Chemical Synthesis of the O‐Antigen Repeating Unit of Escherichia coli O86 by an N‐Formylmorpholine‐Modulated One‐Pot Glycosylation Strategy

The synthesis of the O-antigen pentasaccharide repeating unit of the cell wall of Gram-negative bacteria Escherichia coli O86 is reported. The synthesis features the use of an N-formylmorpholine (NFM)-modulated glycosylation method for the construction of 1,2-cis alpha-glycosidic linkages and an [1+1+2] iterative one-pot alpha-glycosylation strategy to accelerate the assembly of the tetrasaccharide backbone.