Synthesis of selectively 13 C‐labelled benzoic acid for nuclear magnetic resonance spectroscopic measurement of glycine conjugation activity

The synthesis of [4‐ 13 C]benzoic acid (BA) labelled in a single protonated carbon, for use as a probe to measure glycine conjugation activity by nuclear magnetic resonance (NMR) spectroscopy, has been reported. The labelled compound was prepared by a seven‐step synthetic scheme on a relatively small scale using [2‐ 13 C]acetone as the source of label in overall yield of 16 %. The usefulness of [4‐ 13 C]BA was demonstrated by the NMR spectroscopic monitoring of urinary excretion of [4‐ 13 C]hippuric acid in the rat administered with the labelled BA.