Click Chemistry Derived Hexa-ferrocenylated 1,3,5-Triphenylbenzene for the Detection of Divalent Transition Metal Cations.

The 1,3-dipolar cycloaddition reaction (click chemistry approach) was employed to create a hexa-ferrocenylated 1,3,5-triphenylbenzene derivative. Leveraging the presence of metal-chelating sites associated with 1,2,3-triazole moieties and 1,4-dinitrogen systems (ethylenediamine-like), as well as tridentate chelating sites (1,4,7-trinitrogen, diethylene triamine-like) systems, the application of this molecule as a chemosensor for divalent transition metal cations was investigated. The interactions were probed voltammetrically and spectrofluorimetrically against seven selected cations: iron(II) (Fe2+), cobalt(II) (Co2+), nickel(II) (Ni2+), copper(II) (Cu2+), zinc(II) (Zn2+), cadmium(II) (Cd2+), and manganese(II) (Mn2+). Electrochemical assays revealed good detection properties, with very low limits of detection (LOD), for Co2+, Cu2+, and Cd2+ in aqueous solution (0.03-0.09 µM). Emission spectroscopy experiments demonstrated that the title compound exhibited versatile detection properties in solution, specifically turn-off fluorescence behavior upon the addition of each tested transition metal cation. The systems were characterized by satisfactory Stern-Volmer constant values (105-106 M-1) and low LOD, especially for Zn2+ and Co2+ (at the nanomolar concentration level).

Development of 5-fluorouracil-dichloroacetate mutual prodrugs as anticancer agents.

5-Fluorouracil (5-FU) is one of the most widely applied chemotherapeutic agents with a broad spectrum of activity. However, despite this versatile activity, its use poses many limitations. Herein, novel derivatives of 5-FU and dichloroacetic acid have been designed and synthesized as a new type of codrugs, also known as mutual prodrugs, to overcome the drawbacks of 5-FU and enhance its therapeutic efficiency. The stability of the obtained compounds has been tested at various pH values using different analytical techniques, namely HPLC and potentiometry. The antiproliferative activity of the new 5-FU derivatives was assessed in vitro on SK-MEL-28 and WM793 human melanoma cell lines in 2D culture as well as on A549 human lung carcinoma, MDA-MB-231 breast adenocarcinoma, LL24 normal lung tissue, and HMF normal breast tissue as a multicellular 3D spheroid model cultured in standard (static) conditions and with the use of microfluidic systems, which to a great extent resembles the in vivo environment. In all cases, new mutual prodrugs showed a higher cytotoxic activity toward cancer models and lower to normal cell models than the parent 5-FU itself.

Application of Monoferrocenylsumanenes Derived from Sonogashira Cross-Coupling or Click Chemistry Reactions in Highly Sensitive and Selective Cesium Cation Electrochemical Sensors.

This paper reports the synthesis and characterization of novel monoferrocenylsumanenes obtained by means of the Sonogashira cross-coupling or click chemistry reaction as well as their application in cesium cation electrochemical sensors. A new synthetic protocol based on Sonogashira cross-coupling was developed for the synthesis of monoferrocenylsumanene or ethynylsumanene. The click chemistry reaction was introduced to the sumanene chemistry through the synthesis of 1,2,3-triazole containing monoferrocenylsumanene. The designed synthetic methods for the modification of sumanene at the aromatic position proved to be efficient and proceeded under mild conditions. The synthesized sumanene derivatives were characterized by detailed spectroscopic analyses of the synthesized sumanene derivatives. The supramolecular interactions between cesium cations and the synthesized monoferrocenylsumanenes were spectroscopically and electrochemically investigated. Furthermore, the design of the highly selective and sensitive cesium cation fluorescence and electrochemical sensors comprising the synthesized monoferrocenylsumanenes as receptor compounds was analyzed. The tested cesium cation electrochemical sensors showed excellent limit of detection values in the range of 6.0-9.0 nM. In addition, the interactions between the synthesized monoferrocenylsumanenes and cesium cations were highly selective, which was confirmed by emission spectroscopy, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and cyclic voltammetry.

Effective voltammetric tool for simultaneous detection of MMP-1, MMP-2, and MMP-9; important non-small cell lung cancer biomarkers.

