Synthesis of a sulfonic acid mimetic of the sulfated Lewis A pentasaccharide

The first sulfonic acid mimetic of the sulfated Lewis A pentasaccharide in which the natural l-fucose unit is replaced by a d-arabinose ring was synthesized. Formation of the sulfonic acid moiety at a pentasaccharide level could be successfully achieved by means of introduction of an acetylthio moiety into the terminal d-galactose residue and subsequent oxidation. The equatorial arrangement of the acetylthio group linked to C-3 of the galactose ring could be obtained by double nucleophilic substitutions; efficient formation of the gulo-triflate derivatives required low-power microwave (MW) activation. Oxidation of the acetylthio group was carried out using Oxone in the presence of acetic acid.