N-acylkansosamine. A novel N-acylamino sugar from the trehalose-containing lipooligosaccharide antigens of Mycobacterium kansasii

A novel N-acylamino sugar was isolated from the antigenic trehalose-containing lipooligosaccharides IV-VII of Mycobacterium kansasii. The native reducing sugar, its O-acetyl derivative, the methylglycoside, the O-acetylated alditol, and the de-N-acylated N-, O-acetylated alditol were all examined by high resolution 1H NMR, 13C NMR, direct probe and gas-liquid chromatography-mass spectrometry in both the chemical ionization and electron impact modes, and by high resolution mass spectrometry. The dideoxy sugar had a formula weight of 277, an empirical formula of C12H23NO6, C- and O-methyl substituents, and a N-methoxypropionyl branch. Upon alkaline hydrolysis, methoxypropionic acid was released and shown to correspond to the synthetic compound by gas chromatography and chemical ionization and electron impact mass spectrometry. The structure 4,6-dideoxy-2-O-methyl-3-C-methyl-4-(2'-methoxypropionamido)-alpha and beta-L-manno-hexopyranose, with the trivial name N-acylkansosamine, is proposed. The sugar is present in the more polar, highly antigenic lipooligosaccharides and is regarded as exclusive to M. kansasii and as its primary cell wall immunodeterminant.