1: POCl3 / acetonitrile / 0.33 h / 0 °C 2: acetonitrile / 5.5 h / 0 °C 3: 1.45 g / acetic acid; methanol / 5 h / Ambient temperature 4: 95 percent / ethanol / 1.5 h / Ambient temperature View Scheme

1.1: triethylamine; trichlorophosphate / acetonitrile / 0 °C 1.2: 16 h / 20 °C 2.1: acetonitrile / Cooling with ice 3.1: hydrogenchloride; water / tetrahydrofuran / 20 h / 20 °C / pH 3 View Scheme