1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 1 h, 2) 1,2-dichloroethane, a) -22 deg C, 15 min, b) room temperature, 0.5 h 5: 59 percent / ammonia / methanol / 16 h / 80 °C 6: 90.9 percent / n-Bu3SnH, Et3B / benzene; hexane / Ambient temperature 7: 82.4 percent / TBAF / tetrahydrofuran / Ambient temperature View Scheme

1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 3 h, 2) 1,2-dichlorethane, a) 5 deg C, 10 min, b) room temperature, 35 min 5: 94.74 percent / n-Bu3SnH, Et3B / benzene; hexane / Ambient temperature 6: 99.5 percent / TBAF / tetrahydrofuran / Ambient temperature 7: 88.73 percent / sodium methoxide / methanol / 1 h / Ambient temperature View Scheme

1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 2 h, 2) 1,2-dichloroethane, a) 5 deg C, 10 min, b) room temperature, 10 min 5: 76 percent / 30percent aq. H2O2, pyridine / CH2Cl2 / 0.5 h / Ambient temperature 6: 78 percent / TBAF / tetrahydrofuran / Ambient temperature View Scheme

1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 1 h, 2) 1,2-dichloroethane, a) -22 deg C, 15 min, b) room temperature, 0.5 h 5: 90 percent / mercaptoethanol, sodium methoxide / methanol / 4 h / Heating 6: 90 percent / n-Bu3SnH, Et3B / benzene; hexane / Ambient temperature 7: 79 percent / TBAF / tetrahydrofuran / Ambient temperature View Scheme

1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 2 h, 2) 1,2-dichlorethane, a) 5 deg C, 10 min, b) room temperature, 10 min 5: 81.1 percent / n-Bu3SnH, Et3B / benzene; hexane / Ambient temperature 6: 84.8 percent / TBAF / tetrahydrofuran / 3 h / Ambient temperature View Scheme

1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 2 h, 2) 1,2-dichloroethane, a) 5 deg C, 10 min, b) room temperature, 10 min 5: 89 percent / n-Bu3SnH, Et3B / benzene; hexane / 4 h / Ambient temperature 6: 80 percent / TBAF / tetrahydrofuran / 3 h / Ambient temperature View Scheme

1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 1 h, 2) 1,2-dichloroethane, a) -22 deg C, 15 min, b) room temperature, 0.5 h 5: 85.5 percent / methanol; H2O / 18 h / 85 °C 6: 96.5 percent / 30percent aq. H2O2, pyridine / CH2Cl2 / Ambient temperature 7: 90 percent / TBAF / tetrahydrofuran / Ambient temperature View Scheme

1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 1 h, 2) 1,2-dichloroethane, a) -22 deg C, 15 min, b) room temperature, 0.5 h 5: 93 percent / n-Bu3SnH, Et3B / benzene; hexane / Ambient temperature 6: 83 percent / TBAF / tetrahydrofuran / Ambient temperature View Scheme

1: tetrahydrofuran / -78 °C 2: DIBAL-H / toluene / 2 h / -78 °C 3: 96 percent / pyridine, DMAP / CH2Cl2 / 2 h / 0 °C 4: 1) hexamethyldisilazane (HMDS), ammonium sulfate, 2) trimethylsilyl triflate (TMSOTf) / 1) reflux, 2 h, 2) 1,2-dichlorethane, a) 5 deg C, 10 min, b) room temperature, 10 min 5: 71 percent / 30percent aq. H2O2, pyridine / CH2Cl2 / Ambient temperature 6: 90 percent / TBAF / tetrahydrofuran / 3 h / Ambient temperature View Scheme