Simultaneous detection of multiple biomarkers can allow to reduce the costs of medical diagnostics, and thus improve the accuracy and effectiveness of disease diagnosis and prognosis. Here, for the first time, we present a low-cost, simple, and rapid method for simultaneous detection of three matrix metalloproteinases (MMP-1, MMP-2, and MMP-9) that play important roles in the progression of lung cancer. The sensor matrix was constructed using a G2 polyamidoamine dendrimer (PAMAM) containing amino, carboxyl, and sulfhydryl groups. The recognition process was based on specific enzymatic cleavage of the Gly-Ile peptide bond by MMP-1, Gly-Leu bond by MMP-2, and Gly-Met bond by MMP-9, and monitoring was done by square wave voltammetry. The activity of metalloproteinases was detected based on the change of current signals of redox receptors (dipeptides labeled with electroactive compounds) covalently anchored onto the electrode surface. The conditions of the biosensor construction, including the concentration of receptors on the sensor surface and the time of interaction of the receptor with the analyte, were carefully optimized. Under optimal conditions, the linear response of the developed method ranged from 1.0⋅10-8 to 1.0 mg⋅L-1, and the limit of detection for MMP-1, MMP-2, and MMP-9 was 0.35, 0.62, and 1.10 fg⋅mL-1, respectively. The constructed biosensor enabled us to efficiently profile the levels of active forms of MMP-1, MMP-2, and MMP-9 in tissue samples (plasma and lung and tumor extracts). Thus, the developed biosensor can aid in the early detection and diagnosis of lung cancer.

Ferrocene-triazole conjugates: do we know why they are biologically active?

The bioorganometallic chemistry of ferrocene has been gaining significance in recent years. This review presents ferrocene-triazole conjugates displaying significant biological properties. The conjugates have been synthesized via azide-alkyne cycloaddition reactions. The data are summarized according to the type of activity (anticancer, antibacterial and/or antifungal, antiprotozoal, and other effects). The results of studies concerning the understanding of the role of the ferrocene core in their biological activity are highlighted. While generally the mode of action of these organometallic species remains unclear, the importance of redox properties of ferrocene has been postulated in several cases.

Novel drug design framework as a response to neglected and emerging diseases.

A new de novo drug design procedure, applicable in the circumstances of scarcity of experimental data, is proposed. The proposed method integrates de novo and fragment-based drug design approaches. This protocol is uncomplicated, uses openly available resources and can be used to design new molecules that would inhibit the newly discovered or under researched targets. The new potential inhibitors are modelled based on energy minima of small molecules in the binding site. The designed structures are modified following an in-house developed, unambiguous algorithm. These modifications improve predicted binding affinities and pharmacokinetic properties of the designed compounds. The suitability of the proposed drug design approach is confirmed by molecular dynamics simulations, and analysis of both binding modes and binding energies of drug candidates (calculated using MM/PBSA method). Lastly, alternative retrosynthetic approaches to the drug candidates are proposed.Communicated by Ramaswamy H. Sarma.

Poly(amidoamine) dendrimer immunosensor for ultrasensitive gravimetric and electrochemical detection of matrix metalloproteinase-9.

Monitoring the level of matrix metalloproteinase-9 (MMP-9) and inhibiting its expression is important for the diagnosis and treatment of various diseases. However, the analysis of MMP-9 is challenging owing to its very low content in the blood, especially at the early stages of diseases. Therefore, we developed an ultrasensitive and easy-to-use immunosensor based on a three-dimensional (3D) bioplatform for the determination of the total MMP-9 concentration in plasma. The used 3D bioplatform (G2 poly(amidoamine) dendrimer; PAMAM) improved the sensitivity of the determination by significantly expanding the surface area of the receptor layer. The antigen-antibody recognition process was controlled by quartz crystal microbalance with dissipation (QCM-D) and electrochemical impedance spectroscopy (EIS). The effect of the orientation of antibody molecules in the sensing layer on the work parameters of the immunosensor was analyzed using unmodified PAMAM (PAMAM-NH2) and PAMAM functionalized with -COOH groups (PAMAM-COOH). The developed immunosensor based on PAMAM-NH2 was characterized by a lower detection limit (LOD = 2.0 pg⋅mL-1) and wider analytical range (1·10-4 - 5 µg⋅mL-1 for EIS and QCM-D) compared to PAMAM-COOH immunosensor (EIS: 1·10-4 - 0.5 µg⋅mL-1; QCM-D: 5·10-4 - 0.5 µg⋅mL-1). The functionality of the proposed device was verified in spiked plasma. The recoveries determined in commercial human and rat plasma and noncommercial rat plasma were very close to the value of 100% and in the range of 96-120% for Au/PAMAM-NH2/Ab and Au/PAMAM-COOH/Ab immunosensors, respectively. The designed analytical devices showed high selectivity and sensitivity without the use of any amplifiers such as metal nanoparticles or enzymes.

Formylation of a metathesis-derived ansa[4]-ferrocene: a simple route to anticancer organometallics.

Formylation of ansa[4]-ferrocene, obtained through the ruthenium-catalysed olefin metathesis, yields two separable, planar chiral 1,3- and 1,2-ansa-ferrocene aldehydes. Single-crystal X-ray structure analysis reveals that both regioisomers crystallize with spontaneous resolution of the racemate in the chiral P212121 space group with one molecule in the asymmetric unit. The major 1,3-isomer was further transformed into a conjugate with 1,2,3-triazole and uracil using "click" chemistry as the key synthetic step. This inorganic-organic hybrid displays anticancer activity (MCF-7, A549, MDA-MB-231 cell lines) with EC50 values comparable to those for cisplatin.

