1: 1H-indole-3-carboxylic acid With sodium hydride in DMF (N,N-dimethyl-formamide) T=0°C; 0.5 h; 2: 2,2-Dimethyl-propionic acid chloromethyl ester in DMF (N,N-dimethyl-formamide) T=0 - 20°C; 2 h;