2,4(1H,3H)-Pyrimidinedione, 1-(2-deoxy-b-D-erythro-pentofuranosyl)-5-methyl- and 2,4(1H,3H)-Pyrimidinedione, 1-(2-deoxy-b-D-erythro-pentofuranosyl)-5-ethenyl- AIDS-212442 AIDS212442