Dicyclohexylamine → (r)-2-Bromoisovaleric acid dicyclohexylamine salt

To 325.2 g of a hexane solution of (R)-2-bromoisovaleric acid obtained in Example 4 (containing 75.0 g of (R)-2-bromoisovaleric acid), 530.9 g of hexane and 269.7 g of2-propanol were further added. Seed crystals were added when about ⅔ for 72.5 g of dicyclohexylamine was added continuously for 1.0 hour under a nitrogen atmosphere at 5° C. to crystallize. Further, after continuously adding the remaining about ⅓ for dicyclohexylamine at 5° C. for 0.5 hours, they were stirred at 5° C. for 1 hour. The obtained crystals were filtered under a reduced pressure and then the crystals were washed for 3 times with 150 ml of hexane. The obtained wet crystals were dried under a reduced pressure to obtain 126.45 g of a (R)-2-bromoisovaleric acid dicyclohexylamine salt (optical purity 98.0% ee, crystallization yield 87%, apparent purity 98.9%, impurity content 2-hydroxy isovaleric acid: not detected, bromine content: 0.64%).