Papers by enrique melendez
Critical Reviews in Oncology Hematology, 2002
A series of complexes containing titanium, Ti, as a metal center has shown to possess a wide spec... more A series of complexes containing titanium, Ti, as a metal center has shown to possess a wide spectrum of antitumor properties. This series belongs to the non-platinum metal antitumor agents which has been developed mainly in the past 20 years. The bis(β-diketonato)titanium(IV) and titanocene derivatives appear to offer a different alternative for cancer chemotherapy which do not follow the rationale and mechanism of action of the platinum complexes. The hydrolysis of these complexes in aqueous and pseudo aqueous solutions is discussed and the interaction studies of titanium complexes with biomolecules are also presented to unravel the mechanism of action at molecular levels.
Journal of Biological Inorganic Chemistry, 2005
Three new water soluble titanocene–aminoacid complexes have been synthesized via the reaction of ... more Three new water soluble titanocene–aminoacid complexes have been synthesized via the reaction of Cp2TiCl2 and two equivalents of aminoacid (L) in methanol, affording [Cp2TiL 2]Cl2, L=L-cysteine (2), D-penicillamine (3) and L-methionine (4). These complexes have been characterized by 1H, IR and UV-Vis spectroscopies, elemental analysis and cyclic voltammetry. Kinetic studies of ligand hydrolysis have been monitored at low pH using UV-Vis and 1H NMR spectroscopies to assess their stability in aqueous solution. At low pH, aminoacid ligands are lost one order of magnitude faster than cyclopentadienyl. However, at physiological pH, in Tris buffer solution, the complexes decompose rapidly to form an insoluble titanium compound. The affinity of these complexes to apo-transferrin was also investigated to elucidate how the ancillary aminoacid ligands affect the titanium intake by apo-transferrin.
Critical Reviews in Oncology/Hematology, 2002
Cheminform, 1991
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Bulletin des Sociétés Chimiques Belges, 1987
A great variety of reagents have been used to carry out the transformation of thiourea. to 2-amin... more A great variety of reagents have been used to carry out the transformation of thiourea. to 2-aminobenzothiazole derivatives(1) (the so-called Hugershoff synthesis). Among them, halogens either in an inert or acidic(2)solvent and other halogenating agents (thionyl(3) or sulfuryl(4) chloride) can ...
Synthetic Communications, 1989
Journal of Heterocyclic Chemistry, 1990
A general method for the synthesis of the title compounds 5, 6, 10, 14, 15 and 16 is reported. Al... more A general method for the synthesis of the title compounds 5, 6, 10, 14, 15 and 16 is reported. All of them were prepared in one step from readily available dimethyl N,N'-(arylene)bisdithiocarbamates 1 and red mercury(II) oxide. The superiority of these reagents over the corresponding diisothiocyanates 7 and the synthetic utility of tetramethyl N,N'-(arylene)bisdithiocarbonimidates 2 are also discussed.
Molecular Crystals and Liquid Crystals, 1987
A new type of mesogen intermediate, the 5-n-alkoxy-2-pyridinecarboxaldehydes, has been synthesize... more A new type of mesogen intermediate, the 5-n-alkoxy-2-pyridinecarboxaldehydes, has been synthesized. Three homologous series of derivatives were prepared and their mesomorphic properties studied: Schiff's monobases (5-n-alkoxy-2-pyridylmethylene-4′-n-alkoxyanilines), Schiff's dihases (bis-(5′-n-alkoxy-2′-pyridylmethylene)-1,4-phenylenediamines) and azines (his-(5-n-alkoxy-2-pyridylmethylene)-hydrazines). These derivatives are all mesogenic. The principal phases formed are nematic but, to a lesser extent, smectic C phases occur also. In some cases smectic A, B, G
Acta Chemica Scandinavica, 1985
Journal of Electroanalytical Chemistry, 2014
Entrapment of dsSS-DNA into the polypyrrole-polyvinyl sulphonate (dsSS-DNA-PPy-PVS) film over ind... more Entrapment of dsSS-DNA into the polypyrrole-polyvinyl sulphonate (dsSS-DNA-PPy-PVS) film over indium-tin-oxide (ITO) coated glass has been designed to detect titanium and platinum drugs, titanocene dichloride and cisplatin. The disposable dsSS-DNA-PPy-PVS/ITO biosensor was characterized by cyclic voltammetry, attenuated total reflectance Infrared spectroscopy and atomic force microscopy. Amperometric studies by cyclic voltammetry using, dsSS-DNA-PPy PVS/ITO biosensor, demonstrated the ability of this biosensor to detect these metallic drugs in millimolar concentration by monitoring the decrease of the guanine oxidation signal as a result of the DNA damage. The concentration range detected for titanocene dichloride is 0.25 to 1.5 mM and for cisplatin is 0.06 to 1.0 mM.
