Synthesis of the tetrasaccharide repeating unit of the O-antigen from Pseudomonas putida BIM B-1100 having rare D-Quip3NAc

Synthesis of the conjugation ready tetrasaccharide repeating unit of the O-polysaccharide from Halomonas fontilapidosi KR26

Synthesis of the tetrasaccharide repeating unit of the O-polysaccharide from Halomonas fontilapidosi KR26 was accomplished through a convergent [2 + 2]-block strategy using rationally protected monosaccharide synthons derived from commercially available sugars. The target tetrasaccharide was synthesized in the form of its 2-azidoethyl glycoside to ensure further conjugation with specific aglycons without hampering the reducing end stereochemistry. Use of only acyl/aryl protecting groups was targeted to keep the terminal azido-group intact for the utilization of "Click chemistry" for further conjugations.

Chemical synthesis of the rare D-Fuc3NAc containing tetrasaccharide repeating unit of the O-antigenic polysaccharide from E. coli O74

Chemical synthesis of the tetrasaccharide repeating unit of the O-antigen from E. coli O74 is accomplished by a convergent [2 + 2] block synthesis strategy. The challenging rare D-Fuc3NAc has been prepared using DTBP and TIPST mediated deoxygenation reaction. Other monosaccharide synthons are prepared through rational protecting group manipulations and the stereoselective glycosylations are achieved either by the activation of thioglycoside or glycosyl trichloroacetimidate. The target tetrasaccharide is made in the form of its 2-aminoethyl glycoside to facilitate further glycoconjugate formation without affecting the anomeric stereochemistry.