Synthesis, Photophysical, and DNA Binding Studies of Fluorescent Tröger’s Base Derived 4-Amino-1,8-naphthalimide Supramolecular Clefts

Synthesis and biological activity evaluation of hydrazone derivatives based on a Tröger's base skeleton

We report the design and synthesis of novel anticancer agents based on bis-hydrazones separated by a rigid Tröger's base skeleton. This novel approach combines a biologically active moiety (hydrazone) with this scaffold (Tröger's base) to construct DNA intercalators. Evaluation of the anticancer activity of these agents using seven cancer cell lines and two healthy cell lines found that several derivatives had potent anticancer activity and excellent selectivity indexes toward cancer cells. The antimicrobial activities were tested on a set of thirteen bacterial stains, but the prepared compounds were not active. Complexation studies using biologically important metal ions demonstrated that these compounds are able to bind Cu(2+), Fe(3+), Co(2+), Ni(2+) and Zn(2+). DNA intercalation studies showed that the compounds themselves do not interact with DNA, but their metallocomplexes do interact, most likely via intercalation into DNA.

Acid promoted synthesis of cyclic 1,3-dione fused symmetrical 2,8-dioxabicyclo[3.3.1]nonanes

Synthesis of symmetrical 2,8-dioxabicyclo[3.3.1]nonanes (4) is accomplished by the reaction of β-enamino ketones (1) and 1,3-cyclohexanediones (2) in AcOH. However, the presence of TFA in toluene gave xanthenes (5).

Photophysical characterisation of Tröger's base molecular scaffolds: a combined theoretical and experimental study

The photophysics of Tröger's base in the ground and excited states was performed by comparing experimental and theoretical properties predicted using TD-DFT calculations.

Unexpected DNA binding properties with correlated downstream biological applications in mono vs. bis-1,8-naphthalimide Ru(ii)-polypyridyl conjugates

The development of two 1,8-napthalimide-conjugated Ru(ii)-polypyridyl complexes which exhibit different DNA binding and photocleavage behavior is presented.

Cyclic aromatic imides as a potential class of molecules for supramolecular interactions

Prospects of stacking interactions of imides beneficial to generation of new soft materials are projected by analysing examples of primary building blocks that provide a basis for understanding at the molecular level.

Photoluminescence imaging of Zn2+in living systems

Advances in PL imaging techniques, such as confocal microscopy, two photon microscopy, lifetime and optical imaging techniques, have made remarkable contributions in Zn²⁺tracking.

Discovery of Tröger's base analogues as selective inhibitors against human breast cancer cell line: design, synthesis and cytotoxic evaluation

A library of structurally diverse Tröger's base analogues has been constructed via unusual amination of methylene bridge employing Vilsmeier-Haack conditions as well as by the incorporation of five and six membered heterocycles on the aromatic core of Tröger's base framework. The constructed structurally diverse frameworks were evaluated for their cytotoxic activities against a panel of three human cancer lines A549 (lung adenocarcinoma), MDAMB-231 (breast) and SK-N-SH (neuroblastoma). From the activity profile obtained, a redesign of Tröger's base analogues led to the construction of more potent molecular entities. The study led to development of a series of compounds with MDAMB-231 cell line specific cytotoxicity. Of the 30 compounds synthesized and evaluated, 7 compounds were found to possess cytotoxicity that is equivalent or better than standard drug doxorubicin against MDAMB-231 cell line while only one compound was found to be active against SK-N-SH cell line.

Spectroscopic study on the interaction between naphthalimide-polyamine conjugates and DNA

The interaction of naphthalimide-polyamine conjugates with herring sperm DNA was studied by UV/vis absorption and fluorescent spectra under physiological conditions (pH=7.4). The observed spectral quenching of compounds by DNA and the displacement of EB from DNA-EB complex by compounds indicated that these naphthalimide-polyamine conjugates could intercalate into the DNA base pairs. The UV test also showed that these compounds caused the conformational alteration of DNA. Further caloric fluorescent tests revealed that the quenching mechanism was a static type, which Ksv of 1-DNA, 2-DNA and 1-DNA-EB, 2-DNA-EB 3-DNA-EB was 1.208×10(4), 7.792×10(3) and 1.712×10(4), 1.287×10(4), 2.874×10(4), respectively, at room temperature. The obtained quenching constant, binding constant and thermodynamic parameters suggested that binding strength was associated with substituted groups on naphthalene backbone, and the type of interaction force included mainly hydrogen bonding and weak van der Waals. The binding process was mainly driven by hydrogen bond and van der Waals. Additionally, the effect of NaCl on compounds-DNA interaction provided further evidence that their interaction modes were dependent on substituted groups.

