To a solution of the hydroxyester of Step 2 (38.68 g, 84.36 mmol) in 600 mL of toluene at 0° C. was added slowly 225 mL of 1.5M MeMgBr in toluene:THF 3:1 and the mixture was stirred at r.t. for 4 h. It was then poured into 2 L cold 12% NH4OAc and 25 mL of AcOH were added. The products were extracted in EtOAc, washed with brine, dried over Na2SO4 and concentrated. Flash chromatography of the residue with EtOAc:toluene 15:85 and 25:75 afforded first the methyl ketone derivative, then the title compound. Yield 24.06 g, 62%.
