Glucose stereochemistry

Figure 13. Flow of carbon from dihydroxyacetone phosphate to phosphoglyceraldehyde (and, with oxidation, to 3-phosphoglyceric acid and biomass) and to Cg sugars. As shown, fructose-1,6-bisphosphate can be formed by combining dihydroxyacetone phosphate and phosphoglyceraldehyde. The further sugar shown has the structure of glucose (stereochemistry not shown). Carbon positions in such aldohexoses are numbered 1-6, starting with the aldehydic carbon. The processes...

Sorbitol is a sweetener often substituted for cane sugar because it is better tolerated by dia betics It IS also an intermediate in the commercial synthesis of vitamin C Sorbitol is prepared by high pressure hydrogenation of glucose over a nickel catalyst What is the structure (including stereochemistry) of sorbitoP... 

Fischer s original method for conversion of the nitrile into an aldehyde involved hydrolysis to a carboxylic acid, ring closure to a cyclic ester (lactone), and subsequent reduction. A modern improvement is to reduce the nitrile over a palladium catalyst, yielding an imine intermediate that is hydrolyzed to an aldehyde. Note that the cyanohydrin is formed as a mixture of stereoisomers at the new chirality center, so two new aldoses, differing only in their stereochemistry at C2, Tesult from Kiliani-Fischer synthesis. Chain extension of D-arabinose, for example, yields a mixture of D-glucose and o-mannose. 

Adenosine triphosphate, coupled reactions and. 1128-1129 function of, 157, 1127-1128 reaction with glucose, 1129 structure of, 157, 1044 S-Adenosylmethionine, from methionine, 669 function of, 382-383 stereochemistry of, 315 structure of, 1045 Adipic acid, structure of, 753 ADP, sec Adenosine diphosphate Adrenaline, biosynthesis of, 382-383 molecular model of, 323 slructure of, 24... 

Muscalure, structure of, 287 Mutarotation, 985-986 glucose and, 985-986 mechanism of. 986 Mycomycin, stereochemistry of, 330 Mylar, structure of, 819 n yo-Inositol, structure of, 135 Myrcene. structure of, 202 Mvristic acid, catabolism of, 1137 structure of. 1062... 

Sucralose is the sugar sucrose with three of the hydroxyl groups replaced by chlorine atoms. In the process, the stereochemistry of the glucose half of the molecule is changed, making it more like galactose. 

Sucrose contains one unit of glucose and one unit of fructose. Sucrose is made by linking one hydroxyl group of glucose to one hydroxyl group of fructose with the elimination of a molecule of water. Sucrose has nine chiral centers. You get a lot of stereochemistry here for a dollar or so a pound ... 

The cyclic form of glucose is termed glucopyra-nose, since the new ring system is a reduced form of the oxygen heterocycle pyran. Nucleophilic attack onto the planar carbonyl may occur from either of its two faces, generating two different stereochemistries at this new chiral centre, designated as a or p. This new chiral centre is termed the anomeric centre. Since there are other chiral centres in the molecule, the mixture of a- and -anomeric forms is not a racemate, but a mixture of diastereoisomers (see Section 3.4.4). The mixture does not contain 50% of each anomer (see below). Although both forms are produced, the form with the equatorial hydroxyl is thermodynamically favoured (see Section 3.3.2). 

Systematic substitutive nomenclature may be used to name all organic molecules. However, those that are of animal or vegetable origin have often received trivial names, such as cholesterol, oxytocin and glucose. Biochemical nomenclature is based upon such trivial names, which are either substitutively modified in accordance with the principles, rules and conventions described in Chapter 4, Section 4.5 (p. 70), or transformed and simplified into names of stereoparent hydrides, i.e. parent hydrides of a specific stereochemistry. These names are then modified by the rules of substitutive nomenclature. Three classes of compound will be discussed here to illustrate the basic approach carbohydrates amino acids and peptides and lipids. For details, see Biochemical Nomenclature and Related Documents, 2nd Edition, Portland Press, London (1992). 

Sucrose (4.5, common sugar) is an acetal formed from glucose (4.3) and fructose (4.4) ignoring terms which indicate the absolute stereochemistry, a more complete name for sucrose is 2a-glucopyranose-2p-fructofuranose. 

Another line of evidence that supports this pathway comes from a consideration of stereochemistry. In 1953, D. E. Koshland Jr. pointed out the significance of the fact that the formation of glucose-1-phosphate [5] from sucrose [6] occurs with retention of configuration at C-l of the glucose moiety. He postulated that a single displacement, in enzymic chemistry as in... 

The absolute configuration of the -glucose and (3-galactouronic acid groups was confirmed as D by GC analysis of the trimethylsilyl ethers of l(L-a-methylbenzyl-amino)-l-deoxyalditols derived from the water-soluble fraction from acid hydrolysis of (27). The stereochemistry at C-5 was secured by the usual method (hydrolysis and Lemieux degradation of... 

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