1-Naphthylmethylmagnesium chloride was prepared from magnesium turnings (2.88 g) and 1-(chloromethyl)naphthalene (6.98 g) in ether (80 ml) by the method of J. Am. Chem. Soc. (1943) 65, 295. A solution of lithium chloride (167 mg) and copper (II) chloride (266 mg) in THF (10 ml) was added dropwise to the ethereal solution of the Grignard reagent followed by addition of a solution of (2RS,3S)-3-(benzyloxy)-1,2-epoxybutane (3.52 g) in ether (30 ml) below −70° C. The mixture was stirred at −78° C. for 1 h, and then allowed to warm to room temperature and stirred overnight. After cooling, the mixture was quenched with saturated aqueous ammonium chloride solution (100 ml). The insoluble material was filtered through Celite and the filter cake was washed with ether. The filtrate and washings were combined, and the organic layer was washed with water and brine, dried over anhydrous magnesium sulfate and concentrated in vacuo to give an oil. Flash chromatography (hexane:ethyl acetate=9:1→4:1) gave (2S,3S)-2-benzyloxy-5-(1-naphthyl)pentan-3-ol (2.66 g, 42.0%) as the first eluate and (2S,3R)-2-benzyloxy-5-(1-naphthyl)pentan-3-ol (1.36 g, 21.5%) as the second eluate.
