title: Synthesis of multiply-labeled [15N3,13C1]-8-oxo-substituted purine bases and their corresponding 2'-deoxynucleosides.
abstract: Stable isotope-labeled analogues of oxidatively modified purine bases are required as internal standards for accurate quantitation of free radical induced damage in DNA using the isotope-dilution GC/MS technique. For this reason, we report on a facile and expedient method to synthesize the isotope-labeled oxidized DNA bases 8-oxoguanine (8-oxo-Gua, 5a) and 8-oxo-adenine (8-oxo-Ade, 5b). Both routes have in common the introduction of two exocyclic 15N isotopes simultaneously by halogen displacement of chlorine-substituted pyrimidines with [15N]-benzylamine. Debenzylation is achieved by either catalytic hydrogenation or treatment with aluminium chloride in benzene. An additional isotope is incorporated by nitrosation with 15N-labeled sodium nitrite. Cyclocondensation of the triamines with 13C-labeled urea then affords 5a and 5b in overall yields of 34% and 27%, respectively, and each with four isotope labels and at least 99 atom % excess. A further one-step enzyme catalyzed coupling of the C8 adducted purines with 2'-deoxyribose furnishes the isotope-labeled 2'-deoxynucleosides 2'-deoxy-7,8-dihydro-8-oxoguanosine (8-oxo-dGuo) and 2'-deoxy-7,8-dihydro-8-oxoadenosine (8-oxo-dAdo).
authors.affiliation: Nestec Ltd., Nestlé Research Centre, Lausanne, Switzerland.
authors.forename: R H
authors.initials: RH
authors.lastname: Stadler
authors.forename: A A
authors.initials: AA
authors.lastname: Staempfli
authors.forename: L B
authors.initials: LB
authors.lastname: Fay
authors.forename: R J
authors.initials: RJ
authors.lastname: Turesky
authors.forename: D H
authors.initials: DH
authors.lastname: Welti
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003853:Deoxyribonucleosides / Q000138:chemical synthesis*; D008401:Gas Chromatography-Mass Spectrometry; D011687:Purines / Q000138:chemical synthesis*
chemical_list: D003853:Deoxyribonucleosides; D011687:Purines