New modified nucleoside 5 '-triphosphates: synthesis, properties towards DNA polymerases, stability in blood serum and antiviral activity

A series of new nucleoside 5'-triphosphate mimetics, 2, 3, 5, Ci, 8-10, mod ified at the glycone and all three phophate residues, have been synthesised and studied. These compounds only bear the enzymatically labile anhydride bond between the alpha and beta phosphorus atoms. The preparative chemistry involved the preparation of phosphonic salts 30, 31 and 32 and coupling of these species to the morpholidate 33. The mechanism of formation of some o f the intermediates 'en route' to 27 and 28 is discussed. All of the target compounds demonstrated high stability in human blood serum with half lives towards hydrolysis of up to 4.5 days. Some of these nucleoside triphosphon ates have been shown to be selective inhibitors of DNA synthesis catalysed by retroviral reverse transcriptases and terminal deoxynucleotidyl transfer ases. They inhibited replication of the artificial virus containing Moloney murine leukemia virus reverse transcriptase in infected cell culture, prob ably due to the inhibition of a reverse transcription step of a genomic RNA . Compared to the triphosphonates, the corresponding monophosphonates demon strated decreased antiviral activity by 1-2 orders of magnitude. This impli es that the triphosphonates inhibit virus replication directly, rather than by a two-step mechanism based on their hydrolysis to the monophosphonates and subsequent intracellular diphosphorylation. Being totally independent o f the enzymatic phosphorylation pathways of the host cell, the compounds un der study may also be able to inhibit retrovirus reproduction both in kinas e deficient cell lines and in the intercellular blood media.