title: Use of isotopically chiral [4'-13C]penciclovir and 13C NMR to determine the specificity and absolute configuration of penciclovir phosphate esters formed in HSV-1 and HSV-2 infected cells and by HSV-1-encoded thymidine kinase.
abstract: Penciclovir is a potent antiherpesvirus agent which is highly selective due to its phosphorylation only in virus infected cells. Phosphorylation of one of the hydroxymethyl groups of penciclovir (PCV) creates a chiral centre leading to the possible formation of (R)- and (S)-enantiomers. The absolute configuration and stereospecificity of the PCV-phosphates produced in cells infected with herpes simplex viruses types 1 and 2 (HSV-1 and HSV-2), as well as by HSV-1-encoded thymidine kinase, were determined using isotopically chiral [4'-13C]PCV precursors and 13C NMR spectroscopy of the isolated metabolites. The absolute configuration of penciclovir-triphosphate (PCV-TP) produced in HSV-1 infected cells was shown to be S with an enantiomeric purity of greater than 95%. However, in contrast fo HSV-1-infected cells in which none of the (R) enantiomer was detected, about 10% of (R)-PCV-TP was produced in HSV-2-infected cells. Phosphorylation of PCV by HSV-1-encoded thymidine kinase was found to give 75% (S)- and 25% (R)-PCV-monophosphate. The proportion of the (S)-isomer appears to be amplified in the subsequent phosphorylations leading to the triphosphate.
authors.affiliation: SmithKline Beecham Pharmaceuticals, Epsom, Surrey, England.
authors.forename: R A
authors.initials: RA
authors.lastname: Vere Hodge
authors.forename: S J
authors.initials: SJ
authors.lastname: Darlison
authors.forename: D L
authors.initials: DL
authors.lastname: Earnshaw
authors.forename: S A
authors.initials: SA
authors.lastname: Readshaw
mesh_terms: D000212:Acyclovir / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D002250:Carbon Radioisotopes; D002460:Cell Line; D004952:Esters; D006147:Guanine; D018259:Herpesvirus 1, Human / Q000201:enzymology / Q000378:metabolism*; D018258:Herpesvirus 2, Human / Q000201:enzymology / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D004952:Esters; C053539:penciclovir; D006147:Guanine; D013937:Thymidine Kinase; D000212:Acyclovir