[Cl:1][C:2]1[C:10]2[CH:9]([CH2:11][C:12]([O:14]CC)=[O:13])[O:8][B:7]([OH:17])[C:6]=2[CH:5]=[C:4]([OH:18])[CH:3]=1.[OH-].[Li+].Cl>C1COCC1.O>[Cl:1][C:2]1[C:10]2[CH:9]([CH2:11][C:12]([OH:14])=[O:13])[O:8][B:7]([OH:17])[C:6]=2[CH:5]=[C:4]([OH:18])[CH:3]=1To a solution of ethyl 2-(4-chloro-1,6-dihydroxy-1,3-dihydrobenzo[c][1,2]oxaborol-3-yl)acetate (150 mg, 0.55 mmol) in THF (2 mL) was added an aqueous solution of lithium hydroxide (116 mg, 2.77 mmol) in water (1 mL) at 0° C. The resulting mixture was stirred at ambient temperature for 3 h and acidified with diluted hydrochloric acid at 0° C. to pH=1˜2. The mixture was extracted with EtOAc (2×20 mL) and the combined organic layers were dried over anhydrous Na2SO4 and concentrated in vacuo. The residue was purified by prep HPLC to give the title compound as a white powder (78 mg. Yield: 69%). 1H NMR (400 MHz, DMSO-d6) δ 9.95 (s, 1H), 9.40 (s, 1H), 8.15 (s, 1H), 7.06 (d, J=1.6 Hz, 1H), 6.91 (d, J=1.6 Hz, 1H), 5.38-5.41 (m, 1H), 3.14-3.19 (m, 1H), 2.15-2.22 (m, 1H). MS (ESI) m/z=243 [M+H]+.
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