1: 91 percent / thionyl chloride / -10 - 20 °C 2: 98 percent / sodium carbonate / dioxane; H2O / 0 - 20 °C 3: 83 percent / triphenylphosphine; N-bromo-succinimide / tetrahydrofuran / 0 - 20 °C 4: 100 percent / sodium sulfite; H2O / dioxane / 1 h / 100 °C 5: 76 percent / subtilisin; aq. NaOH / aq. phosphate buffer / 4 h / 20 °C View Scheme

Multi-step reaction with 4 steps 1: 85 percent / 1,3-bis(diphenylphosphino)propane; Et3N; trioctylsilane / Pd(OAc)2 / dimethylformamide / 4 h / 70 °C2: 91 percent / NaBH4 / CH2Cl2; methanol / 0.5 h / 20 °C3: NaOH / methanol; H2O / 4 h / 20 °C4: HCl / ethyl acetate / 3 h / 20 °C