To a solution (30 mL) of benzyl [(1S)-1-methyl-2-oxoethyl]carbamate (3.0 g) in tetrahydrofuran was added 1.0 mol/L solution (28.8 mL) of allylmagnesium bromide in tetrahydrofuran under ice-cooling, and the mixture was stirred at room temperature for 18 hr. Water was added to the reaction mixture and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (developing solvent: hexane:ethyl acetate=9:1→1:1) to give benzyl [(1S)-2-hydroxy-1-methylpent-4-en-1-yl]carbamate as a colorless oil. To a solution (10 mL) of the obtained benzyl [(1S)-2-hydroxy-1-methylpent-4-en-1-yl]carbamate in tetrahydrofuran were added 2,6-lutidine (0.629 mL) and tert-butyldimethylsilane trifluoromethanesulfonate (0.91 mL) and the mixture was stirred at room temperature for 30 min. Water was added to the reaction mixture and the mixture was extracted with ethyl acetate. The extract was washed with 1 mol/L hydrochloric acid, saturated aqueous sodium hydrogencarbonate solution and saturated brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (developing solvent: hexane:ethyl acetate=9:1→2:1) to give the title compound as a colorless oil (yield: 610 mg).