Expanding the palette of phenanthridinium cations

5,6-Disubstituted phenanthridinium cations have a range of redox, fluorescence and biological properties. Some properties rely on phenanthridiniums intercalating into DNA, but the use of these cations as exomarkers for the reactive oxygen species (ROS), superoxide, and as inhibitors of acetylcholine esterase (AChE) do not require intercalation. A versatile modular synthesis of 5,6-disubstituted phenanthridiniums that introduces diversity by Suzuki–Miyaura coupling, imine formation and microwave-assisted cyclisation is presented. Computational modelling at the density functional theory (DFT) level reveals that the novel displacement of the aryl halide by an acyclic N-alkylimine proceeds by an S(N)Ar mechanism rather than electrocyclisation. It is found that the displacement of halide is concerted and there is no stable Meisenheimer intermediate, provided the calculations consistently use a polarisable solvent model and a diffuse basis set.

The coumarin–pterocarpan conjugate – a natural product inspired hybrid molecular probe for DNA recognition

Thermally induced cascade sigmatropic rearrangement of a butynyloxycoumarin derivative has led to a quick access to the coumarin–pterocarpan hybrid molecule. Biophysical studies together with molecular modeling show that this nature-inspired hybrid molecule is capable of binding to the minor groove of DNA as a non-conventional entity.

Tröger's base quasiracemates and crystal packing tendencies

A family of 7 Tröger's base (TB) compounds that vary in configuration (quasiracemates, racemates, and enantiomers) and chemical substitutions (Me, Cl, and Br) has been investigated.

Facile access to imidazole and imidazolium substituted dibenzo-diazocines

The C₂-symmetrical 2,8- and 4,10-diimidazo methano dibenzo diazocines were synthesized and converted into alkyl imidazolium salts.

A simple and catalyst free one pot access to the pyrazolone fused 2,8-dioxabicyclo[3.3.1]nonanes

Synthesis of a series of novel aryl and heteroaryl fused 2,8-dioxabicyclo[3.3.1]nonanes (3) was accomplished by one pot, catalyst free reaction of 2-hydroxy chalcones (1) with 3-trifluoromethyl substituted pyrazolones (2) in xylene at reflux temperature. The role of –CF₃ in formation of 3 was confirmed by comparing with 3-methyl pyrazolones.

Synthesis, crystal structure and EPR spectroscopic analysis of novel copper complexes formed from N-pyridyl-4-nitro-1,8-naphthalimide ligands

The synthesis of two new monodentate pyridyl based 4-nitro-1,8-naphthalimide ligands and their corresponding Cu-complexes (using various salts) is described. Of these, complexes 1–3 and 5, all gave rise to structures that were characterised by X-ray crystallography and EPR.

Twisted conformations in complexes of N-(3-imidazol-1-yl-propyl)-1,8-naphthalimide and fluorescence properties

A series of complexes of N-(3-imidazol-1-yl-propyl)-1,8-naphthalimide (L) with divalent ions of manganese, cobalt, zinc, cadmium and mercury are structurally characterized.

Highly efficient and practical resolution of 2,3:6,7-dibenzobicyclo[3.3.1]nona-2,6-diene-4,8-dione and stereoselective synthesis of its chiral diamine derivatives

The rigid V-shaped molecule (±)-4 could be efficiently resolved by commercially available BINOL in high enantiomeric excesses.

Synthesis and photophysical evaluation of a pyridinium 4-amino-1,8-naphthalimide derivative that upon intercalation displays preference for AT-rich double-stranded DNA

The synthesis, characterisation and solid state crystal structure of a cationic 4-amino-1,8-naphthalimide derivative (1) are described. The photophysical properties of 1 are shown to vary with the solvent polarity and H-bonding ability. The fluorescence of 1 is enhanced and blue-shifted in its 1:1 complex with 5'-adenosine-monophosphate while it is partially quenched and red-shifted in its complex with 5'-guanosine-monophosphate. Linear and circular dichroism measurements show that 1 binds to double-stranded DNA by intercalation. Comparative UV-visible and fluorescence studies with double stranded synthetic polynucleotides poly(dA-dT)(2) and poly(dG-dC)(2) show that 1 binds much more strongly to the AT polymer; 1 also has a strong preference for A-T rich sequences in natural DNA. Thermal denaturation measurements also reveal a much greater stabilisation of the double-stranded poly(dA-dT)(2) than of natural DNA.