Step 1): A mixture of 5-dimethylamino-2-nitrobenzoic acid [J. Med. Chem., 24, 742 (1981)](9.0 g, 40 mmol), 4-aminomethyl-1-diphenylmethylpiperidine (12.0 g, 40 mmol), 1-(3-dimethylamino-propyl)-3-ethylcarbodiimido hydrochloride (WSC) (8.0 g, 40 mmol) and 4-dimethylaminopyridine (DMAP) (5 g, 40 mmol) in dichloromethane (400 ml) was stirred at 0° C. for 1 hour, then at room temperature for 3 days. The reaction mixture was washed with 1N HCl, then water. The organic layer was dried (MgSO4) and concentrated. The residue was purified by column chromatography on silica gel (5% methanol in dichloromethane) to give 5-dimethylamino-2-nitro-N-[(1-diphenylmethyl-piperidin-4-yl)methyl]benzamide (47%) as yellow solid: mp 200° C.
