Synthesis of the Pentasaccharide of the K14 Capsular Polysaccharide of Antibiotic Resistant ST25 Acinetobacter baumannii isolate, D46 and O‐Polysaccharide of Acinetobacter baumannii O11

Abstract

Synthesis of the pentasaccharide corresponding to the K14 capsular polysaccharide from ST25 Acinetobacter baumannii isolate, D46 and O‐polysaccharide of Acinetobacter baumannii O11 has been achieved in very good yield using a convergent stereoselective [3+2] block glycosylation strategy. The synthetic scheme includes several regio‐ and stereose lective glycosylations as well as orthogonal glycosylation with high yield. Thioglycosides have been used as glycosyl donors using a combination of copper(II) bromide and tetra‐n‐butylammonium bromide (TBAB) as thiophilic activator for 1,2‐cis glycosylation and a combination of N‐iodosuccinimide (NIS) and trimethylsilyl trifluoromethanesulfonate (TMSOTf) as thiophilic activator for 1,2‐trans glycosylation. Glycosyl trichloroacetimidate derivative was used as glycosyl donor using perchloric acid supported on silica (HClO4–SiO2) as activator. A catalytic transfer hydrogenation reaction has been carried out for the removal of benzyloxy and benzylidene functional groups using triethylsilane as hydrogen source.