Geranyl phosphate

FIGURE 1.4 Proposed biosynthetic route for the biosynthesis of (A) squalene oxide (squalene-2,3-oxide) via the isoprenoid pathway and (B) triterpene saponins of the dammarane-type and oleanane-type from squalene oxide. PP, diphosphate group GPS, geranyl phosphate synthase FPS, farnesyl phosphate synthase NADPH, nicotinamide adenine dinucleotide phosphate. 

Indeed in the same experimental conditions the geranyl phosphate brings the formation of an o-hydroxy phosphonate which can give the citral. 

A new method for the selective demethylation of alkyl methyl phosphates employs a mixture of dimethyl sulphide and methanesulphonic acid. Boron trifluoride etherate catalyses the regio- and stereo-specific alkenylation of phenolic ethers by diisopropyl prenyl or geranyl phosphates (84) in low to moderate yields. 2-(Diethoxyphosphinyl)-1,3-butadienes, e.g., (85), are cleaved by organocopper reagents in some cases this reaction is accompanied by alkylation and rearrangement to an allene structure. ... 

Enzymes in cell-free systems from carrot Daucus carota, Apiaceae) and peppermint Mentha piperita Lamiaceae) catalyze the reversible formation of nerol and neryl phosphate from geraniol and geranyl phosphate, respectively. Geranyl phosphate appears to have been isomerized directly to the neryl derivative without the intervention of an aldehyde intermediate. The presence of a flavin, thiol, and light was required for the reaction (Croteau, 1984). 

Figure 9.4 Monoterpene biosynthesis in peppermint oil gland secretory cells. The enzymes involved in this pathway are (1) 1-deoxy-D-xylulose 5-phosphate synthase, (2) 2-C-methyl-D-erythritol 4-phosphate reductoisomerase, (3) 2-C-methyl-D-erythritol 4-phosphate cytidyltransferase, (4) 4-(cytidine 5 -diphospho)-2-C-methyl-D-erythritol kinase, (5) 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase, (6) isopentenyl diphosphate isomerase, (7) geranyl diphosphate synthase, (8)...

This enzyme [EC 2.5.1.10], also known as farnesyl-di-phosphate synthase, catalyzes the reaction of geranyl diphosphate with isopentenyl diphosphate to produce trans,trans-farnesyl diphosphate and pyrophosphate (or, diphosphate). Some forms of this enzyme will also utilize dimethylallyl diphosphate as a substrate. However, the enzyme will not accept larger prenyl diphosphates as an efficient substitute for geranyl diphosphate. 

Previous methods for the preparation of salts of geranyl diphosphate and other allylic isoprenoid diphosphates are based on condensation between the alcohol and inorganic phosphate by trichloroacetonitrile as originally reported by Cramer and modified by Popjak The reaction generates a complex mixture of organic and inorganic polyphosphates which must be separated by chromatography. The desired diphosphate ester has been prepared on small... 

Previous studies on the cyclization of geranyl diphenyl phosphate have been extended to the corresponding derivatives (43) of cisdrans- and transjrans-farnesol. The main reaction product was a mixture of isomeric bisabolenes (44), bisabolol (45), and a mixture of isomeric farnesenes (46). It has been suggested... 

If sterol content and conformation are so important for membrane stability, we should study the biosynthesis of sterols (Figure 3). The first enzyme in terpenoid biosynthesis is the 3-Hydroxy-3-Methyl-Glutary1-Coenzyme A-reductase (HMG-CoA-reductase) that catalyzes the synthesis of mevalonate. Two phosphorylations and decarboxylation of mevalonate lead to isopentenylpyrophosphate, the basic C -unit in sterol synthesis. Isopentenylpyrophosphate reacts with its isomer, the dimethylally1-pyrophosphate, in a head/tail-reaction to geranyl-pyrophosphate reaction with another C -unit leads to farnesyl-pyro-phosphate, that dimerizes in a tail/tail-reaction to squalene. After expoxidation of its A -double bond, squalene cyclizes to lano-... 

Figure 10.7 All terpenes are derived from allylic diphosphates which are polymers of repeating isopentyl units (IPP) put together by the action of prenyltransferases. In plants, IPP can be derived from the mevalonate biosynthetic pathway (a cytoplasmic pathway) or the methyl erythritol phosphate pathway (a plastidic pathway). Monoterpenes are then derived from the CIO precursor geranyl diphosphate (GPP), sesquiterpenes from the C15 precursor famesyl diphosphate (FPP), and diterpenes from the C20 precursor geranylgeranyl diphosphate (GGPP) by the action of terpene synthases or cyclases, which divert carbon into the specific branch pathways.

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