A solution of (3R,5S,6E)-7-[2-cyclopropyl-4-(4-fluorophenyl)quinolin-3-yl]-3,5-dihydroxy hept-6-enoic acid diisopropylamine salt (10.0 g) in a mixed solvent of ethyl acetate (100.0 mL) and water (100.0 mL) was cooled to 0˜5° C. The pH of the reaction mixture was adjusted to 3.0˜4.0 using 1N hydrochloric acid solution. Water (40.0 mL) was added to the separated organic layer, the pH of which was then adjusted to 9.0˜11.5 using 1N sodium hydroxide solution. Calcium chloride dihydrate (2.8 g) was added to the separated water layer. The reaction mixture was stirred at 20˜25° C. for 2 hours and then filtered under reduced pressure. The resulting white solid was dried to obtain (3R,5S,6E)-7-[2-cyclopropyl-4-(4-fluorophenyl)quinolin-3-yl]-3,5-dihydroxy hept-6-enoic acid 1/2 calcium salt (6.9 g, yield 90%).