New insight into nucleo α-amino acids - Synthesis and SAR studies on cytotoxic activity of ß-pyrimidine alanines.

Three series of the ß-pyrimidine alanines, including willardiine - a naturally occurring amino acid, were prepared from the l-serine-derived sulfamidates. Compounds 3b, 4a and 4b demonstrated antiproliferative activity toward the studied cancer cell lines, albeit the effect of these compounds on human brain astrocytoma MOG-G-CCM cells was more significant than on human neuroblastoma SK-N-AS cells. The cytosine analog of willardiine, compound 4b, reduced viability of MOG-G-CCM cells with EC50 = 36 ± 2 µM, more effectively than AMPA antagonist GYKI 52466. Willardiine showed possible capability of affecting invasiveness of glioblastoma U251 MG cells with no effect on their viability and morphology. Compound 3d, the ethyl ester of willardiine, featured activity toward binding domain hHS1S2I of the GluR2 receptor. Docking analysis revealed that the location mode of compound 3d at the S1S2 domain of hGluR2 (PDB ID: 3R7X) might differ from that of willardiine.

Supramolecular Interactions between ß-Cyclodextrin and the Nucleobase Derivatives of Ferrocene.

Novel conjugates of ferrocene with uracil, 5-fluorouracil, tegafur, or acyclovir are reported. Their synthesis involved (i) the azide-alkyne 1,3-dipolar cycloaddition or (ii) the formation of the ester linkage. For the first time, we present an in-depth insight into the supramolecular interactions between ß-cyclodextrin and ferrocene-nucleobase derivatives. Spectroscopic and voltammetric analyses performed within this work suggested that the ferrocene or adamantane unit of the conjugates interacted with the ß-cyclodextrin's inner cavity. The methods applied for the supramolecular studies included 1H-1H ROESY NMR, 1H NMR titration, Fourier-transform infrared spectroscopy, cyclic voltammetry, fluorescence spectra titration, and 1H DOSY NMR. 1H DOSY NMR was also employed to evaluate the apparent binding constants for all the complexes. The ferrocene-acyclovir conjugate Fc-5 featured the highest apparent binding constant value among all the complexes tested.

Potential bioisosteres of ß-uracilalanines derived from 1H-1,2,3-triazole-C-carboxylic acids.

The 1H-1,2,3-triazole-originated derivatives of willardiine were obtained by: (i) construction of the 1H-1,2,3-triazole ring in 1,3-dipolar cycloaddition of the uracil-derived azides and the carboxylate-bearing alkynes or α-acylphosphorus ylide, or (ii) N-alkylation of the uracil derivative with the 1H-1,2,3-triazole-4-carboxylate-derived mesylate. The latter method offered: (i) reproducible results, (ii) a significant reduction of amounts of auxiliary materials, (iii) reduction in wastes and (iv) reduction in a number of manual operations required for obtaining the reaction product. Compound 6a exhibited significant binding affinity to hHS1S2I ligand-binding domain of GluR2 receptor (EC50 = 2.90 µM) and decreased viability of human astrocytoma MOG-G-CCM cells in higher extent than known AMPA antagonist GYKI 52466.

Covalent mechanochemical functionalization of carbon-encapsulated iron nanoparticles towards the improvement of their colloidal stability.

The mechanochemical covalent functionalization of carbon-encapsulated iron nanoparticles (CEINs) is reported. Unprotected sugars (mannose, galactose, ß-cyclodextrin) and amino sugars (glucosamine and chitosan) were successfully conjugated to the surface of CEINs. The developed grinding-induced methods employ (i) the 1,3-dipolar cycloadditions of nitrile oxides or azomethine ylides and (ii) amidation-type reactions with the inclusion of carboxyl-functionalized CEINs and amino sugars. All the developed mechanochemical processes are fast (reaction time 10 min) and result in high degrees of coverage (7.3-31.5 wt%). The presented functionalization routes also constitute easy to perform and environmentally improved protocols. Moreover, the use of toxic organic solvents is not required. A comprehensive study on the colloidal stability of the sugar-functionalized CEINs is also included in this work. The results of the turbidimetric analyses reveal that both grinding-induced formation of amide bonds and the cycloadditions of sugar moieties to the surface of CEINs result in the significant improvement of their colloidal stability. The highest stability of the aqueous dispersion was found for CEINs functionalized with ß-cyclodextrin. The comparative studies between the classical wet approach and the grinding-induced functionalization of CEINs show that the herein developed environmentally improved method increases the colloidal stability three times. The crucial role of the mechanochemical approach in the covalent functionalization of CEINs and the improvement of their colloidal stability is discussed in this work.

