Azido- and Triazolyl-modified Nucleoside/tide Analogues: Chemistry, Fluorescent Properties, and Anticancer Activities

Authors

Zhiwei WenFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Chemistry

First Advisor's Name

Stanislaw F. Wnuk

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Kevin O'Shea

Second Advisor's Committee Title

committee member

Third Advisor's Name

Kathleen Rein

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

David Becker

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Anthony J. McGoron

Fifth Advisor's Committee Title

committee member

Keywords

azide, aminyl radical, iminyl radical, anticancer, hypoxia, radiosensitizer, triazole, fluorescent, nucleoside analogues

Date of Defense

6-25-2018

Abstract

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 (Φ_F) of 44% while 8‑TrzdG had Φ_F 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.

Identifier

FIDC006844

ORCID

0000-0002-0821-1369

Recommended Citation

Wen, Zhiwei, "Azido- and Triazolyl-modified Nucleoside/tide Analogues: Chemistry, Fluorescent Properties, and Anticancer Activities" (2018). FIU Electronic Theses and Dissertations. 3789.
https://digitalcommons.fiu.edu/etd/3789