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PubMed2005

Amino acid conjugates of 1,1'-diaminoferrocene. Synthesis and chiral organization.

1,1'-bis(tert-butoxycarbonylamino)ferrocene (6), a protected derivative of 1,1'-diaminoferrocene, has been synthesized by a very convenient method and serves as a synthon for 1,1'-diaminoferrocene. Its structure in solid state and in solution has been studied by NMR and X-ray crystallography. 1,1'-bis(tert-butoxycarbonylamino)ferrocene serves as starting material for the synthesis of amino acid conjugates of L- and D-alanine. The structures of these bioconjugates have been studied by NMR and CD spectroscopy and X-ray crystallography and reveal that the chiral organization of the podant amino acid chains is controlled by the chirality of the attached amino acid. The substituents engage in strong intramolecular H-bonding generating 14-membered H-bonded rings, a motif previously unrealized in ferrocene-amino acid and peptide conjugates.

Amino Acids↗
PubMed2005

Group 11 complexes with unsymmetrical P,S and P,Se disubstituted ferrocene ligands.

The reaction of the unsymmetrical ligands 1-diphenylphosphino-1'-(phenylsulfanyl)ferrocene and 1-diphenylphosphino-1'-(phenylselenyl)ferrocene, Fc(EPh)PPh2(E = S, Se), with several group 11 metal derivatives leads to the synthesis of complexes of the type [MX{Fc(EPh)PPh2}](M = Au, X = Cl, C6F5; M = Ag, X = OTf), (OTf = trifluoromethanesulfonate), [M{Fc(EPh)PPh2}2]X (M = Au, X = ClO4; M = Ag, X = OTf), [M(PPh3){Fc(EPh)PPh2}]OTf (M = Au, Ag), [Au2{Fc(SPh)PPh2}2](ClO4)2, [Au(C6F5)2{Fc(SePh)PPh2}]ClO4, [Au(C6F5)3{Fc(EPh)PPh2}], [Au2(C6F5)6{Fc(SePh)PPh2}] or [Cu{Fc(EPh)PPh2}2]PF6(E = S, Se). In these complexes coordination depends upon the metal centre; with gold it takes place predominantly to the phosphorus atom and with silver and copper to both phosphorus and chalcogen atoms. The treatment of some of the gold complexes with other metal centres affords heterometallic derivatives that in some cases are in equilibrium with the homometallic derivatives. Several compounds have been characterized by X-ray diffraction, four pairs of homologous compounds, yet not a single pair is isotypic. In many of them a three dimensional network is formed through secondary bonds such as hydrogen bonds, Au...Cl or Au...Se interactions. The complex [Ag(OTf){Fc(SePh)PPh2}] forms one-dimensional chains through trifluoromethanesulfonate bridging ligands.

Crystallography, X-Ray↗
PubMed2005

An electrochemical immunosensor using ferrocenyl-tethered dendrimer.

We report here an enzyme-amplified, sandwich-type immunosensor for detecting the biospecific interaction between an antibody and antigen using redox mediation. We employed biotin/anti-biotin IgG as a model immunosensing pair. Partially ferrocenyl-tethered dendrimer (Fc-D), whose ferrocene moiety acts as a redox mediator, was immobilized to the electrode surface by covalent binding between the dendrimer amines and the carboxylic acids of a self-assembled monolayer. The unreacted amines of the immobilized Fc-D were modified with biotin groups to allow the specific binding of goat anti-biotin IgG. Rabbit anti-goat IgG-conjugated alkaline phosphatase was bound to goat anti-biotin IgG to catalyze conversion of p-aminophenyl phosphate monohydrate to p-aminophenol. This product is oxidized to quinoimide by the reduction of ferrocenium back to ferrocene, producing an electrocatalytic anodic current. Cyclic voltammograms and surface plasmon resonance experiments showed that the binding of nonspecific proteins is not significant on the biotinylated Fc-D surface. We also examined the change in peak current according to the concentration of anti-biotin IgG and found that the detection range of this immunosensing scheme is between 0.1 and 30 microg mL(-1).

Animals↗
PubMed2005

Synthesis, structure and assessment of the cytotoxic properties of 2,5-dimethylazaferrocenyl phosphonates.

