Photochemical synthesis, intercalation with DNA and antitumor evaluation in vitro of benzo[d]thiazolo[3,2-a]quinolin-10-ium derivatives.

A new anticancer benzo[d]thiazolo[3,2-a]quinolin-10-ium derivatives were synthesized and characterized. Anticancer evaluation in vitro against four cancer cell lines including adenocarcinomic human alveolar basal epithelial cells (A549), hepatocellular carcinoma (HepG2), prostate cancer (PC3) and breast cancer (MCF7) indicated that some of prepared compounds shows higher selectivity in comparison with doxorubicin. DNA interaction studies by optical, CD, NMR spectroscopies showed the high affinity of benzothiazole ligands towards the dsDNA. The ligand-DNA interaction occurs through the intercalation of benzo[d]thiazolo[3,2-a]quinolin-10-ium derivatives with nucleic acid. The investigation of formed ligand - DNA complexes by docking and molecular dynamic calculations was applied for analysis of the relationship between structure and anticancer activity. The results suggested that benzo[d]thiazolo[3,2-a]quinolin-10-ium derivatives might serve as a novel scaffold for the future development to new antitumor agents.

The regioselective [2 + 2] photocycloaddition reaction of 2-(3,4-dimethoxystyryl)quinoxaline in solution.

Herein, the [2 + 2] photocycloaddition between two molecules of (E)-2-(3,4-dimethoxystyryl)-quinoxaline (1) in an acetonitrile solution to form only one cyclobutane isomer out of eleven possible isomers is described. The observed photocycloaddition reaction is reversible; thus, the studied photocycloaddition reaction can be considered as a photoreversible photochromic process. The removal of two methoxy groups from the (E)-2-(3,4-dimethoxystyryl)quinoxaline (1) structure produces compound 2, which participates only in the photoisomerization reaction. The change of the quinoxaline residue in 1 to quinoline results in the formation of compound 3, which demonstrates the regioselective oxidization electrocyclic transformation through the formation of a novel C-N bond.

Regiospecific Photocyclization of Mono- and Bis-Styryl-Substituted N-Heterocycles: A Synthesis of DNA-Binding Benzo[c]quinolizinium Derivatives.

Regiospecific C-N photocyclization of mono- and bis-styryl-substituted N-heterocycles was investigated. We demonstrated that the C-N regiospecificity of the photoinduced electrocyclization is a general feature of ortho-styryl-substituted N-heterocycles comprising one and two nitrogen atoms. This phototransformation provides a straightforward synthesis of the pharmaceutically important benzo[c]quinolizinium cation and its aza-analogues. Noticeably, bis-styryl derivatives undergo only one-fold cyclization with the second styryl fragment remaining uninvolved in the cyclization process. Photocyclization products of monostyryl derivativatives intercalate into calf thymus DNA (ct DNA), whereas photocyclization products of bis-styryl derivativatives possess a mixed binding mechanism with ct DNA. The results can be used for development of novel DNA-targeting chemotherapeutics based on benzo[c]quinolizinium derivatives.

Regiospecific C-N photocyclization of 2-styrylquinolines.

Regiospecific C-N photocyclization of 2-styrylquinolines resulting in formation of potentially biologically active quino[1,2-a]quinolizinium derivatives was investigated. The presence of strong electron-donating groups in the phenyl ring reveals to be a crucial factor managing photocyclization effectiveness. Introduction of a crown ether moiety allows changing the photoreaction parameters by means of complexation with Mg(ClO4)2.

Metal ions drive thermodynamics and photochemistry of the bis(styryl) macrocyclic tweezer.

UV/Vis and NMR spectroscopy were used for the structural elucidation and thermodynamic and photochemical studies of the metal-coordinated crown-containing macrocyclic tweezer (E,E)-1. The bis(styryl) tweezer (E,E)-1 formed two types of complexes with magnesium(II): a 1:1 intramolecular asymmetric sandwich complex [(E,E)-1].Mg(2+) and a 1:2 complex [(E,E)-1].(Mg(2+))(2). In the former case, there is direct cation intramolecular exchange (0.299 s(-1), DeltaG(++)=69.4 kJ mol(-1)) between two parts of the bis(styryl) tweezer (E,E)-1. Addition of barium(II) to the bis(styryl) tweezer (E,E)-1 led to an intramolecular centrosymmetric sandwich 1:1 complex [(E,E)-1].Ba(2+). Irradiation of [(E,E)-1]Ba(2+) afforded reversible intramolecular [2pi+2pi] photocyclization with excellent stereoselectivity and quantitative yield. In contrast, irradiation of [(E,E)-1].(Mg(2+))(2) resulted in reversible stepwise E,Z-isomerization.

Cucurbit[7]uril complexes of crown-ether derived styryl and (bis)styryl dyes.

In this paper, we report the interaction of the CB[7] molecular container with crown ether styryl and (bis)styryl dyes 1-6. The interaction of monostyryl dyes (1 and 2) with CB[7] results in the formation of 1:1 complexes where the CB[7] molecule is located on the region of the guest encompassing the pyridinium ring, C=C double bond, and a portion of the aryl ring of benzocrown ethers 1 and 2. For (bis)styryl dyes (3-5), the formation of two types of complexes with composition dye.CB[7].dye and CB[7].dye.CB[7] was confirmed by a combination of optical and electrospray ionization mass spectroscopy (ESI-MS) methods. In the case of (bis)styryl dye (6), both 2:1 and 1:1 compositions 6.CB[7].6 and CB[7].6 were formed. Complex formation is accompanied by substantial changes in the optical characteristics of the dyes and formation of long-lived excimer species. We tested the stimuli responsiveness of this system in response to metal ions. We find that the metal ions prefer to bind to the electrostatically negative ureidyl C=O portals of the CB[7] rather than with the crown ether moiety of the styryl dyes.

Photoresponsive dendron-like metallocomplexes of the crown-containing styryl derivatives of 2,2'-bipyridine.

We studied 15-crown-5 ether mono- and bis(styryl) derivatives of 2,2'-bipyridine ( and ) as a scaffold to construct photoresponsive complexes possessing metallodendrimer structure. The synthesis and optical properties of one dimensional (1D) Ca(2+)-containing and octahedral 3D Zn(2+)-containing complexes with crowned styryl derivatives of 2,2'-bipyridine are described. Bimetallic Ca(2+), Zn(2+)-containing complexes of and possess well-defined structures and particular optical characteristics. The effective size of the complexes was estimated by diffusion-ordered NMR spectroscopy (DOSY) by measuring translation diffusion coefficients. The NMR data on the compositions of the formed complexes are in full agreement with those obtained by an optical method. The properties of the zinc polypyridyl complexes are modified by intermolecular interactions between the crown ether center and the metal ions, so they are potentially useful in the preparation of chemical sensors.