Structure of a novel sulfate-containing mycobacterial glycolipid.

We described previously the unusual structures of the two major C-mycoside glycopeptidolipids from Mycobacterium fortuitum biovar. peregrinum. More polar glycolipids, potentially more interesting in terms of antigenicity, were also present in the strains. A combination of FAB mass spectrometry, NMR, chemical analyses, and radiolabeling was successfully applied to these glycolipids to arrive at the unexpected and novel structure for the more polar compound. This consisted of the "orthodox" basic structure of the apolar C-mycosides, modified at the alaninol end by the presence of a sulfate group on position 2 of a 3,4-di-O-methylrhamnosyl residue. This novel and second class of sulfate-containing mycobacterial glycolipid may provide a chemical basis for the differentiation and classification of members of the M. fortuitum complex, the main group causing human diseases among the many fast-growing mycobacteria widely distributed in nature.