the unmodified form in vivo preferably within a target cell e g a t cell or hepatocyte or a target organ e g lymph node or spleen conversion of a compound of the invention into a prodrug form may be useful where the active drug is too toxic for safe systemic administration where the unmodified compound is poorly absorbed from the digestive tract or where the body tends to break down the unmodified compound before it reaches its target the term u201c inhibiting a reverse transcriptase u201d refers to a direct or indirect reduction in the formation of dna from a template rna or dna by a reverse transcriptase direct inhibition includes suicide competitive and non competitive inhibition allosteric inhibition or binding of an inhibitor in a non nucleoside pocket examples of indirect inhibition include depletion of nucleosides for dna synthesis induction or contribution to conformational changes etc as used herein the term u201c reducing viral propagation u201d means that the titer of a virus in a sample is lowered the reduction may be effected in a variety of manners including partial or total inhibition of viral replication partial or total inhibition of viral protein processing or assembly inhibition of viral entry into or exit from an infected cell and or clearance of the virus from a system via an immune response to the virus wherein ar q r 1 r 3 and r o are as defined above x is o or nh r 2 is h a pharmaceutically acceptable cation or c 1 3 alkyl when x is o and xr 2 is an n acylated amino acid or amino acid ester when x is nh in preferred embodiments r 1 is selected from among cl br.