AbstractThe methyl esters of 7‐epi‐Neu5Ac (1a), 8‐epi‐Neu5Ac (2a), 7,8‐bis(epi)‐Neu5Ac (3a), 7‐deoxy‐Neu5Ac (4a), 8‐deoxy‐Neu5Ac (5a), 9‐deoxy‐Neu5Ac (6a), and 4,7‐dideoxy‐Neu5Ac (7a) were transformed into their peracetylated mixtures of the α‐anomers1b–7band β‐anomers1c–7c. In the next step the 2‐Cl derivatives were prepared with acetyl chloride/HCl which yielded in the following Königs‐Knorr reaction with 4‐methylumbelliferone (MU) the corresponding methylumbelliferyl 2α‐glycosides 7‐epi‐Neu4,5,7,8,9Ac51Me‐αMU (1d), 8‐epi‐Neu4,5,7,8,9Ac51Me‐αMU (2d), 7,8‐bis(epi)‐Neu4,5,7,8,9Ac51Me‐αMU (3d), 7‐deoxy‐Neu‐4,5,8,9Ac41Me‐αMU (4d), 8‐deoxy‐Neu4,5,7,9Ac41Me‐αMU (5d), 9‐deoxy‐Neu4,5,7,8A41Me‐αMU (6d), and 4,7‐dideoxy‐Neu‐5,8,9Ac31Me‐αMU (7d). In the last case also the β‐anomer of 4,7‐dideoxy‐Neu5,8,9Ac31Me‐βMU (7d′) was formed. Zemplen saponification followed by hydrolysis of the ester group with sodium hydroxide, resulted in the sodium salts of the sialic acid MU 2α‐glycosides 7‐epi‐, 8‐epi‐, 7,8‐bis(epi)‐, 8‐deoxy‐, 9‐deoxy‐ and 4,7‐dideoxy‐Neu5Ac‐MU1e–7e. The enzymatic hydrolysis of these compounds with sialidase fromVibrio choleraeshowed only for3eand7esignificantly reduced rates of cleavage, whic