Facile synthesis of arabinomannose penta- and decasaccharide fragments of the lipoarabinomannan of the equine pathogen, Rhodococcus equi Original Research Article

Pentasaccharide repeating unit 20 of the lipoarabinomannan from the equine pathogen, Rhodococcus equi, and its dimer 31, were synthesized. The pentasaccharide was obtained by assembling a benzoylated 2,6-branched mannosyl trisaccharide acceptor 13 with a free hydroxyl group at C-2′ of the mannose residue attached to the core mannose residue by (1 → 6)-linkage, followed by coupling with 2,3,5-tri-O-benzoyl-α-d-arabinofuranosyl-(1 → 2)-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl trichloroacetimidate (18), and by deacylation. Meanwhile, the decamer 31 was obtained by firstly preparing a benzoylated mannose (1 → 6)-linked tetrasaccharide backbone 26 with 2-, 2″-O-ClAc, and 2′-, 2‴-O-Ac groups, respectively, then by dechloroacetylation and subsequent condensation with perbenzoylated trichloroacetimidate, and then by deacetylation and subsequent coupling with 18, and finally, by deacylation.