| 摘要 |
PURPOSE:To obtain the titled compound useful as an immune carcinostatic agent quantitatively, easily and industrially advantageously, by reacting an erythro-(2RS)-3-amino-2-hydroxy-4-oxo-4-phenylbutyric acid derivative with a base. CONSTITUTION:An erythro-(2RS)-3-amino-2-hydroxy-4-oxo-4-phenylbutyric acid derivative shown by the formula I (R1 is phenyl which may contain substituent group which will not participate in the reaction; R2 is protected amino; R3 is H, or ester residue) is treated with a base (e.g., NaOH, KOH, Na2CO3, NH3, etc.) to give a threo-(2RS)-3-amino-hydroxy-4-oxo-4-phenylbutyric acid derivative shown by the formula II. By this method, most of the erythro isomer shown by the formula I which has been abandoned as a by-product can be made into the threo isomer shown by the formula II.
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