Synthesis of a 6,11-Dioxa Congener of Torgov's Diene: A Platform Intermediate for Oxasteroid Discovery.

We report the de novo synthesis of 6,11-dioxa Torgov's diene, which was accessed via the positional alkene isomerization of an advanced dienone-bearing tetracycle. Other key steps of the synthesis include a Schenck-ene photooxygenation, a cationic annulation reaction, a singlet oxygen-mediated cascade, and a Pd2+-catalyzed Friedel-Crafts cyclization. In addition to 6,11-dioxa Torgov's diene, we accessed a collection of its saturated analogues by applying a set of stereodivergent hydrogenation conditions.