1: (-)-10-CSA / chloroform; methanol 2: 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; 1-hydroxy-7-aza-benzotriazole; N-ethyl-N,N-diisopropylamine / dichloromethane / 20 °C 3: piperidine / N,N-dimethyl-formamide / 0.33 h / 20 °C 4: 1-hydroxy-7-aza-benzotriazole; N-ethyl-N,N-diisopropylamine; 1,2-dichloro-ethane / dichloromethane / 20 °C 5: trifluoroacetic acid; 2-[(2-Hydroxy-1,1-bis[hydroxymethyl]ethyl)amino]ethanesulfonic acid / dichloromethane / 2 h 6: 1-hydroxy-7-aza-benzotriazole; N-ethyl-N,N-diisopropylamine; HATU / dichloromethane / 48 h / 20 °C View Scheme

Multi-step reaction with 4 steps 1: (-)-10-CSA / chloroform; methanol2: 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; 1-hydroxy-7-aza-benzotriazole; N-ethyl-N,N-diisopropylamine / dichloromethane / 20 °C3: piperidine / N,N-dimethyl-formamide / 0.33 h / 20 °C4: 1-hydroxy-7-aza-benzotriazole; N-ethyl-N,N-diisopropylamine; 1,2-dichloro-ethane / dichloromethane / 20 °C  

With  (-)-10-CSA in  methanol; chloroform