Glycosyl bromides

Glycosidic thiol groups can be introduced into glycosyl bromides by successive reactions with thiourea and aqueous sodium disulfite (D. Horton, 1963 M. Cemy, 1961, 1963). Such thiols are excellent nucleophiles in weakly basic media and add to electrophilic double bonds, e.g., of maleic esters, to give Michael adducts in high yields. Several chiral amphiphiles have thus been prepared without any need for chromatography (J.-H. Fuhrhop, 1986 A). 

This ether, developed for the protection of a pyranoside anomeric hydroxyl, is prepared via a Konigs-Knorr reaction from the glycosyl bromide and 2-(ben-zylthio)ethanol in the presence of DIPEA. It is cleaved, after oxidation with dimethyldioxirane, by treatment with LDA or MeONa. ... 

These compounds are made by allowing the salt made from piperidine and sodium hydride to react with CS2 and then with an acetylated glycosyl bromide.56... 

Thioglycosides containing free OH groups readily tolerate silver triflate-pro-moted glycosylations with glycosyl bromides and chlorides, and also tin(II) chloride-silver perchlorate-activated glycosylation, and several examples have... 

Glycosyl bromides can be used as donors in the presence of phenyl se-lenoglycoside acceptors, using silver triflate as a promoter in the presence of collidine. 

As generally expressed in Section I, derivatives of a-D-glucopyranose are thermodynamically more stable than the /3-d anomers, whereas, for the D-glucofuranoses, the opposite stability of the anomers is observed. This regularity also applies to the respective glycosyl bromides and chlorides. 

Reactivity Patterns and Some Useful Reactions of Glycosyl Bromides 68... 

Trifluorozincbromide reagent (CF3ZnBr) is employed for the synthesis of glycosyl fluorides from glycosyl bromides. When 2,3,4,6-tetra-O-acetyl-a-D-glycopyranosyl... 

Fluorination with Silver Fluoride from Glycosyl Bromide [17] A mixture of 2,3,4,6-tetra- O-acetyl-a-D-glucopyranosyl bromide (5 g) and anhydrous silver fluoride (5 g) in dry acetonitrile (25 ml) was shaken under argon overnight. The resulting solution was filtered and aqueous sodium chloride was added to precipitate any silver ions from the solution. The mixture was filtered and concentrated to a syrup that was... 

Stereoselective Glycosylations Employing Glycosyl Bromides and Applications... 

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