1.6- Anhydro-P-D-glucose

Further decomposition of levoglucosan and cellobiosan generates smaller molecules in cellulose pyrolysate. The reaction of levoglucosan formation is one of the main paths in pyrolytic decomposition of cellulose above 400° C, although the pyrolysis conditions such as the presence of acids or bases may favor other mechanisms. The yield of 1.6-anhydro-p-D-glucose in the pyrolysate was reported [13,27] to vary from traces to 40% or more. 

Fourteen DFAs and some oligomers were identified in caramel obtained by thermal treatment of inufin. - Monosaccharides (glucose, fructose), dehydration products (1,6-anhydro-p-D-glucopyranose, 1,6-anhydro-p-D-glucofuranose), disaccharides (gentiobiose and isomaltose), and oligosaccharides were also found in glucose and sucrose caramel. ... 

Dehydration Reactions. Detailed analysis of the pyrolysis tar as discussed previously (Figure 12 and Scheme 3) shows the presence of levoglucosan, its furanose isomer (1,6-anhydro-p-D-glucofuranose) and their transglycosylation products as the main components. In addition to these compounds, the pyrolyzate contains minor amounts of a variety of products formed from dehydration of the glucose units. The dehydration products detected include 3-deoxy-o-erythrohexo-sulose, 5-hydroxymethyl-2-furaldehyde, 2-furaldehyde (furfural), other furan derivatives, levoglucosenone (l,6-anhydro-3,4-dideoxy-P-D-glycerohex-3-enopyranos-2-ulose), l,5-anhydro-4-deoxy-D-hex-l-ene-3-ulose, and other pyran derivatives. The dehydration products are important as intermediate compounds in char formation. 

A number of trehalose-based crown ethers such as (17) have been prepared, and their conformations determined by NMR spectrometry. The NMR study of several other glucose-derivative-containing crown ethers is discussed in Chapter 21. The intramolecular cyclization of some 4-0-oligoethylene glycol derivatives of 1,6-anhydro-P-D-glucopyranose to form crown ethers has been described. ... 

The benzylated 1,6-anhydro 3-D-glucose (93) has been coupled to trimethylsilyl 4-thio a-D-glucoside (94) under acidic conditions to afford the thiodisaccharide 95 in good yield (66% a/P, 15 1) [49] (Scheme 19). A noteworthy comment from the authors reveals, however, the poor reactivity of the 1,6-anhydro disaccharide (not shown). 

An optical rotation-based method of conformational analysis has been applied to methyl P-xylobioside and a semi-empirical model of saccharide optical activity has been used to calculate the NaD rotation of this same compound. Calculated values of optical rotation based on the crystal structures of a series of 1,6-anhydro-p-D-pyranoses of galactose, talose and mannose suggest that solution conformations are very similar to those found in the solid state. However, significant differences were detected for methyl 3,6-anhydro-a- and p-pyranosides of glucose, galactose and mannose. 

Hydrolyses of the glycosidic linkages of phenyl a- and 3-D-glucopyranoside were studied at different alkali concentrations, and the reaction rates increased rapidly above 2M. Mechanisms involving direct hydrolysis and the intermediacy of l,6-anhydro- 8-D-glucose and, with the j3-anomer, the l,2-a-anhydride were proposed. Analogous work with p-acetylphenyl 3- and 5-0-methyl- 3-D-xylo-furanoside led to the conclusion that the 2-oxyanions (and presumably 1,2-anhydrides) were involved as intermediates. ... 

The widespread occurrence of long-range couplings in both furanose and pyranose derivatives explains why so many of the P.M.R. spectra of carbohydrate derivatives are apparently poorly resolved, even when the resolution of the spectrometer is above reproach. For example, the Hi resonance of the 1,6-anhydro-D-glucose derivative (12) is coupled to all of the other six ring protons. A further example of the line-broadening effect follows a consideration of the spectrum of 5,6-dideoxy-5,6-epithio-l,2-0-isopropylidene-/ -L-idofuranose for which the half-height... 

Anhydro-2,4-dideoxy-2,4-bis(diphenylphosphinyl)glucose p-D-I ranose-Zorw P,P -Dioxide, A-577... 

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