Recyclable Fluorous-Tag Assisted Two-Directional Oligosaccharide Synthesis Enabled by Interrupted Pummerer Reaction Mediated Glycosylation

Abstract

Herein, we report a novel fluorous-tag assisted two-directional oligosaccharide assembly strategy, which combines the advantages of solution-phase synthesis and solid-phase synthesis. A well-designed fluorous-tag was decorated on the latent anomeric leaving group in interrupted Pummerer reaction mediated (IPRm) glycosylation. High efficiency of the in-solution phase glycosylation and unique affinity of the fluorous-tag towards polytetrafluoroethylene (PTFE) particles allowed flexible assembly from reducing end to non-reducing end and the fast purification by PTFE-assisted filtration. Moreover, the fluorous-tagged latent anomeric leaving group could be activated by oxidation and cleaved by IPRm glycosylation thus enabled the elongation of carbohydrate chain from non-reducing end to reducing end as well as the recovery of fluorous-tag. The present two-directional synthetic strategy is used to assemble the repeating unit of Streptococcus pneumoniae type 14 capsular polysaccharide