trans-4-hydroxy-L-proline = cis-4-hydroxy-D-proline
trans-4-hydroxy-l-proline = cis-4-hydroxy-d-proline
trans-4-hydroxy-L-proline = cis-4-hydroxy-D-proline
trans-4-hydroxy-l-proline = cis-4-hydroxy-d-proline