Synthesis of Partially O-Acetylated N-Acetylneuraminic Acid Using Regioselective Silyl Exchange Technology

[Image: see text] Postglycosylation acetylation of sialic acid imparts unique roles to sialoglycoconjugates in mammalian immune response making structural and functional understanding of these analogues important. Five partially O-acetylated Neu5Ac analogues have been synthesized. Reaction of per-O-silylated Neu5Ac ester with AcOH and Ac(2)O in pyridine promotes regioselective silyl ether/acetate exchange in the following order: C(4) (2°) > C(9) (1°) > C(8) (2°) > C(2) (anomeric). Subsequent hydrogenolysis affords the corresponding sialic acid analogues as useful chemical biology tools.