1: 37 percent / pyridine, DMAP / 50 °C 2: 93 percent / MeONa / methanol 3: CH2Cl2; hexane / Ambient temperature 4: pyridine, DMAP / Ambient temperature 5: 96 percent / 10-camphorsulfonic acid / methanol / Ambient temperature 6: aq. NaIO4 / acetone / 0 °C 7: NaBH4 / methanol / 0 °C 8: MeONa / methanol 9: 10-camphosulfonic acid / 0 °C 10: pyridine 11: 15-crown-5 / dimethylformamide / 60 °C 12: DIBAL-H / CH2Cl2 / -78 °C 13: CrCl2 / tetrahydrofuran / 3 h / Ambient temperature 14: 89 percent / 10-camforsulfonic acid / methanol / 60 °C 15: 71 percent / Ph3P, diethyl azodicarboxylate / toluene / 36 h / Heating 16: 56 percent / tert-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / 1.) -78 deg C, 10 min, 2.) -78 deg C, 30 min 17: NCS, aq. AgNO3, 2,4,6-collidine / acetonitrile / 0.02 h / 0 °C 18: 65 percent / NaBH(OAc)3 / acetonitrile; acetic acid / 5 h / 0 °C 19: 82 percent / TBAF / tetrahydrofuran / Ambient temperature 20: 87 percent / MnO2 / CH2Cl2 / 3 h / Ambient temperature View Scheme