Total Synthesis of (±)-Cycloclavine and (±)-5-epi-Cycloclavine

Novel routes to the naturally occurring indole alkaloid cycloclavine and its unnatural C(5)-epimer are described. Key features include the rapid construction of the heterocyclic core segments by two Diels-Alder reactions. An indole annulation was accomplished by a late-stage intramolecular Diels-Alder furan cycloaddition, and a methylenecyclopropane dienophile was used for a stereo-selective intramolecular [4 + 2] cycloaddition to give the cyclopropa[c]indoline building block present in cycloclavine.