Two classes of azido-modified pyrimidine nucleosides were synthesized as potential radiosensitizers; one class is 5-azidomethyl-2′-deoxyuridine (AmdU) and cytidine (AmdC), while the second class is 5-(1-azidovinyl)-2′-deoxyuridine (AvdU) and cytidine (AvdC). The addition of radiation-produced electrons to C5-azido nucleosides leads to the formation of π-aminyl radicals followed by facile conversion to σ-iminyl radicals either via a bimolecular reaction involving intermediate α-azidoalkyl radicals in AmdU/AmdC or by tautomerization in AvdU/ AvdC. AmdU demonstrates effective radiosensitization in EMT6 tumor cells.
Transition metal-catalyzed halosulfonylation of 5-ethynyl uracil nucleosides provided (E)-5-(1-chloro-2-tosylvinyl)uridines. Tetrabutylammonium fluoride-mediated direct CH arylation of 5-iodouracil nucleosides with furan or 2-heptylfuran gave 5-furyl-substituted nucleosides without the necessity of using the organometallic substrates. These two classes of 5-substituted uracil nucleosides as well their corresponding ester derivatives were tested against a broad range of DNA and RNA viruses and the human immunodeficiency virus (HIV). The 3',5'-di-O-acetyl-5-(E)-(1-chloro-2-tosylvinyl)-2'-deoxyuridine (24) inhibited the growth of L1210, CEM and HeLa cancer cells in the lower micromolar range. The (β-chloro)vinyl sulfone 24 and 5-(5-heptylfur-2-yl)-2'-deoxyuridine (10) displayed micromolar activity against varicella zoster virus (VZV). The 5-(5-heptylfur-2-yl) analog 10 and its 3',5'-di-O-acetyl-protected derivative showed similar activity against the cytomegalovirus (CMV). The 5-(fur-2-yl) derivatives of 2'-deoxyuridine and arabino-uridine inhibited the replication of herpes simplex virus (HSV) TK strains while the 5-(5-heptylfur-2-yl) derivative 10 displayed antiviral activity against the parainfluenza virus.
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