The reaction of lithiated 2,5-dimethylazaferrocene 1 with diethyl chlorophosphate proceeds to give lateral and ring phosphonate products. The products 2 and 3 were characterized by spectroscopic (1H, 31P{1H} NMR, MS, IR) methods and 3 was treated with W(CO)5(thf) to form a crystalline W(CO)5-complex 4 which was characterized by single-crystal X-ray analysis. The new 2,5-dimethylazaferrocenyl phosphonates were transformed into the corresponding N-methyl iodide salts 5 and 6 in quantitative yields. Both salts are water soluble and stable compounds and an analysis of their cytotoxic and anti-proliferative activity was carried out. Compound 6 possesses anti-metabolic activity which exhibited some preference towards the cancerous HeLa cell line over the non-cancerous NIH 3T3 cell line. These new compounds are the first examples of azaferrrocene (i.e. non-ferrocene) derivatives featuring biologically important phosphonate groups. The preliminary studies into cytotoxic activity indicates that as with ferrocene, azaferrocene can also be regarded as a potential source for organometallic anticancer agents, featuring the iron centre in the +2 oxidation state rather than the often utilized ferrocenium +3 species.

Animals↗
PubMed2005

Amino acid ester salt recognition by ferrocene-based ditopic receptor bearing oligoethylene glycol with pendant bipy subunits: CV, UV-vis and ESR studies.

The novel ferrocene-based ditopic receptor 1 was synthesized. This receptor bears two oligoethylene glycol arms with pendant 2,2'-bipyridine unit at the identical cyclopentadienyl rings, Cu(I) cation binds to 1 to form the 1 : 1 complex (1.Cu(I)) with the cavity consisting of polyether, and the resulting complex acts as a receptor for amino acid ester salts to give the ditopic complex (1.Cu(I).AAOMe-HCl). The 1H NMR spectrum of 1.Cu(I).LeuOMe-HCl exhibits strong broadening at the bipyridine region, and the ESR spectrum of the same sample gives the signals assigned as Cu(II) species. With these data, the binding of 1.Cu(I) towards AAOMe.HCl leads to the conformational change, and the Cu(I) complex is simultaneously oxidized to the Cu(II) complex.

Amino Acids↗
PubMed2006

Clickity-click: highly functionalized peptoid oligomers generated by sequential conjugation reactions on solid-phase support.

N-Substituted glycine peptoid oligomers were used as substrates for azide-alkyne [3 + 2] cycloaddition conjugation reactions and then elaborated through additional rounds of oligomerization and cycloaddition. This novel sequential conjugation technique allowed for the generation of complex peptidomimetic products in which multiple heterogeneous pendant groups were site-specifically positioned along the oligomer scaffold. Studies of a water-soluble estradiol-ferrocene peptoid conjugate demonstrated a potential application for the modular synthesis of biosensors.

Combinatorial Chemistry Techniques↗
PubMed2006

Fluoride anion binding by cyclic boronic esters: influence of backbone chelate on receptor integrity.

A systematic investigation of fluoride anion binding properties as a function of chelate backbone has been carried out for ferrocene functionalised boronic esters of the types FcB(OR)2 and fc[B(OR)2]2 [Fc = ferrocenyl = (eta5-C5H5)Fe(eta5-C5H4); fc = ferrocendiyl = Fe(eta5-C5H4)2]. Cyclic boronic esters containing a saturated five- or six-membered chelate ring are readily synthesized from ferrocene, and selectively bind fluoride via Lewis acid/base chemistry in chloroform solution. The resulting complexes are characterized by relatively weak fluoride binding (e.g.K = 35.8 +/- 9.8 M(-1) for FcBO2C2H2Ph2-S,S), and by cathodic shifts in the ferrocene oxidation potential that form the basis for electrochemical or colorimetric fluoride detection. The fluoride selectivity of these systems is attributed to relatively weak Lewis acidity, resulting in weak F- binding, and essentially no binding of potentially competitive anions. By contrast, more elaborate Lewis acid frameworks based on calix[4]arene (calixH4), such as (FcB)2calix or fcB2calix, do not survive intact exposure to standard fluoride sources (e.g. [nBu4N]F.xH2O solutions in chloroform or acetonitrile). Instead B-O bond cleavage occurs yielding the parent calixarene; the differences between alkoxo- and aryloxo-functionalised derivatives can be rationalised, at least in part, by consideration of the differences in electron donating capabilities of RO- (R = alkyl, aryl).

Boronic Acids↗
PubMed2006

Ferrocene-modified pyrimidine nucleosides: synthesis, structure and electrochemistry.

