Synthesis of oligosaccharide fragments corresponding to the exopolysaccharide released by Streptococcus macedonicus Sc 136

Abstract

Hexa-, penta- and tetrasaccharide fragments related to the repeating unit of the exopolysaccharide secreted by Streptococcus macedonicus Sc 136 were synthesized in a very efficient manner involving minimum number of steps. A general glycosylation condition has been applied for all glycosylation steps and yields were excellent.

Straightforward synthesis of a tetrasaccharide repeating unit corresponding to the O-antigen of Escherichia coli O16

“…The target tetrasaccharide as its p -methoxyphenyl (PMP) glycoside was synthesized following a sequential glycosylation approach from the suitably functionalized monosaccharide intermediates 2 [13], 3 [14], 4 [15] and 5 [16]. These monosaccharide intermediates were prepared from the commercially available reducing sugars by using a number of recently developed reaction conditions (Fig.…”

Straightforward Synthesis of the Pentasaccharide Repeating Unit of the O-Antigenic Polysaccharide from the Enteropathogenic Escherichia coli O142

“…The presence of four amino sugars and, more precisely, three α-linked 2-acetamido-2-deoxy- d -galactose moieties makes the synthesis challenging due to difficulties associated with the construction of 1,2- cis glycosidic linkages. 18 Retrosynthetic analysis (Figure 1 ) revealed that the desired pentasaccharide 1 could be synthesized using a number of suitably protected monosaccharide intermediates 2 , 19 3 , 20 4 21 and 5 , 22 which can be prepared from commercially available monosaccharides using reported reaction conditions. In order to achieve 1,2- cis glycosidic linkages, d -galactose-derived 2-azido-2-deoxy- d -galactose thioglycoside intermediate 4 was used twice in the synthetic strategy for the installation of α-linked 2-acetamido-2-deoxy- d -galactose moieties in compound 1 .…”

Concise chemical synthesis of a tetrasaccharide repeating unit of the O-antigen of Hafnia alvei 10457

“…Selective acetylation of compound 6 via an orthoester formation furnished monosaccharide acceptor 7 in 75% yield. Ethyl 2,3,5,6-tetra-O-benzoyl-1-thio-α-D-galactofuranoside (10) [23,24] was prepared from D-galactose following the reported literature. Compound 13 [25] was prepared from commercially available N-acetylneuraminic acid following a threestep reaction sequence consisting of methyl ester formation, acetylation and thioglycosidation.…”