Journal of Molecular Structure: THEOCHEM, 1987
The molecular geometry of benzalazine derivatives was studied by spectroscopic and semiempirical ... more The molecular geometry of benzalazine derivatives was studied by spectroscopic and semiempirical MO (MNDO, CNDO/P) methods. The existence of a strong intramolecular H-bond (7-10 kcal mol") was determined by 'H NMR spectroscopy in molecules having a hydroxy group in the ortho position with reference to the diazine central bridge. A study of the H-bonds using the MNDO method proved to be unsatisfactory, whereas the results obtained by the CNDO/S method were in excellent agreement with experimental values. Both theoretical calculations (CNDO/S) and experimental evidence (UV and 'H NMR) show that the existence of a first H-bond weakened the force of a second in benzalazines.
Tetrahedron Letters, 1974
Pour discuter la t&s interessante Les a et des sels de diazonium a (1) il est b + H 0' + a + H 0.... more Pour discuter la t&s interessante Les a et des sels de diazonium a (1) il est b + H 0' + a + H 0. 3 -2 N'ayant trouve dans la bquilibre, nous avons determine les pK, des + H3C NrN reactivite chimique et photochimique des diasoasonecessaire de connartre la positidn de L'QquiLibre litterature aucune don&e quantitative sur cet cinq sels de diazonium suivants : 252(4,02) 313(4,20) 251(3,76) 249(3,77) 235(3,70) H3C
Metal-Based Drugs, 2009
Synthesis, structure, electrochemistry and theoretical studies of Ru(II) and Pt(II) complexes bea... more Synthesis, structure, electrochemistry and theoretical studies of Ru(II) and Pt(II) complexes bearing CNC-pincer carbene ligand [1,1 0 -[2,6-pyridinylbis(methylene)]bis[3-methylbenzimidazolium)bromide], 1ÁH 2 Br 2 have been described. The compounds were fully characterized by elemental analysis, NMR, UV-Vis spectroscopy and finally the solid state structure of [Ru(1) 2 ][PF 6 ] 2 , 2, was confirmed by X-ray diffraction studies. The Pt(II)-NHC complex [Pt(1)Cl][PF 6 ], 3 has been synthesized by silver-carbene transfer method and geometry was optimized theoretically. Cyclic voltammetry studies revealed Ru(II)/Ru(III) reversible oxidation couple at 0.57 V and Pt(II)/Pt(IV) couple at 0.48 V. Anticancer activities of complexes 2 and 3 have been studied upon breast (MCF7), colon (HCT116) and lung (A549) cancer cell lines using MTT assay. IC 50 values are compared with cisplatin and carboplatin, among 2 and 3, complex 2 is more potent than complex 3.
Magnetic Resonance in Chemistry, 1985
Journal of Organometallic Chemistry, 2009
A series of new pseudopeptidic macrolides 2a-f based on an amino alcohol were synthesized and eva... more A series of new pseudopeptidic macrolides 2a-f based on an amino alcohol were synthesized and evaluated for in vitro antibacterial and antifungal activities. The structure-activity relationships of these compounds were studied and the results showed that compounds 2a and 2d exhibited moderate antibacterial activity against Staphylococcus aureus, Bacillus subtilis and Escherichia coli, whereas compound 2e showed potent antifungal activity against all the fungal species tested, showing a promising broad-spectrum antifungal activity. All the compounds have been studied in vitro for the hemolytic activity as a measure of their cytotoxicity, showing that these compounds have low lytic properties.
