Building Efficient Diastereo- and Enantioselective Synthetic Routes to trans-Cyclopropyl Esters for Rapid Lead Scale-Up

Cyclopropanes play an important role in drug discovery, and synthetic access to variedly substituted systems is an ongoing challenge for chemistry teams. A variety of scalable synthetic routes were developed and optimized for the construction of 1,2-trans-disubstituted cyclopropyl esters. The use of a stable cyclopropyl trifluoroborate provided a path for the rapid exploration of heteroaryl substituent diversity. Two asymmetric approaches were subsequently enabled as viable alternatives. Our first approach led to the development of a novel sulfoximine-driven Johnson–Corey–Chaykovsky reaction of menthyl acrylates and is the first example of this chemistry for the enantio- and diastereostereoselective construction of trans-cyclopropanes. Ultimately, a scalable process route was fashioned through the optimization of an efficient ring opening/intramolecular C–O phosphate transfer and displacement cascade that builds the trans-cyclopropyl ester from a chiral epoxide with excellent stereocontrol.