To a solution of ethyl 4-[[4-(6-methylpyridin-3-yl)-2,2-dimethyl-(2H)-thiochromen-6-yl]-ethynyl]-benzoate (Compound 233, 70.0 mg, 0.159 mmol) in 3.0 mL THF and 3.0 mL EtOH was added NaOH (120.0 mg, 3.0 mmol, 3.0 mL of a 1M aqueous solution). The resulting solution was stirred overnight at 35° C. Upon cooling to room temperature, the reaction mixture was acidified with 10% aqueous HCl and extracted with EtOAc. The combined organic layers were washed with H2O, saturated aqueous NaCl, and dried (Na2SO4) before removing the solvent under reduced pressure. The residual solid was recrystallized from acetone to give 60.0 mg (92%) of the title compound as a colorless solid. 1H NMR (300 MHz, d6 -acetone) δ: 8.36 (1H, d, J=2.1 Hz), 7.91 (2H, d, J=8.3 Hz), 7.60 (2H, d, J=8.3 Hz), 7.56 (1H, dd, J=2.1 8.0 Hz), 7.45 (2H, m), 7.31 (1H, d, J=8.0 Hz), 7.06 (1H, s), 6.06 (1H, s), 2.51 (3H, s), 1.44 (6H, s).
