1: (S)-N-[(S)-1-(ethoxycarbonyl)butyl]alanine With 1H-imidazole; thionyl chloride in dichloromethane T=-10°C; 2 h; 2: C12H23NO2Si in dichloromethane T=-10 - 25°C; 21 h; 3: tert-butylamine in acetonitrile Heating / reflux;