1: 72 percent / sodium borohydride / CH2Cl2; methanol / 0.67 h / 20 °C 2: 83 percent / triphenylphosphine; N-bromo-succinimide / tetrahydrofuran / 0 - 20 °C 3: 100 percent / sodium sulfite; H2O / dioxane / 1 h / 100 °C 4: 76 percent / subtilisin; aq. NaOH / aq. phosphate buffer / 4 h / 20 °C View Scheme