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Synthesis of Monomeric and Dimeric Repeating Units of the Zwitterionic Type 1 Capsular Polysaccharide from Streptococcus pneumoniae
Author(s) -
Wu Xiangyang,
Cui Lina,
Lipinski Tomasz,
Bundle David R.
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902460
Subject(s) - synthon , chemistry , trisaccharide , uronic acid , monosaccharide , streptococcus pneumoniae , polysaccharide , glycosylation , glycan , galactose , stereochemistry , bacteroides fragilis , biochemistry , glycoprotein , antibiotics
Zwitterionic polysaccharides (ZPSs) from Bacteroides fragilis and Streptococcus pneumoniae display unique T‐cell activities. The first synthesis of a hexasaccharide representing two repeating units of the zwitterionic capsular polysaccharide from S. pneumoniae type 1 (Sp1) is reported. Key elements of the approach are stereoselective construction of 1,4‐ cis ‐α‐galactose linkages based on a reactive trichloroacetimidate donor that incorporates a 6‐ O ‐acetyl group, which may contribute to the high α selectivity in glycosylation. After assembly of the fully protected hexasaccharide from five monosaccharide synthons 2 – 4 , 24 and 25 , selective deprotection of the primary hydroxyl groups of the four galactose residues followed by oxidation to the corresponding uronic acids provides hexasaccharide 19 . The trisaccharide counterpart 1 was synthesized in similar fashion from three synthons, 2 – 4 . This approach employed both conventional and dehydrative glycosylation methodologies and avoids the use of poorly reactive uronic acid derived glycosyl donors and acceptors.