1: 1) LDA; 2) HMPA / 1) THF, -78 deg C, 20 min; 2) THF, 1 h 2: 76 percent / potassium tert-butoxide / tetrahydrofuran / 0.17 h / Ambient temperature 3: 81 percent / sodium borohydride / methanol / 1 h / -78 °C 4: 74 percent / LDA / tetrahydrofuran / 15 h / -78 °C 5: 50 percent / pyridine, diisopropylethylamine, methanesolfonyl chloride / CH2Cl2 / 0.25 h / 0 °C 6: 78 percent / 40percent HF / acetonitrile / 0.17 h / Ambient temperature View Scheme