108895-49-4 2,4(1H,3H)-Pyrimidinedione, 5-ethyl-1-[(2R,5S)-tetrahydro-5-(hydroxymethyl)-2-furanyl]- 5-Et-ddU 5-Ethyl-2',3'-dideoxyuridine AIDS-000223 AIDS000223 D2EtU ddEtUrd