Synthesis of neoglycoproteins containing d-glycero-d-talo-oct-2-ulopyranosylonic acid (Ko) ligands corresponding to core units from Burkholderia and Acinetobacter lipopolysaccharide Original Research Article

Glycal esters of Kdo derivatives were converted into 2,3-anhydro intermediates, which were transformed into d-glycero-d-talo-oct-2-ulopyranosylonic acid (Ko), as well as 3-O- and 4-O-p-nitrobenzoyl-Ko derivatives. The exo-allyl orthoester derivative, methyl {5,7,8-tri-O-acetyl-4-O-(4-nitrobenzoyl)-2,3-O-[(1-exo-allyloxy)-ethylidene]-d-glycero-β-d-talo-oct-2-ulopyranos}onate, prepared from the 4-O-pNBz-protected Ko derivative, was elaborated into the α-Ko allyl ketoside, the reducing disaccharide α-Kdop-(2→4)-Ko and the disaccharide α-Kdop-(2→4)-Kop-(2→OAll). Conversely, methyl[4,5,7,8-tetra-O-acetyl-3-O-(4-nitrobenzoyl)-α-d-glycero-d-talo-2-octulopyranosyl bromide]onate [Carbohydr. Res., 244 (1993) 69–84], was coupled with a Kdo acceptor to give the disaccharide α-Kop-(2→4)-Kdop-(2→OAll) after orthoester rearrangement and deprotection. The allyl glycosides were treated with cysteamine and converted into neoglycoproteins. The ligands correspond to inner core units from Acinetobacter haemolyticus and Burkholderia cepacia lipopolysaccharides.