1.1: 97 percent / piperidine; Ac2O / tetrahydrofuran / 24 h / 80 °C 2.1: 83 percent / NaBH4 / methanol; acetonitrile / 4 h / 0 - 20 °C 3.1: 87 percent / NaOMe; BuONO / methanol / 48 h / 0 °C 4.1: imidazole; K2CO3 / dimethylformamide / 0.5 h / 0 °C 4.2: 88 percent / dimethylformamide / 12 h / 0 - 20 °C 5.1: 99 percent / aq. HCl / tetrahydrofuran / 20 °C 6.1: 89 percent / imidazole / dimethylformamide / 11 h / 0 - 20 °C 7.1: TEMPO; KBr; aq. NaOCl / NaHCO3 / CH2Cl2 / 1 h / 0 °C 8.1: pyridine / ethanol / 20 °C 9.1: 11 percent / TBAF / tetrahydrofuran / 0.5 h / 20 °C 10.1: 98 percent / TEMPO; aq. KBr; NaOCl / NaHCO3 / acetonitrile / 2 h / 0 °C 11.1: 96 percent / TFA; pentamethylbenzene / 2.5 h / 0 - 20 °C 12.1: 100 percent / NBS / acetonitrile / 1 h / 0 °C 13.1: CoCl2*6H2O; NaBH4 / methanol / 0 °C 13.2: i-Pr2NEt; 1-hydroxybenzotriazole; 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide HCl / CH2Cl2; dimethylformamide / 0 - 20 °C 14.1: 75 percent / N-bromosuccinimide / acetonitrile / 2 h / 0 °C 15.1: aq. LiOH / methanol; tetrahydrofuran / 5 h / 0 °C 16.1: TFA / CH2Cl2 / 0 °C 17.1: i-Pr2NEt; PyBOP / CH2Cl2; dimethylformamide / 25 h / 0 - 20 °C 18.1: 43 percent / BBr3; thioanisole / CH2Cl2 / 1 h / 0 - 20 °C View Scheme