1: 80percent aq. AcOH 2: pyridine 3: 92 percent / N,O-bis(trimethylsilyl)acetamide, trimethylsilyl triflate / acetonitrile 4: 87 percent / NH3 / methanol / 4 h / Ambient temperature 5: 92 percent / NaH / dimethylformamide / 37 h / 0 °C 6: debenzylation View Scheme