This paper reports syntheses, crystal structures and electrochemical results for two ferrocene(Fc)-modified pyrimidine nucleosides that could potentially be used for investigating electron transfer in DNA. Fc was directly attached to the 5-position of deoxyuridine and deoxycytidine via the Stille coupling reaction. Fc-modified uridine was incorporated into DNA trinucleotides with standard solid-phase synthesis. The structures of corresponding detritylated compounds were determined by single-crystal X-ray analysis. Electrochemical investigations of all compounds by cyclic voltammetry revealed reversible redox processes.

Crystallography, X-Ray↗
PubMed2006

Synthesis of supramolecular fullerene-porphyrin-Cu(phen)(2)-ferrocene architectures. A heteroleptic approach towards tetrads.

Four supramolecular fullerene-porphyrin-Cu(phen)(2)-ferrocene architectures were accessed by a twofold coordination strategy. At first, the phenanthroline-linked zinc porphyrins , conceived as supramolecular synthons, were combined with a ferrocene module, 3,8-(diferrocenylethynyl)phenanthroline, by a Cu(i)-mediated heteroleptic bisphenanthroline complexation (HETPHEN) protocol to furnish the porphyrin-Cu(phen)(2)-ferrocene aggregates . Subsequently, the fullerene module was incorporated by axial pyridyl coordination to the zinc porphyrin, affording . Their suitability as tetrads was interrogated using electrochemical and photophysical data.

Electrochemistry↗
PubMed1998

Enhanced, simplified glucose sensors: long-term clinical application of wearable artificial endocrine pancreas.

At present, 2 major problems should be solved before long-term application of the wearable artificial endocrine pancreas, the development of a reliable and stable glucose monitoring system and the development of a subcutaneous insulin infusion algorithm. With either a miniaturized extracorporeal glucose monitoring system based on microdialysis sampling method or a ferrocene-mediated needle-type glucose sensor covered with highly biocompatible membrane, poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (poly[MPC-co-BMA]) membrane, subcutaneous glucose concentrations could be monitored for 7 days without any in vivo calibrations, followed by 14 days with one point calibration. Considering the management and safety of the insulin delivery route, subcutaneous insulin infusion is obligatory. With the subcutaneous insulin infusion algorithm using a short acting insulin analogue (Insulin Lispro), near physiological glycemic control could be established in diabetic patients without showing any delayed hyperinsulinemia or hypoglycemia. The wearable artificial endocrine pancreas is now recognized as an excellent therapeutic tool for regulating blood glucose excursions physiologically in ambulatory diabetic patients on a long-term basis.

Animals↗
PubMed2002

Unsymmetrical 1,1'-disubstituted ferrocenes: synthesis of Co(ii), Cu(ii), Ni(ii) and Zn(ii) chelates of ferrocenyl -1-thiadiazolo-1'-tetrazole, -1-thiadiazolo-1'-triazole and -1-tetrazolo-1'-triazole with antimicrobial properties.

Condensation reactions of 1,1''-diacetylferrocene with different heteroaromatic amines such as, 2-amino-1,3,4-thiadiazole, 5-aminotetrazole and 3-amino-1,2,4-triazole to form unsymmetrically 1,1'-disubstituted ferrocenes have been studied. The obtained compounds have been further investigated for their liganding and biological properties upon chelation with Co(II), Cu(II), Ni(II) and Zn(II) metal ions. The synthesized compounds have been characterized by physical, spectral and analytical data and have been screened against pathogenic bacterial strains e.g., Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, showing moderate activity as antibacterials in vitro.

Anti-Bacterial Agents↗
PubMed2005

Organometallic-based antibacterial and antifungal compounds: transition metal complexes of 1,1'-diacetylferrocene-derived thiocarbohydrazone, carbohydrazone, thiosemicarbazone and semicarbazone.

Organometallic-based, 1,1'-diacetylferrocene-derived antibacterial and antifungal thiocarbohydrazone, carbohydrazone, thiosemicarbazone and semicarbazone have been prepared by condensing equimolar amount of 1,1'-diacetylferrocene with thiocarbohydrazide, carbohydrazide thiosemicarbazide and semicarbazide, respectively. These were used as ligands for the preparation of their cobalt (II), copper (II), nickel (II) and zinc (II) metal complexes. All the synthesized ligands and their complexes were characterized by IR, NMR, elemental analyses, molar conductances, magnetic moments and electronic spectral data. These synthesized compounds were screened for their antibacterial activity against Escherichia coli, Bacillus subtillis, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi, and for antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata using the agar-well diffusion method. All the compounds showed good antibacterial and antifungal activity which increased on coordination with the metal ions thus, introducing a novel class of organometallic-based antibacterial and antifungal agents.

