sodium acetate; acetic anhydride T=90°C; 2 h;

triethylamine in dichloromethane; acetone; acetonitrile

dicyclohexyl-carbodiimide in tetrahydrofuran; N,N-dimethyl-formamide 1.) -15 deg C, 2 h; 2.) r. t., 3 h;

1: 1-hydroxy-pyrrolidine-2,5-dione With trifluoroacetic anhydride in N,N-dimethyl-formamide T=0°C; Inert atmosphere; 2: With 2,4,6-trimethyl-pyridine in N,N-dimethyl-formamide T=0°C; Inert atmosphere; 3: 6-(3-carboxyacryloylamino)caproic acid in N,N-dimethyl-formamide T=0 - 20°C; Inert atmosphere;