1: 74.3 percent / N,N'-dicyclohexylcarbodiimide / ethyl acetate / 24 h / Ambient temperature 2: 88.3 percent / mesentericopeptidase / 6 h / 25 °C / pH = 8.0 3: phosphodiesterase I / 6 h / 37 °C / pH = 8.8 4: 86.3 percent / 2 N sodium hydroxide / 12 h / 5 °C View Scheme