1: 40.1 percent / 4-(dimethylamino)pyridine, diisopropylethylamine / 8 h / 45 °C 2: 55.6 percent / LiAlH4 / tetrahydrofuran / 1 h / Heating 3: 92 percent / 2.) 0.5 N aq. sulfuric acid / acetonitrile / 16 h / 23 °C 4: 1.) dimsylsodium, sodium carbonate / 1.) 23 deg C, 20 min, 2.) 23 deg C, 4 h View Scheme

Multi-step reaction with 4 steps 1: 82 percent / chromium trioxide, conc. sulfuric acid / acetone / 1 h / 0 °C2: 1.) (S)-Alpine Borane, 2.) sodium hydroxide, 30 percent hydrogen peroxide / 1.) THF, 23 deg C, 16 h, 2.) THF, 40 deg C, 3 h3: 71 percent / triethylamine / CH2Cl2 / 15 h / Ambient temperature4: 1.) n-butyllithium, 2.) boron trifluoride etherate / 1.) THF, hexane, 2.) THF, hexane, -78 deg C