Synthesis of Pyrrolo[2,3‑<i>b</i>]indole via Iodine(III)-Mediated Intramolecular Annulation

New synthetic procedures for the pyrrolo[2,3-<i>b</i>]indole skeleton have been developed via intramolecular annulation of indole derivatives under iodine(III). A series of indole derivatives with different protecting groups or substitutions were explored to facilitate the corresponding pyrrolo[2,3-<i>b</i>]indole compounds in excellent yields

Copper-Catalyzed Radical Cyclization To Access 3‑Hydroxypyrroloindoline: Biomimetic Synthesis of Protubonine A

An unprecedented copper-catalyzed intramolecular radical cyclization was developed for the synthesis of 3-hydroxypyrroloindoline skeletons in excellent yields. The 3-hydroxyl group was introduced by trapping the radical intermediate with molecular oxygen or TEMPO. This process represents a unique radical oxidation pathway for tryptamine/tryptophan derivatives and allows a rapid biomimetic synthesis of natural product protubonine A

Biomimetic Synthesis of Moschamine-Related Indole Alkaloids via Iron-Catalyzed Selectively Oxidative Radical Coupling

An iron-catalyzed oxidative radical coupling reaction was developed to selectively construct indolofuran or bisphenolic indole cores, which exist in two types of moschamine-related indole alkaloids. Both (+)-decursivine and 4,4″-bis­(<i>N</i>-feruloyl)­serotonin were biomimetically synthesized by using coupling reactions. The proposed reassignment of the structure of montamine as 4,4″-bis­(<i>N</i>-feruloyl)­serotonin was excluded

Copper-Mediated Dimerization to Access 3a,3a′-Bis­pyrrolidino­indoline: Diastereoselective Synthesis of (+)-WIN 64821 and (−)-Ditrypto­phenaline

A copper-mediated cyclization and dimerization of tryptamine or tryptophan was developed to generate a <i>C</i>₂-symmetry C₃(sp³)–C₃(sp³) bridge with two contiguous stereogenic quaternary carbons in one step. Impressively, the ratio between exo and endo cyclization products varies when different protecting groups of Nb are utilized. This dimerization reaction could be conducted in gram scale. With this dimerization method, both endocyclo­tryptophan (+)-WIN 64821 and exocyclo­tryptophan (−)-ditrypto­phenaline were synthesized in 5 steps