To a 25 mL rb flask equipped with a magnetic stir bar was added 0.309 g(0.86 mmol) of the product of Step A, 0.422 g (1.29 mmol) of cesium carbonate, 3 mL DMF and finally 145 μL of 1-bromopinacolone was added. The reaction mixture was stirred at room temperature for 1.5 h then partitioned between EtOAc and water. The organic layer was separated, washed with 10% aq. NaHSO4, water, brine, dried (MgSO4), filtered and evaporated. The residue was purified on s silica gel flash chromatography column eluted with 0–10% EtOAc-hexane. Evaporation of the purified fractions and drying in vacuo afforded the title compound.
