Straightforward access to 2,3- and 3,4-unsaturated derivatives of N-glycolylneuraminic acid

The facile syntheses of previously unreported 2,3- and 3,4-unsaturated derivatives of N-glycolylneuraminic acid are herein described. The procedure involves a ring-opening of the 4,5-oxazoline of N-acetylneuraminic acid, the acylation of the intermediate free amine, its conversion into the 4,5-oxazoline of N-glycolylneuraminic acid and the subsequent Ferrier reaction or C4 nucleophilic substitution.