On the reactivity of mRNA Cap0: C-H oxidative addition of 7-methylguanosine to Pt0 and base pairing studies

Synthesis, Base Pairing Properties, and Biological Activity Studies of Platinum(II) Complexes Based on Uracil Nucleosides

The synthesis and base pairing properties of platinum complexes based on uridine and deoxyuridine nucleosides and preliminary studies of their antiproliferative activity are described. Platinum(II) uridine and deoxyuridine complexes were synthesized by C-I oxidative addition to Pt(0)(PPh3)4. First, the synthesis was performed with protected nucleosides to generate complexes 1 and 2, which were deprotected under basic conditions, affording complexes 3 and 4 in good yields. The synthesis with the unprotected nucleosides was also performed and provided complexes 3 and 4 effectively. Base pairing interactions were measured for complex 1, either for self-base pairing or for the Watson-Crick base pair. Complex 1 undergoes self-base pairing in CDCl3, and this aggregation was found not to be dependent on metalation. Contrastingly, for the Watson-Crick base pair with adenine, base pairing was also observed, but metalation was found to affect hydrogen bonding considerably. Complexes 3 and 4 and the corresponding ligand precursors were evaluated for their antiproliferative activity against human glioblastoma cell line U-251. The compounds showed IC50 values of 3.30 (3) and 1.84 (4) μM but are also toxic for nontumorous cell lines.

Development of Triazoles and Triazolium Salts Based on AZT and Their Anti-Viral Activity against HIV-1

We report herein a set of 3'-azido-3'-deoxythymidine (AZT) derivatives based on triazoles and triazolium salts for HIV-1 infection. The compounds were synthesized via click chemistry with Cu(I) and Ru(II) catalysts. Triazolium salts were synthesized by reaction with methyl iodide or methyl triflate in good yields. The antiviral activity of the compounds was tested using two methodologies: In method one the activity was measured on infected cells; in method two a pre-exposure prophylaxis experimental model was employed. For method one the activity of the compounds was moderate, and in general the triazolium salts showed a decreased activity in relation to their triazole precursors. With method two the antiviral activity was higher. All compounds were able to decrease the infection, with two compounds able to clear almost all the infection, while a lower antiviral activity was noted for the triazolium salts. These results suggest that these drugs could play an important role in the development of pre-exposure prophylaxis therapies.

Synthesis of Platinum(II) N-Heterocyclic Carbenes Based on Adenosine

Organometallic derivatization of nucleosides is a highly promising strategy for the improvement of the therapeutic profile of nucleosides. Herein, a methodology for the synthesis of metalated adenosine with a deprotected ribose moiety is described. Platinum(II) N-heterocyclic carbene complexes based on adenosine were synthesized, namely N-heterocyclic carbenes bearing a protected and unprotected ribose ring. Reaction of the 8-bromo-2′,3′,5′-tri-O-acetyladenosine with Pt(PPh₃)₄ by C8−Br oxidative addition yielded complex 1, with a Pt^II centre bonded to C-8 and an unprotonated N7. Complex 1 reacted at N7 with HBF₄ or methyl iodide, yielding protic carbene 2 or methyl carbene 3, respectively. Deprotection of 1 to yield 4 was achieved with NH₄OH. Deprotected compound 4 reacted at N7 with HCl solutions to yield protic NHC 5 or with methyl iodide yielding methyl carbene 6. Protic N-heterocyclic carbene 5 is not stable in DMSO solutions leading to the formation of compound 7, in which a bromide was replaced by chloride. The cis-influence of complexes 1–7 was examined by ³¹P{¹H} and ¹⁹⁵Pt NMR. Complexes 2, 3, 5, 6 and 7 induce a decrease of ¹J_Pt,P of more than 300 Hz, as result of the higher cis-influence of the N-heterocyclic carbene when compared to the azolato ligand in 1 and 4.