Gold(I)-Catalyzed Cyclization for the Synthesis of 8-Hydroxy-3- substituted Isocoumarins: Total Synthesis of Exserolide F.

A highly regioselective gold(I)-catalyzed 6-endo-dig cyclization of 2,2-dimethyl-5-(alkynyl)-4H-benzo[d][1,3]dioxin-4-ones for the synthesis of 8-hydroxy-3-substituted isocoumarins is described. Key features of the reaction include the broad substrate scope, scalability, and tolerance for protecting groups. The synthetic utility of this novel method is demonstrated by the first total synthesis of exserolide F, an isocoumarin-containing polyol natural product.