To a 50 mL round-bottomed flask was added 5-chloro-4-(1-methyl-1H-pyrazol-5-yl)-2-thiophenecarboxylic acid (147 mg, 0.61 mmol), 2-[(2S)-2-amino-3-(2,5-difluorophenyl)propyl]-1H-isoindole-1,3(2H)-dione (216 mg, 0.61 mmol) [prepared according to the procedure of Preparation 18 except substituting 2,5-difluoro-L-phenylalanine (3.02 g, 15.0 mmol) for 2,6-difluoro-L-phenylalanine] and PyBrop (341.4 mg, 0.73 mmol) in chloroform (6 mL). DIEA (530 μL, 3.03 mmol) was added and the reaction stirred overnight at room temperature. The mixture was adsorbed onto silica and purified via column chromatography (25-70% EtOAc/Hex) affording the title compound (233 mg, 0.43 mmol, 71%): LC-MS (ES) m/z=541 (M+H)+.
