1-Amino-3-azabicyclo[3.1.1]heptane-2,4-dione hydrochloride (2HCl). Compound 8 (50.0 g, 0.187 mol) was dissolved in MeOH (1 L) and Pd/C (10% w/w, 9.50 g) was added in one portion. The reaction vessel was evacuated and backfilled with H2 from a balloon (repeated 3 times), and the suspension was kept under H2 atmosphere with intensive stirring at 45 °C for 24 h. After the reaction was completed (concluded by 1 H NMR spectra of the small aliquots of the reaction mixture) the catalyst was filtered off and the filter cake was washed with hot MeOH (5×200 mL). The filtrate was concentrated under reduced pressure to afford pure 2HCl. Yield 30.1 g, 0.170 mol, 91%.