Synthesis of a Selective Estrogen Receptor Degrader via a Stereospecific Elimination Approach.

An efficient synthesis of a selective estrogen receptor degrader, GDC-0810, bearing a challenging stereodefined (E)-tetrasubstituted all-carbon olefin core, is reported. The described synthetic route involves a highly diastereoselective addition of an arylmagnesium reagent 3a to ketone 4, yielding the key tertiary alcohol 2a in >99:1 dr. The corresponding tert-butyl carbonate derivative was identified among other leaving groups to provide the desired olefin geometry in a 98:2 E/Z ratio via a concerted elimination. A four-step telescoped process was then developed starting from the tertiary alcohol 2a to produce GDC-0810 API as a pyrrolidine salt in 70% yield.