Studies directed toward the total synthesis of cortistatin A

Studies directed toward the total synthesis of the cytotoxic steroidal alkaloid cortistatin A were carried out. In a model system, it was determined that a sequence of reactions involving a lithiocyclopropene addition-intramolecular [4 + 2] cycloaddition cascade and subsequent cyclopropylcarbinyl rearrangement allowed for ready access to the BCD rings of the core steroid. Implementation of this methodology en route to the fully functionalized natural product proved an effective means for the elaboration of the A ring carbocyclic framework.