Structure of the O-polysaccharide of Providencia alcalifaciens O35 containing an N-[(S)-1-carboxyethyl]-l-alanine (alanopine) derivative of 4-amino-4,6-dideoxyglucose

•A lipopolysaccharide was isolated from a strain of Providencia alcalifaciens O35.•An O-polysaccharide was released by mild acid delipidation of the lipopolysaccharide.•The polysaccharide was studied by chemical analyses and 2D NMR spectroscopy.•N-[(S)-1-Сarboxyethyl]-l-alanine (alanopine) N-linked to d-Qui4N was identified.•The structure of the pentasaccharide repeat of the O-polysaccharide was established.

The O-polysaccharide of Providencia alcalifaciens O35 was studied by sugar and methylation analyses along with 1H and 13C NMR spectroscopy, including 2D 1H,13C HMBC, and NOESY experiments in D2O and, to detect correlations for NH protons, in a 9:1 H2O/D2O mixture. A unique N-(1-carboxyethyl)alanine (alanopine, Alo) derivative of 4-amino-4,6-dideoxyglucose (Qui4N) was identified as the polysaccharide component. Alanopine was isolated by solvolysis of the polysaccharide with triflic acid followed by acid hydrolysis, and its (2S,4S)-configuration was determined by the specific optical rotation. The following structure of the O-polysaccharide was established (the d configuration of Qui4N was ascribed tentatively):Figure optionsDownload full-size imageDownload as PowerPoint slide

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