Short total syntheses of both the putative and actual structures of the clerodane diterpenoid (±)-sacacarin by double annulation

matrix presented The putative structure of the naturally occurring clerodane diterpenoid (±)-sacacarin has been prepared in only 10 steps, six of which are C-C bond-forming steps, in a chemo-, regio-, and diastereoselective manner. The key part of the synthesis is the double annulation (double Michael, Pinner, and Dieckmann reaction) of a tethered carbon diacid and 3-butyn-2-one. A corrected structure for sacacarin is proposed, and the structure is proven by synthesis.