Polysaccharide Synthesis with Polyprenols

There is now a great deal of evidence that liposaccharide intermediates are involved in some biosyntheses of polysaccharides in animals and bacteria. This is an alternative to the UDP-sugar process (11.60) and utilises various nucleoside diphosphate sugars together with a polyprenol phosphate. The presence of a long hydrocarbon chain in the latter is believed to facilitate biosynthesis in the hydrophobic regions of membranes. 

A polyprenol phosphate such as dolichol phosphate (10.63) can react with a nucleoside diphosphate sugar in one of two ways (11.119) and (11.120). As an example of a synthesis proceeding 

The biosynthesis of peptidoglycans involves the formation of both UDP-NAG (11.121a) and UDP-NAM (11.121b) as essential intermediates, which then take part in reactions of type (11.119) above. 

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The structures of polyprenyl diphosphate-linked intermediates of Salmonella O-specific-polysaccharide biosynthesis were confirmed by chemical synthesis of their analogs derived from the plant polyprenols ficaprenol and moraprenol (structurally related to bacterial polyprenol57) with the following study of their behavior as substrates of enzymic reactions. Synthetic polyprenyl a-D-galactopyranosyl diphosphate291,292 was found to serve as an effective acceptor for the transfer of L-rhamnosyl groups.293"295 Two synthetic, isomeric disaccharide derivatives,292 13 and296 14, were tested as acceptors for enzymic D-mannosyl transfer from GDP-Man, but only the former was found to be an efficient substrate.294... 

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