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