First synthesis of a pentasaccharide repeating unit of the O-antigenic polysaccharide from enterohaemorrhagic Escherichia coli O48:H21

Influence of remote functional groups towards the formation of 1,2-cis glycosides: special emphasis on β-mannosylation

The influence of remote functional groups for the stereoselective formation of 1,2-cis glycosides and β-mannosides is reported.

Convergent Synthesis of Oligosaccharide Fragments Corresponding to the Cell Wall O-Polysaccharide of Salmonella enterica O53

Conventional glycoconjugate vaccines are prepared with polysaccharides isolated from bacterial fermentation, an approach with some significant drawbacks such as handling of live bacterial strains, the presence of biological impurities, and inter-batch variations in oligosaccharide epitope structure. However, it has been shown in many cases that a synthetic fragment of appropriate structure conjugated to a protein can be an effective vaccine that circumvents the shortcomings of using full-length oligosaccharides. The development of synthetic strategies to prepare glycoconjugate derivatives against pathogenic bacterial strains is therefore of great interest. Oligosaccharide fragments corresponding to the repeat unit of the cell wall O-antigen of Salmonella enterica strain O53 were synthesized in good yield. Sequential and block glycosylation strategies were used for the synthesis of the target compounds. A number of recently developed reaction conditions were used in the synthetic strategy. A one-pot reaction scheme was also developed for the multiple glycosylation steps. The stereoselective outcomes of all glycosylation reactions were very good.

Chemical Synthesis of the Tumor-Associated Globo H Antigen

A derivative of the tumor-associated globo H antigen, a complex hexasaccharide, was synthesized by a convergent and efficient [3+2+1] strategy using various glycosylation methods. All glycosylation reactions afforded good to excellent yields and outstanding stereoselectivity, including the installation of cis α-linked D-galactose and L-fucose. The longest linear sequence for this synthesis was 11 steps from a galactose derivative 11 to give an overall yield of 2.6%. The synthetic target had a free and reactive amino group at the glycan reducing end, facilitating its conjugation with other molecules for various applications.

Convergent synthesis of the pentasaccharide repeating unit of the O-antigenic polysaccharide of enterohaemorrhagic Escherichia coli O113

An acidic pentasaccharide repeating unit corresponding to the O-antigenic polysaccharide of enterohaemorrhagic Escherichia coli O113 as its p-methoxyphenyl glycoside has been synthesized in a convergent manner by adopting a [3+2] block glycosylation strategy. During the synthetic endeavor a one-pot reaction condition for stereoselective glycosylation and protecting group manipulation has been applied. All glycosylation steps are highly stereoselective with good to excellent yield.

Convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9

A convenient synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9 has been achieved in excellent yield using a [2 + 2] block glycosylation strategy. TEMPO-mediated selective oxidation of the primary alcohol of the tetrasaccharide derivative 8 to the carboxylic group followed by deprotection of the functional groups furnished target tetrasaccharide 1 as its 4-methoxyphenyl glycoside in high yield.