1: 98 percent / p-toluenesulfonic acid / ethanol; H2O / 18 h / 20 °C 2: 61 percent / NaBH4, semicorrin, CoCl2*6H2O / dimethylformamide; ethanol / 4 h / 20 °C 3: triphenylphosphine dibromide / CH2Cl2 / 6 h / 20 °C 4: 18-crown-6 / acetonitrile / 22 h / 40 °C View Scheme