To a solution of {6-[2-(3-tert-butoxycarbonylamino-propoxy)-pyrimidin-4-yloxy]-1-hydroxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl}-acetic acid ethyl ester (0.45 g, 0.89 mmol) in THF:H2O (1:1, 6 mL) at 0° C. was added a solution of LiOH (0.043 g, 1.79 mmol) in water (1 mL). The solution was allowed to warm to room temperature over 3 hours then acidified to pH 4 with 1N HCl and extracted with EtOAc (2×10 mL). The organic extracts were dried and concentrated in vacuo to give crude {6-[2-(3-tert-Butoxycarbonylamino-propoxy)-pyrimidin-4-yloxy]-1-hydroxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl}-acetic acid (0.3 g) which was used without further purification. MS (ESI) m/z=472 [M−H]−.
