1,2-Anhydrosugars

Although the pyrolysis of some classes of polysaccharide materials has been studied quite extensively in the food, petrol and tobacco industry, very little has been published specifically on polysaccharide binders (arabic gum, tragacanth gum, fruit tree gum, honey and starch). The pyrolysis of glucane based polymers, especially cellulose, has been studied in detail [6,55], highlighting how anhydrosugars and furan derivatives are the main pyrolysis products, together with one-, two- and three-carbon aldehydes and acids. 

Glucose, galactose, xylose and arabinose give rise to the formation of the corresponding anhydrosugars. 

O-stannylene acetals,84 glycals and 1,2-anhydrosugars,85 and to selective de-O-benzylation of position-2 with TIBAL, DIBAL-H57 or Lewis acid catalysts,86 or to the one-pot access to 3-O-benzyl-4,6-0-benzylidene glucosides by tandem catalysis recently reported.87 The 1,2-lactones recently reported by Linker and co-workers35 are also synthons which provide... 

SOLID SUPPORT GLYCAL ASSEMBLY VIA 1,2-ANHYDROSUGAR DONORS... 

Polymer-supported glucal 37 was converted to the protected thioethyl glucosyl donor 39 as outlined in Scheme 2.11. Compound 37 was first epoxidized by the action of DMDO. The resulting 1,2-anhydrosugar was opened by a mixture of ethanethiol and dichloromethane (1 1) in the presence of a trace of trifluoroacetic acid. Polymer-bound 38 was thus obtained in 91% yield. This was a substantial improvement over the 78% yield obtained by the same protocol in solution. Protection by reaction with pivaloyl chloride occurred in quantitative yield to furnish 39a. 

At higher temperatures (>250°C), endothermic depolymerization reactions dominate and generate volatile anhydrosugars and related monomeric compounds, see pathway... 

The stereoselective glycosidation of the secoaglycon 1338 was achieved by reaction of the sodium salt of 1338 with the a-l,2-anhydrosugar 1339 to give the p-glucopyranoside 1340 in 48% yield. After the removal of the SEM protecting group with TBAF, the photocyclization of compound 1341 afforded the indolocarbazole... 

R. Blattner and D. M. Page, Radical addition to levoglucosenone, synthesis of anhydrosugar herbicide analogues, J. Carbohydr. Chem. 132 21 (1994). 

Finally the so-called mono- and macro-tracer approaches can be applied for determining source contributions. These methods rely on the fact that a number of chemical compounds can be directly linked to biomass combustion emissions. For example, ambient concentrations of water-soluble potassium, certain PAHs, anhydrosugars and many other tracers have been used as indicators for the impact of biomass burning. When the fractions of one of these tracers in PM and carbonaceous aerosols emitted by wood burning are known (emissions ratios), the contribution of wood burning at a receptor site can be calculated based on the concentration of the considered tracer (mono tracer method). 

The most efficient photosubstitution reaction, with many applications in synthesis, is the photobromination method developed by FERRIER s group [24]. The substitution of H-5 is regioselective and stereoselective for pentopyranosides [25], hexo-pyranosides [26], 1-6 anhydrosugars [27], uronic acids [24, 28] heterocyclic derivatives from deoxyinosones [29], nucleosides [30, 31], etc.. . using bromine or N-bromo-succinimide in carbon tetracloride under irradiation. 

M. Cavicchioli, A. Mele, V. Montanari, and G. Resnati, A stereoselective and preparative entry to 1,2-anhydrosugars through oxidation of glycals with perfluoro-c -2,3-dialkyl-oxaziridines, J. Chem. Soc., Chem. Common., (1995) 901-902. 

C. Sund, S. Thiering, J. Thiem, J. Kopf, and M. Stark, Photochemical transformation of levoglucosan imides to anhydrosugar-annelated azepanediones and azocanediones, Monatsh. Chem., 133 (2002) 485 497. 

L. F. Wiggins, Ethylene oxide-type anhydrosugars, Methods Carbohydr. Chem., 2 (1963) 188-191. 

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