When 5-butylthiazole-2-carboxylic acid or 2-butylthiazole-4-carboxylic acid was orally administrated to rats, the corresponding chain elongated products, thiazolepropionic acid and thiazoleacrylic acid accompanied with ω-oxidation, were detected from their urine. Similar results have been already reported on the metabolism of 5-alkylpyridine-2-carboxylic acid and that of 5-alkylpyrimidine-2-carboxylic acid. On the other hand, no metabolite due to the chain elongation was detected on the experiments by using 5-pentylisoxazole-3-carboxylic acid, 3-pentylpyrazole-5-carboxylic acid, 5-pentyloxazole-2-carboxylic acid and 4-pentylimidazole-2-carboxylic acid. The relationship between the chain elongation and the structure of substrates was discussed.
