To a solution of 2-methyl-propane-2-sulfinic acid {1-[5-(1-methyl-6-oxo-8-phenyl-1,6-dihydro-9-oxa-1,2-diaza-cyclopenta[a]naphthalen-7-yl)-pyridin-2-yl]-cyclobutyl}-amide (34 mg, 0.0645 mmol) in MeOH (6 mL) was added a solution of HCl in dioxane (4 M, 0.32 mL, 1.28 mmol). The reaction mixture was stirred at RT for 30 min before evaporating to dryness. The resulting residue was dissolved in a mixture of MeOH (1 mL), water (4 mL) and then chromatographed on a 5 g C18 cartridge {gradient 20 to 60% MeOH in water+1 M HCl (60 μL in each 10 mL of eluent)} to give the title compound (24.3 mg, 82%) as an off-white solid. 1H NMR (400 MHz, DMSO-d6): δ 8.78 (br s, 3H), 8.41 (dd, J=2.2 and 0.8 Hz, 1H), 8.29 (s, 1H), 7.89-7.81 (m, 3H), 7.75 (d, J=8.3 Hz, 1H), 7.59-7.57 (m, 2H), 7.51-7.41 (m, 3H), 4.41 (s, 3H), 2.60-2.55 (m, 4H), 2.26-2.15 (m, 1H), 2.05-1.94 (m, 1H). LCMS (Method E): =3.22 min, [M+H]+=423.
