27.6 g of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 54.0 g of (N-methoxy-2-pyrrolidone-3-yl)triphenylphosphonium bromide and 33.0 ml of triethylamine were heated at 50° C. in ethanol for four hours. After distilling the ethanol off, the residue was dissolved in chloroform, washed with water and then a saturated saline solution and dried over anhydrous magnesium sulfate. After distilling the chloroform off, the residue was treated with the column chromatography, using silica gel and a carrier liquid of benzene and acetone and recrystallized with a mixture of ethyl acetate and hexane to give 26.5 g of the title compound.
