Carbohydrate epitope structural elucidation by ¹H‐NMR spectroscopy of a new <i>Mycobacterium kansasii</i> phenolic glycolipid antigen

Abstract

The complete primary structure of the carbohydrate moiety of a new phenolic glycolipid antigen namely PheGl K-IV from Mycobacterium kansasii was successfully established from only one- and two-dimensional 1H-NMR data. Among the scalar two-dimensional techniques, correlated spectroscopy with a 45 degree mixing pulse and phase-sensitive double-quantum-filtered correlated spectroscopy were selected, combined with two-dimensional dipolar techniques (nuclear Overhauser effect). These techniques using milligram of quantities native PheGl K-IV allowed the following monoacetylated tetrasaccharide to be proposed for its carbohydrate part: 4-O-Me-alpha-Manp-(1----3)-4-O-Ac-2-O-Me-alpha-Fucp-(1----3) -2-O-Me-alpha-Rhap- (1----3)-2,4-di-O-Me-alpha-Rhap. The PheGl K-IV shares, with the other phenolic glycolipids isolated from M. kansasii (K-I, K-II), a common core assigned to the lipid aglycone glycosylated by the monoacetylated trisaccharide part. It differs in the structure of the distal monosaccharide residue.