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: HCl, i-amylnitrite / tetrahydrofuran; dimethylformamide / 0.25 h / -15 °C 2: NEt3 / tetrahydrofuran; dimethylformamide / 1 h / 15 °C 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 View Scheme