Synthesis of [1-3H]-Geranylgeranyl Pyrophosphate and its Incubation with Taxus x Media Densiformis

Abstract

<p> Recently, the discovery that taxol (2), a highly modified diterpenoid available from Taxus species, possesses anticancer activity has attracted considerable interest. The synthesis of [1-3H]-geranylgeranyl pyrophosphate(1b), a labelled form of the precursor to the diterpenoids(1a), and its incubation with a cell-free enzyme preparation from Taxus x media densiformis, a species of yew tree, were investigated.</p> <p> The investigation into the biosynthesis of taxol(2) was to be accomplished by monitoring the enzymatic transformations of (1b). The synthesis of 1b was accomplished via a convergent method using geraniol, a ten carbon compound, as the starting material. Essentially two molecules of geraniol were chemically manipulated and condensed to give geranyl geraniol which was oxidized to the corresponding aldehyde and then reduced using sodium borotritide. The radioactive alcohol was subsequently converted to the pyrophosphate (1b) using standard methodology. Cell-free extracts of Taxus x media densiformis were prepared and incubated with [1-3H]-GGPP (1b), the intermediates were extracted, and then analyzed by scintillation counting and radioactive gas chromatography. Identification of these labelled intermediates was attempted in order to provide information about the biosynthesis of 2. (Diagram included in thesis)</p>