A solution of benzyl 3-(2-(tert-butoxycarbonyl)phenyl)-4-oxo-1-phenyl-1,3,8-triazaspiro[4.5]decane-8-carboxylate (1.86 g, 3.44 mmol, 1 equiv) in a mixture of ethyl acetate and ethanol was charged with 10% palladium on carbon (360 mg, 20%/wt) and the resulting mixture was hydrogenated at atmospheric pressure for 16 h. The reaction was filtered over Celite and the filtrate was concentrated and dried in vacuo to afford the title compound as a white foam (1.44 g, 96.4%); 1H NMR (400 MHz, DMSO-d6): δ 1.49 (s, 9H); 1.71 (d, 2H, J=13.2 Hz); 2.41-2.49 (m, 2H); 2.84-2.88 (m, 2H); 3.08-3.13 (m, 2H); 5.07 (s, 2H); 6.78 (t, 1H, J=7.2 and 7.6 Hz); 6.98 (s, 1H); 7.00 (s, 1H); 7.23-7.27 (m, 2H); 7.46-7.49 (m, 1H); 7.60 (dd, 1H, J=1.2 and 1.6 Hz); 7.65-7.69 (m, 1H); 7.77 (dd, 1H, J=1.2 and 1.6 Hz); MS for C24H29N3O3 m/z 408.22 (M+H)+.
