C[O:2][C:3]([C:5]1[C:6]2[C:7](=[O:21])[CH:8]=[C:9]([C:16]([O:18]CC)=[O:17])[NH:10][C:11]=2[C:12]([Cl:15])=[CH:13][CH:14]=1)=[O:4].[OH-].[K+]>C(O)C>[Cl:15][C:12]1[C:11]2[NH:10][C:9]([C:16]([OH:18])=[O:17])=[CH:8][C:7](=[O:21])[C:6]=2[C:5]([C:3]([OH:4])=[O:2])=[CH:14][CH:13]=1To a solution of 24 (10.0 g, 32.3 mmol) in ethanol (100 mL) was added 10% aqueous KOH solution (100 mL) at room temperature. The reaction mixture was heated at 100° C. for 24 h and then cooled to room temperature. The reaction mixture was concentrated in vacuum. The resulting aqueous solution was acidified with 2N HCl to pH=6.5, where a solid precipitated and was collected through a filtration. The solid was washed with H2O (100 mL) and Et2O (100 mL), and dried in vacuum at 60° C. to give an off-white solid (25, 8.00 g, 92.9%). 1H NMR (DMSO-d6, 300 MHz) δ ?7.97 (d, J=7.8 Hz, 1H), 7.39 (d, J=7.8 Hz, 1H), 6.90 (s, 1H).
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