Patent ID: 8901345
Filing Date: 2014-12-02
Classification: C07C,C07D

Abstract:
1. A process for the preparation of anhydrous crystals of a compound represented by the following formula (1): wherein Boc represents a tert-butoxycarbonyl group, the method comprising the steps of: treating a compound represented by the following formula (1a): wherein Boc is as defined above, with dropwise addition of anhydrous oxalic acid at 50 to 80° C. in a hydrous organic solvent containing 4 to 10% water, and after completion of the dropwise addition, the reaction mixture is further stirred at 50 to 80° C. for 2 to 5 hours to obtain monohydrate crystals of a compound represented by the following formula (1b): wherein Boc is as defined above; and stirring the monohydrate crystals of the compound represented by formula (1b) in an organic solvent with a water content of less than 1% by weight under heating at 50 to 80° C., wherein the organic solvent is distilled off by ½ to 4/7 of the total volume of the organic solvent under reduced pressure in the range of 40 to 75° C. and then re-adding an organic solvent in an amount corresponding to the amount distilled off.