Total Synthesis of Dictyodendrins by the Gold-Catalyzed Cascade Cyclization of Conjugated Diynes with Pyrroles

In total and formal syntheses of dictyodendrins B, C, E, and F, the key step involved the direct construction of the pyrrolo[2,3-c]carbazole core by the gold-catalyzed annulation of a conjugated diyne with a pyrrole to form three bonds and two aromatic rings. The subsequent introduction of substituents at the C1 (Suzuki–Miyaura coupling), C2 (addition to an aldehyde), N3 (alkylation), and C5 positions (Ullman coupling) provided divergent access to dictyodendrins.