To a warm solution of 4-bromo-5-benzyloxy-1-(phenylsulfonyl)-1H-indole (Intermediate 3, 4.74 g, 10.7 mmol) in toluene (100 mL) was added tributylvinyltin (6.80 g, 21.4 mmol) and Pd(PPh3)2Cl2 (0.37 g, 0.50 mmol). The solution was heated at reflux for two hours and more Pd(PPh3)2Cl2 (0.20 g, 0.30 mmol) was added and the reaction mixture was refluxed overnight. A teaspoon of silica gel was added and the mixture was filtered through a pad of silica gel. The solvent was removed under reduced pressure and the resulting oil was triturated with petroleum ether to give a semicrystalline mass (3.6 g) that was dissolved in dioxane (110 mL) and 2,6-lutidine (2.00 g, 18.7 mmol) and OsO4 (0.24 g, 0.94 mmol) were added. The mixture was stirred at room temperature for five minutes. To the dark solution was added a solution of sodium periodate (8.02 g, 37.5 mmol) in water (35 mL) and the resulting suspension was stirred for 30 minutes. More dioxane (40 mL) was added and the mixture was filtered. The filtrate was evaporated to give a dark red oil. The crude product was purified by flash chromatography on silica gel using petroleum ether/EtOAc 90:10 followed by 80:20 as eluent to give the title compound (2.44 g) as a yellow solid. MS m/z 392 [M+H]+.
