Glucopyranosyl bromide, tetra-O-acetyl

Glucopyranosyl bromide, tetra-O-acetyl-a-D-, 0X0 reaction with, 109 —, 2,5,6-tri-0-acetyl-3-0-(methylsulfonyl)-a-D-, 265... 

Bromo-l-deoxy, hepta-Ac 4-0-(2,3,4,6-Tetra-0-acetyl ix-D-glucopyranosyl)-tri-O-acetyl-a-D-glucopyranosyl bromide. Hepta-O-acetyl-4-O-a-D-glucopyrano-syl-a-D-glucopyranosyl bromide. Acetobromomaltose [14257-35-3]... 

Under conditions, the reaction of tetra-o-acetyl-o-glucopyranosyl bromide with A-4-thiazoline-2-thione provides the glycosylamine (76) (N-alkylation) (Scheme 36) (163). However, treatment of 5-... 

Cinnolin-3(2//)-one (7) is methylated with diazomethane or methyl sulfate to give 2-methylcinnolin-3(2H)-one. In a similar manner, benzylation with benzyl chloride, cyanoethylation with acrylonitrile in the presence of benzyltrimethylammonium hydroxide and glucosidation with tetra-O-acetyl-a-o-glucopyranosyl bromide in the presence of a base affords the corresponding 2-substituted cinnolin-3(2//)-ones. However, glucosidation of the silver salt of cinnolin-3(2//)-one produces the corresponding O-substituted compound. 

Initially it was necessary to devise an improved method for the preparation of 2-hydroxyglycal esters, because the standard procedure (treatment of an acylglycosyl bromide with diethylamine in benzene or chloroform solution) was inconveniently lengthy in time and frequently afforded only a moderate yield of product (5). As a result of their recent thorough investigation of the kinetic features of the dehydrobromination of tetra-O-acetyl-a-D-glucopyranosyl bromide Lemieux and Lineback... 

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. 

The synthesis93 of N-(2,4-dinitrophenyl)-3-0-(tetra-0-acetyl-/ -D-glu-copyranosyl)-L-threonine methyl ester (131) involved a two-step procedure. First, formation of the intermediate, L-threonine orthoester 130 was achieved by treatment of tetra-O-acetyl-a-D-glucopyranosyl bromide (128) with the methyl ester of N-(2,4-dinitrophenyl)-L-threonine94 (129) under the conditions of the Koenigs-Knorr reaction (see next paragraph), and this was then converted into the L-threonine glycoside 131. 

The Helferich-Wedemeyer procedure may give mixtures of the anomers, depending on the nature of the aglycon. For example, condensation of bromide 128 with N-(benzyloxycarbonyl)-L-threonine penta-chlorophenyl ester (171) gave both N-(benzyloxycarbonyl)-3-0-(2,3,4,6-tetra-O-acetyl-a- and -/J-D-glucopyranosyl)-L-threonine pen-tachlorophenyl ester135 (172 and 173, respectively), but only the fi-D... 

Ci4H19Br09 Tetra-O-acetyl-a-D-glucopyranosyl bromide TAGPBR 37 393... 

Similarly, treatment of the salt with 2,3,4,6-tetra-O-acetyl-a-D-glucopyra-nosyl bromide 46 gave 4-[2,3,4,6-tetra-0-acetyl-/3-D-glucopyranosyl]-4//-pyrido[2,3-e][l,2,4]triazin-3-one 1-oxide 47. Antileukemia tests for the 4-alkyl derivatives showed no activity. 

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... 

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