1.1: 47 percent / TBAF / tetrahydrofuran / 0 - 20 °C 2.1: Dess-Martin periodinane / CH2Cl2 / 3 h / 0 - 20 °C 2.2: 2-methyl-2-butene; NaClO2; NaH2PO4*H2O / tetrahydrofuran; H2O / 5 h / 0 - 20 °C 2.3: HOBt; EDC; triethylamine / CHCl3 / 36 h / 20 °C 3.1: O3 / CH2Cl2; methanol / -78 °C 3.2: 83 percent / Me2S / CH2Cl2; methanol / -78 - 20 °C View Scheme