To a solution of 3,3-diphenylpiperidine (Example 24A, 0.24 g, 1.00 mmol) in dichloromethane (20 mL) was added 2-(2-oxo-3,3-diphenylpiperidin-1-yl)acetic acid (Example 68E, 0.308 g, 1.00 mmol), under nitrogen. To the reaction was added N1-((ethylimino)methylene)-N3,N3-dimethylpropane-1,3-diamine hydrochloride (0.38 g, 2.00 mmol) and N,N-dimethylpyridin-4-amine (0.012 g, 0.10 mmol), and the reaction mixture was stirred overnight at room temperature. The reaction was concentrated, and the residue was partitioned in ethyl acetate:water (8:2). The organic layer was separated, washed with water and then brine, dried over MgSO4, filtered and concentrated. Silica gel chromatography eluting with 3% methanol/dichloromethane gave the title compound. 1H NMR (300 MHz, CDCl3) δ ppm 7.12-7.33 (m, 20H), 4.23 (s, 2H), 4.13 (s, 2H), 3.35-3.46 (m, 4H), 2.57-2.64 (m, 2H), 2.45-2.51 (m, 2H), 1.72-1.85 (m, 2H), 1.46-1.56 (m, 2H); MS (DCI+) m/z 529 (M+H)+.
