6-(3-((5-fluoro-2-oxoindolin-3-ylidene)methyl)benzamido)hexanoic acid methyl ester (410 mg, 1 mmol) and 300 ml of CH3OH were stirred at room temperature while 25 ml of 4 N solution of LiOH in H2O was added. The mixture was stirred for 24 hours at room temperature. The mixture is neutralized with concentrated hydrochloric acid to pH 7 and evaporated under vacuum to remove methanol. The residue was adjusted to pH 3 with concentrated hydrochloric acid. The solids were collected by vacuum filtration, washed with water and dried under vacuum to give the title compound (289 mg, 73% yield) as a brown solid. LC-MS (m/z) 397 (M+1).
