Isolation using triflic acid solvolysis and identification of Nε-[(R)-1-carboxyethyl]-Nα-(d-galacturonoyl)-l-lysine as a component of the O-specific polysaccharide of Proteus mirabilis O13

An amino acid was released from the O-specific polysaccharide of Proteus mirabilis O13 by acid hydrolysis and identified as Nε-[(R)-1-carboxyethyl]-l-lysine by comparison with the authentic sample. An amide of this amino acid with d-galacturonic acid was isolated from the polysaccharide by solvolysis with anhydrous trifluoromethanesulfonic (triflic) acid and characterised by 1H and 13C NMR spectroscopy. These and published data enabled determination of the full structure of the repeating unit of the polysaccharide.