Doctor of Philosophy (PhD)
First Advisor's Name
Stanislaw F. Wnuk
First Advisor's Committee Title
Second Advisor's Name
Second Advisor's Committee Title
Third Advisor's Name
Third Advisor's Committee Title
Fourth Advisor's Name
Fourth Advisor's Committee Title
Fifth Advisor's Name
Anthony J. McGoron
Fifth Advisor's Committee Title
azide, aminyl radical, iminyl radical, anticancer, hypoxia, radiosensitizer, triazole, fluorescent, nucleoside analogues
Date of Defense
Two classes of C5 azido-modified pyrimidine nucleosides were synthesized and explored as radiosensitizers. The 5-azidomethyl-2'-deoxyuridine (AmdU) was prepared from thymidine and converted to its cytosine counterpart (AmdC). The 5-(1-azidovinyl) modified 2'-deoxyuridine (AvdU) and 2'-deoxycytidine (AvdC) were prepared employing regioselective Ag-catalyzed hydroazidation of 5-ethynyl pyrimidine substrates with TMSN3. AmdU and AmdC were converted to 5'-triphosphates AmdUTP and AmdCTP, and incorporated into DNA-fragments via polymerase-catalyzed reaction during DNA replication and base excision repair. Radiation-mediated prehydrated electrons formed in homogeneous aqueous glassy (7.5 M LiCl) systems in the absence of oxygen at 77 K led to site-specific formation of π-type aminyl radicals (RNH•) from AmdU, AmdC, AvdU, and AvdC. The ESR spectral studies and DFT calculations showed RNH• undergo facile conversion to thermodynamically more stable σ-type iminyl radicals, R=N•. For AmdU, conversion of RNH• to R=N• was bimolecular involving α-azidoalkyl radical as intermediate; however, for AvdU, RNH• tautomerized to R=N•. Our work provides the first evidence for the formation of RNH• attached to C5 position of azidopyrimidine nucleoside and its facile conversion to R=N• under reductive environment. These aminyl and iminyl radicals can generate DNA damage via oxidative pathways. The azido-nucleosides were successfully applied as radiosensitizers in EMT6 cancer cells in both hypoxic and normoxic conditions. To explore the generation and reactivity of 2'‑deoxyguanosin-N2-yl radical (dG(N2-H)•) postulated to generate from guanine moiety towards •OH, 2-azido-2'-deoxyinosine (2-N3dI) was prepared by conversion of 2-amino group in protected dG into 2-azido via diazotization with tert-butyl nitrite followed by displacement with azide and deprotection. The investigation of dG(N2-H)• generated from 2-N3dI and its subsequent reactions using ESR will be discussed.
Cycloaddition between 5-ethynylpyrimidine or 8-ethynylpurine nucleosides and TMSN3 in the presence of Ag2CO3, CuI, or CuSO4/sodium ascorbate provided N-unsubstituted 1,2,3-triazol-4-yl analogues of the parental DNA bases (i.e. 5-TrzdU, 5‑TrzdC, 8-TrzdA, and 8-TrzdG). These novel triazolyl nucleosides showed excellent fluorescent properties: 8-TrzdA exhibits the highest quantum yield (ΦF) of 44% while 8‑TrzdG had ΦF of 9%. The 5-TrzdU and 5-TrzdC showed a large Stokes shift of ~110 nm. The application of these fluorescent nucleosides to cell imaging and DNA modifications will also be discussed.
Wen, Zhiwei, "Azido- and Triazolyl-modified Nucleoside/tide Analogues: Chemistry, Fluorescent Properties, and Anticancer Activities" (2018). FIU Electronic Theses and Dissertations. 3789.
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