To a solution of 2-tert-butoxy-2-(4-(4-fluorophenyl)-2-isopropyl-8,8-dimethyl-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid (example 1) (10.1 mg, 0.024 mmol) in CH2Cl2 (5 mL) was added Et3N (9.85 μl, 0.071 mmol) followed by 2-(4-fluorophenyl)acetyl chloride (6.10 mg, 0.035 mmol) and the resulting mixture stirred at room temperature. (Mixture became a clear, colorless solution within 30 min.) After 3 h, the solvent was removed and the residue was taken up in MeOH/DMF and purified by preparative HPLC (10% AcCN/90% H2O/0.1% NH4OAc, Sunfire 19×100 mm, C18, 5 μm). The product containing fractions were concentrated to remove the organic solvent and the resulting precipitate isolated by filtration and washed with water to give 2-tert-butoxy-2-(4-(4-fluorophenyl)-6-(2-(4-fluorophenyl)acetyl)-2-isopropyl-8,8-dimethyl-5,6,7,8-tetrahydro-1,6-naphthyridin-3-yl)acetic acid (1.6 mg, 11.78% yield) as a white solid. 1H NMR (400 MHz, CD3OD) δ ppm 7.13-7.53 (5H, m), 6.88-7.09 (3H, m), 4.80-4.88 (1H, m), 4.32-4.46 (0.5H, m), 4.18-4.32 (1H, m), 3.97 (0.5H, d, J=16.56 Hz), 3.79-3.92 (1.5H, m), 3.55-3.68 (3H, m), 3.52 (0.5H, d, J=13.05 Hz), 1.37 (3H, d, J=6.53 Hz), 1.32 (3H, d, J=7.53 Hz), 1.27 (3H, dd, J=6.27, 5.02 Hz), 1.15 (3H, dd, J=6.53, 4.77 Hz), 0.91-1.06 (9H, m). 19F NMR (400 MHz, CD3OD) δ ppm −114.90, −115.19, −117.98, −118.41. LCMS (M+H) calcd for C33H39F2N2O4: 565.28. found: 565.4.
