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

Glycal esters of Kdo derivatives were converted into 2,3-anhydro intermedia tes, which were transformed into D-glycero-D-talo-oct-2-ulopyranosylonic ac id (Ko), as well as 3-O- and 4-O-p-nitrobenzoyl-Ko derivatives. The exo-all yl orthoester derivative, methyl {5,7,8-tri-O-acetyl-4-O-(4-nitrobenzoyl)-2 ,3-O-[(1-exo-allyloxy)-ethylidene]-D-glycero-beta -D-talo-oct-2-ulopyranos} onate, prepared from the 4-O-pNBz-protected Ko derivative, was elaborated i nto the alpha -Ko allyl ketoside, the reducing disaccharide alpha -Kdop-(2 --> 4)-Ko and the disaccharide alpha -Kdop-(2 --> 4)-Kop-(2 -->, OAll). Con versely, methyl[4, 5,7,8-tetra-O-acetyl-3-O-(4-nitrobenzoyl)-alpha -D-glyce ro-D-talo-2-octulopyranosyl bromide]onate [Carbohydr. Res., 244 (1993) 69-8 4], was coupled with a Kdo acceptor to give the disaccharide alpha -Kop-(2 -->4)-Kdop-(2 --> OAll) after orthoester rearrangement and deprotection. Th e allyl glycosides were treated with cysteamine and converted into neoglyco proteins. The ligands correspond to inner core units from Acinetobacter hae molyticus and Burkholderia cepacia lipopolysaccharides. (C) 2000 Elsevier S cience Ltd. All rights reserved.