A Short Enantioselective Total Synthesis of the Third-Generation Oral Contraceptive Desogestrel

Desogestrel ( 1 ) has been synthesized enantioselectively by a 14-step process from the known and readily available precursor 3, as outlined in Chart 2. At the heart of this process is the short, convergent, and stereocontrolled method for forming the tetracyclic ring system and the critical 11-exomethylene function, that is, the sequence of steps 6 → 8 → → 12 . All steps of the synthesis proceed in good yield.