1: 98 percent / D-Camphor-10-sulfonic acid / benzene / 12 h / Heating 2: 84 percent / LiAlH4 / tetrahydrofuran / 0.25 h / 0 °C 3: 83 percent / DMSO, oxalyl chloride, NEt3 / 1) CH2Cl2, -78 deg C, 1 h, 2) 0 deg C, 1 h 4: 1) n-butyllithium / 1) THF, hexane, -78 deg C, 4 min, 2) -78 deg C, 30 min 5: 72 percent / DMSO, oxalyl chloride, NEt3 / 1) CH2Cl2, -78 deg C, 1 h, 2) 0 deg C, 1 h 6: 75 percent / aq. HCl / methanol / 96 h / Ambient temperature View Scheme