1: diethoxyphosphoryl-acetic acid ethyl ester With sodium hydride in N,N-dimethyl-formamide T=0 - 20°C; 0.5 h; 2: 3-Oxo-pyrrolidine-1-carboxylic acid tert-butyl ester in N,N-dimethyl-formamide T=0 - 20°C; 1 h; 3: With palladium 10 on activated carbon; hydrogen in ethanol; water T=20°C; 2 h;