Metabolically Stable tert-Butyl Replacement

Susceptibility to metabolism is a common issue with the tert-butyl group on compounds of medicinal interest. We demonstrate an approach of removing all the fully sp3 C–Hs from a tert-butyl group: replacing some C–Hs with C–Fs and increasing the s-character of the remaining C–Hs. This approach gave a trifluoromethylcyclopropyl group, which increased metabolic stability. Trifluoromethylcyclopropyl-containing analogues had consistently higher metabolic stability in vitro and in vivo compared to their tert-butyl-containing counterparts.