1: 67.3 percent / DCC / ethyl acetate / 24 h / Ambient temperature 2: 87.3 percent / Tween-8, alkaline mesintericopeptidase / H2O / 25 °C / Trisma-buffered solution; pH=7.8 3: 83.4 percent / 0.5 M HCl / 0.5 h / 50 °C View Scheme