Reaction Steps
Compound 10 (81.5 mg, 0.29 mmol) was treated with 4-nitrophenyl chloroformate carbonochloridate (213 mg, 1.06 mmol) and DMAP (108 mg, 0.88 mmol) in anhydrous CH2Cl2 (4 mL) at room temperature for 16 h. The mixture was washed successively with saturated NaHCO3(aq.) and 1 M HCl(aq) until the solution became transparent. The organic phase was dried over MgSO4, filtered, concentrated, and purified by flash chromatography on a silica gel column with elution of CH2Cl2/MeOH (100:0.5 to 9:1) to give the title compound (70 mg, 56% yield). C20H18N4O6S; pale yellow solid; mp 114-118° C.; IR vmax (neat) 2923, 2854, 1725, 1655, 1520, 1346, 1259, 1163, 1111, 1056, 1024, 862, 748 cm−1; 1H NMR (400 MHz, CDCl3) δ 8.22 (2H, d, J=10.2 Hz), 8.02 (1H, d, J=8.0 Hz), 7.62 (2H, t, J=8.0 Hz), 7.55 (1H, d, J=8.0 Hz), 7.40 (1H, t, J=8.0 Hz), 7.27 (1H, d, J=10.2 Hz), 4.73 (2H, s), 3.70 (6H, br s), 3.62 (2H, br s); 13C NMR (100 MHz, CDCl3) δ 165.4, 165.1, 155.5, 151.7, 144.7, 141.0, 132.1, 126.5, 125.4, 124.9 (2×), 123.0, 122.0 (2×), 120.2, 44.7, 44.5, 44.2, 43.8, 43.6; ESI-HRMS calcd for C20H19N4O6S: 443.1025. found: m/z 443.1042 [M+H]+.
