Preparation of the pentasaccharide hapten of the GPL of Mycobacterium avium serovar 19 by achieving the glycosylation of a tertiary hydroxyl group

The chemical synthesis of the glycopeptidolipid-type pentasaccharide hapten of Mycobacterium avium serovar 19 with a trifluoroacetamido spacer at the reducing end is described. The spacer-armed pentasaccharide 31, when conjugated to an immunogenic protein, can be applied to the serodiagnosis of mycobacterial infections. The questionable structure of the penultimate monosaccharide unit was clarified as 6-deoxy-3-C-methyl-2,4-di-O-methyl-l-mannopyranose. The occurrence of the 6-deoxy-3-C-methyl-2,4-di-O-methyl-l-talopyranose could be excluded by the presence of the large H-1′–H-2′ coupling constant, which proves the 4C1 (l) conformation as the favoured one.

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