Koenigs-Knorr Glycosylation with Neuraminic Acid Derivatives

Earlier we reported a convenient and efficient method of preparing α2-6 sialooligosaccharides in conditions of Koenigs-Knorr reaction. The use of Ag₂CO₃ allowed carrying out α2-6 sialylation of galacto-4,6-diol of mono- and disaccharides with chloride of acetylated N-acetylneuraminic acid methyl ester as glycosyl donor. In this study we applied this approach to other derivatives of neuraminic acid, namely, Neu5Gc, 9-deoxy-9-NAc-Neu5Ac, Neu5Acα2-8Neu5Ac, and Neu5Acα2-8Neu5Acα2-8Neu5Ac as glycosyl donors; eight compounds were synthesized: Neu5Gcα-O(CH₂)₃NH₂ (8), Neu5Gcα2-6Galβ1-4GlcNAcβ-O(CH₂)₃NH₂ (10), 9-deoxy-9-NAc-Neu5Ac-O(CH₂)₃NH₂ (15), 9-deoxy-9-NAc-Neu5Acα2-6Galβ1-4GlcNAcβ-O(CH₂)₃NH₂ (17), Neu5Acα2-8Neu5Acα-O(CH₂)₃NH₂(23) Neu5Acα2-8Neu5Acα-OCH₃ (24), Neu5Acα2-8Neu5Acα-OCH₂(p-C₆H₄)NHCOCH₂NH₂ (25), and Neu5Acα2-8Neu5Acα2-8Neu5Acα-O(CH₂)₃NH₂ (32). These sialosides were used for characterization of siglecs and other carbohydrate-binding proteins.