[Synthesis]
3-Benzyl-6-tert-butyl-3,6-diazabicyclo[3.2.0]heptane-3,6-dicarboxylate (2.61 mmol) was used as a raw material and dissolved in methanol (0.1 M) in a Parr vial. Palladium/carbon catalyst (Johnson Mathey, 5% wt, 61.1% H2O, 60 mg) was added. The mixture was placed on a Parr shaker and the air was removed by vacuum. The system was purged repeatedly with nitrogen followed by shaking at 15 PSI for about 1.5 hr. The progress of the reaction was monitored by TLC to confirm complete consumption of raw materials. Upon completion of the reaction, the mixture was filtered through a diatomaceous earth pad. The filtrate was concentrated to afford a viscous clear residue, tert-butyl 3,6-diazabicyclo[3.2.0]heptane-6-carboxylate, in 66.1% yield. The product was sufficiently pure to be used in subsequent reactions without further purification. Mass spectrometry (ESI) calculated value: C10H18N2O2, 198.26; measured value: m/z 199.2 [M + H]+. 1H NMR (400 MHz, CDCl3) δ 4.73-4.50 (m, 1H), 3.98 (t, J = 8.3 Hz, 1H), 3.46-3.15 (m, 2H), 3.09-2.99 (m , 1H), 2.93-2.82 (m, 1H), 2.73-2.62 (m, 1H), 2.53-2.42 (m, 1H), 2.31 (s, 1H), 1.43 (s, 9H). |