Towards Anticancer and Antibacterial Agents: Design and Synthesis of 1,2,3-Triazol-quinobenzothiazine Derivatives

In this paper, we describe a new method for synthesizing hybrid combinations of 1,2,3-triazoles with a tetracyclic quinobenzothiazinium system. The developed approach allowed for the production of a series of new azaphenothiazine derivatives with the 1,2,3-triazole system in different positions of the benzene ring. In practice, the methodology consists of the reaction of triazole aniline derivatives with thioquinanthrenediinium bis-chloride. The structure of the products was determined by 1H-NMR, 13C-NMR spectroscopy, and HR-MS spectrometry, respectively. Moreover, the spatial structure of the molecule and the arrangement of molecules in the crystal (unit cell) were determined by X-ray crystallography. The anticancer activity profiles of the synthesized compounds were tested in vitro against human cancer cells of the A549, SNB-19, and T47D lines and the normal NHDF cell line. Additional tests of antibacterial activity against methicillin-sensitive and methicillin-resistant staphylococci, vancomycin-sensitive and vancomycin-resistant enterococci, and two mycobacterial strains were also performed. In fact, the dependence of anticancer and antibacterial activity on the substituent type and its position in the quinobenzothiazinium system was observed. Furthermore, the distance-guided property evaluation was performed using principal component analysis (PCA) and hierarchical clustering analysis (HCA) on the pool of the calculated descriptors. Finally, the theoretically approximated partition coefficients (clogP) were (inter-)correlated with each other and cross-compared with the empirically specified logPTLC parameters.

Towards Property Profiling: SYNTHESIS and SAR Probing of New Tetracyclic Diazaphenothiazine Analogues

A series of new tertiary phenothiazine derivatives containing a quinoline and a pyridine fragment was synthesized by the reaction of 1-methyl-3-benzoylthio-4-butylthioquinolinium chloride with 3-aminopyridine derivatives bearing various substituents on the pyridine ring. The direction and mechanism of the cyclization reaction of intermediates with the structure of 1-methyl-4-(3-pyridyl)aminoquinolinium-3-thiolate was related to the substituents in the 2- and 4-pyridine position. The structures of the compounds were analyzed using ¹H, ¹³C NMR (COSY, HSQC, HMBC) and X-ray analysis, respectively. Moreover, the antiproliferative activity against tumor cells (A549, T47D, SNB-19) and a normal cell line (NHDF) was tested. The antibacterial screening of all the compounds was conducted against the reference and quality control strain Staphylococcus aureus ATCC 29213, three clinical isolates of methicillin-resistant S. aureus (MRSA). In silico computation of the intermolecular similarity was performed using principal component analysis (PCA) and hierarchical clustering analysis (HCA) on the pool of structure/property-related descriptors calculated for the novel tetracyclic diazaphenothiazine derivatives. The distance-oriented property evaluation was correlated with the experimental anticancer activities and empirical lipophilicity as well. The quantitative shape-based comparison was conducted using the CoMSA method in order to indicate the potentially valid steric, electronic and lipophilic properties. Finally, the numerical sampling of similarity-related activity landscape (SALI) provided a subtle picture of the SAR trends.

Photophysical transformations induced by chemical substitution to salicylaldimines

The role of electron-acceptor strength and microenvironment polarity on the photophysical properties of salicylaldimines.

Solvent control in the formation of supramolecular host–guest complexes of isoniazid with p-sulfonatocalix[4]arene

The position of the anti-tuberculosis drug isoniazid inside (endo) or outside (exo) to the macrocyclic cavity of p-sulfonatocalix[4]arene can be regulated by the appropriate choice of the solvent system.

