A mixture of 4-[3-Methyl-1-(8-methyl-quinoline-3-ylamino)-butyl]-benzoic acid ethyl ester (62 mg, 0.16 mM) and 1N aqueous NaOH solution (0.413 mL, 0.413 mM) in THF-MeOH (1:1, 3.3 mL) was heated to 50° C. for 4 h. The reaction was cooled, concentrated to remove organic solvent. The aqueous solution was diluted with DCM (5 mL), acidified by 1N HCl solution to pH=3-4. The organic solution was separated and the aqueous solution was extracted with 10% i-PrOH-DCM (5×5 mL). The combined organic solution were dried (Na2SO4) and concentrated to give a yellow solid product (45.7 mg, 79%). 1H NMR (400 MHz, CD3OD) δ ppm 0.98 (d, J=6.44 Hz, 3 H) 1.03 (d, J=6.25 Hz, 3 H) 1.56-1.68 (m, 1 H) 1.73-1.93 (m, 2 H) 2.68 (d, 3 H) 4.60-4.68 (m, 1 H) 7.23-7.35 (m, 2 H) 7.38 (d, 1 H) 7.44 (d, 1 H) 7.48-7.61 (m, 2 H) 7.96 (d, 2 H) 8.53 (dd, 1 H), two protons (COOH and NH) were exchanged. This material will be used for the next step reaction without further work-up.
