Celite/basic alumina column

Di-0-dichloroacetyl-l-0-benzyloxycarbonyl-(4,6-0-ethylidene)-p-D-glucopyranose Palladium on carbon 4 -Demethyl-epi-podophyllotoxin Zinc acetate dihydrate Boron trifluoride etherate Trimethylsilyl trifluoromethane sulfonate Celite/basic alumina column... 

Trimethylaluminum (20 mL of a 2 M solution in toluene, 40 mmol) is added to titanocene dichloride (5.0 g, 20 mmol) under inert gas. The resulting mixture is stirred at room temperature for 3 d with evolution of methane. The mixture is then cooled to 0 °C and a solution of phenyl benzoate (4.0 g, 20 mmol) in THE (20 mL) is added over 5 min. The resulting mixture is left to warm to room temperature within 45 min and is then diluted with anhydrous diethyl ether (50 mL). Approximately 50 drops of a 1 M aqueous sodium hydroxide solution are carefully added over 10-20 min. When gas evolution has ceased anhydrous sodium sulfate is added and the slurry is filtered through a pad of Celite. After rinsing with diethyl ether the combined filtrates are concentrated and the product is purified by column chromatography (150 g basic alumina, pentane/diethyl ether 9 1). 2.8 g (70%) of the title compound is obtained. NMR (250 MHz, CDCI3) 5 4.45 (d, 2.3 Hz, IH), 5.05 (d, 2.3 Hz, IH), 7.06-7.11 (m, 3H), 7.29-7.38 (m, 5H), 7.66-7.70 (m, 2H). 

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