To a solution of a compound 46 prepared in Example 30 (0.325 mmol, 150 mg) in methanol (5 mL) was added paraformaldehyde (0.813 mmol, 25 mg), Na(OAc)3BH and a catalytic amount of HOAc at room temperature. The resulting mixture was kept stirred at room temperature overnight. Then EtOAc (20 mL) was added to the mixture and the mixture was washed with saturated NaHCO3 and water. The organic layer was dried over Na2SO4 and concentrated to dryness. The crude product was purified through a column of silica gel with a gradient of 0% to 50% MeOH in DCM to afford the title compound 47. 1H NMR (CDCl3): δ 8.21 (d, J=8.1 Hz, 1H), 8.18 (br s, 1H), 8.04 (d, J=8.1 Hz, 1H), 7.87 (dd, J=7.84, 7.86 Hz, 1H), 4.63 (m, 1H), 4.15 (m, 1H), 3.95 (m, 1H), 3.52 (m, 1H), 3.23 (m, 1H), 2.90-2.55 (m, 3H), 2.70 (d, J=5.4 Hz, 3H), 2.07-1.54 (m, 8H), 1.00 (m, 6H), 0.92 (m, 2H), 0.80 (m, 2H). LC: 100%. MS: 490.2 (M+1).
