944 mg of ethyl 3-(3-bromo-5-[(tertiary butoxycarbonyl)amino]methyl-4-hydroxyphenyl)-2-isopropoxypropionate was dissolved in 5 ml N,N-dimethylformamide, and 0.15 ml iodomethane and 500 mg of potassium carbonate were successively added. After stirring at room temperature for 2 hours, the reaction mixture was diluted with ethyl acetate. The organic layer was washed with water and brine, dried over anhydrous magnesium sulfate and the solvent was evapoarated. The residue was purified by silica gel column chromatography, and from fractions eluted with hexane-ethyl acetate (4:1), 876 mg of ethyl 3-(3-bromo-5-[(tertiary butoxycarbonyl)amino]methyl-4-methoxyphenyl)-2-isopropoxypropionate was obtained.
