Hexopyranosyl bromide

Compound 61 was derived from 3,4,6-tri-0-acetyl-2-deoxy-n-arafet no-hexopyranosyl bromide, which was produced by direct addition of hydrogen bromide to the double bond. The bromodeoxy sugar 62 was, presumably, formed by addition to a 2,3-unsaturated, rearrangement product of the type known118 to arise from tri-O-acetyl-D-glucal in the presence of acid. 

When 56 is treated with hydrogen bromide in nonpolar solvents, simple addition occurs, to give 3,4,6-tri-0-acetyl-2-deoxy-D-arafemo-hexopyranosyl bromide.117 The conversion of 3,4-di-0-acetyl-6-0-p-tolylsulfonyl-D-glucal into crystalline 4-0-acetyl-3-bromo-2,3-dideoxy-fi-O-p-tolylsulfonyl-a-D-arobino-hexopyranosyl bromide in 75% yield, on treatment with hydrogen bromide in glacial acetic acid for 3 hours at room temperature, has also been reported.118... 

A further example has been given of the synthesis of a 2-deoxy-aldose by the addition of water to a glycal, but, as this reaction is known to be accompanied by competing eliminations,1 it is being replaced in synthetic work by more-specific addition procedures, for example, methoxymercuration (see p. 210). From the 4-deoxy derivative of D-glucal, prepared by standard procedures from 2,3,6-tri-O-acetyl-4-deoxy-D-xy/o-hexopyranosyl bromide, 2,4-dideoxy-D-threo-hexose was obtained.35... 

Nitrophenyl-a-L-fuco/galacto/rhamno/manno-pyranosides can be made by the reaction of the acetate protected sugar with p-nitrophenol and zinc chloride at 120 °C under vacuum [7]. p-Nitrophenyl-p-D-gluco/galactopyranoside can be generated from the reaction of the acetylated hexopyranosyl bromides with sodium p-nitrophenoxide in DMF [8], followed by deprotection, and /7-nitrophenyl-(3-D-mannopyranoside can be synthesised from mannose via 2,3 4,6-di-0-cyclohex-ylidene-a-D-mannopyranose [9]. 

In order to resolve synthetic racemic lomatin, a hydroxylated dihydropyranocoumarin, the racemate was converted into its diastereomeric a-L-glycosides by reaction with 3,4-di-0-acetyl-2,6-dideoxy-a-L-aroftino-hexopyranosyl bromide the separable isomers were subsequently hydrolysed, and a 2-deoxysugar was used to facilitate this acidic hydrolysis, since lomatin itself is sensitive to acid.2l... 

Routine syntheses of glycosyl isothiocyanates, involving reaction of the corresponding hexopyranosyl bromides with potassium thiocyanate, and then-subsequent conversion to thiourea and thiosemicarbazide derivatives on reaction with amines and hydrazine, respectively, have been reported. Partially protected -D-galactopyranosylamine derivatives, e g. (25) and (26), have been obtained by reaction of the corresponding galactosyl isothiocyanate with a-aminoaceto-phenones and a-aminoacetone, respectively. In acetic anhydride, the thiourea (25) qrclised to compound (27). ... 

The bromide (2a) reacted smoothly with 2,4-diethoxy-5-methylpyrimi-dine to give, after de-ethylation and deacylation, l-(2-deoxy-/ -D-arabino-hexopyranosyl)thymine (3) (15). The new nucleoside (3) is the first truly competitive inhibitor of a pyrimidine phosphorylase (7), that is, it inhibits the phosphorylase, yet is not a substrate for the enzyme. It was recently shown that 3 enhances the incorporation of 2 -deoxy-5-iodouridine in vivo in cats (8). 

The bromide (2a) reacted also with chloromercuri-N-benzoyladenine to give, after debenzoylation, 9- (2-deoxy-/ -D-arabino-hexopyranosyl) -adenine (15). A later paper reported (18) on the coupling of 2a with... 

Dideoxy-L-/> xo-hexopyranosyl-c-pyrromicinone and l-Aeoxy-n-erythro-pentopyranosyl-carminomycinone.-daunomycinone, and - -pyrromicinone have been prepared from the appropriate mycinone and glycosyl bromide by Koenigs-Knorr procedures. ... 

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