Abstract: Disclosed herein are novel phosphonate nucleosides and thiophosphonate nucleosides comprising a phosphonalkoxy-substituted or phosphonothioalkyl-substituted five-membered, saturated or unsaturated, oxygen-containing or sulfur-containing ring coupled to a heterocyclic nucleobase such as a pyrimidine or purine base. The invention further relates to compounds having HIV (Human Immunodeficiency Virus) replication inhibiting properties and to compounds having antiviral activities with respect to other viruses. The invention also relates to methods for preparation of all such compounds and pharmaceutical compositions comprising them. The invention further relates to the use of said compounds as a medicine and in the manufacture of a medicament useful for the treatment of subjects suffering from HIV infection, as well as for treatment of other viral, retroviral or lentiviral infections and to the treatment of animals suffering from FIV, viral, retroviral or lentiviral infections.

Abstract: 6-substituted-3-substituted-3H-furo[2,3-d]pyrimidin-2-one and 6-substituted-2-substituted-furo[2,3-d]pyrimidine novel compounds are useful in the treatment of viral infection, in particular cytomegalovirus viral infection. The substituents are independently selected from alkyl, aryl, alkenyl and alkynyl. The preferred substituent at the 6 position is alkyl.