In order to estimate the generality of the chain elongation reaction observed on the metabolism of fusaric acid (5-butylpyridine-2-carboxylic acid) in rat liver, the metabolism of the following heteroaromatic carboxylic acids, 5-alkylpyrimidine-2-carboxylic acid (3a-d), 2-alkylpyrimidine-5-carboxylic acid (4a-d), 6-pentylpyridazine-3-carboxylic acid (5), and 5-pentylpyrazine-2-carboxylic acid (6), was investigated. Although 4a-d, 5, and 6 did not undergo the chain elongation, in the metabolites of 3a-d collected from the rat urine, pyrimidine-2-propionic acids, pyrimidine-2-acrylic acids, pyrimidine-2-(3-hydroxypropionic)acids, and pyrimidine-2-(3-oxopropionic)acids were detected together with the ω-oxidation products by gas chromatography-mass spectrometry technique. This is a rare example of chain elongation in drug matabolism as well as the case of 5-alkylpyridine-2-carboxylic acids.
