1: pyridine / CH2Cl2 / 3 h / -20 °C 2: sodium azide / dimethylformamide / -20 °C 3: 95 percent / sodium borohydride / propan-2-ol / 48 h / Heating 4: 3-<(dimethylamino)propyl>-1-ethylcarbodiimide hydrochloride / CH2Cl2 / Ambient temperature 5: acetic acid / H2O / 45 °C View Scheme

1: 1.) pyridine, (CF3CO)2O, 2.) NaN3 / 1.) CH2Cl2, -15 deg C, 15 min; 2.) CH2Cl2, DMF, room temperature, 5 h 2: 75 percent / p-TsOH / methanol; CH2Cl2 / 12 h / Ambient temperature 3: 95 percent / H2S / pyridine; H2O / 48 h / Ambient temperature View Scheme

1: 1.) pyridine, (CF3CO)2O, 2.) NaN3 / 1.) CH2Cl2, -15 deg C, 15 min; 2.) CH2Cl2, DMF, room temperature, 5 h 2: 75 percent / p-TsOH / methanol; CH2Cl2 / 12 h / Ambient temperature 3: 75 percent / pyridine / 6 h / -10 °C View Scheme

1: 1.) pyridine, (CF3CO)2O, 2.) NaN3 / 1.) CH2Cl2, -15 deg C, 15 min; 2.) CH2Cl2, DMF, room temperature, 5 h 2: 75 percent / p-TsOH / methanol; CH2Cl2 / 12 h / Ambient temperature View Scheme

1: pyridine / CH2Cl2 / 3 h / -20 °C 2: sodium azide / dimethylformamide / -20 °C 3: H2O; acetic acid / 45 °C 4: 92 percent / sodium borohydride / propan-2-ol / 48 h / Heating 5: 3-<(dimethylamino)propyl>-1-ethylcarbodiimide hydrochloride / CH2Cl2 / Ambient temperature View Scheme

1: pyridine / CH2Cl2 / 3 h / -20 °C 2: sodium azide / dimethylformamide / -20 °C 3: 95 percent / sodium borohydride / propan-2-ol / 48 h / Heating 4: 3-<(dimethylamino)propyl>-1-ethylcarbodiimide hydrochloride / CH2Cl2 / Ambient temperature 5: acetic acid / H2O / 45 °C View Scheme

1: pyridine / CH2Cl2 / 3 h / -20 °C 2: sodium azide / dimethylformamide / -20 °C 3: H2O; acetic acid / 45 °C 4: 92 percent / sodium borohydride / propan-2-ol / 48 h / Heating 5: 3-<(dimethylamino)propyl>-1-ethylcarbodiimide hydrochloride / CH2Cl2 / Ambient temperature View Scheme