To a stirred mixture solution 3,3-dimethyl-2-[3-(4-o-tolyl-piperazin-1-yl)-phenyl]-1,2,3,4-tetrahydro-quinoline-6-carboxylic acid ethyl ester (1.0 g, 2.1 mmol) in methanol (5.0 mL) and tetrahydrofuran (6.0 mL) was added 50% sodium hydroxide in water (2.0 mL). The reaction mixture was stirred at 70° C. for 6 hours. The mixture was neutralized with a 3 N aqueous hydrochloric acid solution and extracted with ethyl acetate (2×100 mL), washed with water, dried over anhydrous sodium sulfate and then concentrated in vacuo. 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 3,3-dimethyl-2-[3-(4-o-tolyl-piperazin-1-yl)-phenyl]-1,2,3,4-tetrahydro-quinoline-6-carboxylic acid (850 mg, 90%) as a white solid: LC/MS m/e calcd for C29H33N3O2 (M+H)+: 456.61, observed: 456.2.
