[N:1]1([CH2:6][C:7]2[CH:12]=[CH:11][CH:10]=[C:9]([NH:13]C(OC(C)(C)C)=O)[CH:8]=2)[CH:5]=[CH:4][N:3]=[CH:2]1.OS(O)(=O)=O>CO.O1CCOCC1>[N:1]1([CH2:6][C:7]2[CH:12]=[CH:11][CH:10]=[C:9]([NH2:13])[CH:8]=2)[CH:5]=[CH:4][N:3]=[CH:2]1The title compound from Step B above (7.64 g, 27.95 mmoles) was dissolved in methanol (148 mL) and 10% conc. H2SO4 in dioxane (v/v) (380.8 mL) was added. The solution was stirred at 25° C. for 4 h. The solution was diluted with methanol and BioRad AG® 1-X8 (OH−) resin was added until the pH was basic. The resin was filtered off and washed with methanol. The combined filtrates were evaporated to dryness and the residue was chromatographed on silica gel using 2.5% (10% conc. NH4OH in methanol)-dichloromethane as the eluant to give the title compound (4.36 g, 90%): CIMS: m/z 174.25 (MH+); δH (CDCl3), 3.44 (2H, bs, NH2), 5.02 (2H, s, CH2-Im), 6.39 (1H, s, Im-H5), 6.55 (1H, d, Ar—H4), 6.62 (1H, dd, Ar—H5), 6.91 (1H, s, Im-H4), 7.07 (1H, s, Ar—H2), 7.13 (1H, m, Ar—H6) and 7.54 ppm (1H, s, Im-H2); δC (CDCl3) CH2: 50.8; CH: 113.4, 114.8, 117.2, 119.5, 129.8, 130.0, 137.7; C, 137.6, 147.1.
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