Reaction Steps
[7-(Methanesulfonylamino-methyl)-1,1-dioxo-1,4-dihydro-1λ6-thieno[2,3-e][1,2,4]thiadiazin-3-yl]-acetic acid (prepared as described in Example 2c; 0.113 g, 0.320 mmol), O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (0.134 g, 0.352 mmol) and 4-methylmorpholine (0.070 mL, 0.637 mmol) were added sequentially to a solution of rac-2-[(4-fluoro-benzylamino)-methyl]-butyric acid ethyl ester (0.081 g, 0.320 mmol) in N,N-dimethylformamide (4 mL) at 25° C. The reaction mixture was stirred at 25° C. for 18 h, and then was concentrated in vacuo. The residue was partitioned between 1.0 M aqueous hydrochloric acid solution (100 mL) and ethyl acetate (2×100 mL). The organic layers were dried over sodium sulfate and were concentrated in vacuo. The residue was dissolved in ethanol (10 mL) at 25° C. A 21 wt. % solution of sodium ethoxide in ethanol (0.622 mL, 1.92 mmol) was added and the reaction mixture was heated to 70° C. for 18 h. After cooling to 25° C., the reaction mixture was partitioned between 1.0 M aqueous hydrochloric acid solution (100 mL) and ethyl acetate (2×100 mL). The organic layers were dried over sodium sulfate and were concentrated in vacuo. The residue was purified by flash chromatography (Teledyne Isco RediSep column; 50-100% ethyl acetate in hexanes) to afford (after trituration with diethylether) rac-N-{3-[5-ethyl-1-(4-fluoro-benzyl)-4-hydroxy-2-oxo-1,2,5,6-tetrahydro-pyridin-3-yl]-1,1-dioxo-1,4-dihydro-1λ6-thieno[2,3-e][1,2,4]thiadiazin-7-ylmethyl}-methanesulfonamide (0.061 g, 0.112 mmol, 35%) as a white solid. 1H NMR (400 MHz, DMSO-d6) δ: 0.78 (3H, t, J=7.0 Hz), 1.30-1.38 (1H, m), 1.60-1.66 (1H, m), 2.95 (3H, s), 3.22 (1H, dd, J=4.5 Hz, J2=12.1 Hz), 3.56 (1H, dd, J=4.2 Hz, J2=12.8 Hz), 4.24 (2H, d, J=6.3 Hz), 4.45 (1H, d, J=14.7 Hz), 4.75 (1H, d, J=14.9 Hz), 7.14-7.18 (2H, m), 7.25 (1H, s), 7.36-7.39 (2H, m), 7.64 (1H, t, J=5.0 Hz). LC-MS (ESI) calculated for C21H23FN4O6S3 542.08. found 543.0 [M+H+].
