Glucopyranoses, structure

Figure Bl.11.10. 400 MHz H NMR spectrum of nrethyl-a-glucopyranose (structure as in figure Bl.l 1.12)...

The configurations of monosaccharides are described by several types of formulas. As an example, the following formulas are shown for a-D-glucopyranose structural, Haworth, modified Fischer, and Fischer. In Fischer formulas the -H or -OH groups are above or below the plane formed by the hemiacetal bonds and the carbon chain (-H bonds are shown shorter). 

Figure Bl.11.12. H- H COSY-45 2D NMR spectrum of methyl-a-glucopyranose (structure shown). The coupling links and the approximate couplings can be deduced by inspection.

Cellulose contains adsorbed water which is held in the glucopyranose structure by hydrogen bonding, hence the separation proceeds via a partition mechanism. Cellulose materials are used almost exclusively for separating hydrophilic substances, for instance, amino acids and sugars in contrast to silica gel and alumina which are used for the separation of lipophilic compounds. Similar eluants, as for the PC application, can be selected. The partial structure of the cellulose molecule is shown in Figure 3.4. 

In spite of their easy interconversion in solution a and p forms of carbohydrates are capable of independent existence and many have been isolated m pure form as crys talline solids When crystallized from ethanol d glucose yields a d glucopyranose mp 146°C [a]o +112 2° Crystallization from a water-ethanol mixture produces p d glucopyranose mp 148-155°C [aj +18 7° In the solid state the two forms do not mterconvert and are stable indefinitely Their structures have been unambiguously con firmed by X ray crystallography... 

Fig. 9. Partial structural formulas and shorthand notations for principal hemiceUuloses found in wood, where the sugar units ate noted as P-D-xylopyranose (Xylp), 4-Omethyl-a-D-glucopyranosyluronic acid (GlupU), a-L-arabinofuranose (Araf), P-D-glucopyranose (Glup), P-D-mannopyranose (Manp), and P-D-galactopyranose (Galp) for (a) arabino-4-O-methylglucuronoxylan from softwood, (b) 0-acetyl-galactoglucomannan from softwood, and...

Fig. 1. Chemical structure of a-cyclodextrin. Six glucopyranose units are numbered G1 to G6. The numbers on the G1 glucopyranose refer to those of the carbon atoms...

Several mono-carba-oligosaccharidic alpha amylase inhibitors, such as acarbose and its homologs, amylostatins, trestatins, oligostatins, adipo-sins, and so on, have been isolated from cultures of micro-organisms, and considerable interest in the biochemistry and chemistry of this class of inhibitors has been stimulated. The characteristic core-structure for inhibitory action is composed of a trihydroxy(hydroxymethyl)cyclohexene moiety and a 4-amino-4,6-dideoxy-D-glucopyranose moiety, bonded by way of an imino linkage at the allylic position. A similar structural unit has been found in the antibiotic validamycins. 

Amide derivatives have proved especially useful sugars for study by c.d. spectroscopy. The amide substituent is the same as the chromophore found in proteins, so that its optical properties have been extensively studied both experimentally and theoretically. 2-Acetamido sugars are found in many glycoproteins. The structure of 2-acetamido-2-deoxy-a-D-glucopyranose is given as an example in formula 7. 

In muramic acid, the 2-hydroxyl group of D-glucose is replaced by an amine group, and a lactic acid group is attached to OH-3. The structure of muramic acid [2-amino-3-0-(D-l-carboxyethyl)-2-deoxy-D-glucopyranose] is given in formula 12. 

ATCC 9245), Cunninghamella sp. (NRRL 5695), and Rhizopus arrhizus (ATCC 11145) produced the 6-glucopyranose conjugate [59]. The structures of the related starting and transformed molecules are shown in Fig. 8. 

Fig. 8 Structures of sampangine, 3-methoxysampangine, and the transformed 4 -0-methyl-/S-glucopyranose and /S-glucopyranose conjugates [59]...

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