Lithium diisopropylamide (8.3 mL, 16.6 mmol, 2.0M, heptane/THF/ethylbenzene) is added to a solution of (γS)-α-(2-methylpropyl)-γ-trityloxymethyl-γ-butyrolactone (5.67 g, 13.7 mmol), THF (50 mL), and HMPA (2.9 mL) at -78° C. After stirring for 30 minutes at -78° C., a solution of allyl bromide (1.46 mL, 16.9 mmol) and THF (8.0 mL) is added. The solution is allowed to stir for 4 hours at -78° C. and is then quenched with aqueous ammonium chloride (50 mL). After warming to room temperature, aqueous workup (EtOAc, MgSO4) and purification by flash chromatography (6:1 hexane:EtOAc) to give 5.12 g of the title compound (82%) as a white powder (mp 84°-85° C.).
