1: 84 percent / 0.5N NaOH / acetone; H2O / 24 h / Ambient temperature 2: 84 percent / Et3N, isobutyl chlorocarbonate / dimethylformamide; tetrahydrofuran / -18 - 25 °C 3: hydrazine hydrate / methanol / Heating 4: 98 percent / 25percent HBr/AcOH / 2 h View Scheme