To an ethyl acetate (20 ml) solution of (4S,5R)-tert-butyl 5-(4-ethynylphenyl)-4-(fluoromethyl)-2,2-dimethyloxazolidine-3-carboxylate (1.35 g, 4.0 mmol) is added a dimethylformamide solution of (E)-ethyl 2-chloro-2-(hydroxyimino)-acetate (12.5 ml, 1.5 g, 2.5 equiv). Sodium hydrogen carbonate (3.5 g) is added to the solution and it is allowed to stir overnight at room temperature. The mixture is filtered and diluted with ethyl acetate (100 ml). After washing with water (4×25 ml) the organic phase is concentrated to give the crude product, which is purified on silica gel using a gradient of ethyl acetate in hexanes (0% to 20% ethyl acetate) to give the title compound (567 mg): 1H NMR (400 MHz, CDCl3) 1.43-1.56 (m, 14H) 1.62 (s, 3H) 1.74 (br. s., 3H) 4.50 (q, J=7.24 Hz, 3H) 5.20 (d, J=7.33 Hz, 1H) 6.96 (s, 1H) 7.60 (d, J=8.34 Hz, 2H) 7.86 (d, J=8.59 Hz, 2H), m/z (CI) 449 ([M+H]+.
