Dimethyl allyl pyrophosphate

The biosynthesis of monoterpenoids and camphor has been described by several authors (108-llU). Ruzicka (115,116) proposed a unified biogenetic scheme for terpenes. The biosynthetic building blocks for these terpenes are iso-prene units. The biosynthetically active isoprene units are isopentenyl pyrophosphate [l] and dimethyl allyl pyrophosphate [2] the compounds that are derived from acetate via mevalonic acid (Scheme V). Geranyl pyrophosphate [3] is the C-10 precursor for the terpenes (117). Banthorpe and Baxendale (ll8) confirmed the biosynthetic pathway of (iamphor via acetate mevalonate by conducting degradation study of camphor, biosynthesized from l c labelled mevalonic acid. The biosynthesis of camphor is summarised in Scheme VI. 

The isopentenyl pyrophosphate [l] derived from mevalonic acid isomerized into dimethyl allyl pyrophosphate [2] and... 

The biosynthesis of the ergot alkaloids involves condensation of dimethyl-allyl pyrophosphate (derived from mevalonic acid) with tryptophan. Closure of the C- and D-rings of the alkaloid involves specific hydroxylations by cytochrome P450-dependent oxidases and rearrangements. Further modifications involve N-methylation in the presence of S-adenosyl methionine and/or condensation with amino acids and peptides. Coupling of lysergyl CoA with certain peptides forms the peptide alkaloids which are the most bioactive of the ergot alkaloids. 

Several bacterial species produce C45 and C50 carotenoids which contain one or two extra isoprenyl groups. Although their biosynthesis has not been studied, it is probable that instead of proton-initiated cyclisation at the polyene termini, attack by dimethyl allyl pyrophosphate results in substances such as the symmetrical decaprenoxanthin (P439) (68). The stereochemistry of the isolated acyclic double bond was shown to be trans by the n.m.r. spectrum of the corresponding aldehyde. Other carotenoids present in Flavobacterium... 

Many natural products contain an isolated isoprene unit derived from mevalonic acid hence, these compounds may be considered as hemiterpenoid derivatives. In most cases the immediate precursor is probably dimethyl allyl pyrophosphate... 

Ergot Alkaloids.—The hemiterpenoid unit of the ergot alkaloids is interesting in that, as expected, only one carbon atom is labelled by [2- C]mevalonic acid [marked by in formulae (14)—(17)] but the stereochemistry of this atom changes. Extensive studies by Floss etalf indicate that chanoclavine I (14) is converted into elymoclavine (17) via the aldehyde (15) and possibly via agroclavine (16) (however, see ref. 36a). This process involves two isomerisations about the isolated double bond. In dimethyl allyl pyrophosphate (5) the trans-methyl is labelled by... 

Normally it is assumed that in terpenoid biosynthesis each isoprenoid unit will be equally labelled by [2- C]mevalonic acid. However, Banthorpe et al. have found that in camphor (30) biosynthesis most of the radioactivity was located at C-6. A significant size pool of dimethyl allyl pyrophosphate (5) is suggested. This... 

Dimerization first produces acetoacetyl-CoA (II), and this reacts further to produce )3-hydroxyl jS-methyl glutaryl CoA (III), mevalonic acid (IV), iso-penteny 1-pyrophosphate (V), and, finally, dimethyl allyl pyrophosphate (VI) ... 

The chain formation results from dimethyl allyl pyrophosphate and isopentenyl pyrophosphate ... 

It has been generally accepted that C-2 of mevalonic acid becomes the methyl group trans to the ester function of dimethyl-allyl pyrophosphate. Since the latter couples with isopentenyl pyrophosphate to give geraniol (131), it follows that the C-10 of... 

FIGURE 4.18. Structure of the allylic oligoisoprene pyrophosphates. DMAPP dimethyl allyl pyrophosphate, GPP geranyl pyrophosphate, FPP famesyl pyrophosphate, GGPP geranylgeranyl pyrophosphate. 

The first step involves the intermolecular olefin alkylation between two molecules of dimethyl allyl pyrophosphate. A 1,3-proton elimination from the methylene group gives chrysanthemyl pyrophosphate while a 1,2-proton elimination affords the lavandulol skeleton. Of course, these transformations can be equally well represented by formation of either a bridged, non-classical carbonium ion or an intermediate covalently bound to a nucleophile (e.g., X group on an enzyme surface... 

The isopentenyl pyrophosphate is then obtained with adenosine triphosphate via a series of intermediary stages, and part is converted to dimethyl allyl pyrophosphatef ... 

After the initiating step, more IPP units can be inserted, which constitutes the elementary step of propagation or chain growth. Adding one IPP unit to GPP catalyzed by the trans-prenyl transferase enzyme yields famesyl pyrophosphate (FPP) and HOPP. FPP has a dimethyl allyl head group (green), two repeat imits in trans configuration (blue). 

Glyceryl-1-allyl ether N-Methyl-2-pyrrolidone printed circuit boards Copper pyrophosphate Poly (oxy-p-phenylenesulfonyl-p-phenylene) resin Tetrahydrofurfuryl methacrylate Toluene bis (dimethyl urea) printing... 

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