1: ethyl (S)-3-butanoylamino-3-(4-cyanophenyl)propanoate With hydrogenchloride 3 h; Heating; 2: di-tert-butyl dicarbonate With potassium carbonate in 1,4-dioxane; water T=20°C; 5 h;

1.1: 1.33 g / SOCl2 2.1: Candida antarctica lipase A / diethyl ether / 1 h / 20 °C 3.1: hydrochloric acid / 3 h / Heating 3.2: K2CO3 / dioxane; H2O / 5 h / 20 °C View Scheme