The product of Step A (8.50g, 19.07 mmol) was dissolved in THF (130 mL) and cooled to 0° C. Triethylamine (10.69 mL, 76.28 mmol) was added followed by p-toluenesulfonyl chloride. The mixture was stirred for three hours and an aqueous solution of ethylamine (20 mL) was added. The mixture was stirred overnight at room temperature and then evaporated to a residue which was diluted with ethyl acetate (100 mL). The ethyl acetate was separated, dried (MgSO4) and evaporated to provide a brown residue which was purified by column chromatography (silica, hexane-ethyl acetate gradient) to give 3.5 g (37.6%) of the desired compound as an oil.
