To a suspension of 60% sodium hydride (192 mg, 4.8 mmol) in N,N-dimethylformamide (2.5 mL) was added methanesulfonamide (466 mg, 4.9 mmol) at room temperature. The resulting mixture was stirred at 25° C. for 1 h. A solution of 3,3-dimethyl-2-[3-(4-methyl-2,3-dioxo-piperazin-1-yl)-phenyl]-1,2,3,4-tetrahydro-quinoline-6-carboxylic acid (200 mg, 0.5 mmol) and 1,1′-carbonyldiimidazole (200 mg, 1.2 mmol) in N,N-dimethylformamide (2.0 mL) was stirred at 70° C. After stirring at 70° C. for 1 h, the above suspension of methanesulfonamide and sodium hydride in N,N-dimethylformamide was added and the mixture was allowed to stir at 25° C. for 1 h. Purification by Waters automated flash system (column: Xterra 30 mm×100 mm, sample manager 2767, pump 2525, detector: ZQ mass and UV 2487, solvent system: acetonitrile and 0.1% ammonium hydroxide in water) afforded N-{3,3-dimethyl-2-[3-(4-methyl-2,3-dioxo-piperazin-1-yl)-phenyl]-1,2,3,4-tetrahydro-quinoline-6-carbonyl}-methanesulfonamide (51 mg, 20%) as a white solid: LC/MS m/e calcd for C24H28N4O5S (M+H)+: 485.58, observed: 485.2.
