To a solution of trimethylsulfonium iodide (2.128 g, 10.4 mmoles) in 20 mL of anhydrous THF at -10° C. was added dropwise a solution of n-butyllithium 1.6M in hexanes (4.9 mL, 0.75 equiv.). Then the temperature was raised to 21° C. for 2 hours. To this mixture cooled to 0° C., the alkene (step 2) (967 mg, 2.86 mmoles) in 5 mL THF was added and the solution stirred overnight. Hydrolysis with 25% aqueous NH4OAc, extraction with EtOAc and flash chromatography on silica using EtOAc:toluene 2.5:97.5 afforded the title compound.
