Short total syntheses of both the putative and actual structures of the clerodane diterpenoid (+/-)-sacacarin by double annulation.
[reaction: see text] 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.
[n + 1] Annulation Route to Highly Substituted Cyclic Ketones with Pendant Ketone, Nitrile, and Ester Functionality
Two carbon acids connected by a tether containing a ketone undergo two Michael reactions to 3-butyn-2-one to afford highly substituted and functionalized cyclic ketones with pendant ketone, nitrile, and ester functionality. The stereochemical courses of the double Michael reactions vary remarkably with the structure of the starting material. Double Michael adducts with equatorially disposed cyano groups can be hydrogenated to afford trans-fused bicyclic amines.
Teulamifin B, a neo-clerodane diterpenoid from Teucrium lamiifolium and T. Polium
Abstract From the aerial parts of Teucrium lamiifolium and T. polium , a neo-clerodane diterpenoid, teulamifin B has been isolated, besides the previously known diterpenoids 19-deacetylteuscorodol and teucroxide. The structure of teulamifin B[15,16-epoxy-6β,12 S ,18-trihydroxy-neo-cleroda-3,13(16),14-trien20,19-olide] was established by chemical and spectroscopic means and by correlation with 19-deacetylteuscorodol.