Two modi®cations of 5-acetimidoylamino-7-acetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic acid (5-N-acetimidoyl-7-N-acetyllegionaminic acid) in the O-chainpolysaccharide (OPS) of theLegionellapneumophila serogroup 1 lipopolysaccharide (LPS) concern N-methyla-tionof the 5-N-acetimidoyl group in legionaminic acid. Both N-methylated substituents, the (N,N-dimethylacetimidoyl) amino and acetimidoyl(N-methyl)amino group, could be allocated to one single legionaminic acid residue in the long-and middle-chain OPS, respectively. .
