1: 440 mg / NaBH4, 2M HCl / tetrahydrofuran; ethanol 2: 95 percent / triethylsilane / trifluoroacetic acid / 0.5 h 3: 72 percent / toluene-p-sulphonic acid / CH2Cl2 / 15 h / Ambient temperature 4: 54 percent / triphenylphosphine / various solvent(s) / 40 h / Heating 5: 80 percent / 2M H2SO4 / tetrahydrofuran / 2 h / 50 °C View Scheme