Stereocontrolled Synthesis of the Daphenylline Pentacyclic ACDEF Ring System.

An azapentacyclic compound with the daphenylline ACDEF ring framework was synthesized from a benzo[]indole intermediate efficiently obtained by a 5-- radical cyclization of a bicyclic trichloroenamide. Stereocontrolled processes were used to generate the three stereogenic methine carbons in the pyrrolidine C ring including the all-carbon quaternary stereocenter at C5. Ring closure to build both seven- and five-membered rings was achieved by Friedel-Crafts reactions.