1: 73 percent / H2 / PtO2 / acetic acid / 18 h / 2432 Torr 2: 77 percent / 1 N aq. NaOH / dimethylsulfoxide / 29 h / 20 - 25 °C 3: 1.) i-BuOCOCl, Et3N / 1.) DMF, from 20 to 25 deg C, 15 min, 2.) DMF 4: 90 percent / 1 N aq. NaOH / methanol / 40 h / 20 - 25 °C View Scheme

1.1: H2; gl. AcOH / PtO2 / 18 h 1.2: 3percent H2O2 / 20 h 2.1: 5 N NaOH / dimethylsulfoxide / 0.17 h / 20 °C View Scheme