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

1058-1063A revised and simplified method has been developed for the synthesis of the pentasaccharide, related to the repeating unit of the O-antigen from Shigella dysenteriae type-4. The disaccharide donor 10 and the trisaccharide acceptor 8 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 -L-fucopyranosyl-(1→3)-2-acetamido-2-deoxy--D-glucopyranosyl-(1→3)-2-acetamido-2-deoxy-4-O-( -L-fucopyranosyl)- -D-glucopyranosyl-(1→4)-[2-(trimethylsilyl)ethyl -D-glucopyranosid] uronate 15