1.1: imidazole / dimethylformamide / 20 °C 2.1: AD-mixα; methanesulfonamide / H2O; 2-methyl-propan-2-ol; CH2Cl2 / 0 °C 3.1: TBAF / tetrahydrofuran / 4 h / 20 °C 4.1: triethyl orthoformate; pyridinium p-toluenesulfonate / 1,2-dichloro-ethane / 5 h / 60 °C 4.2: K2CO3 / methanol; 1,2-dimethoxy-ethane / 20 °C View Scheme

1.1: imidazole / dimethylformamide / 20 °C 2.1: AD-mixα; methanesulfonamide / H2O; 2-methyl-propan-2-ol; CH2Cl2 / 0 °C 3.1: TBAF / tetrahydrofuran / 4 h / 20 °C 4.1: triethyl orthoformate; pyridinium p-toluenesulfonate / 1,2-dichloro-ethane / 5 h / 60 °C 4.2: K2CO3 / methanol; 1,2-dimethoxy-ethane / 20 °C 5.1: 76 percent / Dess-Martin periodinane / CH2Cl2 / 2 h / 20 °C 6.1: 90 percent / L-Selectride / tetrahydrofuran / -78 °C 7.1: 80 percent / DMAP / CH2Cl2 / 20 °C 8.1: 80 percent / H2 / Pd(OH)2/C / methanol; tetrahydrofuran / 6 h / 20 °C View Scheme

1.1: imidazole / dimethylformamide / 20 °C 2.1: AD-mixβ; methanesulfonamide / H2O; 2-methyl-propan-2-ol; CH2Cl2 / 0 °C 3.1: 2.1 g / TBAF / tetrahydrofuran / 4 h / 20 °C 4.1: triethyl orthoformate; pyridinium p-toluenesulfonate / 1,2-dichloro-ethane / 5 h / 60 °C 4.2: 73 percent / K2CO3 / methanol; 1,2-dimethoxy-ethane / 20 °C 5.1: 260 mg / DMAP / CH2Cl2 / 20 °C 6.1: 74 percent / H2 / Pd(OH)2/C / tetrahydrofuran; methanol / 6 h / 20 °C View Scheme