1: DIBAL-H / CH2Cl2; toluene / 2 h / -90 °C 2: molecular sieves (4 Angstroem), BF3*OEt2 / diethyl ether / 0.5 h 3: 1.) 1,1,1,3,3,3,-hexamethyldisilazane, ammonium sulfate, 2.) SnCl4, TMSOTf / 1.) reflux, 2 h, 2.) 1,2-dichloroethane, RT, 2 h 4: TBAF / tetrahydrofuran / 8 h 5: K2CO3 / methanol View Scheme

1: DIBAL-H / CH2Cl2; toluene / 2 h / -90 °C 2: molecular sieves (4 Angstroem), BF3*OEt2 / diethyl ether / 0.5 h 3: 1.) 1,1,1,3,3,3-heksamethylenedisilazane, ammonium sulfate, 2.) SnCl4, TMSOTf / 1.) reflux, 2 h, 2.) 1,2-dichloroethane, RT, 2 h 4: TBAF / tetrahydrofuran / 8 h / Ambient temperature View Scheme

1: DIBAL-H / CH2Cl2; toluene / 2 h / -90 °C 2: molecular sieves (4 Angstroem), BF3*OEt2 / diethyl ether / 0.5 h 3: 1.) 1,1,1,3,3,3,-hexamethyldisilazane, ammonium sulfate, 2.) SnCl4, TMSOTf / 1.) reflux, 2 h, 2.) 1,2-dichloroethane, RT, 2 h 4: TBAF / tetrahydrofuran / 8 h / Ambient temperature View Scheme

1: 1.) LDA / 1.) THF, hexane, 30 min, 2.) THF, hexane, 3 h 2: 97 percent / 49percent aq. HF / acetonitrile / 18 h / Ambient temperature 3: 96 percent / 2,6-lutidine / CH2Cl2 / 1.5 h / 0 °C 4: 83 percent / (i-Pr)2NEt / propan-2-ol / 3.5 h 5: aq. LiOH / 1,2-dimethoxy-ethane / 0.5 h 6: imidazole / 1,2-dimethoxy-ethane / 20 h / 0 - 20 °C 7: 92 percent / 1-ethyl-3-<3-(dimethylamino)propyl>carbodiimide hydrochloride, HOBt, Et3N / dimethylformamide / 18 h / 0 - 20 °C 8: 69 percent / 8N HCl / propan-2-ol / 6 h / Ambient temperature View Scheme

1: 1.) LDA / 1.) THF, hexane, 30 min, 2.) THF, hexane, 3 h 2: 97 percent / 49percent aq. HF / acetonitrile / 18 h / Ambient temperature 3: 96 percent / 2,6-lutidine / CH2Cl2 / 1.5 h / 0 °C 4: 83 percent / (i-Pr)2NEt / propan-2-ol / 3.5 h 5: aq. LiOH / 1,2-dimethoxy-ethane / 0.5 h 6: imidazole / 1,2-dimethoxy-ethane / 20 h / 0 - 20 °C 7: 92 percent / 1-ethyl-3-<3-(dimethylamino)propyl>carbodiimide hydrochloride, HOBt, Et3N / dimethylformamide / 18 h / 0 - 20 °C 8: 69 percent / 8N HCl / propan-2-ol / 6 h / Ambient temperature 9: 76 percent / Et3N / dimethylformamide / 12 h View Scheme