1: NaBH4 / tetrahydrofuran 2: imidazole / dimethylformamide 3: 95 percent / NaBH4 / methanol / 0.5 h / -5 °C 4: DMAP, pyridine / CH2Cl2 5: N,O-bis-trimethylsilyl acetamide / SnCl4 / 3 h / -15 °C 6: 41 percent / TBAF / tetrahydrofuran 7: H2 / Pd-C / ethanol; H2O View Scheme