Chemical Synthesis of the Pentasaccharide Repeating Unit of the O-Antigen from <i>E. coli</i> O36 with Extensive Use of Chemo-selective Glycosylations

Chemical synthesis of the pentasaccharide repeating unit of the O-antigen from <i>Escherichia coli</i> O36 in the form of its 2-aminoethyl glycoside is reported. Chemo-selective glycosylations with armed and disarmed thioglycosides have been successfully used extensively throughout the total synthesis. Challenging 1,2-<i>cis</i> fucosyl glycosylations were achieved satisfactorily by NIS-mediated thioglycoside activation at a low temperature. All new compounds are adequately characterized by modern analytical techniques to prove their structural identity unambiguously.