Synthesis of the pentasaccharide repeating unit corresponding to the capsular polysaccharide of Escherichia coli O20:K83:H26. (10th September 2022)

• Record Type: Journal Article
• Authors: Shit, Pradip; Misra, Anup Kumar
• Is Part Of: Tetrahedron. Volume 122(2022)
• Publication Date: 2022-09-10
• Subjects: Pentasaccharide -- Polysaccharide -- E. coli -- Glycosylation -- Oxidation -- HClO4–SiO2; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2022.132948
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: A concise synthetic strategy has been developed for the synthesis of the pentasaccharide repeating unit of the capsular polysaccharide of Escherichia coli ( E. coli ) strain applying block [2 + 3] stereoselective glycosylation. A functionalized disaccharide thioglycoside donor prepared using "armed-disarmed" glycosylation concept, was coupled with suitably protected trisaccharide glycosyl acceptor in the presence of a combination of N -iodosuccinimide (NIS) and perchloric acid supported over silica (HClO4 –SiO2 ) to give the target pentasaccharide derivative in 65% yield. A late-stage regioselective oxidation of the primary hydroxyl group using a combination of TEMPO and Bis(acetoxy)iodobenzene (BAIB) furnished d -galacturonic acid moiety in the functionalized pentasaccharide derivative. Graphical abstract: Image 1 Highlights: Pentasaccharide of the capsular polysaccharide of E. coli O20:K83:H26 was synthesized. A combination of NIS and HClO4 –SiO2 as glycosylation activator. A convergent stereoselective [2 + 3] glycosylation furnished pentasaccharide derivative. "Armed-disarmed" glycosylation applied in the synthetic strategy. TEMPO and BAIB mediated selective oxidation of 1° hydroxyl group to carboxylic acid.