Annonaceous Acetogenins and Terpene Polyethers

SCHEME 4.3 Epoxide hydrolase-based synthesis of an acetogenin tetrahydrofuran. 

Terpene polyethers have also been proposed to arise through epoxide-opening cascade reactions. These structures are distinct from the other compound classes in this chapter because their carbon frameworks are not derived from polyketide synthase pathways. However, epoxide hydrolases are commonly encountered in terpene biosynthetic pathways [18], indicating that epoxides are viable intermediates in the construction of these compounds. 

While the involvement of epoxides in the biosynthesis of the natural products in this section has been confirmed to different levels, the process of ring formation through intramolecular addition to epoxides is quite attractive for structures that contain an oxygen atom on a carbon that is adjacent to an annulation site. Significantly, the elegant hypotheses for the biosynthesis of these structures have inspired numerous efforts to design mimics for the processes that make many of the structures available through chemical synthesis. 

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