1.1: carbon tetrabromide; triphenylphosphine / N,N-dimethyl-formamide / 3 h / 20 °C 1.2: 14 h / 20 °C 2.1: pyridine; 4-(N,N-dimethlyamino)pyridine / 12 h / 20 °C 3.1: pyridine / 3 h / 20 °C 4.1: trifluoroacetic acid / methanol; dichloromethane / 2 h / 20 °C 5.1: 2-cyanoethyl N,N,N',N'-tetra-isopropylphosphorodiamidite / dichloromethane / 2 h / 20 °C / Inert atmosphere; Molecular sieve 5.2: 1.5 h / 20 °C 5.3: 0.17 h / 0 - 20 °C 6.1: Pearlman's catalist; hydrogen; acetic acid / methanol / 7 h / 20 °C / 760.05 Torr View Scheme

1: 72.3 percent / pyridinium chlorocromate / CH2Cl2 / 24 h / Ambient temperature 2: 51.7 percent / trimethylsilyl trifluoromethanesulfonate / CH2Cl2 / 72 h / -10 °C View Scheme