Structural elucidation of the capsular polysaccharide isolated from Kaistella flava

The Gram-negative bacterium under study belongs to the genus Kaistella. It was isolated from a soil sample of the Haian Island in China, and it produces a lipophilic polysaccharide characterised by a branched hexasaccharide repeating unit, counting four 6-deoxy-α-l-mannose (Rha) residues, one 2-acetamido-2-deoxy-β-d-glucose (GlcNAc) and a 2-acetamido-2,6-dideoxy-β-d-galactose (FucNAc) unit.The structure of the repeating unit, assigned through 2D-NMR spectroscopy, is herein reported for the first time: