1: imidazole / dimethylformamide / 60 °C 2: 96 percent / pyridine / CH2Cl2 3: HF; pyridine / CH2Cl2 / 0 °C 4: 90 percent / pyridine / 0 °C View Scheme

Multi-step reaction with 7 steps 1.1: pyridine; DMAP / 20 °C2.1: 3.5 g / DMAP; Et3N / CH2Cl2 / 2 h / 20 °C3.1: DABCO / dioxane / 0.5 h / 20 °C3.2: DBU / dioxane / 20 °C4.1: 1.1 g / aq. NaOH / tetrahydrofuran; methanol / 0.08 h / 0 °C5.1: 70 percent / NaH / dimethylformamide / 1.5 h / 0 °C6.1: pyridine / 1 h / 20 °C7.1: 90 percent / TBAF / tetrahydrofuran / 1 h / 20 °C