1.1: lithium hydroxide hydrate / tetrahydrofuran; water / 0 - 20 °C 1.2: pH 1 - 2 2.1: benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; N-ethyl-N,N-diisopropylamine / tetrahydrofuran; dichloromethane / 0.17 h 3.1: triethylamine; trifluoroacetic anhydride / dichloromethane / 0 °C View Scheme

1.1: lithium hydroxide hydrate / tetrahydrofuran; water / 0 - 20 °C 1.2: pH 1 - 2 2.1: benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; N-ethyl-N,N-diisopropylamine / tetrahydrofuran; dichloromethane / 0.17 h 3.1: triethylamine; trifluoroacetic anhydride / dichloromethane / 0 °C 4.1: sodium hydrogencarbonate / methanol / 2 h / 70 °C / pH 6 / aq. phosphate buffer 5.1: benzotriazol-1-yloxyl-tris-(pyrrolidino)-phosphonium hexafluorophosphate; N-ethyl-N,N-diisopropylamine / dichloromethane / 0.17 h / 0 °C 5.2: 0 - 20 °C 6.1: trifluoroacetic acid / dichloromethane / 0 - 20 °C 7.1: benzotriazol-1-ol; N-ethyl-N,N-diisopropylamine; HATU / dichloromethane; acetonitrile 8.1: triethylsilane; trifluoroacetic anhydride / 2 h / 0 - 20 °C 9.1: triethylamine / dichloromethane / 3 h / 0 - 20 °C View Scheme

1: With lithium hydroxide hydrate in tetrahydrofuran; water T=0 - 20°C; 2: With potassium hydrogensulfate in tetrahydrofuran; water pH=1 - 2;