C([O:3][C:4](=[O:24])[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]=[CH:22][N:21]=[CH:20][N:19]=3)[CH:14]=[C:15]([CH3:16])[C:7]1=2)C.[Li+].[OH-].Cl>C1COCC1.O.O>[OH:11][B:9]1[C:8]2[CH:12]=[C:13]([O:17][C:18]3[CH:23]=[CH:22][N:21]=[CH:20][N:19]=3)[CH:14]=[C:15]([CH3:16])[C:7]=2[CH:6]([CH2:5][C:4]([OH:24])=[O:3])[O:10]1To a solution of [1-hydroxy-4-methyl-6-(pyrimidin-4-yloxy)-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl]-acetic acid ethyl ester (0.4 g, 1.21 mmol) in THF:H2O (1:1, 10 mL) at 0° C. was added LiOH (0.087 g, 3.65 mmol) in water (1 mL). The solution was allowed to warm to room temperature over 6 hours then acidified to pH 2 with 1N HCl at 0° C. and extracted with EtOAc (2×10 mL). The organic extracts were dried and concentrated in vacuo. The residue was purified by preparative HPLC to give [1-hydroxy-4-methyl-6-(pyrimidin-4-yloxy)-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl]-acetic acid (0.3 g, 82%). 1H NMR (400 MHz, DMSO): δ 9.25 (s, 1H), 8.73 (s, 1H), 8.65 (d, J=5.6 Hz, 1H), 7.26 (d, J=2.0 Hz, 1H), 7.12 (d, J=7.2 Hz, 2H), 5.51 (dd, J=2.4, 9.6 Hz, 1H), 3.07 (dd, J=2.0, 15.2 Hz, 1H), 2.29 (s, 3H), 2.17-2.11 (m, 1H). MS (ESI) m/z=301 [M+H]+.
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