chloroformic acid ethyl ester; triethylamine in tetrahydrofuran; N,N-dimethyl-formamide 1.) -10 deg C, pH 7.5, 1 h; 2.) 4 deg C, overnight;

1: 100 percent / 2 N HCl, H2 / Pd / methanol 2: 84 percent / NEt3, ethyl chlorocarbonate / tetrahydrofuran; dimethylformamide / 1.) -10 deg C, pH 7.5, 1h; 2.) 4 deg C, overnight 3: 100 percent / 2 N HCl, H2 / Pd / methanol 4: pyridine / 3 h / Ambient temperature View Scheme

1: 84 percent / NEt3, ethyl chlorocarbonate / tetrahydrofuran; dimethylformamide / 1.) -10 deg C, pH 7.5, 1h; 2.) 4 deg C, overnight 2: 100 percent / 2 N HCl, H2 / Pd / methanol 3: pyridine / 3 h / Ambient temperature View Scheme

1: 100 percent / 2 N HCl, H2 / Pd / methanol 2: pyridine / 3 h / Ambient temperature View Scheme

1: HCl, i-amylnitrite / tetrahydrofuran; dimethylformamide / 0.25 h / -15 °C 2: NEt3 / tetrahydrofuran; dimethylformamide / 1 h / 15 °C 3: 55 °C / thermitase, H2O, pH 8.0 4: 67 percent / NEt3, ethyl chlorocarbonate / tetrahydrofuran; dimethylformamide / 1.) -10 deg C, pH 7.5, 1 h; 2.) 4 deg C, overnight View Scheme

1: 55 °C / thermitase, H2O, pH 8.0 2: 67 percent / NEt3, ethyl chlorocarbonate / tetrahydrofuran; dimethylformamide / 1.) -10 deg C, pH 7.5, 1 h; 2.) 4 deg C, overnight View Scheme

18 h; Ambient temperature;

1: 97 percent / acetic acid / 18 h / Ambient temperature 2: 95 percent / 18 h / Ambient temperature View Scheme

in pyridine 3 h; Ambient temperature;