[OH:1][C:2]1[C:7]2[O:8][CH:9]([CH3:13])[C:10](=[O:12])[NH:11][C:6]=2[CH:5]=[C:4]([CH:14]=[O:15])[CH:3]=1.C(=O)([O-])[O-].[Cs+].[Cs+].I[CH2:23][CH3:24]>CN(C=O)C>[CH2:23]([O:1][C:2]1[C:7]2[O:8][CH:9]([CH3:13])[C:10](=[O:12])[NH:11][C:6]=2[CH:5]=[C:4]([CH:14]=[O:15])[CH:3]=1)[CH3:24]To a 20 mL screw cap vial was added 8-hydroxy-2-methyl-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carbaldehyde 398A (0.619 g, 2.99 mmol) and cesium carbonate (0.973 g, 2.99 mmol). The mixture was suspended in DMF (5.98 mL) and then cooled in an ice bath. Iodoethane (0.241 mL, 2.99 mmol) was added in 2 portions over 5 minutes. The reaction mixture was stirred for 2 hr, slowly warmed to 23° C., and the stirred for 18 hr. The crude material was purified by prep HPLC-MS (30-50% MeCN in water, basic mode) and the fractions were collected and concentrated in vacuo. The resulting solid was isolated by filtration, washed with water and dried in vacuo to give a tan solid (0.404 g, 57% yield): 1H NMR (400 MHz, DMSO-d6) δ ppm 1.36 (t, J=6.95 Hz, 3H) 1.46 (d, J=6.82 Hz, 3H) 4.14 (qd, J=6.99, 1.77 Hz, 2H) 4.72-4.88 (m, 1H) 7.07 (d, J=1.77 Hz, 1H) 7.24 (d, J=1.77 Hz, 1H) 9.82 (s, 1H) 10.92 (s, 1H). ESI-MS: m/z 236.1 (M+H)+.
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