1: 72 percent / titanium tetrachloride / diethyl ether 2: 83 percent / potassium t-butoxide / tetrahydrofuran / 2 h / Heating 3: 82 percent / aq. oxalic acid / Ambient temperature 4: CH2Cl2 / Ambient temperature 5: RuO2, NaIO4 / acetone; H2O 6: H3O(1+) / H2O / 6 h / Heating View Scheme