Short and efficient preparations of isoxazole-3-carboxylic acid and imino-oxopentanoic acid potent precursors of 4-hydroxyisoleucine

Herein, we describe short and efficient syntheses of isoxazole-3-carboxylic acid 3a and imino-oxopentanoic acid 8 achiral precursors of 4-hydroxyisoleucine. The developed procedures involve readily available and cheap starting materials and can easily be transposed to the large scale.

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