Mild acid degradation of lipopolysaccharides from Pseudomonas aeruginosa O10a and O10a,b (Lányi classification) resulted in O-specific polysaccharides built up of trisaccharide repeating units containing 2-acetamido-2,6-dideoxy-D-glucose (N-acetylquinovosamine, DQuiNAc), 2-acetamido-2,6-dideoxy-D-galactose (N-acetylfucosamine, DFucNAc), and 5-acetamido-3,5,7,9-tetradeoxy-7-[(R)-3-hydroxybutyramido] -L-glycero-L-manno-nonulosonic acid. The latter is a di-N-acyl derivative of a new sialic-acid-like sugar which was called by us pseudaminic acid (PseN2). A 3-hydroxybutyric acid residue was also found in natural carbohydrates for the first time. In the O10a,b polysaccharide pseudaminic acid carried an O-acetyl group at position 4. For selective cleavage of the O10a polysaccharide, solvolysis with hydrogen fluoride was employed which, owing to the relatively high stability of the glycosidic linkage of pseudaminic acid, led to the disaccharide with this sugar on the non-reducing terminus. Performing the solvolysis in methanol afforded the methyl glycoside of this disaccharide which proved to be more advantageous for further analysis. Carboxyl-reduction made the glycosidic linkage of pseudaminic acid extremely labile, and mild acid hydrolysis of the carboxyl-reduced 010a polysaccharide afforded the trisaccharide with a ketose derivative on the reducing terminus. Establishing the structure of the oligosaccharide fragments obtained and interpreting the 13C nuclear resonance spectra of the polysaccharides allowed to determine the following structure for their repeating units: (formula: see text) In the polysaccharides the N-acetylquinovosamine residue is attached not to pseudaminic acid itself, but to its N-acyl substituent, 3-hydroxybutyryl group, and thus the monomers are linked via both glycosidic and amidic linkages.

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7	C8	C9
7,3,3,2	Ac	?	22.8-23.5
7,3,3	aDFucpN	99.3	51.3	68.3	76.7	68.1	16.8
7,3,2	Ac	?	22.8-23.5
7,3	bDQuipN	99.9	56.0	80.6	77.4	72.8	17.9
7	lR3HOBut	?	44.8	73.6	20.6
5	Ac	?	22.8-23.5
	bXPse?	171.8	102.1	36.8	67.6	49.0	74.8	54.7	69.2	17.7


1H NMR data:
missing...

The spectrum also has 4 signals at unknown positions (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

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

734.753 g/mol (C₃₁H₅₀R₂N₄O₁₆, R = next and previous repeats, not counted in mol weight)

Mild acid degradation of lipopolysaccharides from Pseudomonas aeruginosa O10a and O10a,b (Lányi classification) resulted in O-specific polysaccharides built up of trisaccharide repeating units containing 2-acetamido-2,6-dideoxy-D-glucose (N-acetylquinovosamine, DQuiNAc), 2-acetamido-2,6-dideoxy-D-galactose (N-acetylfucosamine, DFucNAc), and 5-acetamido-3,5,7,9-tetradeoxy-7-[(R)-3-hydroxybutyramido] -L-glycero-L-manno-nonulosonic acid. The latter is a di-N-acyl derivative of a new sialic-acid-like sugar which was called by us pseudaminic acid (PseN2). A 3-hydroxybutyric acid residue was also found in natural carbohydrates for the first time. In the O10a,b polysaccharide pseudaminic acid carried an O-acetyl group at position 4. For selective cleavage of the O10a polysaccharide, solvolysis with hydrogen fluoride was employed which, owing to the relatively high stability of the glycosidic linkage of pseudaminic acid, led to the disaccharide with this sugar on the non-reducing terminus. Performing the solvolysis in methanol afforded the methyl glycoside of this disaccharide which proved to be more advantageous for further analysis. Carboxyl-reduction made the glycosidic linkage of pseudaminic acid extremely labile, and mild acid hydrolysis of the carboxyl-reduced 010a polysaccharide afforded the trisaccharide with a ketose derivative on the reducing terminus. Establishing the structure of the oligosaccharide fragments obtained and interpreting the 13C nuclear resonance spectra of the polysaccharides allowed to determine the following structure for their repeating units: (formula: see text) In the polysaccharides the N-acetylquinovosamine residue is attached not to pseudaminic acid itself, but to its N-acyl substituent, 3-hydroxybutyryl group, and thus the monomers are linked via both glycosidic and amidic linkages.

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7	C8	C9
7,3,3,2	Ac	?	22.8-23.5
7,3,3	aDFucpN	99.1	51.2	68.3	76.1	68.1	16.8
7,3,2	Ac	?	22.8-23.5
7,3	bDQuipN	99.9	56.1	80.1	77.4	72.7	18.1
7	lR3HOBut	?	44.6	73.7	20.4
4	Ac	173.7-175.8	21.4
5	Ac	?	22.8-23.5
	bXPse?	?	103.0	34.2	70.3	46.4	74.3	54.5	69.4	17.7


1H NMR data:
missing...

The spectrum also has 5 signals at unknown positions (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]O[C@H]1[C@@H](C)O[C@H](O[C@H]2[C@H](O)[C@@H](C)O[C@@H](O[C@H](C)CC(=O)N[C@@H]([C@H](C)O)[C@@H]3O[C@@]([*])(C(=O)O)C[C@H](OC(C)=O)[C@@H]3NC(C)=O)[C@@H]2NC(C)=O)[C@H](NC(C)=O)[C@H]1O

776.79 g/mol (C₃₃H₅₂R₂N₄O₁₇, R = next and previous repeats, not counted in mol weight)