Synthesis of neoglycoproteins containing 5-O-phosphorylated Kdomonosaccharide, 4-O- and 5-O-phosphorylated α-Kd↬(2 6)-2-acetamido-2-deoxy- -D-glucopyranosyl disaccharide residues

Abstract

Radical addition of cysteamine to anomeric allyl glycosides of Kdo 5-phosphates 1 and 4 afforded good yields of the corresponding 3-(2-aminoethylthio)propyl glycosides. Similar reactions with the α-allyl glycoside of Kdo 4-phosphate 7 led to substantial formation of the dephosphorylated product 10 through intramolecular hydrolysis of the 4-O-phosphomonoester by the terminal amino function of the spacer group. Similar side reactions occurred upon deblocking of the 4- O-phosphorylated 6-aminohexyl-α-glycoside lactone derivative 18. Allyl glycosides of 4'- O- and 5'- O-phosphorylated Kd↬ (2 6)-glucosamine derivatives were prepared in good yields via phosphorylation using the amidite procedure. The 4'-phosphate moiety was introduced following intramolecular protection of the 5'-OH group as a lactone. Subsequent deprotection gave the allyl glycosides 25 and 33 which were transformed into the corresponding stable spacer derivatives 26 and 34 by coupling with cysteamine. The ligands were activated with thiophosgene and reacted with bovine serum albumin to give the neoglycoconjugates 3, 6, 27 and 35 to be used in immunochemical studies of monoclonal antibodies directed against Haemophilus influenzae Re-mutant and related lipopolysaccharides.