Directed stereoselective synthesis of α- and β-N-acetyl neuraminic acid–galactose disaccharides using 2-choro and 2-fluoro derivatives of neuraminic acid allyl ester

Abstract

N-Acetyl neuraminic acid (carboxy-protected as the allyl ester) is converted stereoselectively into the 2,6-disaccharide with the α- or β-configuration with 1,2 : 3,4-di-isopropylidenegalactose starting from its acetyl-protected 2-chloro or 2-floro derivative; the advantages of the allyl protecting function are discussed.