Journal of Organometallic Chemistry, 2011
The possible inclusion complexes of Cp(2)NbCl(2) into calixarenes hosts have been investigated. T... more The possible inclusion complexes of Cp(2)NbCl(2) into calixarenes hosts have been investigated. The existence of a true inclusion complex in the solid state was confirmed by a combination of NMR, ab-initio calculations, thermogravimetric analysis, FTIR, Raman and PXRD. Ab-initio calculations, (1)H NMR solution and solid state (13)C CP MAS NMR results demonstrated that p-sulfonic calix[6]arene does form an inclusion complex with Cp(2)NbCl(2). Raman spectroscopy showed, for the inclusion compound of p-sulfonic calix[6]arene-Cp(2)NbCl(2), a band between 500-850 cm(-1) characteristic of Nb-O vibration. This result suggests that Nb(V) may engage in coordination with the oxygen of the sulfonate group, as part of the host-guest interaction. However, it is important to mention that the niobocene dichloride (Cp(2)NbCl(2)) dissolves in water and undergoes oxidation and hydrolysis processes to yield Cp(2)NbCl(2)(OH) species. For that reason this band does not exclude that the Nb-O band belongs to Cp(2)NbCl(2)(OH). Solid State (13)C CP MAS NMR and solution (1)H NMR spectroscopies together with ab-initio results showed that Cp(2)NbCl(2) is included in the p-sulfonic calix[6]arene cavity, with both Cp rings inside the cavity. In contrast, the solution (1)H NMR results demonstrated that calix[6]arene does not form inclusion complex with Cp(2)NbCl(2) in CDCl(3) solution. Cp(2)NbCl(2) is not included in the calix[6]arene cavity, possibly due to the lack of sulfonate heads which promote Nb-O interactions and assist the inclusion of Cp(2)NbCl(2) into the cavity.
Journal of Organometallic Chemistry, 2004
A series of Ru(acac) 2 (g 4 -diene) complexes containing cis-and trans-diene coordination have be... more A series of Ru(acac) 2 (g 4 -diene) complexes containing cis-and trans-diene coordination have been investigated by cyclic voltammetry to correlate structural bonding and conformation patterns of diene ligands with redox behaviors. The solid-state structure of Ru(acac) 2 (2,3-dimethyl-1,3-butadiene) has been determined by single crystal X-ray diffraction methods. Ru(acac) 2 (2,3-dimethyl-1,3butadiene) crystallizes in the monoclinic space group C2/c with a = 12.368(2) Å , b = 17.0600(2) Å , c = 16.0110(2) Å , b = 98.4405(10)°and V = 3341.38(10) Å 3 for Z = 8. A structural comparison between several Ru-trans-g 4 -diene complexes and Ru-g 4 -1,3-cyclohexadiene revealed no difference in the Ru-C(diene) bond distances. However, through cyclic voltammetry experiments these species demonstrated different redox behavior, as function of the coordinated diene ligand.
Journal of Organometallic Chemistry, 1996
The reaction of Ru(acac)3 in ethanol in the presence of dienes (diene = 2,5-dimethyl-2,4-hexadien... more The reaction of Ru(acac)3 in ethanol in the presence of dienes (diene = 2,5-dimethyl-2,4-hexadiene, isoprene, 1,2,4,5-tetramethyl-1,4-cyclohexadiene) with zinc as reducing agent affords Ru(acac)2(diene) complexes. For the acyclic diene ligands, the Ru(acac)2 unit exhibits a preference for the trans-diene coordination. The structures for the 2,5-dimethyl-1,3-hexadiene and 1,2,4,5-tetramethyl-1,4-cyclohexadiene derivatives have been determined crystallographically. The Ru(acac)2(hexadiene) complex crystallizes in the monoclinic space group
Journal of Organometallic Chemistry, 2012
The Journal of Organic Chemistry, 1984
... Carlos Cativiela, Maria D. Diaz de Villegas, Jose A. Mayoral, and Enrique MelBndez* Departmen... more ... Carlos Cativiela, Maria D. Diaz de Villegas, Jose A. Mayoral, and Enrique MelBndez* Department of Organic Chemistry, University of Zaragoza, Zaragoza, Spain ... (6) Meyers, A. I. "Heterocycles in Organic Synthesis"; Wiley: New (7) von Auwers, K.; Kanig, F. Ann. ...
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Papers by enrique melendez