Polyterpenoids Polyprenols

Rubber, gutta, and chicle are 1,4-polyisoprenes of different molecular weights and geometries. These products are of great commercial significance and are discussed in some detail in Chap. 10. 

A short-hand convention to describe structures of polyprenols has been suggested (392). Abbreviations a (co-isoprene residue), T (/A flrA25 -isoprene residue), C (c/5-isoprene residue), and S (saturated isoprene residue) are used to designate a structure. Thus, the all- / aA25 -nonaprenol, solanesol, the first polyprenol to be isolated from nature, can be represented as cu-T-T-[T]5-T-OH. 

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). 

All ra 5-polyprenols are believed to be formed from GFPP by the chain extension process already discussed (Sect. 8.1.1.2), followed by hydrolysis by appropriate phosphatases. There is evidence to show that synthesis of all- raAi -poly-prenol pyrophosphates occurs in mitochondrial membranes and chloroplasts. Biosynthetic studies have shown that c/5, ra 5-polyprenols are synthesized from FPP or GGPP by cw-prenylation by IIP (189, 369, 392). 

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Polyterpenoids.—The presence of dolichols (202) with up to 23 isoprene units, in various sources, has been reported.In addition to these dolichols, which have their terminal isoprene unit saturated, fully unsaturated polyprenols have been found. Bovine pituitary contains a mixture of cis-trans-isomers of decaprenol (203), a Cioo prenol from bovine thyroid has been shown by n.m.r. to have eighteen cis- and two frans-isoprene residues, and 2,3-dehydrodoli-chyl pyrophosphate (204) has been identified as a product of a chick enzyme system and isopentenyl pyrophosphate.The structure of ulmoprenol from Eucommia ulmoides has been elucidated (207). ... 

Polyterpenoids.—Needles of Juniperus communis contain a range of polyprenols up to ca. Choj major component being the C95 alcohol (137). The series of syntheses of polyisoprenyl sugar phosphates has been extended to dolichyl /8-d-mannopyranosyl phosphate (138). A simple procedure for the preparation of... 

Polyterpenoids.— C N.m.r. has been used to investigate the structure of the C55 polyprenol moraprenol-11 (190) from leaves of Moms alba. The main component has the trans-trans-trans-cis-cis-cis-cis-cis-cis-cis-OH configuration. The monophosphate of this compound was prepared in 34% yield by treatment with o-phenylenephosphorochloridate. Biosynthetic studies have provided evidence for the formation of 2,3-dehydrodolichyl phosphate (191) as an intermediate in dolichyl phosphate (192) biosynthesis. Most of the members of a series of C2S—C40 acyclic hydrocarbons obtained from crude oil have isoprenoid or degraded isoprenoid structures. The mokupalides from a marine sponge have been shown to be hexaprenoids with structures (193)—(195). ... 

Polyterpenoids.—A general review has been published of the structures, occurrence, biosynthesis, and metabolism of polyprenols and isoprenylated quin-ones. A diol from insect wax has been identified by spectroscopic methods as the C25 isoprenoid to-hydroxygeranylfarnesol (189). CN.m.r. has shown... 

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