O-Polysaccharides were released by mild acid degradation of lipopolysaccharides of Providencia alcalifaciens O35 and Proteus vulgaris O76 and were studied by 1D and 2D (1)H and (13)C NMR spectroscopies, including HMBC and NOESY (ROESY) experiments. Both polysaccharides were found to contain N-(1-carboxyethyl)alanine (alanopine) that is N-linked to 4-amino-4,6-dideoxyglucose. Analysis of published data [Vinogradov, E.; Perry, M. B. Eur. J. Biochem.2000, 267, 2439-2446] shows that alanopine is present also on the same sugar in the lipopolysaccharide core of Proteus mirabilis O6 and O57.