1: 42 percent / SnCl4; molecular sieves 4A / CHCl3; CH2Cl2 / 14 h / -5 - 20 °C 2: 87 percent / NaOMe / methanol / 15 h / 25 °C 3: 98 percent / Et3N / CH2Cl2 4: 62 percent / IBX / dimethylformamide / 36 h 5: 50 percent / aq. HF / acetonitrile / 20 °C View Scheme