Valenzisomerisierungen, 17. Persubstituiertecis-9,10-Dihydronaphthaline und ihre Valenzisomerisierungen

Total Synthesis of (-)-Mitrephorone A

The first synthesis of (-)-mitrephorone A is disclosed along with discussion and study of synthetic strategies. The natural product includes a highly congested hexacyclic ent-trachylobane diterpenoid framework featuring a rare, embedded oxetane. The synthetic analysis presented dissects a number of approaches for the synthesis of the central oxetane, including carbonyl-olefin photocycloadditions, Prins-type cyclizations, and oxidative ring closures. In the successful route, three [4 + 2] cycloadditions enable rapid construction of all carbocycles. A novel late-stage oxidative cyclization of a hydroxy diosphenol with Koser's reagent furnishes the pivotal oxetane moiety.

Intramolecular Diels-Alder reactions of 5-vinyl-1,3-cyclohexadienes

[reaction: see text] The intramolecular Diels-Alder reaction of 5-vinyl-1,3-cyclohexadienes affording substituted tricyclo[3.2.1.0(2,7)]oct-3-enes is studied.