Teichoic acids glycosidation

The proportion of 1,4-anhydroribitol formed by treatment of teichoic acids and synthetic poly(ribitol phosphate) with alkali is small, and the major hydrolytic pathway involves the cyclic phosphate sequence. No 1,4-anhydroribitol glycosides have been observed in the alkaline hydrolyzates of teichoic acids possibly, the presence of a glycosyl substituent makes the reaction sterically less favorable than when such substituents are absent. 

The exterior surface of Gram-positive bacteria is covered by teichoic acids. These are ribitol-phosphate or glycerol-phosphate polymer chains that are frequently substituted by alanine and glycosidically linked monosaccharides (Figure A2.4). They are attached to the peptidoglycan by a phosphate diester link. Teichoic acids can act as receptors to bacteriophages and some appear to have antigenic properties. 

The biosynthetic cycle for the assembly of teichoic acid of the wall of Bacillus licheniformis ATCC 9945 may be taken as an example (Hancock and Baddiley, 1972 Figure 3.4). In this polymer the basic repeating unit is -glycerol-P-glycosyl-, so that phosphate ester and simple glycosidic linkages alternate. 

Properties.— The properties of glycoside hydrolases have been reviewed. As part of a series on surface carbohydrates of the prokaryotic cell, a comprehensive chapter deals with enzymes acting on bacterial surface carbohydrates. Enzymes hydrolysing capsular and slime polysaccharides, lipopolysaccharides, and teichoic acids are treated in detail. 

The preparation of some glycosylated ribitols as useful building blocks for the synthesis of certain teichoic acids has been described. The 1,6-anhydro-P-D-talopyranose (13), a key intermediate, is readily accessible from l,6-anhydro-23-< -(S)-benzylidene-p-D-mannopyranose. Thus coupling of (13) with S-ethyl-2,3,4-tri-0-acetyl-l-thio-a-L-rhamnopyranoside affords the L-ribitol derivative (14) after further IM Ocessing. Also the 4-0-allyl derivative (IS) is a suitable precursor of glycoside (16). 

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