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.