Intermolecular interactions in inclusion complexes

The whole range of interactions can be found between host and guest in supramolecular assemblies from ion-ion interactions, ion-dipole interactions, dipol-dipol interactions through hydrogen bonding, cation-π interactions, π-π stacking to van der Waals forces. Additionally, the same interactions exist between the supramolecular complex and its surrounding, i.e. solvent molecules, neighboring complexes, gases, etc. Recently the interest of scientists in the field of supramolecular chemistry is focused on design and synthesis of water-soluble synthetic macrocyclic ligands which are good receptors for biologically important guest molecules and can mimic the models of biological systems. Studying such complexes may provide new insight into the mechanisms of the formation of similar natural systems and as a consequence will help in better understanding the processes which occur in biological systems and in developing new materials with specific properties and functions. In this presentation the interactions which are stabilizing inclusion complexes of calix[n]arenes and cyclodextrins (host molecules) with guest molecules of biological interest, especially drug molecules will be discussed. This research was partly financed by the European Union within the European Regional Development Fund (POIG.01.01.02-14-102/09)

Molecular Swiss Cheese: new complexes and conformations of p-sulphonato[8]arene

"The crystal structures of the salts of para-sulphonatocalix[8]arene with two flexible guest molecules 1,2-bis(4-pyridyl)-ethane (BPE) and 1,3-bis(4-pyridyl)-propane (BPP) are presented. para-Sulphonatocalix[8]arene molecule adopts new types of conformations: ""double facing cone"" in BPP complex and "up-flat-down" in BPE complex. Although the difference between BPE and BPP is only a presence or absence of a single carbon atom in the central bridge, the structures of their complexes with para-sulphonatocalix[8]arene are remarkably different. While the salt with BPE shows true porosity and can be compared to that of an extremely complex zeolite or to a solid state molecular Swiss Cheese, the second structure with BPP shows no porosity and is of the type of organic clay firstly observed for the sodium salt of para-sulphonato-calix[4]arene [1], and can be compared to a Gruyere Cheese. The structure of the para-sulphonatocalix[8]arene with BPE salt (Figure 1) shows a complex network of interconnecting channels of variable size, one of which contains a BPE cation effectively blocking this channel, the others contain water and solvents and are thus accessible. A total of six different channels are observed in this structure. Gas take-up has been demonstrated, to show the porous nature of the solid. The effect of a single carbon atom between the cations on the complexity of the Supramolecular Organic Framework (SOF), is remarkable. Work is currently underway to study other complexes of para-sulphonatocalix[8]arene with rigid and flexible organic cations and to open up the way to novel SOFs. Figure 1. Solvent accessible surface in para-sulphonatocalix[8]arene and 1,2-bis(4-pyridyl)-ethane complex: view along [001] axis."

Structural characterization of inclusion complexes of para-sulphonato-calix[8]arene with 1,2-bis(4-pyridyl)-ethane and 1,3-bis(4-pyridyl)-propane. New ‘double cone’ and ‘up–flat–down’ conformations of para-sulphonato-calix[8]arene

Two new conformations of para-sulphonato-calix[8]arene have been found in supramolecular complexes with BPE and BPP, the gas take-up has been demonstrated for S8C–BPE complex.

β-Cyclodextrin as the suitable molecular container for isopulegol enantiomers

Isopulegol, an insoluble in water and highly volatile compound, due to its neuroactive properties is a potentially important agent for medical applications. Formation of "host-guest" molecular complexes with cyclodextrins would lead to the increase of its water solubility and bioavailability. Interactions between native cyclodextrins (α, β and γ) and isopulegol enantiomers were studied in solution proving the formation of inclusion complexes for β- and γ-cyclodextrins. For the more stable complexes with β-cyclodextrin crystal structures were obtained showing the formation of molecular capsules forming molecular container able to accommodate two guest molecules.

Amidophenol-modified amphiphilic calixarenes: synthesis, interfacial self-assembly, and acetaminophen crystal nucleation properties

Three amidophenol-modified calixarenes have been produced reacting the parent 5,11,17,23-tetracarboxy-25,26,27,28-tetradodecyloxycalix[4]arene with o-, m-, and p-aminophenol. The produced amphiphiles have been shown to form stable monomolecular Langmuir layers on water. Working on subphases containing 1 mM acetaminophen (APAP), it has been demonstrated that the produced amphiphiles interact with this active pharmaceutically ingredient (API) with a relevant preference for the para-derivative that possesses in its structure substituents that are analogous to the target. Working at supersaturating concentrations of APAP, it has been demonstrated that the so-produced calixarene Langmuir monolayers do favor crystallization of APAP (polymorph I), with a clear effect of the packing density of the amphiphile at the interface on the quantity of produced crystals. Monolayers of the para-derivative have been transferred on solid substrates using the Langmuir-Blodgett technique; the so-produced ultrathin films have been shown to initiate surface crystal nucleation of APAP. The produced solids have been analyzed by single-crystal X-ray crystallography and shown to preferentially grow in the [010] direction.

