1.1: 99 percent / Et3N; 4-dimethylaminopyridine / CH2Cl2 / 0 - 20 °C 2.1: 80 percent Turnov. / cholesterol esterase; aq. NaOH / 36 h / 5 °C / pH 7.7 3.1: 98 percent / imidazole / dimethylformamide / 0.67 h / 20 °C 4.1: 81 percent Turnov. / LiOH*H2O / methanol / 48 h / -5 °C 5.1: diphenylphosphorazidate; Et3N / benzene / 1 h 5.2: toluene / 1 h / 110 °C 6.1: n-BuLi / tetrahydrofuran; pentane / 0.5 h / -100 °C 6.2: tetrahydrofuran; toluene; pentane / 0.75 h / -100 °C 7.1: NaH / dimethylformamide / 0.5 h / -5 °C 7.2: dimethylformamide / 0.25 h / -5 °C 8.1: 76 percent / pyridinium p-toluenesulfonate / methanol / 2 h / 20 °C 9.1: 30 percent / benzene / 48 h / 5 °C / UV-irradiation 10.1: NaBH4 / ethanol / 16 h / 20 °C 11.1: 12.9 mg / aq. H2O2 / tetrahydrofuran; ethanol / 22 h / 20 °C 12.1: NaH / tetrahydrofuran / 0.33 h / 20 °C 12.2: 94 percent / tetrahydrofuran / 20 h / 20 °C 13.1: pyridine; trimethylamine-N-oxide dihydrate; H2O / OsO4; acetone / 2-methyl-propan-2-ol; tetrahydrofuran / 15 h / 20 °C 14.1: 19.2 mg / p-TsOH / 2 h / 20 °C 15.1: tetrabutylammonium fluoride / tetrahydrofuran / 0.83 h / 0 °C 16.1: 7.1 mg / Burgess reagent / benzene / 16 h / Heating 17.1: 3.3 mg / K2CO3; H2O / methanol / 20 °C 18.1: n-BuLi; oxygen / tetrahydrofuran; hexane / 0.25 h / -78 °C 18.2: 45 percent / NH4Cl; H2O; dimethylsulfide / tetrahydrofuran; hexane / 1 h / 20 °C 19.1: 59 percent / H2O / p-toluenesulfonic acid / CHCl3; methanol / 0.5 h / 0 °C View Scheme

1: Et3N, 4-(dimethylamino)pyridine (DMAP) / CH2Cl2 / 24 h / Ambient temperature 2: dimethyl diazomalonate, rhodium octanoate dimer / benzene / 0.5 h / Ambient temperature View Scheme