The product of Step A (1.8 g) in dry acetonitrile (40 mL) was treated sequentially with tetrakis(triphenylphosphine)palladium(0) (0.1 g), triethylamine (1.27 g), and CuI (10 mg) then heated at 60° C. for 30 minutes. The mixture was cooled to ambient temperature, treated with 3-butyn-1-ol (0.361 g) and heated at reflux temperature for 18 hours. The mixture was cooled to ambient temperature and evaporated to dryness. The residue was crystallized, twice, from acetone to afford the title compound (1.02 g).
