n-BuLi (2.5 M solution in hexanes, 1.13 mL, 2.82 mmol) was added to a solution of 3,5-bis-trifluoromethylaniline (437 μL, 2.82 mmol) in THF (0.5 mL) at room temperature. The resulting dark brown colored solution was stirred for 10 min at room temperature. A solution of 3-cyclobutyl-1-(2,6-dimethylphenyl)-5-oxo-pyrrolidine-3-carboxylic acid methyl ester (prepared from step a, 283 mg, 0.94 mmol) in THF (3 mL) was added and stirred for 30 min at 100° C. in a sealed vial. Saturated aqueous NH4Cl solution (10 mL) was added, extracted with EtOAc (3×25 mL). The combined organic layer was washed with water (40 mL), brine (40 mL), dried (Na2SO4) and evaporated. The reaction mixture was then purified by automated flash chromatography (SiO2, 20→70% EtOAc/hexanes). Selected fractions were combined and concentrated under reduced pressure. The obtained product was further purified twice by preparative HPLC (5→90% gradient of MeCN—H2O with 0.1% TFA) to obtain the desired product 3-cyclobutyl-1-(2,6-dimethylphenyl)-5-oxo-pyrrolidine-3-carboxylic acid (3,5-bis-trifluoromethylphenyl)-amide (7 mg, 1.5% yield). LC-MS: Rt (retention time): 3.17 min, MS: (ES) m/z 499.1 (M+H+). 1H NMR (400 MHz, CDCl3) δ 8.08 (s, 3H), 7.63 (s, 1H), 7.12-7.16 (m, 1H), 7.04-7.09 (m, 2H), 4.18 (d, 1H, J=8.5 Hz), 3.58 (d, 1H, J=8.5 Hz), 3.18 (d, 1H, J=17 Hz), 2.8 (d, 1H, J=17 Hz), 2.2 (s, 3H), 2.17 (s, 3H), 1.85-2.0 (m, 2H), 0.68-0.8 (m, 1H), 0.5-0.62 (m, 2H), 0.15-0.2 (m, 2H).
