Phytol derivatives

At present, it is evident that diaeetylene ean be used for the ereation of profitable pilot-seale faeilities to produee simple and funetionalized thiophenes, pyrroles, pyrazoles, pyrimidines, pyridines, and other heteroeyeles, as well as vitamins A and PP, geraniole, phytole derivatives, and many other high-prieed speeialty ehemieals. 

Figure 3. Geochemically reversible and irreversible reactions. Only the reactions are listed for which we have evidence from the fringelites, the fossil porphyrins, and the phytol-derived hydrocarbons (5).

Branched alkenes from zooplankton Phytol-derived olefinic hydrocarbons have been isolated in low concentration from marine zooplankton (1) isomeric mono-olefins from mixed zooplankton from the Gulf of Maine by Blumer and Thomas (1965b) (2) isomeric phytadienes derived by dehydration of phytol, presumably by acid catalysis (Blumer and Thomas, 1965a) (3) C19 di- and tri-olefinic hydrocarbons (Blumer et al., 1969). These olefins are not present in ancient sediments and in petroleum and are therefore valuable markers in the distinction between marine hydrocarbons from organisms and from oil pollution. 

Blumer, M., Robertson, J.C., Gordon, J.E. and Sass, J., 1969. Phytol-derived C19 di- and triolefinic hydrocarbons in marine zooplankton and fishes. Biochemistry, 8 4067— 4074. 

A further group of branched-chain acids differ from those already discussed in that they are produced from isoprenoid precursors and not by the normal de novo pathway or some simple modification of it. These acids are based on the diterpene phytol derived from chlorophyll and the more common acids are phytanic (C20), pristanic (C19) and a Cie homologue. These molecules contain chiral centres and the natural forms are not always the same enantiomer. These acids occur widely, but at low levels, in the lipids of land and aquatic animals and have been identified in ancient sediments. In animals they occur in tissue, milk and blood lipids and are present as trace components of butter fat. The tissue lipids of humans suffering from the rare neurological disorder Refsum s disease contain up to 50% of phytanic acid because of an inability to metabolize this unusual branched-chain acid (Section 12.6). 

Since carotenoids are isoprenoids, they share a common early pathway with other biologically important isoprenoids such as sterols, gibberellins, phytol and the terpenoid quinones (Fig. 13.3). In all cases, these compounds are derived from the C5 isoprenoid, isopentenyl diphosphate (IPP). Until a few years ago it was believed that a single pathway from the Cg precursor mevalonic acid (MVA) formed IPP, which itself was synthesised from hydroxymethylglutaryl coenzyme A (HMG CoA) by the action of HMG... 

Since carotenoids are derived for the central isoprenoid pathway (Fig. 13.3), the regulation of their formation must involve a co-ordinated flux of isoprenoid imits into this branch of the pathway as well as into others such as the biosynthesis of sterols, gibberellins, phytol and terpenoid quinones. An imderstanding of the complexities of regulation of the pathway is necessary in order to target the regulatory steps for genetic manipulation. 

From these stractural features it is interesting to note that each molecule of chlorophylls a and b consists of a hydrophilic part (tetrapyrrole macrocycle) and a hydrophobic portion (long terpenoid chain of phytol esterifying the acid group at C-17). Figure 2.1.2 shows the structures and nomenclature of chlorophylls a and b and their major breakdown derivatives. 

Racemase deficiency. The biological role of 2-methyl-acyl-CoA racemase has only recently been clarified. This peroxisomal enzyme is essential for certain steps of the oxidation of phytol and bile acid derivatives, which are stereospecific. Biochemically there is accumulation of pristanic acid and C27 bile acid intermediates. Clinical symptoms may include adult-onset peripheral neuropathy, pigmentary degeneration of the retina and liver disease [ 13]. 

The isoprenoid hycrocarbons pristane and phytane (derived from the phytol side chain of chlorophyll), as well as porphyrins, have been detected in organic extracts of the Nonesuch Shale of 1.1 billion year age [23]. Their presence points to the existence of photosynthetic pigments in the Precambrian era, but it is also possible that these extractable substances could have been contributed to the rock at a later time. However, in this instance contamination appears to be less likely on account of the large abundance of organic material in this shale. 

Our reference values for the straight-chain fatty acids were established using 157 controls (see Table 3.4.3). The concentrations of VLCFA in controls were independent of age. Phytanic and pristanic acid - or their precursor phytol - are exclusively derived from the diet. Accordingly, the reference values for these substances are somewhat age-dependent, especially below the age of 2 years [11]. The upper refer-... 

The concentration of dolichyl phosphate in eukaryotic tissues is very low and is probably rate-limiting for the glycosylation processes. Variation of the concentration in the endoplasmic-reticulum membranes is a possible way of controlling the rate of glycosylation. It is important to point out that the early steps in the dolichol biosynthesis are common to such other prenyl derivatives in plants as steroids, essential oils, hormones, phytol, and carotenes (see Scheme 1), and parameters affecting those reactions that may control the dolichol to dolichyl phosphate step could be another mechanism for regulation of the level of dolichyl phosphate. 

The four names are actually derived not from the common terpene names of hydrocarbons but from those of the corresponding alcohols, that is, geraniol, linalool, nerol, and phytol. 

Figure 9.37 Chemical structures of chlorophylls-a and b which contain a propionic acid esterified to a C20 phytol chlorophylls-cj and C2 have an acrylic acid that replaces the propionic acid. Also included are the pheopigments, the four dominant tetrapyrrole derivatives of chloropigments (pheopigments) found in marine and fresh-water/estuarine systems (chlorophyllide, pheophorbide, pheophytin, pyropheophorbide.) More specifically, chlorophyllase-mediated de-esterification reactions (loss of the phytol) of chlorophyll yield chlorophyllides. Pheophytins can be formed when the Mg is lost from the chlorophyll center. Pheophorbides are formed from removal of the Mg from chlorophyllide or removal of the phytol chain from pheophytin, and pyrolyzed pheopigments, such as pyropheophorbide and pyropheophytin, are formed by removal of the methylcarboxylate group (-COOCH3) on the isocylic ring from the C-13 propionic acid group.

Branched and cyclic hydrocarbons have also been used as paleomarkers, principally in lake sediments, to interpret past changes in organic matter sources. In particular, isoprenoid hydrocarbons such as pristane (C19 isoprenoid hydrocarbon) and phytane (C20 isoprenoid hydrocarbon) (both derived from phytol) have been used as indicators of herbivorous grazing and methanogenesis, respectively. 

Phytane C20 isoprenoid hydrocarbon derived from phytol—shown to be a useful indicator of herbivorous grazing. 

Oxidation reactions of this nature are common in the literature. For example, selenium dioxide in refluxing etiumolic solution brought about the allylic oxidative rearrangement geranyl acetate, which was further functionalized in a synthesis of the norsesquiterpenoid gytinidal (equation 46). This trans formation was also used in a total synthesis of phytol. Similarly, an a, -unsaturated aldehyde was obtained undm similar conditions in studies of a synthesis of pentalenic acid derivatives (equation 47). ... 

Straight Long Chain Alcohols. Linear long-chain alcohols with carbon numbers between C22 and C32 are present in olive oil both free and esterihed (waxes). The components are abundant in the epicarp of the fruit and concentrate in solvent extracted oil. Phytol, probably derived from biodegradation of chlorophyll, is also present along with geranyl (38). 

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