| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for removing impurities from a crude material of a dihydrobenzopyran compound, while substantially keeping the ratio of the optical isomers in the racemic modification of the crude material, in a method for preparing a dihydrobenzopyran compound with a high purity by purifying the crude material which, like impurities-containing crude nipradilol, contains four kinds of optical isomers as a mixture of two kinds of racemic modification A and racemic modification B. SOLUTION: The crude material of the dihydrobenzopyran compound is dissolved in an organic solvent having a dielectric constant of 6-35 to prepare a raw material solution; then a poor solvent is added to the solution to precipitate the crystal of the dihydrobenzopyran compound. COPYRIGHT: (C)2007,JPO&INPIT |
