Convenient synthesis of the pentasaccharide repeating unit corresponding to the cell wall O-antigen of Escherichia albertii O4

Abstract

A straightforward sequential synthetic strategy has been developed for the synthesis of a pentasaccharide repeating unit corresponding to the cell wall O-antigen of the Escherichia albertii O4 strain in very good yield with the desired configuration at the glycosidic linkages using thioglycosides and trichloroacetimidate derivatives as glycosyl donors and perchloric acid supported over silica (HClO4/SiO2) as a solid supported protic acid glycosyl activator. The expected configuration at the glycosidic linkages was achieved using a reasonable selection of protecting groups in the manosaccharide intermediates.

Synthesis of the tetrasaccharide repeating unit of the O-specific polysaccharide of Azospirillum doebereinerae type strain GSF71T using linear and one-pot iterative glycosylations

“…The selection of the p-methoxybenzyl (PMB) group for the temporary protection of the chain elongation C-3 hydroxy group in the ʟ-rhamnosyl thioglycoside donor 3 allowed carrying out the stereoselective glycosylation steps followed by the removal of the PMB group [25] in one pot. This was achieved by using a combination [26][27][28][29][30] of N-iodosuccinimide (NIS) and perchloric acid supported on silica (HClO 4 -SiO 2 ) [31,32]. HClO 4 -SiO 2 was used as a noncorrosive solid acid in the glycosylation reactions.…”