1: 1,8-diazabicyclo[5.4.0]undec-7-ene / tetrahydrofuran / 10 h / Reflux; Inert atmosphere 2: water; sodium hydroxide / tetrahydrofuran / 15 h / Reflux; Inert atmosphere 3: tetrahydrofuran / 2 h / 20 °C / Inert atmosphere 4: sodium periodate / tetrahydrofuran; water / 2 h / 20 °C / Inert atmosphere 5: diisobutylaluminium hydride / tetrahydrofuran / 5 h / Inert atmosphere; Cooling with ice 6: potassium tert-butylate / tetrahydrofuran / 1 h / Reflux; Inert atmosphere View Scheme