To a solution of the compound prepared in Example 28 (0.05 g, 0.15 mmol) in THF (10 mL), triphosgene (0.054 g, 0.182 mmol) and N,N-diisopropylethylamine (0.08 mL, 0.456 mmol) were added at 0° C. and the reaction mixture warmed to room temperature. After stirring for 1 h, the reaction mixture was concentrated to dryness and the crude residue was dissolved in THF. To this mixture, the compound prepared in Example 6 (0.065 g, 0.152 mmol) and N,N-diisopropylethylamine (0.08 mL, 0.456 mmol) were added at 0° C., and the reaction warmed to room temperature. After stirring for 4 h, the mixture was diluted with ice cold water and extracted with ethyl acetate (2×50 mL). The organic layer was washed with brine, dried and concentrated. Purification by flash chromatography (silica gel, 40 g, 20-60% ethyl acetate/hexanes) provided the title compound (0.045 g, 39%) as a white solid.
