Benzyl 4-[1-(ethoxycarbonyl)but-3-en-1-yl]piperidine-1-carboxylate (4.08 g, 11.8 mmol) was dissolved in tetrahydrofuran (45 mL), and osmium tetroxide (0.45 mL, 2.5% solution in t-butanol) was added followed by a solution of sodium periodate (7.57 g, 35.4 mmol) in water (37 mL). After 24 h, the reaction was diluted with saturated aqueous sodium sulfite and saturated aqueous sodium bicarbonate and extracted with ethyl acetate (4×). The combined organic extracts were dried over sodium sulfate, filtered and concentrated. Purification by silica gel chromatography (50% hexanes/ethyl acetate→100% ethyl acetate) to give the title compound (2.39 g). MS 348.1 (M+1).