Addition of azomethine ylides to carbon-encapsulated iron nanoparticles.

The Prato reaction was applied for the covalent introduction of a variety of organic moieties onto carbon-encapsulated iron nanoparticles. The developed method is versatile and employs a broad range of commercially available reactants, including both aromatic and aliphatic aldehydes. The reported functionalization route provides high functionalization yields (ca. 12-21 wt%).

Multicomponent reactions in nucleoside chemistry.

This review covers sixty original publications dealing with the application of multicomponent reactions (MCRs) in the synthesis of novel nucleoside analogs. The reported approaches were employed for modifications of the parent nucleoside core or for de novo construction of a nucleoside scaffold from non-nucleoside substrates. The cited references are grouped according to the usually recognized types of the MCRs. Biochemical properties of the novel nucleoside analogs are also presented (if provided by the authors).

Synthesis of novel aza-analogues of tiazofurin with 2-[5,5-bis(hydroxymethyl)pyrrolidin-2-yl] framework as sugar mimic.

The novel aza-analogues of tiazofurin (TZF) with 2-[5,5-bis(hydroxymethyl)pyrrolidin-2-yl] moiety, as sugar mimic, were synthesized from O,O-cyclohexylidene derivative of 4,4-bis(hydroxymethyl)-4-nitrobutanal in multi-gram scale. The synthetic route consisted of three stages: (i) the synthesis of corresponding derivative of 5,5-bis(hydroxymethyl)pyrrolidine-2-carbonitrile, (ii) the construction of ethyl thiazole-2-carboxylate part by the conversion of the pyrrolidine-2-carbonitrile into the N-trifluoroacetyl derivative followed by cyclocondensation with L-cysteine ethyl ester and then by dehydrogenation, and (iii) the final transformation of the ethyl thiazole-4-carboxylate into the aza-analogues of TZF. The TZF aza-analogues were evaluated for their antiviral activities in cell-culture-based assays.

Studies on the synthesis of N'-acetyl aza-analogues of ganciclovir-unexpected liability of N'-(2-hydroxyethyl)-azanucleosides under basic conditions.

The O'-pivaloyl diesters of N'-acetyl-azanucleosides were obtained from N-[1,3-di(pivaloyloxy)prop-2-yl]-N-(pivaloyloxymethyl)acetamide and a silylated nucleobase under Vorbruggen's conditions. Unexpectedly, de-pivaloylation of the diesters under basic conditions afforded the corresponding nucleobase and N-acetylserinol. Mechanistic investigations showed that these products result from the following cascade of spontaneous transformations initiated by the mono de-pivaloylation of the starting diesters. N'-Deacetylation of the resultant mono-esters via the intramolecular N-O acetyl migration is the key step of the cascade; the corresponding NH-azanucleosides in the form of O-acetyl-O'-pivaloyl diesters are formed. Fragmentation of these diester intermediates gives the nucleobase and O-acetyl-O'-pivaloylserinol. Conversion of the latter to N-acetylserinol involves the selective O-N acetyl migration followed by de-pivaloylation of the resulting N-acetyl-O-pivaloylserinol.

Synthesis and antiviral activity evaluation of acyclic 2'-azanucleosides bearing a phosphonomethoxy function in the side chain.

Acyclic 2'-azanucleosides with a phosphonomethoxy function in the side chain were obtained by coupling of diethyl {2-[N-(pivaloyloxymethyl)-N-(p-toluenesulfonyl)amino]ethoxymethyl}phosphonate with the pyrimidine nucleobases via the Vorbrüggen-type protocol. The compounds were evaluated in vitro for activity against a broad variety of RNA and DNA viruses.

Synthesis and antiviral evaluation of acyclic azanucleosides developed from sulfanilamide as a lead structure.

The acyclic azanucleosides with 2-, 3-, or 4-aminobenzenesulfonyl function at the nitrogen atom of the sugar mimic were prepared by coupling of 2-, 3-, or 4-nitro-N-(2-pivaloyloxyethyl)-N-(pivaloyloxymethyl)benzenesulfonamide with the silylated pyrimidine nucleobases followed by the reduction of the nitro group with sodium dithionite in aqueous solution or the palladium-catalysed transfer hydrogenation. The azanucleosides were evaluated for, but found to be devoid of, activity against several RNA- and DNA-viruses in vitro.

Synthesis and antiviral properties of aza-analogues of acyclovir.

Aza-analogues of Acyclovir were obtained from N-(2-pivaloyloxyethyl)-N-(pivaloyloxymethyl)-p-toluenesulfonamide via a one-pot base silylation/nucleoside coupling procedure. The antiviral activities of all aza-nucleosides in vitro against a variety of viruses were evaluated. None of these compounds displayed any specific antiviral effects.