Aryl ethynyl anthraquinones: a useful platform for targeting telomeric G-quadruplex structures

2,7-Diaryl ethynyl anthraquinones have been synthesized by Sonogashira cross-coupling and evaluated as telomeric G-quadruplex ligands, with good G-quadruplex/duplex selectivity

Quinone Methides as DNA Alkylating Agents: An Overview on Efficient Activation Protocols for Enhanced Target Selectivity

The following review analyzes the most effective activation protocols for the generation of transient electrophilic quinone methides, merged into the recent strategies to achieve recognition and alkylation of nucleic acids. The covalent targeting has to be specific for selected oligonucleotide sequences (sequence-specificity) or for those oligonucleotides capable to fold into supramolecular structures, such as G-quadruplexes (structure-specificity). The reversibility of the DNA alkylation process by QM is reviewed underlining the opportunities (in term of selectivity and delivery) and drawbacks (in term of product characterization of the covalent damage) in the DNA targeting

Vinylidene–Quinone Methides, Photochemical Generation and β-Silicon Effect on Reactivity

Irradiation of 2-alkynylphenols resulted in the generation of vinylidene−quinone methides (QMs), which were detected by laser flash photolysis in organic solvents and aqueous acetonitrile. QMs' spectroscopic properties and electrophilicity were both significantly affected by β-silicon effect. The hydration of the alkynyl moiety was an acid- and base-catalyzed process. The addition of amines was fast, yielding ketimines, with primary amine

Protecting Group Free Synthesis of 6-Substituted Naphthols and Binols

A straightforward route for the preparation of 6-substituted naphthols and 6,6'-disubstituted binols (binol=2,2'-dihydroxy-1,1'-binaphthyl) is presented. The synthesis has been accomplished by a one-step procedure starting from 6-bromo derivatives via direct lithiation with n-BuLi, followed by the addition of several electrophiles

Vinylidene–Quinone Methides, Photochemical Generation and β-Silicon Effect on Reactivity

Irradiation of 2-alkynylphenols resulted in the generation of vinylidene–quinone methides (QMs), which were detected by laser flash photolysis in organic solvents and aqueous acetonitrile. QMs' spectroscopic properties and electrophilicity were both significantly affected by β-silicon effect. The hydration of the alkynyl moiety (22 and 900 M^–1 s^–1 for <b>QM-1</b> and <b>QM-2</b>, in aqueous acetonitrile) was an acid- and base-catalyzed process. The addition of amines was fast (9.2 × 10³ M^–1 s^–1 < <i>k</i>₂ < 1.3 × 10⁸ M^–1 s^–1), yielding ketimines, with primary amines

Hybrid ligand\u2013alkylating agents targeting telomeric G-quadruplex structures

The synthesis, physico-chemical properties and biological effects of a new class of naphthalene diimides (NDIs) capable of reversibly binding telomeric DNA and alkylate it through an electrophilic quinone methide moiety (QM), are reported. FRET and circular dichroism assays showed a marked stabilization and selectivity towards telomeric G4 DNA folded in a hybrid topology. NDI-QMs' alkylating properties revealed a good reactivity on single nucleosides and selectivity towards telomeric G4. A selected NDI was able to significantly impair the growth of melanoma cells by causing telomere dysfunction and down-regulation of telomerase expression. These findings points to our hybrid ligand-alkylating NDIs as possible tools for the development of novel targeted anticancer therapies

Aryl ethynyl anthraquinones: a useful platform for targeting telomeric G-quadruplex structures

Aryl ethynyl anthraquinones have been synthesized by Sonogashira cross-coupling and evaluated as telomeric G-quadruplex ligands, by the FRET melting assay, circular dichroism, the DNA synthesis arrest assay and molecular docking. Both the binding properties and G-quadruplex vs. duplex selectivity are controlled by the structures of the aryl ethynyl moietie

Photogeneration and Reactivity of Naphthoquinone Methides as Purine Selective DNA Alkylating Agents

A one-step protecting-group-free synthesis of both 6-hydroxy-naphthalene-2-carbaldehyde and the bifunctional binaphthalenyl derivative afforded 6-hydroxymethylnaphthalen-2-ol, 6-methylaminomethyl-naphthalen-2-ol, [(2-hydroxy-3-naphthyl)methyl]trimethyl ammonium iodide, and a small library of bifunctional binol analogues in good yields. Irradiation of naphthol quaternary ammonium salt and binol-derivatives at 310 and 360 nm resulted in the photogeneration of the 2,6-naphthoquinone-6-methide (NQM) and binol quinone methide analogues (BQMs) by a water-mediated excited-state proton transfer (ESPT). The hydration, the mono- and bis-alkylation reactions of morpholine and 2-ethanethiol, as N and S prototype nucleophiles, by the transient NQM (λmax 310, 330 nm) and BQMs (λmax 360 nm) were investigated in water by product distribution analysis and laser flash photolysis (LFP). Both the photogeneration and the reactivity of NQM and BQMs exhibited striking differences. BQMs were at least 2 orders of magnitude more reactive than NQM, and they were generated much more efficiently from a greater variety of photoprecursors including the hydroxymethyl, quaternary ammonium salt and several binol-amino acids. On the contrary, the only efficient precursor of NQM was the quaternary ammonium salt. All water-soluble BQM precursors were further investigated for their ability to alkylate and cross-link plasmid DNA and oligonucleotides by gel electrophoresis: the BQMs were more efficient than the isomeric o-BQM (binol quinone methide analogue of 2,3-naphthoquinone-3-methide). Sequence analysis by gel electrophoresis, HPLC, and MS showed that the alkylation occurred at purines, with a preference for guanine. In particular, a BQM was able to alkylate N7 of guanines resulting in depurination at the oligonucleotide level, and ribose loss at the nucleotide level. The photoreactivity of BQM precursors translated into photocytotoxic and cytotoxic effects on two human cancer cell lines: in particular, one compound showed promising selectivity index on both cell line