Neoglycoconjugates from synthetic tetra- and hexasaccharides that mimic the terminus of the O-PS of Vibrio cholerae O:1, serotype Inaba

Abstract

A glycosyl acceptor and a glycosyl donor having the N-3-deoxy-L-glycero-tetronic acid side chain already attached have been prepared and used for the synthesis of the di- through to the hexasaccharide that mimic the upstream terminus of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Inaba. The target tetra- and the hexasaccharide, which were obtained in the form of 5-methoxycarbonylpentyl glycosides, were linked to BSA using squaric acid diester chemistry. The conjugation reactions were monitored by surface enhanced laser desorption ionization-time of flight mass spectrometry (SELDI-TOF MS). This allowed the progression of the conjugation of the synthetic oligosaccharides in a controlled way and termination of the reaction when the desired molar hapten/BSA ratio had been reached, yielding neoglycoconjugates with predetermined carbohydrate/carrier ratios. The ability to monitor the conjugation by the SELDI-TOF MS technique made it possible to prepare, from one hapten in a one-pot reaction, several neoglycoconjugates having different, predetermined carbohydrate/carrier ratios.