Sugar sulfoxides

Sulfoxides and seienoxides are known to easily undergo beta-elimination reactions. Sugar sulfoxides obtained by oxidation of respective thioglycosides were efficiently transformed to glycals upon heating in toluene (O Scheme 20) [160]. 

On the other hand, the conformational behaviour of diastereomeric sugar sulfoxides at the glycosidic linkage has been analyzed by NMR. The conformational behaviour was shown to depend on the absolute configuration (R/S) of the stereogenic sulphur atom. 

Fortunately, the oxidation of l,2 5,6-di-0-isopropylidene-a-D-glucofura-nose to l,2 5,6-di-0-isopropylidene-a-D-nfoo-hexofuranos-3-ulose (1) can be accomplished using either phosphorus pentoxide (10, 44) or acetic anhydride (10, 52) in methyl sulfoxide although this oxidation is effected with ruthenium tetroxide (6,7, 46), it is exceeding difficult with other oxidizing agents (53). Keto-sugar 1 is reduced stereospecifically... 

Bajugam and Flitsch [217] have described the synthesis of glycosylamines from mono-, di-, and trisaccharides by direct microwave-assisted Kochetkov amination (Scheme 6.110). The reaction was found to be effective with just a fivefold excess (w/w) of ammonium carbonate with respect to the sugar, as compared to the 40-or 50-fold excess needed under thermal conditions. All transformations were completed within 90 min in dimethyl sulfoxide as solvent, maintaining the vessel temperature at an apparent 40 °C using the heating-while-cooling technique (see Section 2.5.3). 

Stilbenes, photocyclization of, 30, 1 StiUe reaction, 50, 1 Stobbe condensation, 6, 1 Substitution reactions using organocopper reagents, 22, 2 41, 2 Sugars, synthesis by glycosylation with sulfoxides and sulfinates, 64, 2 Sulfide reduction of nitroarenes, 20, 4 Sulfonation of aromatic hydrocarbons and aryl halides, 3, 4 Swem oxidation, 39, 3 53, 1... 

Of the many substituted and functionalized alkenes that have been combined with diazo dipoles to give A -pyrazolines or products derived from them (i.e., A -pyrazolines, pyrazoles, cyclopropanes), only a selection will be mentioned. These include ot-alkylidene-cycloalkanones (62), -flavanones, -thioflavanones, -chroma-nones, and thiochromanones (63,64) a-arylidene-indanones and -indolones (65) diarylideneacetones (66) l-benzopyran-2(77)-ones (coumarins) (67,68) 4-nitro-1,2-oxazoles (69) 2-alkylidene-2-cyanoacetates (70) dimethyl 2,3-dicyanofuma-rate (71) tetracyanoethylene (72) tetraethyl ethylenetetracarboxylate (72) 1,4-quinones (35,73-75) 2-X-l,l,l-trifluoro-2-propene [X = Br, (76), SPh, SOPh, S02Ph (77)] nitroalkenes (78) including sugar nitroalkenes (79) 1-diethoxyphos-phoryl-1-alkenyl-sulfoxides (80) methyl 2-(acetylamino)cinnamate and -acrylate... 

The structures of four sulfur derivatives of sugars have thus far been solved. Two are sulfides, the third is a C-sulfonate, and the fourth is a sulfoxide. Sinigrin, from the seeds of black mustard,... 

The method was used in studies of a fungal heterogalactan.150 The polysaccharide was subjected to successive tritylation, methylation, detritylation, p-toluenesulfonylation, reaction with sodium iodide, and, finally, reaction with sodium p-toluenesulfinate. The product was then treated with sodium methylsulfinyl carbanion in dimethyl sulfoxide, the product remethylated, and the polysaccharide material recovered by gel chromatography. The polymer was hydrolyzed, and the sugars in the hydrolyzate were analyzed, as the alditol acetates, by g.l.c.-m.s.1 The analysis revealed that —60% of the hexose residues that were unsubstituted at C-6 had been eliminated. As the product was still polymeric, it was concluded that these residues had constituted a part of side chains linked to a main chain of (1 — 6)-linked D-galactose residues. 

Water is the only solvent in which the composition of sugars has been systematically explored. Stevens1674 has determined the composition of several aldoses in pyridine-d5 by -n.m.r, spectroscopy at 300 MHz. There are scattered data on solutions in organic solvents (mainly pyridine, dimethyl sulfoxide, and N,N-dimethylformamide), but only rarely have four (or more) components of such solutions been quantitatively determined. The data that have been encountered are collected in Table VII undoubtedly, there are others that have been missed. 

When compared with those in other Tables, the data in Table VII show that Perlin s conclusions are generally valid. 2,3-Anhydro-D-mannose and 2-C-(hydroxymethyl)-D-ribose (hamamelose) are exceptions there is actually somewhat less furanose in their solutions in dimethyl sulfoxide and pyridine, respectively, than in water but these can hardly be regarded as typical sugars. 

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