Synthesis of two analogues of the Sda determinant. Replacement of the sialic acid residue by a sulfate or a carboxymethyl group

Two analogues of the Sda determinant tetrasaccharide have been synthesized in order to investigate the physiological role of this carbohydrate moiety. These saccharides, having two different anionic substitutes for the sialic acid residue, are: β-d-GalpNAc-(1 → 4)-3-O-SO3H-β-d-Galp-(1 → 4)-β-d-GlcpNAc-(1 → O)(CH2)5NH2 and β-d-GalpNAc-(1 → 4)-3-O-CH2COOH-β-d-Galp-(1 → 4)-β-d-GlcpNAc-(1 → 0)(CH2)5NH2. 5-Azidopentyl (2,6-di-O-benzyl-β-d-galactopyranosyl)-(1 → 4)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-d-glucopyranoside served as a general building block. The trisaccharides were obtained after prior selective derivatization of HO-3′ of the disaccharide derivative via a dibutyltin oxide mediated reaction, followed by coupling at HO-4′ with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-galactopyranosyl trichloroacetimidate, and processing of the formed trisaccharide derivatives into their free forms. Two analogues of the Sda determinant tetrasaccharide have been synthesized aimed at the investigation of the physiological role of this carbohydrate moiety. These saccharides, having two different anionic substitutes for the sialic acid residue, are; β-d-GalpNAC-(1 → 4)-3-O-SO3H-β-d-Gal p-(1 → 4)-β-d-GlcpNAC-(1 → O)(CH2)5NH2 and β-d-GalpNAC-(1 → 4)-3-O-CH2COOH-β-d-Galp-(1 → 4)-β-d-GlcpNAC-(1 → O)(CH2)5NH2.