(d,l)-threo and allo-2-amino-4,4,4-trifluoro-3-hydroxybutanoic acids are  synthesised from ethyl trifluoroacetoacetate via reduction and saponification of  the 4,4,4-trifluoro-3-hydroxy-2-methoxyiminobutanoate. threo-Isomers are  stereospecifically obtained by epimerisation of allo-isomers via the  corresponding oxazolidinones. An acylation and stereoselective reduction  sequence performed on ethyl N,N-dibenzylaminoacetate also leads to  threo-isomers (1A) in good yields. An enantioselective synthesis of  (L)-4-fluorothreonine by regiospecific opening of (2S),  (3R)-3-benzyloxyoxiranecarboxylic acid is reported.
                                    (d,l)-threo和allo-2-
氨基-4,4,4-三
氟-3-羟基
丁酸是通过乙基三
氟乙酰乙酸酯的还原和
水解4,4,4-三
氟-3-羟基-2-甲氧基亚
氨基
丁酸酯来合成的。通过相应的唑烷酮的差向异构化可以立体特异性地获得threo异构体。在乙基N,N-二苄基
氨基
乙酸酯上进行的酰化和立体选择性还原序列也能以良好的产率得到threo异构体(1A)。报道了一种通过(2S),(3R)-3-苄氧基
环氧乙烷羧酸的区域特异性开环来选择性合成(L)-4-
氟苏
氨酸的方法。