The specific capsular polysaccharide produced by Rhodococcus equi serotype 3 was found to be a high-molecularweight acidic polymer composed of D-glucose, D-galactose, D-glucuronic acid, 4-O-[(S)-1-carboxyethyll-D-mannose, and pyruvic acid in equal molar proportions. Structural analysis, employing a combination of chemical and nuclear magnetic resonance techniques, established that the polysaccharide is composed of linear repeating tetrasaccharide units [structure], in which (R)-1-carboxyethylidene groups bridge the O-2 and O-3 positions of the β-D-glucuronic acid residues. The 1H and 13C NMR resonances of the native and depyruvulated serotype 3 polysaccharides were fully assigned by homo- and heteronuclear chemical shift correlation methods. The absolute configurations of the lactate-substituted mannopyranosyl residues and the pyruvate acetals were determined from 1H-1H NOE measurements on the intact polysaccharide. Unequivocal determination of the absolute chirality of the 4-O-[(S)-1-carboxyethyll-β-D-mannopyranoseresidues was achieved by 1H-1H NOE measurements on an acetylated lactone derivative of the glycose.

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
4,4,3	bDGlcp	99.83	74.40	75.73	80.28	76.14	62.14
4,4,4	lSLac	174.70-178.60	77.86	19.12
4,4	bDManp	101.20	68.80	79.65	78.08	76.22	62.14
4	bDGlcpA	104.60	74.50	75.50	81.50	76.00	174.70-178.60
	bDGalp	104.30	72.72	75.92	78.28	73.72	61.90

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@@H]1[C@@H](CO)O[C@@H](O[C@@H]2[C@H](O)[C@H](O[C@@H]3[C@@H](C(=O)O)O[C@@H](O[C@H]4[C@@H](CO)O[C@@H](*)[C@H](O)[C@H]4O)[C@H](O)[C@H]3O)O[C@H](CO)[C@H]2O[C@@H](C)C(=O)O)[C@H](O)[C@H]1O

734.61 g/mol (C₂₇H₄₂R₂O₂₃, R = next and previous repeats, not counted in mol weight)