Diastereoselective formal total synthesis of (+/-)-triptolide via a novel cationic cyclization of 2-alkenyl-1,3-dithiolane

A concise and diastereoselective formal total synthesis of triptolide, a natural product with a wide range of biological properties, is described. The key reaction is an unprecedented 6-endo-Trig cationic cyclization of a 2-alkenyl-1,3-dithiolane precursor induced by TMSOTf as Lewis acid.