1: 6-hydrazinopyridine-3-carboxylic acid; acetone With triethylamine in N,N-dimethyl-formamide T=20°C; 4 h; Inert atmosphere; 2: 1-hydroxy-pyrrolidine-2,5-dione With 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride in N,N-dimethyl-formamide Inert atmosphere;