Reaction Steps
A solution of (R)—N-(sec-butyl)-2-(4-(2,4-difluorophenoxyl)piperidin-1-yl)-5,6,7,8-tetrahydropyrido[3,4-b]pyrazin-3-amine TFA salt (136.4 mg) in DCM (2.57 mL) at 0° C. was treated with pyridine (0.062 mL, 0.770 mmol), followed by acetic anhydride (0.048 mL, 0.513 mmol). The reaction mixture was stirred for 1 h. The reaction mixture was concentrated under reduced pressure. The residue was taken up in MeOH, filtered through a Millipore® 0.45 μm syringe filter, and purified by HPLC Method A to give title compound, as a TFA salt, as a yellow solid (52.0 mg, 32.2% over two steps). 1H NMR (500 MHz, methanol-d4) δ ppm 0.98 (m, 3H), 1.26 (m, 3H), 1.67 (m, 2H), 1.96 (m, 2H), 2.13 (m, 2H), 2.19 (s, 1.1H), 2.21 (s, 1.9H), 2.73 (td, J=5.9, 1.5 Hz, 0.7H), 2.84 (td, J=5.9, 1.5 Hz, 1.3H), 3.08 (m, 2H), 3.43 (m, 2H), 3.82 (t, J=5.9 Hz, 1.3H), 3.86 (m, 0.7H), 3.97 (m, 1H), 4.49 (m, 1H), 4.59 (m, 0.7H), 4.63 (s, 1.3H), 6.87 (m, 1H), 6.98 (ddd, J=11.3, 8.4, 3.2 Hz, 1H), 7.17 (td, J=9.3, 5.4 Hz, 1H); ESI-MS m/z [M+H]+ 460.0.
