Plant polyprenols structure

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... 

Table I summarizes the plant polyprenols that have been isolated and whose sources and some structural aspects have been characterized. These polyprenols occur in different species as mixtures, differing from each other in one isoprene unit. One or two members of the family are very abundant and normally account for 80% of the total polyprenol content of the plant. Most long-chain polyprenols have Z, E double bonds, the E-isoprene units being adjacent to the -residue and to a variable number of Z residues, depending on the plant (see Table I).

The chemical structure of naturally occurring ais polyisoprenes was determined by 13C NMR spectroscopy using acyclic terpenes and polyprenols as model compounds. The arrangement of the isoprene units along the polymer chain was estimated to be in the order dimethylallyl terminal unit, three trans units, a long block of ais units, and ais isoprenyl terminal unit. This result demonstrates that the biosynthesis of cis-polyisoprenes in higher plants starts from trans,trans,trarcs-geranylgeranyl pyrophosphate. ... 

Polyprenols of higher plants have mostly been isolated from leaves solanesol (C45) was first obtained in 1956 from tobacco leaves. However, their occurrence in certain woody tissues has been demonstrated. Silver birch (Betula verrucosa) wood has been shown to contain fatty acid esters of betulaprenols -6 to -9 the major polyprenol, betulaprenol-7 has the structure cu-T-T-C-[C]2-C-OH (573) the poli renols from the leaves were free, and the major component had 11 isoprene units (188, 256). 

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