OH-5. The exchange of substituents at C-2 leads to an eminently unfavorable conformation which shifts to 1.25, the lesser of two evils, but where strong 1,3-diaxial interactions remain. 

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