A −78° C. solution of Example 113F (75 mgs, 0.148 mmol) in tetrahydrofuran (2.1 mL) was treated with n-butyllithium (2.45 M in hexanes, 0.121 mL, 0.295 mmol) dropwise over 3 minutes, and the reaction was stirred for 2 minutes. Cyclobutanone (0.022 mL, 0.295 mmol) was added, and the reaction was stirred for 1 hour at −78° C. The reaction was quenched by the addition of saturated aqueous ammonium chloride. The mixture was extracted with ethyl acetate. The organic layer was washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The concentrate was purified by flash chromatography on a silica gel column, eluting with a gradient of 0% to 4% methanol in dichloromethane, to provide the title compound. MS ESI(+) m/z 499.2 [M+H]+.
