1: With 4-(N,N-dimethlyamino)pyridine; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride in dichloromethane T=20°C; 4 h; 2: With sodium tetrahydroborate; acetic acid in tetrahydrofuran T=20°C; 2 h; 3: With water; sodium hydrogencarbonate in tetrahydrofuran