Synthesis of the tetracyclic core skeleton of the lundurines by a gold-catalyzed cyclization

Synthetic Studies toward Lapidilectine-Type Kopsia Alkaloids

“…A majority of the synthetic efforts aimed at these compounds have been focused on the lundurine class of molecules. 4 The most advanced approach, which arrives at the tetracyclic core of lundurine using creative ring closing metathesis reactions, was recently reported by Martin and coworkers. 5 …”

Novel Approach to the Lundurine Alkaloids: Synthesis of the Tetracyclic Core

“…There are no reported syntheses of any of the lundurines to date, although a few approaches to the skeleton have been reported. 3 …”

Regioselective Direct C‐Alkenylation of Indoles

“…Gold catalysts are also effective in the ring closure of indoles bearing an alkyne moiety tethered at C‐3 by two or three carbon atoms. This process results in the formation of dihydro‐ or tetrahydrocarbazole systems in satisfactory yields (68–100 %), and has been successfully used for the preparation of the tetracyclic core skeleton of lundurine alkaloids …”

“…This process resultsi nt he formation of dihydroor tetrahydrocarbazole systemsi ns atisfactory yields (68-100 %), [143] andh as been successfully used for the preparation of the tetracyclic core skeleton of lundurine alkaloids. [144] The regioselectivity observed in the ring closure of these substrates is highly catalyst-dependent since the utilization of PtCl 2 or Brønsted acids affords terahydrocarbolined erivatives resultingf rom a6 -exo-dig process (Scheme 70). [145] Ac ouple of the obtained products have been converted into naturaloccurring alkaloids of the arborescidinefamily.…”