Hydrochloric Acid → 2-(6-(Ethoxycarbonyloxy)-1-hydroxy-4-methyl-1,3-dihydrobenzo[c][1,2]oxaborol-3-yl) acetic acid

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Reaction Steps

To the suspension of crude 2-(1,6-dihydroxy-4-methyl-1,3-dihydrobenzo[c][1,2]oxaborol-3-yl)acetic acid (250 mg, 1.126 mmol) in 2 ml H2O was added NaOH (90 mg, 2.25 mmol) in 6 ml H2O, followed by ethyl chloroformate (134.4 mg, 1.24 mmol) dropwise. The reaction mixture was stirred at room temperature for 20 min and acidified by 1N HCl to pH=5.0. The mixture was extracted with EtOAc (3×20 mL) and the combined organic layers were dried over anhydrous Na2SO4 and concentrated to dryness. The residue was purified by prep HPLC to give the title compound as an off-white powder (120.5 mg, yield: 34%, two steps). 1H NMR (400 MHz, DMSO) δ 12.37-12.36 (t, J=3.6 Hz, 1H), 9.29 (s, 1H), 7.30 (d, J=2.0 Hz, 1H), 7.14 (d, J=2.0 Hz, 1H), 5.53-5.50 (m, 1H), 4.28-4.22 (m, 2H), 3.10-3.05 (m, 1H), 2.31 (s, 3H), 2.11-2.17 (m, 1H), 1.32-1.27 (m, 3H); MS (ESI) m/z=285 [M+H]+.

Provenance & Evidence