To a slurry of Intermediate No. 9 (642 mg, 1.68 mmol), 3-azetidinole hydrochloride (370 mg, 2 equiv.) and triethylamine (1.4 mL, 6 equiv.) in 100 mL of dichloromethane, was added NaBH(OAc)3 (1.07 g, 3 equiv.) at room temperature. The reaction was stirred for 12 hour at room temperature and then quenched with 1N—NaOH. It was extracted with ethyl acetate and washed twice with brine. The collected organic layer was dried over anhydrous sodium sulfate and then concentrated in vacuo. The resulting residue was purified by silica gel chromatography (DCM/MeOH) to afford desired Compound No. 141 as a pale yellow solid (540 mg, 73%); MS (ESI) m/z 438 [M+H]+; 1H NMR (300 MHz, DMSO-d3) δ 9.72 (s, 1H), 8.59 (s, 1H), 8.52 (d, 1H, J=5.4 Hz), 7.95 (s, 1H), 7.45 (s, 2H), 7.14 (s, 1H, J=5.4 Hz), 4.41 (m, 1H), 4.05 (m, 4H), 3.70 (s, 3H), 3.35 (m, 2H), 2.42 (s, 3H), 2.34 (s, 3H).
