[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]=1.[H-].[Na+].[CH3:21][N:22]([CH3:26])[C:23](Cl)=[O:24]>CN(C=O)C>[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][C:23](=[O:24])[N:22]([CH3:26])[CH3:21])[CH:3]=1To a solution of ethyl 2-(4-chloro-1,6-dihydroxy-1,3-dihydrobenzo[c][1,2]oxaborol-3-yl)acetate (60 mg, 0.22 mmol) in DMF (3 mL) was slowly added NaH (27 mg, 0.66 mmol) at 0° C. The mixture was stirred for 20 min and N,N-dimethylcarbamic chloride (29 mg, 0.27 mmol) was added at 0° C. The reaction mixture was stirred overnight at room temperature and quenched with ice water. The resulting mixture was extracted with EtOAc (2×15 mL) and the combined extracts were dried over anhydrous Na2SO4 and concentrated in vacuo. The residue was used directly in the next step reaction without further purification. MS (ESI) m/z=342 [M+H]+.
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