The pyridone (Step 3, 57 mg, 0.19 mmol) and lithium hydroxide (16 mg, 0.38 mmol) were stirred at room temperature in a solution of 2 mL of MeOH and 0.3 mL of H2O, for 2 h. The reaction mixture was diluted with water and the pH was adjusted to pH ˜2 with concentrated H2SO4. The mixture was extracted 3×20% IPA:CHCl3 and the combined organic fractions were dried over MgSO4 and concentrated. The crude residue was purified to obtain the title compound as a white powder (48 mg, 89%). MS m/z: 285 (M+1).
