1: 99 percent / DCC, Cl2CHCOOH / dimethylsulfoxide / 0.25 h / 23 °C 2: 1.) Py, 2.) DMAP / 1.) MeCN, 0 deg C, 15 min, 2.) 23 deg C, 30 min 3: 88 percent / HCl(gas), HCOOH / toluene / 19 h 4: KOH / H2O; methanol; tetrahydrofuran / 10 h / 100 °C View Scheme

1: 99 percent / DCC, Cl2CHCOOH / dimethylsulfoxide / 0.25 h / 23 °C 2: 1.) Py, 2.) DMAP / 1.) MeCN, 0 deg C, 15 min, 2.) 23 deg C, 30 min 3: 88 percent / HCl(gas), HCOOH / toluene / 19 h 4: KOH / H2O; methanol; tetrahydrofuran / 10 h / 100 °C 5: tetrahydrofuran View Scheme