The synthesis and antiviral activity of amino acid esters of 1-(β-D-ribofuranosyl)-1,2,4-triazole-3-carboxamide (ribavirin, 1) is described.To date a number of nucleoside derivatives have been found which are active inhibitors of viral replication. Among them 1-(β-D-ribofuranosyl)-1,2,4-triazole-3-carboxamide (ribavirin, 1) has shown in vitro antiviral activity against RNA and DNA viruses1. It inhibits also the replication of HIV in human T lymphocytes2. The biochemistry and clinical application of ribavirin has been reviewed1.Several derivatives of ribavirin, such as the 2',3',5'-triacetate3, 5'-acid esters4 and some phosphates5 have also been shown to exhibit promising in vitro effect. It is suggested that this antiviral activity probably is due to intracellular hydrolysis of the analog back to active ribavirin.There are several strategies for designing prodrugs of biologically active nucleosides. A general approach is the synthesis of amino acid or peptide analogs. These modification usually result in increased stability, lipofilicity and permeation of the active compound through plasma membranes. This approach has been successively exploited for preparation of prodrugs of AZT6, 5-fluorouridine7 and ara-C8 In this report we describe the synthesis and in vitro evaluation of 5'-amino acid esters of 2',3' isopropylidene ribavirine 3-7 as inhibitors of several viruses in vitro