To a 0° C. suspension of cuprous iodide (12.7 g, 67.0 mmol) in 150 mL ether was added CH3Li (1.4M in ether, 96 mL, 134 mmol). The solution was cooled to -78° C. and treated with TMSCl (8.5 mL, 67 mmol) and a solution of the unsaturated ester from Step 3 (6.79 g, 15.8 mmol) in 30 mL of THF. The yellow suspension was allowed to warm to room temperature and was stirred 2.5 h. The reaction mixture was poured into saturated NH4Cl and extracted with EtOAc. The organic extracts were washed with water and brine and dried over Na2SO4. Purification by flash chromatography (20% ethyl acetate/hexanes) provided 5.13 g of the title product as a crystaline solid.
