Stereoselectivity of Glycosylation May Change During the Reaction Course: Highly α‐Stereoselective Sialylation Achieved by Supramer Approach

Abstract

Abstract The stereoselectivity of NIS/TfOH‐promoted glycosylation with O ‐acetylated N ‐acetylneuraminic acid phenyl thioglycoside was found to be dependent on the reaction time. Highly α‐stereoselective sialylation (27:1 anomer ratio) was achieved by decreasing the reaction time (from 3 h to 15 min) and by adding a non‐reacting compound (1 equiv.) capable of modifying the structure of hydrogen‐bonded supramolecular aggregates (supramers) of the glycosyl donor. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)