Acid Hydrolysis of Phenylthiohydantoins of Amino Acids

Abstract

The phenylthiohydantoins (PTHs) derived from amino acids were hydrolysed in boiling hydriodic acid for 24 hr. Good yields of free amino acids were obtained for all PTH derivatives except methionine. In contrast to hydrolysis with hydrochloric acid, hydrolysis with hydriodic acid converts PTH-threonine, PTH-serine, and PTH-tryptophan respectively to oc-amino-n-butyric acid, alanine, and a mixture (approx. 2: 1) of glycine and alanine. This procedure provides a useful adjunct to thin-layer chromatography and ultraviolet spectroscopy for quantitative identification of the PTH derivative.