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