Synthesis of regioisomeric methyl α-l-arabinofuranobiosides

The three regioisomers of methyl α-l-arabinofuranobioside, namely methyl O-α-l-arabinofuranosyl-(1 → 3)-α-l-arabinofuranoside, methyl O-α-l-arabinofuranosyl-(1 → 3)-α-l-arabinofuranoside, and methyl O-α-l-arabinofuranosyl-(1 → 5)-α-l-arabinofuranoside, were synthesized for use as substrates in studies of the specificity of α-l-arabinofuranosidase. The regiospecifically protected precursors, namely methyl 3,5-di-O-benzoyl-α-l-arabinofuranoside,methyl 2,5-di-O-benzyl-α-l-arabinofuranoside, and methyl 2,3-di-O-benzoyl-α-l-arabinofuranoside, were prepared from 2,3,5-tri-O-benzoyl-α-l-arabinofuranosyl chloride (4) and methyl 5-O-trityl-α-l-arabinofuranoside, respectively, and glycosylated with 4 in the presence of silver trifluoromethanesulfonate and s-collidine. 1H and 13C NMR data for all compounds are presented.