To a solution of 1.0M potassium tert-butoxide in tetrahydrofuran (46.0 mL, 46.0 mmol) at 0° C. was added diethyl cyanomethylphosphonate (7.8 mL, 48 mmol). The bath was removed and the reaction mixture was allowed to warm to room temperature over 1 hour. The reaction was re-cooled to 0° C., and a solution of 3-{[tert-butyl(diphenyl)silyl]oxy}cyclobutanone (15.7 g, 48.4 mmol, from Step 3) in tetrahydrofuran (80 mL) was added. During the course of the addition, additional tetrahydrofuran (50 mL) was added into the receiving flask to facilitate stirring. Upon complete addition of the ketone, the bath was removed and the reaction allowed to reach room temperature and stirred overnight. The reaction mixture was partitioned between water and ethyl acetate and the aqueous was extracted with ethyl acetate a total of three times. The combined extracts were washed with brine, dried over sodium sulfate, decanted and concentrated. Flash chromatography, eluting with a gradient of 0-10% ethyl acetate in hexanes afforded product (16.1 g, 96%). 1H NMR (300 MHz, CDCl3): δ 7.74-7.58 (m, 4H), 7.49-7.34 (m, 6H), 5.13 (dddd, 1H), 4.34 (tt, 1H), 3.16-2.90 (m, 4H), 1.05 (s, 9H).
