Patent ID: 7323592

Claim:
A method for crystallization of a compound (1) of the following general formula (1): in which R is CH 3 , CH 2 OH, CH 2 OCOR 1 , CO 2 R 2 , CONR 3 R 4 , OH, CH 2 OR 1 or CH 2 NR 3 R 4 ; R 1 is a C 1-5 alkyl group; R 2 is H or a C 1-5 alkyl group; R 3 and R 4 are independently selected from among H and C 1-5 alkyl groups; a and b each is a double bond, one of a and b is a single bond with the other being a double bond or a and b each is a single bond, which comprises preparing a slurry with a necessary suspension amount of the compound (1) for inhibiting oil formation and scaling of the compound (1) in advance, and then carrying out a main crystallization in the presence of said slurry by mixing a solution of the compound (1) in a water-miscible good solvent with water.