1: N-methyl-N-nosyl-L-isoleucine phenacyl ester With benzenethiol sodium salt in N,N-dimethyl-formamide T=20°C; 3 h; Inert atmosphere; 2: With sodium carbonate in water pH=9; 3: (9H-Fluoren-9-yl)-methyl chloroformate in 1,4-dioxane T=0°C;