To a solution of Example 213d (0.927 g, 1.514 mmol) in CH2Cl2 (50 mL) was added 1M BBr3 in CH2Cl2 (10.6 mL, 10.6 mmol) at −78° C. The reaction was slowly warmed to room temperature and stirred overnight. The solvent was evaporated. To a suspension of the residue in THF (60.0 mL) was added triethylamine (1.48 mL, 10.6 mmol) and Boc2O (0.380 g, 1.74 mmol). The reaction was stirred for 8 hours, diluted with 50% brine, and extracted with EtOAc. The organic layers was dried over MgSO4, filtered, concentrated, and purified on a 40 g column using the ISCO Companion flash system eluting with CH2Cl2/EtOAc to give the title compound.
