Revised synthesis of the pentasaccharide related to the repeating unit of the O-antigen from <i style="">Shigella dysenteriae</i> type-4 in the form of its methyl ester 2-(trimethylsilyl)ethyl glycoside

Abstract

A revised and simplified method has been developed for the synthesis of the pentasaccharide, related to the repeating unit of the <i style="">O</i>-antigen from <i style="">Shigella dysenteriae</i> type-4.<i style=""> </i>The disaccharide donor <b>10</b> and the trisaccharide acceptor <b>8</b> with two hydroxyl groups are first synthesized which are then allowed to react in the presence on NIS and TfOH to give a pentasaccharide derivative from which, removal of protecting groups affords the desired repeating unit, namely methyl <img src='/image/spc_char/alpha.gif' border=0>-L-fucopyranosyl-(1→3)-2-acetamido-2-deoxy-<img src='/image/spc_char/alpha.gif' border=0>-D-glucopyranosyl-(1→3)-2-acetamido-2-deoxy-4-<i style="">O</i>-(<img src='/image/spc_char/alpha.gif' border=0> -L-fucopyranosyl)-<img src='/image/spc_char/alpha.gif' border=0> -D-glucopyranosyl-(1→4)-[2-(trimethylsilyl)ethyl <img src='/image/spc_char/beta.gif' border=0>-D-glucopyranosid] uronate <b>15</b>.