Synthesis of naturally occurring quinones

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The largest group of naturally occurring pigments is a set of compounds known as quinones. However, despite their bright yellow or red colours, their contribution to natural colour is relatively small. Nevertheless, they are widespread in Nature and are essential for many life processes in that they readily participate in biological oxidation and reduction reactions (redox processes). Thus for example, the ubiquinones are the essential electron-transfer agents in our respiratory chain. Other quinone natural products also possess potent biological activity, doxorubicin, for example, being one of the front-line cancer chemotherapy treatments in the UK. The synthesis and study of quinones is therefore of immense importance given the biological activity associated with many such compounds, and hence it is an extremely active area of research worldwide, with considerable importance to the UK.The proposed research seeks to look at new ways of making these important molecules. Four naturally occurring quinones (tridentoquinone, lanciaquinone, longithorone B and longithorone D) have been chosen to illustrate the methods. All of these natural products have unusual structures and are biologically active. The proposals include some new developments of an old reaction, the so-called Claisen rearrangement, whereby it will be used to introduce the necessary carbon chains into the molecules. This, in combination with a reaction that mimics the way that Nature makes the compound, will be used to access tridentoquinone, a molecule that has not been synthesised before. Likewise, lanciaquinone and longithorone D have never been made previously, and the proposed routes attempt to use the Claisen rearrangement in imaginative new ways.