4-Hydroxy-piperidine-1-carboxylic acid tert-butyl ester (3.03 mmol, 610 mg) and sodium hydride (10.6 mmol, 255 mg) were dissolved in dry THF (20 mL) and stirred for 30 minutes at room temperature. Then, (6-chloro-5-nitro-pyrimidin-4-yl)-(4-methanesulfonyl-phenyl)-amine (3.03 mmol, 1.0 g) was added. The reaction was stirred at room temperature for 30 minutes. Its progress was monitored by thin layer chromatography and LCMS. Sodium hydride was quenched with water and the desired compound was extracted in ethyl acetate. Organic solvents were evaporated in vacuo. Flash chromatography (Silica gel 60; 30/70 EtOAc/Hexanes) provided Compound A1 as a yellow solid (1.2 g, 68%). 1H NMR (400 MHz, CDCl3) δ (ppm): 10.10 (s, 1H), 8.33 (s, 1H), 7.90 (d, 2H), 7.79 (d, 2H), 5.51 (heptet, 1H), 3.58 (m, 2H), 3.46 (m, 2H), 2.97 (s, 3H), 1.84 (m, 4H), 1.36 (s, 9H). LCMS (ESI), m/z 494.4 (M+H+, 100%).
