(The following reaction is done in an anhydrous N2 atmosphere.) Suspend EDC.HCl (376 mg, 1.96 mmol) and Et3N (275 μL, 1.96 mmol) in anhydrous DCM (2.0 mL) and stir the resulting solution for 5 min at rt. Add 3-(3,4,5-Trimethoxy-phenyl)-propionic acid (346 mg, 1.44 mmol) and DMAP (17 mg, 0.14 mmol) and stir the resulting solution for 15 min. Add 1-(Ethoxycarbonylmethyl)piperazine (43) (224 mg, 1.30 mmol) and stir the reaction solution overnight at rt. Quench reaction solution with water, separate layers and extract aqu. layer with EtOAc (3 times). Filtrate the combined organic layer through a short pad of silica gel and remove solvent. Purify the crude product by preparative radial chromatography (silica gel, EtOAc/MeOH 9+1) to obtain {4-[3-(3,4,5-Trimethoxy-phenyl)-propionyl]-piperazin-1-yl}-acetic acid ethyl ester (45) (426 mg, 83%) as a colorless oil. 1H NMR (400 MHz, CDCl3): 1.26 (t, 3H, J=7.1 Hz); 2.45-2.70 (br.m, 6H); 2.89 (t, 2H, J=7.7 Hz); 3.26 (br.s, 2H); 3.43-3.56 (br.m, 2H); 3.61-3.76 (br.m, 2H); 3.80 (s, 3H); 3.83 (s, 6H); 4.18 (q, 2H, J=7.1 Hz); 6.41 (s, 2H).
