| 摘要 |
PURPOSE:To readily obtain a racemic modification for obtaining the R-isomer useful as a raw material for medicines by heat-treating the subject substance and then treating the resultant substance with water or a base and acid. CONSTITUTION:The S-isomer expressed by formula I is heated in the absence of a solvent at 185-200 deg.C for about 2hr to provide a ceramic modification and a dehydration product expressed by formula II, which are then isolated, directly used or post-treated with water, a base or acid to afford the racemic modification. The treatment with the base is carried out in a solvent at -10 to 100 deg.C using NaOH, etc. If the water is used as the solvent, the reaction mixture can be treated with an acid, such as hydrochloric or phosphoric acid, after completing the reaction to afford the racemic modification as crystals. |
