The spirocyclic 1,2,7,7a-tetrahydrocycloprop-[1,2-c]indol-4-one subunit of CC-1065 and duocarmycin A, which comprises the common pharmacophore of the two antibiotics, has been efficiently synthesized in six steps from readily available starting materials. The key step of the synthesis utilizes a zirconocene-stabilized benzyne complex.