Synthesis of the Hexasaccharide Repeating Unit Corresponding to the Cell Wall O -Antigen of Providencia alcalifaciens O9:H8 Strain

A straightforward synthesis of the hexasaccharide repeat-ing unit of the O-specific polysaccharide of Providencia alcalifaciensO9:H8 strain was achieved in very good yield by applying a stereo- andregioselective [4+2] block glycosylation strategy. The tetrasaccharideacceptor and disaccharide donor were synthesized by sequential stereo-and regioselective glycosylations. Thioglycoside and glycosyl trichloro-acetimidate derivatives were used as glycosyl donors in the syntheticstrategy. The glycosylation steps were high-yielding and gave satisfac-tory stereochemical outcomes.