Scheme 1. Synthesis of the N-Boc Difluoromethylcyclopropyl Amino Acid 29.

Reagents and conditions: (a) KOtBu, THF, −78 °C to rt, 44%; (b) separation by a SFC column; (c) (Boc)₂O, DMAP, rt, 2 h,THF, 85%; (d) (CH₃)₃SO⁺I^–, NaH, DMSO, 80 °C, 2 h, 48%; (e) NaOH, MeOH, rt, 18 h, 87%.