To a solution of 0.565 g (0.858 mmol) of 91a in 8 mL of CH2Cl2, was added dropwise 8.58 mL of 1M BCl3 /CH2Cl2 at -78° C. The reaction mixture was stirred at -78° C. for 2 hr and then at -40° C. for 2 hr. MeOH (2.5 mL) was added dropwise and stirring was continued at -40° C. for 10 min. The reaction mixture was diluted with EtOAc (75 mL). The EtOAc solution was washed with H2O (50 mL), sat. NaHCO3 solution (50 mL), sat. NaCl solution (50 mL), dried (Na2SO4), and evaporated. The residue was suspended in a small amount of CHCl3 and then filtered. The solid product was washed with portions of CHCl3 and recrystallized from MeOH to give 0.271 g (81%) of 92 as white crystals. MP: 172°-175° C. (dec). 1H NMR (DMSO-d6): d 8.62 (s, 1, 7-H), 5.89 (d, 1, 1'-H, J1'-2' =8.0 Hz), 5.52 (d, 1, 2'-OH, J2'-2'OH =6.5 Hz), 5.46 (t, 1, 5'-OH, J5'-5'OH =4.5 Hz), 5.31 (d, 1, 3'-OH, J3'-3'OH =4.5 Hz), 4.39 (m, 1, 2'-H, J2'-3' =5.5 Hz), 4.14 (m, 1, 3'-H, J3'-4' =2.0 Hz), 4.04 (m, 1, 4'-H, J4'-5' =J4'-5" =2.5 Hz), 3.72 (m, 2, 5'-H and 5"-H, J5'-5" =12.0 Hz). 13C NMR (DMSO-d6): d 142.44 (C2), 138.56 (C3a), 131.95 (C7a), 126.91 (C4), 124.52, 122.39 (C5 and C6), 113.55 (C7), 89.58 (C1'), 86.44 (C4'), 71.95 (C2'), 69.53 (C3'), 60.82 (C5'). Anal. Calcd. for C12H10Cl4N2O4 : C, 37.14; H, 2.60; N, 7.22. Found: C, 37.01; H, 2.60; N, 7.01.
