(The following reaction is done in an anhydrous N2 atmosphere.) Suspend EDC.HCl (188 mg, 0.98 mmol) and Et3N (137 μL, 0.98 mmol) in anhydrous DCM (1.0 mL) and stir the resulting solution for 5 min at rt. Add 2-(3,4,5-Trimethoxy-phenyl)-acetic acid (163 mg, 0.72 mmol) and DMAP (8 mg, 0.07 mmol) and stir the resulting solution for 10 min. Add 1-(Ethoxycarbonylmethyl)piperazine (43) (112 mg, 0.65 mmol) and stir the reaction solution overnight at rt. Quench reaction solution with sat. aqu. NH4Cl and water, separate layers and extract aqu. layer with DCM (3 times). Wash the combined organic layer with water and brine and dry with Na2SO4. Purify the crude product by preparative radial chromatography (silica gel, EtOAc/MeOH 10+1) to obtain {4-[2-(3,4,5-Trimethoxy-phenyl)-acetyl]-piperazin-1-yl}-acetic acid ethyl ester (44) (99 mg, 40%) as a colorless oil. 1H NMR (400 MHz, CDCl3): 1.25 (t, 3H, J=7.1 Hz); 2.48 (br.m, 2H); 2.58 (br.m, 2H); 3.21 (br.s, 2H); 3.53 (br.m, 2H); 3.65 (s, 2H); 3.71 (br.m, 2H); 3.81 (s, 3H); 3.82 (s, 6H); 4.16 (q, 2H, J=7.1 Hz); 6.42 (s, 2H).
