A method of preparing N-formyl-L-aspartic anhydride

摘要

N-formyl-L-aspartic anhydride is prepared by a process which comprises reacting L-aspartic acid with acetic anhydride and formic acid in a molar amount of 1.05 times as large as that of aspartic acid or larger and centrifugation of the suspension of N-formyl-L-aspartic anhydride after said reaction in the presence or absence of an aromatic hydrocarbon while conducting the following steps: (1) starting to supply said suspension to a separation device under a back pressure of 100 mmHg or higher; (2) releasing said back pressure at the time when half or more of said suspension has already been supplied; and, (3) subsequently filtrating and/or conducting dehydration of the cake while if necessary washing the cake. This method provides anhydride crystals having a small amount of residual formic acid.