C([O:3][C:4](=[O:27])[CH2:5][CH:6]1[O:10][B:9]([OH:11])[C:8]2[CH:12]=[C:13]([O:17][C:18]3[CH:23]=[N:22][C:21]([C:24](=[O:26])[NH2:25])=[CH:20][N:19]=3)[CH:14]=[C:15]([CH3:16])[C:7]1=2)C.[Li+].[OH-]>C1COCC1.O>[C:24]([C:21]1[N:22]=[CH:23][C:18]([O:17][C:13]2[CH:14]=[C:15]([CH3:16])[C:7]3[CH:6]([CH2:5][C:4]([OH:27])=[O:3])[O:10][B:9]([OH:11])[C:8]=3[CH:12]=2)=[N:19][CH:20]=1)(=[O:26])[NH2:25]A solution of [6-(5-carbamoyl-pyrazin-2-yloxy)-1-hydroxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl]-acetic acid ethyl ester (77 mg, 0.21 mmol) in THF (4 mL) was treated with LiOH (35 mg, 0.84 mmol) in water (4 mL) at room temperature for 1 h. The reaction was concentrated to dryness. The residue was diluted with water and adjusted to pH 3. The mixture was purified by preparative HPLC to give the title compound (38 mg). 1H NMR (300 MHz, CD3OD) δ 8.76 (s, 1H), 8.46 (s, 1H), 7.29 (s, 1H), 7.16 (s, 1H), 5.73-5.69 (m, 1H), 3.33-3.18 (m, 1H), 2.42 (s, 3H), 2.38-2.33 (m, 1H). MS found: (M+H)+: 344.1.
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