The acidic hydrolysis of N -acetylneuraminic 4,5-oxazoline allows a direct functionalization of the C5 position of Neu5Ac2en (DANA).

The acidic hydrolysis of N -acetylneuraminic 4,5-oxazoline affords the corresponding 2,3-unsaturated amino ester, which was not previously detected (nor isolated) due to the unexpected rearrangement into its corresponding alcohol. In this work, we unveiled the mechanism of these reactions and optimized the conditions to obtain either synthetic intermediate.