N,N-Dicyclohexylcarbodiimide (0.476 mL of a 1.0 M solution in dichloromethane, 0.476 mmol) was added to a solution of (7-methanesulfonylamino-1,1-dioxo-1,4-dihydro-1λ6-benzo[1,4]thiazin-3-yl)-acetic acid (Example 8h, 0.190 g, 0.572 mmol) and 1-(3,3-dimethyl-butylamino)-1H-pyrrole-2-carboxylic acid allyl ester (Example 4c, 0.119 g, 0.475 mmol) in a 3:1 mixture of dichloromethane and N,N-dimethylformamide (6 mL) at 25° C. The reaction mixture was stirred at 25° C. for 1 h then was filtered. The filtrate was concentrated in vacuo and the residue was dissolved in ethanol (12 mL) at 25° C. A 21% solution of sodium ethoxide in ethanol (0.23 mL, 0.71 mmol) was added and the reaction mixture was heated at 80° C. for 5 h. After cooling to 25° C., the mixture was partitioned between 1.0 M aqueous hydrochloric acid solution (150 mL) and ethyl acetate (2×150 mL). The organic layers were dried over sodium sulfate, filtered and concentrated in vacuo. Purification of the residue by flash column chromatography (Merck silica gel 60, 40-63 μm, 40→100% ethyl acetate in hexanes) afforded a solid which was triturated with diethyl ether to afford the desired product, N-{3-[1-(3,3-dimethyl-butyl)-4-hydroxy-2-oxo-1,2-dihydro-pyrrolo[1,2-b]pyridazin-3-yl]-1,1-dioxo-1,4-dihydro-1λ6-benzo[1,4]thiazin-7-yl}-methanesulfonamide (0.101 g, 0.20 mmol, 42% yield) as a yellow solid. 1H NMR (400 MHz, CDCl3) δ: 1.07 (9H, s), 1.65-1.72 (2H, m), 3.09 (3H, s), 4.25-4.29 (2H, m), 5.54 (2H, s), 6.43-6.45 (1H, m), 7.01-7.03 (1H, m), 7.08-7.09 (1H, m), 7.30 (1H, d, J=8.5 Hz), 7.39 (1H, bs), 7.61 (1H, dd, J1=2.3 Hz, J2=8.6 Hz), 7.73 (1H, d, J=2.4 Hz). LC-MS (ESI) calcd for C22H26N4O6S2 506.13. found 507.27 [M+H+].
