Unified Strategy to Monoterpene Indole Alkaloids: Total Syntheses of (±)-Goniomitine, (±)-1,2-Dehydroaspidospermidine, (±)-Aspidospermidine, (±)-Vincadifformine, and (±)-Kopsihainanine A

Total syntheses of (±)-goniomitine, (±)-1,2-dehydroaspidospermidine, (±)-aspidospermidine, (±)-vincadifformine, and (±)-kopsihainanine A were achieved featuring two common key steps: (1) a palladium-catalyzed decarboxylative vinylation that provides quick access to cyclopentene intermediates containing all of the carbons present in the natural products and (2) an integrated oxidation/reduction/cyclization (iORC) sequence for skeletal reorganization that converts the cyclopentenes to the pentacyclic structures of the natural products. By incorporation of a geometric constraint to iORC substrates, both the chemoselectivity (C7 vs N1 cyclization) and the stereoselectivity (trans- vs cis-fused ring system) of the cyclization process can be controlled.