A concise strategy for the chemical synthesis of the tetrasaccharide repeating unit
of the O-antigen from E. coli O174:H28 is reported. Synthesis of the target structure is accomplished by sequential
glycosylation of rationally protected monosaccharide synthons derived from commercially
available sugars. Glycosylation reactions were achieved by the activation of the thioglycosides
using N-iodosuccinimide in the presence of H2SO4–silica. The carboxylic acid moiety of the glucuronic acid unit was successfully installed
by a late TEMPO-mediated oxidation of the primary hydroxy group. Phthalimido groups
were successfully used as the precursors of the required acetamido functionalities
for 1,2-trans-glycosylations.
Key words
bacterial
O-antigen - acetamido sugars - H
2SO
4–silica
