To a suspension of methyltriphenylphosphonium bromide (1.07 g) was portionwise added potassium t-butoxide (337 mg) with stirring under ice-cooling. The mixture was stirred at ambient temperature for 2 hours. To the solution cooled on ice-bath was added dropwise (2S,4R)-1-benzyl-2-formyl-4-(t-butyldimethylsilyloxy)pyrrolidine (0.92 g) in toluene (2 ml) and the mixture was stirred at the same temperature for 1 hour. The reaction mixture was poured into a mixture of water (10 ml) and ethyl acetate (20 ml). The organic layer was separated, washed with saturated aqueous sodium chloride, dried over anhydrous magnesium sulfate and evaporated in vacuo to give a residue. To the residue was added n-hexane (30 ml). The resulting precipitates were filtered off and the filtrate was evaporated in vacuo. The resulting residue was chromatographed on silica gel (1 g) eluting with a mixture of n-hexane and ethyl acetate (5:1 v/v). The fractions containing the desired compound were collected and evaporated in vacuo to give (2S,4R)-1-benzyl-2-vinyl-4-(t-butyldimethylsilyloxy)pyrrolidine (765 mg).
