C([O:3][C:4](=[O:19])[CH2:5][CH:6]1[O:10][B:9]([OH:11])[C:8]2[CH:12]=[C:13]([O:17][CH3:18])[CH:14]=[C:15]([CH3:16])[C:7]1=2)C.[Li+].[OH-].Cl>C1COCC1.O>[OH:11][B:9]1[C:8]2[CH:12]=[C:13]([O:17][CH3:18])[CH:14]=[C:15]([CH3:16])[C:7]=2[CH:6]([CH2:5][C:4]([OH:19])=[O:3])[O:10]1
To a solution of (1-hydroxy-6-methoxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl)-acetic acid ethyl ester (0.85 g, 3.22 mmol) in THF (7 mL) was added a solution of LiOH (0.385 g, 16.1 mmol) in water (7 mL) at 0° C. The resulting mixture was stirred at room temperature for 1.5 hours then acidified to pH 2 using dilute hydrochloric acid. The mixture was concentrated to remove THF and the white precipitate collected and washed with water to give pure product as a white powder (0.571 g, 75.1%); mp 157-158° C. 1HNMR (400 MHz, DMSO-d δ 9.10 (s, 1H), 7.02 (d, J=2.34 Hz, 1H), 6.83 (d, J=1.76 Hz, 1H), 5.42 (dd, J=9.67, 2.64 Hz, 1H), 3.73 (s, 3H), 3.01 (dd, J=15.38, 2.49 Hz, 1H), 2.24 (s, 3H), 2.03 (dd, 1H). MS (ESI) m/z=235 [M−H]−.
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