1: 87 percent / tetrabutylammonium fluoride / tetrahydrofuran / 0 - 20 °C 2: 51 percent / Ph2S2 / cyclohexane; dioxane / 3 h / Photolysis 3: 78 percent / PDC / dimethylformamide / 3 h / 40 - 50 °C 4: 79 percent / DCC; HOBt / CH2Cl2 / 20 °C 5: 79 percent / p-toluenesulfonic acid / CH2Cl2 / 1 h / 20 °C 6: 69 percent / BF3*Et2O / various solvent(s) / 1 h / 20 °C View Scheme