1: 2) Amberlyst A-21 / 1) 5 min, ice bath, 2) 7 h, rt 2: K2Cr2O7, Bu4NHSO4, 30percent H2SO4 / CH2Cl2 / 2 h / -10 °C 3: 90 percent / methanol / 12 h 4: 90 percent / LiALH4 / tetrahydrofuran / 1.5 h / 0 °C 5: 95 percent / Amberlyst A-15 / acetone; H2O / 5 h / 80 °C View Scheme