This invention discloses compounds of Formula III:wherein:MPO3H2 is a phosphonic acid selected from the group consisting of 9-(2-phosphonylmethoxyethyl)adenine, (R)-9-(2-phosphonylmethoxypropyl)adenine, 9-(2-phosphonylmethoxyethyl)guanine, 9-(2-phosphonylmethoxyethyloxy)adenine, 9-(2- phosphonylmethoxyethyl)-2,6-diaminopurine, (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine, (S)-1-(3-hydroxy-2- phosphonylmethoxypropyl)adenine, 9-(3-hydroxy-2-phosphonylmethoxypropyl)guanine, and (S)-9-(3-fluoro-2-phosphonylmethoxypropyl)adenineV is selected from a group consisting of phenyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-furanyl, 3-furanyl, 2-thienyl, and 3-thienyl, all optionally substituted with 1-3 substituents selected from a group consisting of F, Cl, Br, C1-C3 alkyl, CF3 and OR6R6 is selected from group consisting of C1-C3 alkyl, and CF3and pharmaceutically acceptable salts thereof.
