Synthetic Study of Caulerpin: Construction of the Core Structure through Gold-Catalyzed Cascade Cyclization of Azido-Alkynes.

Abstract

In this synthetic study, a gold-catalyzed cascade cyclization reaction for the construction of the caulerpin scaffold, suitable for the preparation of unsymmetrical caulerpin derivatives, was developed. The reaction proceeds through the formation of an α-imino gold(I) carbene from an azido-alkyne, followed by nucleophilic attack of an alkenylindole moiety on the gold carbene, leading to the formation of the bis-indole-fused 8-membered ring, the caulerpin core structure. The use of ethyl enol ether and a bulky phosphine ligand is suitable for successful ring closure at the desired position.