Synthesis Development of the Selective Estrogen Receptor Degrader (SERD) LSZ102 from a Suzuki Coupling to a C–H Activation Strategy

The development of the synthetic process to the selective estrogen receptor degrader (SERD) drug candidate LSZ102 from the medicinal chemistry synthesis to the streamlined large-scale manufacturing route is described. The synthesis of LSZ102 could be significantly improved in regard to overall yield, removal of all chromatographic purifications, and reduction in the number of steps by revisiting the original disconnection strategy. Key features of the final process include construction of the benzothiophene core via Higa cyclization, late-stage phenolation using a Pd-catalyzed hydroxylation of an aryl bromide, and end-game assembly through a Pd-catalyzed C–H activation step. The overall yield could be significantly improved, and the costs could be reduced.