Anti-Bacterial Agents↗
PubMed1998

Reactivity of the horseradish peroxidase compounds I and II toward organometallic substrates. A stopped-flow kinetic study of oxidation of ferrocenes.

Reactivity of horseradish peroxidase compounds I and II (HRP-I and HRP-II) toward organometallicic substrates, viz water-soluble ferrocenes RFc (R = COOH and CH2NMe2), has been studied at 25 degrees C, pH 6.0 and ionic strength 0.1 M. The second-order rate constants k2 for the reaction of HRP-I with FcCOOH and FcCH2NMe2 equal (1.00 +/- 0.04) x 10(6) and (0.27 +/- 0.01) x 10(6) M-1 s-1, respectively. The values of k3 for the reaction of HRP-II with FcCOOH and FcCH2NMe2 equal (1.1 +/- 0.1) x 10(4) and (0.25 +/- 0.01) x 10(4) M-1 s-1, respectively. The steady-state kinetic study of the HRP-catalyzed oxidation of the ferrocenes by H2O2 under the same conditions gave the second-order rate constants of (0.94 +/- 0.03) x 10(4) and (0.24 +/- 0.06) x 10(4) M-1 s-1 for FcCOOH and FcCH2NMe2, respectively, which are in a good agreement with k3. The results reported here confirm the proposal that the rate-limiting step of the steady-state oxidation of ferrocenes is the electron transfer from the substrate to HRP-II.

Catalysis↗
PubMed2001

Ferrocene-chloroquine analogues as antimalarial agents: in vitro activity of ferrochloroquine against 103 Gabonese isolates of Plasmodium falciparum.

The in vitro activities of ferrochloroquine, chloroquine, quinine, mefloquine, halofantrine, amodiaquine, primaquine, atovaquone and artesunate were evaluated against Plasmodium falciparum isolates from children with uncomplicated malaria from Libreville (Gabon), using an isotopic, micro, drug susceptibility test. The IC(50) values for ferrochloroquine were in the range 0.43-30.9 nM and the geometric mean IC(50) for the 103 isolates was 10.8 nM (95% CI 8.6-13.5 nM), while the geometric means for chloroquine, quinine, mefloquine, amodiaquine and primaquine were 370 nM, 341 nM, 8.3 nM, 18.1 nM and 7.6 microM, respectively. Ferrochloroquine was active against P. falciparum isolates, 95% of which showed in vitro resistance to chloroquine. Weak positive significant correlations were observed between the responses to ferrochloroquine and that to chloroquine, amodiaquine and quinine, but too low to suggest cross-resistance. There was no significant correlation between the response to ferrochloroquine and those to mefloquine, halofantrine, primaquine, atovaquone or artesunate. Ferrochloroquine may be an important alternative drug for the treatment of chloroquine-resistant malaria.

Animals↗
PubMed2003

In vitro susceptibility to a new antimalarial organometallic analogue, ferroquine, of Plasmodium falciparum isolates from the Haut-Ogooué region of Gabon.

OBJECTIVES: To assess the activity of a new organometallic chloroquine analogue, ferroquine, against numerous Plasmodium falciparum isolates from Gabon. METHODS: The in vitro susceptibility of 116 P. falciparum isolates to chloroquine and ferroquine was assessed using the isotopic microtest. All isolates were from outpatients in the Franceville and Bakoumba medical centres in the province of Haut-Ogooué, south-east Gabon. RESULTS: The in vitro resistance to chloroquine was 51.8% in Franceville and 96.7% in Bakoumba. The IC50 geometric mean (95% CI) of ferroquine against isolates in Franceville was 16.0 (14.4-17.8) nM, with individual values ranging from 1.0 to 47.0 nM; in Bakoumba it was 27.9 (23.4-33.2) nM, with individual values ranging from 1.0 to 62.0 nM. Compared with chloroquine, ferroquine was 5.3 times more active on isolates susceptible to chloroquine, and 13.3 times more active on isolates resistant to chloroquine. A weak positive correlation was observed between responses of these two drugs, but too low to demonstrate cross-resistance. CONCLUSIONS: Ferroquine may be useful as an alternative drug for treating chloroquine-resistant malaria.

Aminoquinolines↗