Short Total Synthesis of (±)-Gelliusine E and 2,3′-Bis(indolyl)ethylamines via PTSA-Catalyzed Transindolylation

A first and short total synthesis of the marine sponge 2,3′-bis­(indolyl)­ethylamine (2,3′-BIEA) alkaloid (±)-gelliusine E was performed in both a three-step divergent approach and a one-pot three-component approach with an overall yield of up to 58%. A key feature of the novel strategy is PTSA-catalyzed transindolylation of the readily synthesized 3,3′-BIEAs with tryptamine derivatives. The structure of the isolated natural product is revised as protonated (±)-gelliusine E (4′). By design, this modular route allows the rapid synthesis of other members of the 2,3′-BIEA family, for example, (±)-6,6′-bis-(debromo)-gelliusine F and analogues with step economy, operational simplicity, and reduced waste. Furthermore, their cytotoxicity in breast cancer cells was investigated.