Total Synthesis of C30 Botryococcene and epi-Botryococcene by a Diastereoselective Ring Opening of Alkenylcyclopropanes.

Trialkylaluminum compounds perform a diastereoselective 1,6-ring fragmentation of alkenylcyclopropane. This new tool allows the preparation of hydrocarbon compounds containing two distant stereocenters with a good diastereocontrol. Inspired by the biosynthesis of botryococcene this methodology was applied successfully to the diastereo- and enantioselective preparation of this triterpene and its epimer.