Acyl groups bacterial polysaccharides

Acyl groups are common in bacterial polysaccharides. The parent acids are fatty acids, hydroxy acids, and amino acids. The simplest acid, formic acid, has only been found as the amide. The occurrence of O-formyl groups had been reported, but proved to be incorrect. A-Formyl groups have been found in different polysaccharides for example, in the 0-specific side-chains of the LPS from Yersinia enlerocolitica 0 9, which are composed of 4,6-dideoxy-4-formamido-D-mannopyranosyl residues. The formyl group can assume two main conformations, s-cis (41) and s-trans (42), which are... 

F.a.b.-m.s. has been applied to three types of problem in the bacterial polysaccharide area assigning compositions (including the number and type of O-acyl groups), sequencing, and identifying cyclic structures. The last application is covered in Section VI,5. 

O-Acylation also provides a frequent modification of monosaccharide residues in bacterial polysaccharides, and, in most cases, substitution with acyl groups is only partial. 

Acyl (for example, O-acetyl) groups are common structural features in bacterial polysaccharides. The proportion and position of O-acyl groups can be determined by a method devised by de Beider and Norrman. ... 

All of the free hydroxyl groups are protected as acetals by reaction with methyl vinyl ether. The 0-acyl groups are then split off by treatment with alkali, and the resulting material is methylated (see Scheme 20). After hydrolysis of the methylated material, and analysis of the hy-drolyzate as alditol acetates by g.l.c.-m.s., it is possible to determine the positions and proportions of O-methyl groups and, hence, the substitution pattern of the 0-acyl groups. This procedure has been used to locate 0-acetyl groups in bacterial polysaccharides and wood polysaccharides. ... 

Disaccharides to have been examined are two D-ribofuranosyl-D-ribitols produced from two bacterial capsular polysaccharides, and several aa-trehalose derivatives prepared as model bacterial cord factors [F.D. cationization with cesium iodide gave intense (M + Cs) ions]. The same group of workers have also reported on this method applied to the natural cord factor of Corynebacterium diphtheriae, and they found at least 22 species differing in the chain lengths of the two trehalose acyl substituents. A further report describes the determination of the sites of substitution of the acyl groups.Daunosamine-containing disaccharides have been examined by negative ion, positive ion, chemical ionization, and electron-impact methods. 

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