BrOnsted acid promoted intramolecular cyclization of O-alkynyl benzoic acids: Concise total synthesis of exserolide F

Herein we report the stereoselective total synthesis of Exserolide F. The key step involves triflic acid catalyzed highly regioselective intramolecular cyclization of an O-alkynyl benzoic acid derivative to accomplish the core isocoumarin skeleton of the natural product via 6-endo-dig mode of cyclization. The other important steps are: Sharpless asymmetric epoxidation, Barbier propargylation, Sonogashira coupling en route to access the O-alkynyl benzoic acid derivative. [GRAPHICS] .