1: (2S,4R)-4-hydroxy-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester With benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride in tetrahydrofuran T=0°C; 0.25 h; 2: dimethyl amine in tetrahydrofuran; water T=20°C; 15.1667 h;

4-(N,N-dimethlyamino)pyridine; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; N-ethyl-N,N-diisopropylamine in dichloromethane T=20°C; 30 h;

1: (2S,4R)-4-hydroxy-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester With benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride in tetrahydrofuran T=0°C; 0.25 h; 2: dimethyl amine in tetrahydrofuran; water T=20°C; 15 h;

hydrogenchloride; sodium chloride; triethylamine in tetrahydrofuran; methanol; ethyl acetate