The Solid-State Inclusion Complex between the Mono-Anion of Calix[4]Arene and Protonated Diamino-Bicycloundecane

Diamino-bicycloundecane mono-deprotonates H-calix[4]arene and the solid-structure of the resulting salt has been determined by X-ray crystallography. Two different complexes are present in the structure with the Diamino-bicycloundecane cation held in the calix[4]arene cavity by CH-p interactions. In the packing there is a hydrogen-bonded polymeric chain. Both the complexes formed layered structures with differing inter-layer distances.

Solid-state interactions of calixarenes with biorelevant molecules

Among all crystalline complexes of calix-type calix[n]arenes those with organic molecules which are biologically relevant are especially of interest due to their potential medical and pharmaceutical applications. The co-crystallization of drugs with water-soluble calixarenes offers the opportunity to modify chemical and physical properties of APIs (active pharmaceutical ingredients) and to control drug conformation. Such co-crystallization can improve solubility, bioavailability and stability of pharmaceutically active molecules and/or eliminate polymorphism. In this article the solid-state interactions between calixarene hosts and biologically relevant guest molecules are summarized for the currently available structures solved by single-crystal X-ray crystallography.

Calorimetric and X-ray studies of clathrate hydrates of tetraisoamylammonium polyacrylates

The structure of clathrate hydrates with tetraisoamylammonium polyacrylate salt incorporated as guest has been studied in this work. Also, quantitative studies on the stability changes of the clathrate hydrates with different degrees of cross-linking of the guest polymer (varied from 0 to 3%) have been conducted. A single crystal X-ray diffraction study of a crystal of the hydrate with linear (uncross-linked) tetraisoamylammonium polyacrylate as guest reveals a hexagonal structure (space group P6m2, a = 12.15 A, c =12.58 A at 100 K) with 39 host framework water molecules per one guest monomeric unit. Powder X-ray diffraction analyses confirm the identity of the above crystal structure of the hydrate with linear guest polymer and the crystal structure of the hydrates with cross-linked guest (hexagonal, a = 12.25 A, c =12.72 A at 276 K). In order to quantitatively determine the stability differences of the hydrates with the included guests having various degrees of cross-linking of the anionic chain, a series of differential scanning calorimetry measurements of the fusion enthalpy of the hydrate samples has been carried out. On the basis of the results obtained, a structural model describing the decrease in the stability of the clathrate hydrates with tetraisoamylammonium polyacrylate guest as a function of the degree of cross-linking of the guest polymer has been suggested.

[(8a,9,9a-eta)-9-(eta5-cyclopentadienyl)-9-nickelafluorenyl](eta5-pentamethylcyclopentadienyl)nickel(II)

The title compound, [Ni(2)(C(5)H(5))(C(10)H(15))(C(12)H(8))] or [Ni(C(10)H(15)){Ni(C(5)H(5))(C(12)H(8))}], is a rare example (and the first obtained from nickelafluorenyllithium) of an analogue of nickelocene in which the central Ni atom is coordinated to one pentamethylcyclopentadienyl ring and one nickelafluorenyl ring. Both rings lie almost parallel to one another: the dihedral angle between the planes which include these rings is 4.4 (1) degrees . Slip parameter analysis indicates that the bonding mode of the central Ni atom to the nickelacyclic ring is between eta(3) and eta(5). Two-dimensional layers of molecules are formed by C-H...pi interactions.

