1: CaCO3 / 24 h 2: 1.) H2O, Amberlyst-15 resin, 2.) aq. NaOH / 1.) THF, 37 deg C, 18 h, 2.) MeOH, reflux, 5 min 3: 94 percent / 2.67 M chromic acid / acetone / 8 h / 0 °C View Scheme

1: CaCO3 / 24 h 2: 1.) H2O, Amberlyst-15 resin, 2.) aq. NaOH / 1.) THF, 37 deg C, 18 h, 2.) MeOH, reflux, 5 min 3: 94 percent / 2.67 M chromic acid / acetone / 8 h / 0 °C 4: 71 percent / Et3N, diphenylphosphoryl azide / dioxane / 5 h / Heating 5: 100 percent / H2 / 5percent Pd/C / methanol / 1 h View Scheme