Studies on the synthesis of the antitumour agent CC-1065. Synthesis of the cyclopropapyrroloindole portion

Using a regioselective Mannich reaction the 3,3′-bipyrrole (4) is converted into the acid chloride (10), which is transformed into the tricyclic phenol (11); selective reduction of (11) using triethylsilane in trifluoroacetic acid gives (12), which is converted by further reduction into (14), which by the intermolecular Mitsunobo reaction gives the cyclopropapyrroloindole (17).