Prolinehydantoin

1,5-Trimethylenehydantoin

1,4,5,6-tetrahydropyrrolo[3,4-d]iMidazole

Hexahydro-3H-pyrrolo[1,2-c]imidazole-1,3-dione

Hexahydro-1H-pyrrolo[1,2-c]imidazole-1,3-dione

5,6,7,7a-Tetrahydro-1H-pyrrolo[1,2-c]imidazole-1,3(2H)-dione