2.3.4.6- Tetra-O-acetyl-a-D- glucopyranosyl bromide

The carbohydrate 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide reacts with NaCo(CO)4 and PPh3 under 10 atm of CO to yield the expected acetyl (XXIX) and the corresponding alkyl 210). The former decarbonylates readily on storage or chromatography. Retention of configuration at carbon accompanies CO elimination. 

Compound 33 also lends itself to the synthesis of 1,5-linked disaccharides. Thus, its condensation180 with 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide, and with methyl 2,3,4-tri-O-acetyl-a-D-glucopyranosyluronate bromide, respectively, yields the corresponding /3-D-linked disaccharides (97 and 98). 

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... 

Tetra-O-acetyl-a-D-glucopyranosyl bromide Glucopyranosyl bromide tetraacetate, a-D-, a-D-glucopyranosyl bromide, 2,3,4,6-tetraacetate, (572-09-8), 65, 236... 

The mixtnre of 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide (20 g, 48.7 mmol), and silver 3-methoxy-2-pyridoxide (18 g, 77.6 mmol) in 260 mL of toluene was refluxed for 1 h. The mixture was filtered over Celite, washed with CH2C12, and evaporated. Purification by flash chromatography on silica gel (EtOAc-hexane-CH2Cl2, 1 1 1), gave 3-methoxy-2-pyridyl 2,3,4,6-telra-0-acetyl-(3-D-gIucopyranoside (17 g, 77%) mp 102°-103°C, [a]D +4.5° (c 0.8, CHClj). 

Tetra-O-acetyl-a-D-glucopyranosyl bromide (43 81.59 g, 198.4mmol) and Hg(A h V s> 395.8 mmol) were combined and pulverized. The mixture was melted at 85 C under argon as escri... 

Isomerization of organic thiocyanates to isothiocyanates is also discussed in other articles.25 29 The first sugar isothiocyanate reported, namely, 2,3,4,6-tetra-O-acetyl-/3- D-glucopyranosyl isothiocyanate (2) was synthesized by Emil Fischer7 in 1914 by treatment of 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide (1) with silver thiocyanate in anhydrous xylene. It was also prepared by Muller and Wilhelms8 by thermal isomerization of the corresponding thiocyanate 3, obtained by treatment of 1 with potassium... 

Experiment 5.109 2.3.4.6-TETRA-O-ACETYL-a-D-GLUCOPYRANOSYL BROMIDE ([Pg.647]

The reaction can be followed by TLC using 0.25-nn silica gel 60 F-254 plates (E. Merck Company) and ethyl acetate/hexane (1 1) eluent 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide (Rf = 0.39) 2, 3, 4, 6-tetra-0-acetyl-1,5-anhydroglucitol (Rf = 0.28) l-deoxy-2,3,4,6-tetra-0-acetyl-l-(2-cyano-ethyl)-6-D-glucopyranose (Rf = 0.20) l-deoxy-2,3,4,6-tetra-0-acetyl-l-(2-cyanoethyl)-a-D-glueopyranose (Rf = 0.16). 

Method B was evaluated with the diglucosyl diselenide 216, prepared in two steps by reaction of the 6-deoxy-6-iodo derivative 214 with selenourea and transformation of the pseudourea resulting 215 and 217. The selenoate was generated by reduction of 216 and allowed to react with 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide in DMF, affording protected disaccharide 217. The free (1 - 6)-/Minked 6-selenodisaccharide 218 was obtained in 70% yield after deacetylation. This methodology could find... 

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