(2S)-1-[(2R)-3,3,3-trifluoro-2-(sulfanylmethyl)propanoyl]pyrrolidine-2-carboxylic acid
(2S)-1-[(2R)-3,3,3-trifluoro-2-(mercaptomethyl)-1-oxopropyl]-2-pyrrolidinecarboxylic acid
(2S)-1-[(2R)-3,3,3-trifluoro-2-(mercaptomethyl)propanoyl]proline