Synthesis of tetrasaccharide related to the repeating unit of the <i>O</i>-antigen from <i>Shigella boydii </i>type 5 in the form of its <i>tert</i>-butyl ester and 2-(trimethylsilyl)ethyl glycoside

Abstract

130-136Starting from D-mannose, D-glucose and L-rhamnose, two disaccharide blocks ethyl 2,3,4-tri-O-benzyl- -L-rhamnopyranosyl-(1→3)-2-O-benzyl-4,6-O-benzylidene-1-thio--D-mannopyranoside and tert-butyl 2-O-benzyl-4,6-O-benzylidene--D-mannopyranosyl-(1→4)-[2-(trimethylsilyl)ethyl 2,3-di-O-benzyl--D-glucopyranosid]uronate have been synthesized. Schmidt’s inverse addition technique of trichloroacetimidate is utilized for the construction of a disaccharide with a -mannosidic linkage in good yield. Coupling of this two disaccharides give the desired tetrasaccharide derivative, tert-butyl 2,3,4-tri-O-benzyl- -L-rhamnopyranosyl-(1→3)-2-O-benzyl-4,6-O-benzylidene--D-mannopyranosyl-(1→3)-2-O-benzyl-4,6-O-benzylidene--D-mannopyranosyl-(1→4)-[2-(trimethylsilyl)ethyl 2,3-di-O-benzyl--D-glucopyranosid]­uronate, which is related to the repeating unit of Shigella boydii type 5. The tetrasaccharide can be coupled with a suitable protein for the preparation of a synthetic vaccine