Methyl arabinoside preparation

CB tribenzyl-D-arabinofuranoside 59 was efficiently prepared from methyl tribenzyl-D-arabinofuranoside 57 as shown in Scheme 3. Treatment of 57 with acetyl bromide in trifluoroacetic acid and subsequent coupling of the resulting crude arabinofuranosyl bromide with benzyl 2-(hydroxymeAyl)benzoate (1) followed by selective hydrogenoiysis of the resulting BCB arabinofuranoside 58 (a/p=4 l) afforded the desired CB arabinoside 59. CB 3,5-di-(9-benzoyl-2-0-benzylarabinofuranoside 60 was also prepared in like fashion. 

A high yield of 1,4-jS-linked product was obtained when methyl 2,3-anhydro-j3-D-ribopyranoside was condensed with 3,4-di-0-acetyl-2-0-benzyl-a-D-xylopyranosyl bromide, and use of tri-O-acetyl-a-D-xylopyranosyl bromide afforded the related product which, on base-catalysed hydrolysis, gave the methyl jS-xylobioside. Several 2-0-glycosyl-D-arabinoses have been prepared by glycosylation of benzyl 3,4-0-isopropylidene-j8-D-arabinopyranoside, and from benzyl 2-0-j3-D-glucopyranosyl-jS-D-arabinoside the aldobiuronic acid was produced. ... 

Hudson 143), The specific and unusual method used for the preparation (see formulas below) depends on the action of zinc chloride, under acetylat-ing conditions, in rupturing the oxygen-carbon linkage of the pyranose ring of the methyl D-arabinosides. As intermediate products, the fully acetylated hemiacetal (I) and the chloro derivative (II) are produced. Deacetylation of the final product gives D-arabinose dimethyl acetal. 

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