Investigation of the stability of thiosialosides toward hydrolysis by sialidases using NMR spectroscopy.

[formula: see text] 1H NMR spectroscopy has been used to investigate whether the alpha(2-->6)-linked thiosialoside 3 and the alpha(2-->3)-linked thiosialoside 9 are hydrolyzed in the presence of Vibrio cholerae sialidase. Similarly, the hydrolysis of the O-ketosides Neu5Ac-2-O-alpha-(2-->3)-Gal beta Me (4) and the alpha-(2-->6)-sialyllactoside 7, representing natural alpha(2-->3)- and alpha(2-->6)-linked sialosides, respectively, was investigated. The results of the 1H NMR experiments clearly demonstrate that the thiosialosides are not hydrolyzed by Vibrio cholerae sialidase. As expected, the O-sialosides are hydrolyzed to give N-acetyl-alpha-D-neuraminic acid as the first product of substrate cleavage.