[Synthesis]
Di-tert-butyl dicarbonate (5.81 g, 26.6 mmol) and 3-benzyl-3-azabicyclo[3.2.1]octan-8-one (5.0 g, 22.0 mmol) were used as raw materials in ethyl acetate (74 mL) with Pearlman's catalyst (1.55 g, 23.2 mmol). The reaction system was stirred overnight at 25 °C under 100 psi hydrogen pressure after passing through three nitrogen substitutions and two hydrogen substitutions. After completion of the reaction, the mixture was filtered through a diatomaceous earth pad and washed with ethyl acetate. The filtrate was concentrated and purified by silica gel column chromatography (elution gradient: heptane/ethyl acetate, 0:100 to 100:0) to afford 3-Boc-3-azabicyclo[3.2.1]octan-8-one (4.49 g, 90% yield) as a solid. The product was analyzed by LC/MS showing [M-Me] = 211.1; 1H NMR (400 MHz, CDCl3) δ 4.38 (d, J = 14.0 Hz, 1H), 4.20 (d, J = 14.0 Hz, 1H), 3.27 (d, J = 13.3 Hz, 1H), 3.17 (d, J = 13.3 Hz, 1H), 2.24 ( d, J = 15.6 Hz, 2H), 1.76-1.99 (m, 4H), 1.49 (s, 9H). |