18.9 g of N-(Ethyl-N′-(3-dimethylaminopropyl)carbodiimide hydrochloride are added to a cooled solution of 20.04 g of (S)-Pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester, 14.9 g of 4-methoxyphenethylamine, 16.9 ml of diisopropylethylamine and 13.2 g of 1-hydroxy-benzotriazole in 250 ml of CH2Cl2. The reaction mixture obtained is stirred at rt for 16 hours, the reaction is quenched with aq. 2N HCl solution and the aq. phase obtained is extracted with CH2Cl2. The combined organic phases obtained are washed with aq. 2N HCl solution, brine and aq. saturated NaHCO3 solution, dried and solvent is evaporated. The residue obtained is purified by recrystallisation with EtOAc/hexane (1/3) to afford the title compound.
