1: 90 percent / 4-dimethylaminopyridine; triethylamine / CH2Cl2 / 1 h / 20 °C 2: BH3-DMS / tetrahydrofuran / -10 - 20 °C 3: 0.16 g / hydrochloric acid / ethanol; tetrahydrofuran / 1 h / Heating 4: 100 percent / Amberlite IRA 400 (OH(1-)); aqueous acetic acid View Scheme