Comparative Study on the Effects of Picoloyl Groups in Sialylations Based on Their Substitution Pattern.

A novel 8-O-picoloylated sialyl donor has been developed, and the performance of various picoloylated sialyl donors in glycosylations with primary glycosyl acceptors has been evaluated. 8-O-Picoloyl and 4,9-di-O-picoloyl sialyl donors produced moderate to excellent yields of disaccharides with complete α-stereoselectivities. Synergistic effects between picoloyl and the accompanying O-protecting groups (benzoyl vs acetyl) were evaluated, as well as the effects of triflic acid concentration on the 8-O-picoloyl donor. 1H NMR analysis was also carried out to assess differences in the hydrogen-bonding net between sialyl donors.