(2S)-3-(1H-indol-3-yl)-2-(2-sulfanylpropanoylamino)propanoic acid
(2S)-3-(1H-indol-3-yl)-2-[(2-mercapto-1-oxopropyl)amino]propanoic acid
(2S)-3-(1H-indol-3-yl)-2-(2-mercaptopropanoylamino)propionic acid