| 摘要 |
A process for the preparation of salts of (6R)-N(5),N(10)-methenyl-5,6,7,8-tetrahydrofolic acid of a particular formula (I). The process comprises: (i) mixing at least one acid S1 with an aqueous solution having dissolved therein an ammonium- or alkali metal-salt of (6RS)-N(10)-formyl-5,6,7,8-tetrahydrofolic acid of a particular formula (II) until a pH in the range of about 5.5 to 7.5 is obtained; (ii) adding a water-soluble alkaline earth metal salt to the mixture obtained from step (i); (iii) precipitating a solid and isolating the solid; (iv) providing a solid of formula (I) by suspending the solid obtained from step (iii) in water, adding an acid S2, which will not precipitate with an alkaline earth metal cation, until the pH stabilizes to a value of 1.0 to 2.0, and separating the resulting solid.
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