To a stirred solution of N,N-diisopropylamine (1.74 ml) in tetrahydrofuran (8 ml) at −78° C. was added dropwise a solution of n-butyllithium (7.71 ml, 1.6 M in hexane) and the reaction mixture was then warmed to 0° C. for 15 min. After re-cooling to −78° C., a solution of diethyl 1-phenylethyl phosphonate (2.76 ml) in tetrahydrofuran (8 ml) was added dropwise. The mixture was stirred at −78° C. for 30 min and then a solution of (S)-2,2-dimethyl-4-(2-oxo-ethyl)oxazolidine-3-carboxylic acid tert-butyl ester (2.00 g, CAS 147959-19-1) in tetrahydrofuran (8 ml) was added dropwise over 20 min. The mixture was then allowed to warm to room temparature and stirring continued at room temperature for 48 hours. The mixture was then quenched by addition of aqueous hydrochloric acid (2N) and then made basic by addion of aqueous sodium hydroxide solution (1N). The mixture was taken up in ethyl acetate and the phases separated. The organic layer was washed sequentially with water and with saturated brine, dried over Na2SO4 and concentrated in vacuo. The residue was purified by column chromatography (SiO2, heptane/EtOAc gradient) to yield a yellow oil, (1.16 g, 44%); MS (ISP): 332.1 ([M+H]+).
