O-Polysaccharides were isolated by mild acid degradation of the lipopolysaccharides of Escherichia coli O123 and Salmonella enterica O58 and studied by chemical methods and 2D (1)H and (13)C NMR spectroscopy, including experiments in a H(2)O/D(2)O mixture, which enabled observation of correlations for nitrogen-linked protons. The following structure of the O-polysaccharide of E. coli O123 was established: →3)-β-D-Quip4NAlaHb-(1→6)-α-D-GlcpNAc-(1→3)-α-L-QuipNAc-(1→3)-α-D-Glcp (6)(approx. 30% OAc)NAc-(1→ where L-QuipNAc stands for 2-acetamido-2,6-dideoxy-L-glucose and D-Qui4NAlaHb for 4-{N-[(S)-3-hydroxybutanoyl]-D-alanyl}amino-4,6-dideoxy-D-glucose. The latter was isolated as an ethylene glycol glycoside by three sequential Smith degradations of the O-deacetylated O-polysaccharide. The structure established in this work is at variance with the E. coli O123-polysaccharide structure reported earlier [Clark, C. G.; Kropinski, A. M.; Parolis, H.; Grant, C. C.; Trout-Yakel, K. M.; Franklin, K.; Ng, L. K.; Paramonov, N. A.; Parolis, L. A.; Rahn, K.; Tabor, H. J. Med. Microbiol.2009, 58, 884-894]. In accordance with the genetic data, the O-polysaccharide of S. enterica O58 has the same structure, except for it lacks the O-acetylation.

O-antigen, Escherichia coli, Salmonella enterica, 6-dideoxy-d-glucose, 4-amino-4, O-Polysaccharide structure, Smith degradation

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
1,3,3,2	Ac	174.6	23.5
1,3,3	aLQuipN	98.4	55.1	72.2	76.7	69.3	17.7
1,3,2	Ac	175.4	23.7
1,3	aDGlcpN	97.8	54.5	76.9	69.3	73.1	61.5
1,4,2	lS3HOBut	175.1	45.8	66.4	23.3
1,4	xDAla?	175.7	51.2	17.5
1	bDQuip4N	103.9	73.9	77.5	58.2	72.6	17.8
	x?Gro	72.4	72.0	63.8


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
1,3,3,2	Ac	-	1.97
1,3,3	aLQuipN	4.97	3.93	3.66	3.23	4.19	1.25
1,3,2	Ac	-	2.04
1,3	aDGlcpN	5.01	4.04	3.85	3.60	4.24	3.83
1,4,2	lS3HOBut	-	2.42	4.18	1.24
1,4	xDAla?	-	4.22	1.28
1	bDQuip4N	4.47	3.44	3.79	3.80	3.44	1.18
	x?Gro	3.67-3.97	3.93	3.60-3.68


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
1,3,3,2	Ac		23.5/1.97
1,3,3	aLQuipN	98.4/4.97	55.1/3.93	72.2/3.66	76.7/3.23	69.3/4.19	17.7/1.25
1,3,2	Ac		23.7/2.04
1,3	aDGlcpN	97.8/5.01	54.5/4.04	76.9/3.85	69.3/3.60	73.1/4.24	61.5/3.83
1,4,2	lS3HOBut		45.8/2.42	66.4/4.18	23.3/1.24
1,4	xDAla?		51.2/4.22	17.5/1.28
1	bDQuip4N	103.9/4.47	73.9/3.44	77.5/3.79	58.2/3.80	72.6/3.44	17.8/1.18
	x?Gro	72.4/3.67-3.97	72.0/3.93	63.8/3.60-3.68

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

CC(=O)N[C@@H]1[C@H](O[C@H]2[C@H](O)[C@@H](CO)O[C@H](O[C@@H]3[C@@H](O)[C@H](OCC(O)CO)O[C@H](C)[C@H]3NC(=O)[C@@H](C)NC(=O)C[C@H](C)O)[C@@H]2NC(C)=O)O[C@@H](C)[C@H](O)[C@H]1O

784.81 g/mol (C₃₂H₅₆N₄O₁₈)