Preparation of compound A24: To a solution of A23 (10.0 g, 44.8 mmol) in methanol (300 mL) was added potassium carbonate (12.4 g, 89.8 mmol). The reaction mixture was stirred for 12 h at room temperature and then quenched by pouring into ice water. The pH was adjusted to 8-9 with 2N hydrochloric acid and subsequently extracted with ethyl acetate (2 x 100mL). The organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give compound A24 (8.00 g, 99% yield) as a yellow solid.1H NMR (400 MHz, DMSO-d6) δ: 10.0 (s, 1H), 8.18 (d, J=2.4 Hz, 1H), 7.54 (d, J=2.8 Hz, 1H), 4.32- 4.26 (q, J=3.2Hz, 2H), 2.57 (s, 3H), 1.33-1.29 (t, J=3.2Hz, 3H).
