Org Lett 2019 Jul 2;21(14):5757-5761. Epub 2019 Jul 2.
Laboratori de Química Orgànica, Facultat de Farmàcia, IBUB , Universitat de Barcelona , Av. Joan XXIII s/n , Barcelona 08028 , Spain.
An azapentacyclic compound with the daphenylline ACDEF ring framework was synthesized from a benzoindole 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.