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.