1: 85 percent / pyridine / 20 h / 20 °C 2: 1.) 1,1'-carbonyldiimidazole / 1.) DMF, 40 deg C, 30 min, 2.) 20 deg C, 11 h 3: methanolic NaOH 4: Et3N / tetrahydrofuran; CH2Cl2 / 0.17 h / 0 °C 5: LiCl / dimethylformamide / 0.08 h / 110 °C 6: HBr/AcOH / 4 h / 20 °C 7: methanol / 24 h / 20 °C View Scheme

Multi-step reaction with 5 steps 1: 85 percent / pyridine / 20 h / 20 °C2: 1.) 1,1'-carbonyldiimidazole / 1.) DMF, 40 deg C, 30 min, 2.) 20 deg C, 11 h3: methanolic NaOH4: Et3N / tetrahydrofuran; CH2Cl2 / 0.17 h / 0 °C5: LiCl / dimethylformamide / 0.08 h / 110 °C