[Cl:1][C:2]1[C:10]2[CH:9]([CH2:11][C:12]([O:14][CH2:15][CH3:16])=[O:13])[O:8][B:7]([OH:17])[C:6]=2[CH:5]=[C:4]([O:18]C2CCCCO2)[CH:3]=1.Cl>C1COCC1>[Cl:1][C:2]1[C:10]2[CH:9]([CH2:11][C:12]([O:14][CH2:15][CH3:16])=[O:13])[O:8][B:7]([OH:17])[C:6]=2[CH:5]=[C:4]([OH:18])[CH:3]=1To a solution of the crude ethyl 2-(4-chloro-1-hydroxy-6-(tetrahydro-2H-pyran-2-yl-oxy)-1,3-dihydrobenzo[c][1,2]oxaborol-3-yl)acetate in THF (3 mL) was added concentrated HCl (1.5 mL) at 0° C. and the mixture was stirred at 0° C. for 30 min. The reaction mixture was concentrated under reduced pressure and the residue was purified by column chromatography on silica gel (EtOAc/PE=1:1) to give the title compound as a yellow oil (580 mg. Yield: 60.2%). 1H NMR (400 MHz, DMSO-d6) δ9.94 (d, J=2.8 Hz, 1H), 9.39 (s, 1H), 7.07-7.08 (d, J=2.0 Hz, 1H), 6.92-6.92 (d, J=2.0 Hz, 1H), 5.40-5.48 (m, 1H), 3.19-3.23 (m, 1H), 2.34-2.40 (m, 1H), 1.31-1.50 (m, 5H); MS (ESI) m/z=271 [M+H]+.
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