To a stirred solution of (E)-methyl 4-(3-(7-(3,4-dimethoxyphenylamino)thiazolo[5,4-d]pyrimidin-5-yl)styryl)benzoate (90 mg, 0.17 mmol) in 3 mL of 1,4-dioxane and 3 mL of H2O was added NaOH (140 mg, 3.5 mmol) at room temperature. Then the reaction was stirred at room temperature overnight and then treated by conc. HCl until pH=3-4. The solvent was removed under reduce pressure the residue was purified by preparative HPLC to give (E)-4-(3-(7-(3,4-dimethoxyphenylamino)thiazolo[5,4-d]pyrimidin-5-yl)styryl)benzoic acid (33 mg, 38%) as a yellow solid. 1H NMR (300 MHz, DMSO): δ 12.95 (brs, 1H), 10.09 (s, 1H), 9.38 (s, 1H), 8.37-8.30 (m, 2H), 7.82-7.78 (m, 3H), 7.47-7.32 (m, 5H), 6.92-6.78 (m, 3H), 3.81 (s, 3H), 3.80 (s, 3H). LC-MS: 511 [M+H]+, 509 [M−H]−, tR=1.71 min. HPLC: 99.30% at 214 nm, 99.65 at 254 nm, tR=4.98 min.
