1.1: trifluoroacetic acid / 168 h 2.1: sodium hydride / tetrahydrofuran / 0.25 h / -78 °C 2.2: tetrahydrofuran / 1 h / 20 °C 3.1: 28 percent / sodium iodide; trifluoroacetic acid / acetonitrile / 0 °C 4.1: ozone / methanol / 0.17 h / -40 °C 4.2: methyl sulfide / methanol 4.3: 45 percent / sodium borohydride / methanol / 2 h / 0 °C View Scheme