The syntheses of anomeric ethyl ketosides of 5-N-acetyl-D-neuraminic acid are described. The alpha-anomer prepared by a modified Koenigs-Knorr procedure starting from acetochloroneuraminic acid is quantitatively cleaved by Vibrio cholerae neuraminidase. Proton-catalyzed reaction of 5-N-acetyl-D-neuraminic acid with ethanol yields the beta-anomer.
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