5-Methylisoxazole-4-carboxylic acid

This intermediate provides the essential isoxazole ring system that forms a core structural component of Leflunomide. During the synthesis, it undergoes conversion into the corresponding amide and is further transformed through cyclization and functional-group modifications to build the final active molecule. Its defined heterocyclic framework and reactivity make it crucial for ensuring an efficient, reliable, and high-purity synthetic route to Leflunomide. 5-Methylisoxazole-4-carboxylic acid is a key starting intermediate employed to synthesize Leflunomide, an immunomodulatory drug for rheumatoid arthritis.