Olefin cross-metathesis in the preparation of polycyclopropanes: formal synthesis of FR-900848

Olefin cross-metathesis was used for the efficient incorporation of an E-olefin between two cyclopropane residues. The generation of a bis-cyclopropyl alkene homodimer, followed by cross metathesis with a terminal vinyl polycyclopropane, provided excellent yields of the targeted compounds with good olefin stereoselectivity. The strategy was applied to generation of a quinta-cyclopropane intermediate found in a previous synthesis of the natural product FR-900848.