Iodine Promoted Condensation of Aldoses and α-Ketoacid- Terminated Saccharides with o-Phenylenediamines for Synthesis of Glycoconjugates
Date Issued
2009
Date
2009
Author(s)
Lai, Po-Ting
Abstract
Carbohydrate molecules act as markers on the outer membrane of cell surface to play a central role in biological recognition events. Different species of bacteria have different types of polysaccharides except for the core structure of oligosaccharide that links to protein. GalNAc is the linking saccharide for most Gram-positive bacteria, whereas Kdo (3-deoxy-D-manno-octulosonic acid) is for Gram-negative bacteria. Various methods have been applied for modification of the unprotected terminal GalNAc, but there is no effective method has been explored for Kdo conjugation. We report here a novel method for condensation of unprotected saccharides with o-phenylenediamines using iodine in acetic acid solution to form aldo-benzimidazoles. This method is applied to mono-, di-, and trisaccharides. We also found that α-keto acids reacted with o-phenylenediamines using iodine in acetic acid solution to form the corresponding quinoxalinones. The formation of quinoxalinones from polysaccharides was verified by fluorescence spectra. By using an appropriate diamine linker, we demonstrated the conjugation of lipid A-free polysaccharides with aminated polystyrene gel. The content of glycoconjugates was determined by a simple phenol–sulfuric acid method. This method provides a convenient way to synthesize glycoconjugates containing the polysaccharide from the outer surface of Gram-negtive bacteria. This method is potentially useful in conjugation of carrier proteins with polysaccharides, which can be a good antigen for inducing antibodies against antibiotic-resistance bacteria.
Subjects
iodine
carbohydrate
polysaccharide
glycoconjugate
LPS
Type
thesis
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