1.1: 96 percent / trimethylsilyl triflate / CH2Cl2 / 16 h / -78 °C 2.1: sodium naphthalenide / tetrahydrofuran / -25 °C 2.2: 82 percent / triethylamine / tetrahydrofuran / 4 h / -25 - 20 °C 3.1: Rose Bengal; oxygen / tetradeuteriomethanol / 0.5 h / Irradiation; acetone/dry ice cooling 4.1: TMSOTf / CH2Cl2 / 0.33 h / -78 °C 4.2: 1.39 mg / water; CSA / CH2Cl2 / 3 h / 20 °C View Scheme

Stage #1: With  ozone in  methanol; dichloromethane T=-78 - 20°C; ozonolysis; Stage #2: With  dimethylsulfide in  methanol; dichloromethane T=20°C; Reduction; 3 h;