Enzymatic phosphorylation of the antiherpetic agent 9-[(2,3-dihydroxy-1-propoxy)methyl]guanine

Abstract

The antiherpetic agent 9-[(2,3-dihydroxy-1-propoxy)methyl]guanine (iNDG) is phosphorylated by HSV1 thymidine kinase, and its phosphorylated products inhibit DNA polymerase activity. iNDG exists in two enantiomeric forms, each with a primary and a secondary hydroxyl; thus, a number of possibilities for preferential phosphorylation exist, which were explored in this study. HSV1 thymidine kinase phosphorylates the primary hydroxyl of both the R and the S isomers of iNDG. This was established by comparison with analogues in which either the primary or the secondary hydroxyl was replaced by fluorine or hydrogen and also by a study of the NMR spectrum of the monophosphate. GMP kinase phosphorylates the R and the S monophosphates to the respective diphosphates. Further phosphorylation, however, is much more efficient with the S than with the R isomer. Furthermore, (S)-iNDG triphosphate is a more potent inhibitor of HSV1 DNA polymerase than (R)-iNDG triphosphate. These differences in the biochemical specificities of the two isomers account for the observed higher antiviral potency of (S)-iNDG as compared to that of (R)-iNDG.

An Alternative Approach to Isoganciclovir: A Prominent Impurity in the Antiviral Drug Ganciclovir

“…), but substantially less effective than ganciclovir 2 . This higher efficacy of 2 is due to its higher degree of solubility in water as well as its bioavailability [ 2 , 3 ]. Further improvement has been reported where 2 was converted into its prodrug, valganciclovir hydrochloride 4 , an L-valyl ester of ganciclovir that exists as a mixture of two diastereomers.…”

(Z)- and (E)-2-(1,2-Dihydroxyethyl)methylenecyclopropane Analogues of 2′-Deoxyadenosine and 2′-Deoxyguanosine. Synthesis of All Stereoisomers, Absolute Configuration, and Antiviral Activity

“…Regarding the mechanism of antiviral action of active 1,2-dihydroxyethyl analogues, we hypothesize that the phosphorylation cascade generally applicable for activation of nucleosides (including methylenecyclopropane analogues), phosphate → diphosphate → triphosphate, is also operative here. Because none of the compounds is active against HSV-1 or HSV-2, viral thymidine kinase likely seems unable to effect the first phosphorylation in contrast to ganciclovir analogue 11 where the hydroxymethyl group is phosphorylated by this enzyme . There is evidence that methylenecyclopropanes 1b , 2b , and 3b are phosphorylated by the action ,− of HCMV-encoded phosphotransferase pUL97, and this appears to be the case with ent - 12b as well.…”

“…Because none of the compounds is active against HSV-1 or HSV-2, viral thymidine kinase likely seems unable to effect the first phosphorylation in contrast to ganciclovir analogue 11 where the hydroxymethyl group is phosphorylated by this enzyme 10. There is evidence that methylenecyclopropanes 1b, 2b and 3b are phosphorylated by the action3,22–25 of HCMV-encoded phosphotransferase pUL97 and this appears to be the case with ent -12b as well.…”

“…We determined that 9-[(2,3-dihydroxy-1-propoxy)methyl]guanine ( 11 ) would be a good starting point for such a design. Structurally, it is a positional isomer of ganciclovir ( 10 ) with a strong potency against herpes simplex viruses 1 and 2 (HSV-1, HSV-2) and HCMV. , The S -enantiomer of 11 is more potent than the R -enantiomer. A design of methylenecyclopropane analogues based on compound 11 is stereochemically more complex.…”

The Enantioselectivity of Enzymes Involved in Current Antiviral Therapy Using Nucleoside Analogues: A New Strategy?

“…Experiments with purified HSV-1 TK have confirmed these results, and the phosphorylation of GCV catalysed by this enzyme gave only (S)-GCV monophosphate (Karkas et al, 1987), whereas the phosphorylation of PCV was found by NMR analysis of the reaction medium to give 75% (S)-and 25% (R)-PCV monophosphates (Vere . HSV-1 TK phosphorylates the primary hydroxyl group of both the (R)-and (S)-enantiomers of the antiherpetic agent 9-[(2,3-dihydroxy-1-propoxy)methyl]guanine (Karkas et al, 1986). Recently, the crystal structures of HSV-1 TK complexed with various ligands [D-dT and ATP (Wild et al, 1995), DdT or GCV (Brown et al, 1995), acyclovir or PCV, ADP or D-dTMP (Champness et al, 1998), and D-dT or 5-IdUMP (Wild et al, 1997)] have been disclosed.…”