Methane, dichloromethoxy- → methyl (R)-7-(4-fluorophenyl)-7-(3-formyl-6-hydroxy-2,4,5-trimethylphenyl)heptanoate

To a solution of methyl (R)-7-(4-fluorophenyl)-7-(2-hydroxy-3,4,6-trimethylphenyl)heptanoate (0.8 g, 2.1 ol) and dichloromethyl methyl ether (0.62 ml) in dichloromethane (10 ml) was added dropwise a solution of titanium tetrachloride (0.76 ml) in dichloromethane (3 ml) under argon atmosphere while maintaining the temperatures of the reaction mixture at a range from -10° C. to -12° C. The reaction mixture was then stirred for 30 minutes at the same temperature range. The reaction mixture was then added to ice-water, which was subjected to extraction with ethyl acetate. The organic layer was washed with water, an aqueous solution of sodium hydrogencarbonate, water and a saturated aqueous saline solution, successively, followed by drying over magnesium sulfate. The solvent was distilled off under reduced pressure. The residue was recrystallized from chloroform/hexane to afford 0.63 g of methyl (R)-7-(4-fluorophenyl)-7-(3-formyl-6-hydroxy-2,4,5-trimethylphenyl)heptanoate. Physico-chemical properties and spectral data of the product were shown in [Table 4].