Tosyl synthesis (via hydroxyl group):
p-Toluenesulphonyl chloride (19.4 g, 102 mmol) was added to a solution of the compound described in hydroxyl compound (4.29 g, 35.2 mmol) in pyridine (50 ml), and stirred at room temperature for 16 hours. The mixture was then partitioned between brine (50 ml) and diethyl ether (2 x 50 ml). The combined organic extracts were washed with brine (50 ml), dried over magnesium sulphate, filtered and evaporated under reduced pressure to give gum. This crude residue was purified by column chromatography eluting with 5% ethyl acetate in pentane to give the title compound as a white solid (4.31 g, 44%).
Patent reference: WO2010032200 (Pfizer)