Studies towards the total synthesis of pyxidatol C; New insights into the Cope rearrangement

Studies towards the total synthesis of pyxidatol C I, isolated from the medicinal mushroom Clavicorona pyxidata, are described herein. Pyxidatol C I is a member of the africanane family of sesquiterpenes, which share a decahydro-1H-cyclopropa[e]azulene core structure. Chapter 1 provides an introduction while Chapter 2 outlines work on a desmethyl model system. A Cope rearrangement was used to prepare synthetic cycloheptadiene IX. Unfortunately, the analogous rearrangement using the gem-dimethyl substituted divinylcyclopropane X was unsuccessful. As such, the reactivity of a range of substituted divinylcyclopropanes towards the thermal Cope rearrangement was investigated (Chapter 3). The effects of gemdimethyl substitution on the cyclopropane, the alkene geometry, the relative stereochemistry of the cyclopropane and the steric and electronic effects of a range of functional groups were all examined, and the methods developed were used to synthesise a range of functionalised 1,4-cycloheptadienes in high yields. Chapters 4 and 5 describe studies towards the total synthesis of pyxidatol C. Advanced intermediates were prepared including ester XII and lactone XIII containing the requisite gem-dimethyl substituted 7-membered ring, the cyclopropane moiety and the methyl ketone side chain in place.