1: 72 percent / Et3N, acetyl chloride / 20 h / 0 °C 2: 1) tetrabutylammonium fluoride, 2) ozone / 1) THF, -78 deg C, 1 h, 2) CH2Cl2, -78 deg C, 2 min 3: 91 percent / DBU / CH2Cl2 / 8 h 4: 93 percent / oxone, NaHCO3 / H2O; methanol / 18 h / Ambient temperature; pH 3 5: 96 percent / H2 / Pd/C / ethyl acetate / 1 h / Ambient temperature View Scheme

Multi-step reaction with 2 steps 1: 72 percent / Et3N, acetyl chloride / 20 h / 0 °C2: 1) tetrabutylammonium fluoride, 2) ozone / 1) THF, -78 deg C, 1 h, 2) CH2Cl2, -78 deg C, 2 min