A solution containing 1-(4-pyridyl)-4-carboxymethylpiperazine dihydrochloride 1/4H2O(400 mg, 1.33 mMoles), triethylamine (0.4 ml, 2.66 mMoles) and HOBT (0.2 g, 1.46 mMoles) in dry dimethylformamide (20 ml) was treated with diisopropylcarbodiimide (0.23 ml, 1.46 mMoles) and the mixture was stirred for 5 minutes. Ethyl 4-carboxymethylpiperidine was added and the mixture was stirred for a further 4 hours. The mixture was concentrated to half volume under reduced pressure and then poured into water (50 ml) and extracted with ethyl acetate (3×20 ml) and dichloromethane (3×20 ml). The combined organic extracts were concentrated under reduced pressure and the residue was purified by chromatography (flash column made with grade III alumina and eluted with a gradient of 0-1% methanol in dichloromethane) to give the title compound (130 mg) as a colourless oil; NMR (d6DMSO): 0.9-1.1 (m,2H), 1.2 (t,3H), 1.65 (d,2H), 1.8-2.0 (m,1H), 2.2 (d,2H), 2.5 (m,2H), 2.9-3.4 (m,10H), 4.0 (q,2H+m,1H), 4.3 (d,1H), 6.8 (d,2H), 8.15 (d,2H); m/e 375 (M+H)+.