The Structure of the Tetra-Potassium Salt of Calix[4]Arene Dihydroxyphosphonic Acid

The solid-state structure of the tri-potassium calix[4]arene dihydroxyphosphonate salt is presented. In this structure, two potassium cations bridge between layers of dimeric calixarene diphosphonate units and two other potassium cations bridge along the face of the layers. The ubiquitous dimeric association of the calixarenes shows the highest interdigitation value so far observed. As expected, the cations are solvated and are complexed exo with respect to calixarene crown. The octahedral coordination sphere of the potassium cations is formed by two phosphonate groups of the calixarenes and four water molecules. Electrostatic forces represent the major element of interaction in the solid-state system.

Sensitive and selective PET-based diimidazole luminophore for Zn(II) ions: a structure-activity correlation

3-(3-Ethoxymethyl-1H-imidazol-2-yl)-3-(1-ethoxymethyl-1H-imidazol-2-yl)-3H-benzo[de]isochromen-1-one, 4, is a novel photoinduced electron transfer (PET) chemosensor that becomes fluorescent upon binding metal ions and shows a strong preference toward Zn(II) ions. The new bisimidazol PET sensor and its zinc complex were prepared and characterized in terms of their crystal structures, absorption and emission spectra, and orbital energy diagrams. Free 4 is a weakly luminescent species. On the basis of detailed DFT calculations, we suggest that the poor luminescence yield of free 4 originates from its orbital structure in which two pi-orbitals of the two imidazole rings, HOMO and HOMO-1, are situated between two pi-orbitals of the isochromene-one system, HOMO-2 and LUMO. The absorption and emission processes occur between the two pi-orbitals of the isochromene-one system, HOMO-2 and LUMO, and the two pi-imidazole orbitals serve as quenchers for the excited state of the molecule through nonradiative processes. Upon binding Zn(II) ions, 4 becomes a highly luminescent species having a luminescence maximum peaking at 375 nm (lambda(ex) = 329 nm). The significant 900-fold enhancement in luminescence upon binding of the Zn(II) ions is attributed to the stabilization of the pi-orbitals of the imidazole rings upon their engagement in new bonds with the zinc ion. The affinity of 4 to zinc ions in acetonitrile is found to be very high, Ka > 3 x 10(6) M(-1), while with other metals ions, the association constants are considerably weaker.

Diastereoselective Lower Rim (1S)-Camphorsulfonylation as the Shortest Way to the Inherently Chiral Calix[4]arene

[structure: see text]. A diastereomeric mixture of chiral 25-(1S)-camphorsulfonyloxy-26-isopropoxycalix[4]arene 2a (de 15%) and 25-isopropoxy-26-((1S)-10-camphorsulfonyl)calix[4]arene 2b has been obtained by asymmetrical lower rim (1S)-camphorsulfonylation of the monoisopropoxycalix[4]arene. Pure diastereomer 2a has been obtained by simple crystallization, and its absolute configuration has been determinated by X-ray analysis. Enantiomerically pure inherently chiral 5,11-dibromo-26-isopropoxycalix[4]arene 4 has been synthesized by the upper rim dibromination of the diastereomer 2a followed by hydrolytical removal of the auxiliary camphorsulfonyl group.

Anion-Binding Properties of the Tripyrrolemethane Group: A Combined Experimental and Theoretical Study

Tripyrrolemethane- and bistripyrrolemethane-containing systems were recently reported to be efficient and selective hosts for anions. Nevertheless, the basic intrinsic properties of tripyrrolemethane as a ligand for anions have not yet been explored. Here we report the study of the anion-binding properties of the tripyrrolemethane group. We applied a combined experimental and theoretical approach to determine the affinity of the tripyrrolemethane system for different anions in the gas phase, in solution and in the crystalline state. In the crystal, the tripyrrolemethane group forms a number of different complexes with the bromide ion, some involving the participation of more than one ligand species. Despite the very similar basicity of fluoride and dihydrogen phosphate, the tripyrrolemethane ligand exhibits a clear preference for the fluoride anion in solution, which indicates an anion-binding system and not merely deprotonation. Although the affinity of the tripyrrolemethane ligand for other ions was negligible in solution, gas-phase studies show that complexation with larger halide ions is favoured over complexation with fluoride.