6-O-sulfo sialylparagloboside and sialyl Lewis X neo-glycolipids containing lactamized neuraminic acid: synthesis and antigenic reactivity against G159 monoclonal antibody.

Synthesis and antigenic reactivity of 6-O-sulfo sialylparagloboside (SPG) and sialyl Lewis X (sLeX) neo-glycolipids containing lactamized neuraminic acid are described. The suitably protected GlcNAc-beta (1-->3)-Gal-beta (1-->4)-GlcOSE derivative was glycosylated with NeuTFAc-alpha (2-->3)-Gal imidate to give NeuTFAc-alpha (2-->3)-Galbeta (1-->4)-GlcNAc-beta (1-->3)-Gal-beta (1-->4)-GlcOSE pentasaccharide. The partial N,O-deacylation in the NeuTFAc-alpha (2-->3)-Gal part afforded N-deacetylated SPG derivative which was converted to the desired oligosaccharide containing lactamized neuraminic acid. Similar treatment of the sLeX hexasaccharide derivative, NeuTFAc-alpha (2-->3)-Gal-beta (1-->4) [Fuc-alpha (1-->3)]-GlcNAc-beta (1-->3)-Gal-beta (1-->4)-GlcOSE, gave the key hexasaccharide intermediate containing lactamized neuraminic acid. These suitably protected SPG and sLex oligosaccharides were converted stepwise into the desired neo-glycolipids (GSC-551 and GSC-552) by the coupling with 2-(tetradecyl)hexadecanol, 6-O-sulfation at C-6 of the GlcNAc residure, and complete deprotection. Both lactamized-sialyl 6-O-sulfo SPG (GSC-551) and sLex (GSC-552) neo-glycolipids were clearly recognized with G159 monoclonal antibody showing that both the lactamized neuraminic acid and the 6-O-sulfate at C-6 of GlcNAc would be involved in the G159-defined determinant. However, the Fuc residue and the lipophilic (ceramide) part may not be critical for this recognition.