cis-3-Hydroxypyrrolidine-2-carboxylic Acid Trifluoroacetic Acid is a derivative salt of cis-3-Hydroxy-DL-proline (H950755). cis-3-Hydroxy-DL-proline is a derivative of DL-Proline (P756050), a racemic mixture of both L-Proline (P755995) and D-Proline (P755990).