1: 81 percent / DIBAL / tetrahydrofuran / 18 h / -78 - 20 °C 2: 71 percent / KOH / dimethylsulfoxide / 1.5 h 3: 72 percent / m-CPBA / CH2Cl2 / 24 h / 0 - 20 °C 4: Py*9HF / CH2Cl2 / 12 h / -10 °C View Scheme

1: 73 percent / DIBAL / toluene / 5 h / -78 °C 2: 1.) NaH, 2.) n-Bu4NHSO4 / 1.) THF, 2.) THF, RT, 10 h 3: 1.) (-)-Ipc2BH, 2.) aq. H2O2, aq. NaOH / 1.) THF, -25 deg C, 6 h, 2.) THF, RT, 5 h View Scheme