1: 1.) (COCl)2, DMSO, 2.) Et3N / 1.) CH2Cl2, from -50 deg C to -20 deg C, 1.5 h, 2.) CH2Cl2, from -20 deg C to RT, 1 h 2: 815 mg / camphorsulfonic acid / 12 h / 24 °C 3: 1.) O3, 2.) Me2S / 1.) MeOH, CH2Cl2, -78 deg C, 1 h, 2.) MeOH, CH2Cl2, from -78 deg C to RT 4: 430 mg / NaBH4 / ethanol / 0.25 h / 0 °C 5: 350 mg / camphorsulfonic acid / CH2Cl2 / 12 h / 23 °C View Scheme