Synthesis 2023; 55(10): 1553-1560
DOI: 10.1055/s-0042-1751419
paper

Concise Synthesis of the Hexasaccharide Repeating Unit of the Capsular Polysaccharide of Klebsiella K19 Strain

Samim Sahaji
,
Pradip Shit
,
Anup Kumar Misra
S.S. thanks the University Grants Commission (UGC-MANF), India and P.S. thanks the Bose Institute for financial support. This work was supported by the Science and Engineering Research Board (SERB), New Delhi (Project No. CRG/2019/000352 dated 23.01.2020) (A.K.M.).


Abstract

A convergent [4+2] stereoselective block glycosylation strategy has been developed for the synthesis of the hexasaccharide repeating unit of the capsular polysaccharide of Klebsiella K19 strain in very good yield. The p-methoxybenzyl (PMB) group was used as a temporary alkyl protecting group, which was removed by tuning the glycosylation conditions. A thioglycoside was used as a glycosyl acceptor in an orthogonal glycosylation reaction. A late-stage TEMPO-mediated selective oxidation of a primary hydroxyl group into carboxylic acid allowed incorporation of the d-glucuronic acid moiety in the hexasaccharide. A combination of N-iodosuccinimide (NIS) and perchloric acid supported over silica (HClO4–SiO2) was used as a thiophilic promoter for the activation of thioglycosides. HClO4–SiO2 was also used as a solid acid activator for a glycosyl trichloroacetimidate derivative.

Supporting Information



Publication History

Received: 23 November 2022

Accepted after revision: 16 January 2023

Article published online:
15 February 2023

© 2023. Thieme. All rights reserved

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany