Lewis Acid Mediated Nazarov Cyclization as a Convergent and Enantioselective Entry to C-nor-D-homo-Steroids.

A straightforward synthesis of C-nor-D-homo steroids starting from (+)-Wieland-Miescher ketone is reported. This convergent synthetic strategy utilizes a scalable diastereoselective Nazarov cyclization of functionalized chiral aryl vinyl ketones, allowing for further functionalization. The ability to conduct this key transformation on a multi-gram scale paves the way for the synthesis of a variety of completely new C-nor-D-homo steroids, without the need of a classic steran steroid rearrangement or achiral linear reaction sequences.