To the material of Example 4b (1.0 g, 0.0026 mol) in DMF (15 mL) was added dropwise a mixture of acetic anhydride (0.283 mL, 0.003 mol) and pyridine (0.243 mL, 0.003 mol) in DMF (5 mL). Contents were stirred overnight, diluted with water (75 mL), and filtered to give the desired as a white solid, 1.0 g (90% yield). FABHRMS m/z 426.1235 (M+H, C20H20N5O4S requires 426.1236). 1H NMR (DMSO-d6/300 MHz) 9.80 (s, 1H); 8.00 (d, 2H); 7.75 (d, 2H); 7.60 (s, 1H); 7.48 (s, 2H); 7.39 (s, 1H); 7.30 (d, 1H); 7.15 (s, 1H); 2.90 (s, 4H); 1.92 (s, 3H). Anal. Calcd for C20H19N5O4S (1H2O): C, 54.17; H, 4.77; N, 15.79. Found: C, 54.20; H, 4.97; N, 15.77.
