The synthesis of glycine conjugated 3-oxo-bile acids

The glycine conjugates of the 3-oxo-derivatives of lithocholic, deoxycholic, chenodeoxycholic and cholic acids have been synthesized from their respective parent bile acid using established procedures. The reaction sequence involved oxidation using either chromic acid or silver carbonate--Celite followed by a conjugation step employing the peptide coupling reagent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline. The final products were obtained in both high yield and purity for use as reference compounds in the analysis of conjugated bile acids in bile and faecal samples by high performance liquid chromatography. Analysis of the prepared 3-oxo-glycobile acids by fast atom bombardment negative ion mass spectrometry, infrared spectroscopy and nuclear magnetic resonance proton spectroscopy is also discussed along with the thin-layer chromatographic properties.