Concise synthesis of the tetrasaccharide repeating unit of the O-polysaccharide isolated from Edwardsiella tarda PCM 1156 strain

Concise synthesis of the tetrasaccharide repeating unit of the O-antigen from Escherichia coli O131 containing N-acetyl neuraminic acid

Synthesis of the tetrasaccharide repeating unit of the O-antigen from E. coli O131 was accomplished through a linear strategy involving rationally protected monosaccharide units derived from commercially available sugars. The challenging α-glycosylation of N-acetyl neuraminic acid was achieved through activation of thioglycoside using NIS-mediated glycosylation strategy. The target tetrasaccharide in the form of its 3-aminopropyl glycoside may be used for further glycoconjugate formation without hampering the anomeric stereochemistry.

One-Pot Regioselective Diacylation of Pyranoside 1,2-cis Diols

A one-pot strategy for functionalizing pyranoside 1,2-cis-diols with two different ester protecting groups is reported. The approach employs regioselective acylation via orthoester hydrolysis promoted by a carboxylic acid, e.g., levulinic acid, acetic acid, benzoic acid, or chloroacetic acid. Upon removal of water and introduction of a coupling agent, the carboxylic acid is esterified to the hydroxyl group liberated during hydrolysis. Although applied to 1,2-cis-diols on pyranoside scaffolds, the method should be applicable to such motifs on any six-membered ring.

Convergent synthesis of the hexasaccharide related to the repeating unit of the O-antigen from E. coli O120

The hexasaccharide repeating unit of the O-antigen from E. coli O120 has been synthesized in the form of its 4-methoxyphenyl glycoside by a convergent [2 + 4] strategy.