trifluoroacetic acid 2 h; Ambient temperature;

1: 93 percent / HCl / H2O / 4 h 2: 68 percent / diethyl phosphorocyanidate, Et3N / dimethylformamide / 1 h 3: 95 percent / HBr-AcOH 25percent / acetic acid / 0.17 h 4: 74 percent / NaHCO3, 7N HCl / ethyl acetate; H2O View Scheme

1: 93 percent / HCl / H2O / 4 h 2: 67 percent / diethyl phosphorocyanidate, Et3N / dimethylformamide / 1 h 3: HCl / ethyl acetate 4: 53 percent / ethyl acetate; ethanol View Scheme

1: 93 percent / HCl / H2O / 4 h 2: 67 percent / diethyl phosphorocyanidate, Et3N / dimethylformamide / 1 h 3: HCl / ethyl acetate View Scheme

hydrogenchloride in water 4 h;