1. Show how a-pinene (Figure 6.8) can be derived from geranyl pyrophosphate. What kind of enzyme is required to convert it to ds-verbenol?

2. a-Sinensal, found in orange peel, has the structure below. What is it made from and how has it acquired the functional group indicated with the question mark?

3. If mevalonic acid was labelled in its methyl group, show where this label should appear in iridomyrmecin.

4. Show farnesene folded as it must be as a precursor to the formation of periplanone A (Figure 6.20). Indicate what further changes have been made to give periplanone A.

5. Fold the molecule of farnesene in a way that is probable as an intermediate to caryophyllene oxide (Figure 6.20) and indicate further changes necessary to arrive at the final structure.

6. Suggest a route from (£)-(3-farnesene to ancistrodial and ancistro-furan (both Figure 6.20).

7. Gyrinidal and gyrinidone are compounds from the defensive glands of whirligig water beetles (Gyrinus sp.). Suggest schemes for their biosynthesis from farnesol. Note the resemblance to iridoids.

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