Efficient inhibition of iron superoxide dismutase and of Trypanosoma cruzi growth by benzo[g]phthalazine derivatives functionalized with one or two imidazole rings

The synthesis and trypanosomatic behavior of a new series of 1,4-bis(alkylamino)benzo[g]phthalazines 1−4 containing the biologically significant imidazole ring are reported. In vitro antiparasitic activity against Trypanosoma cruzi epimastigotes is remarkable, especially for compound 2, whereas toxicity against Vero cells is very low. Conversion of epimastigotes to metacyclic forms in the presence of the tested compounds causes significant decreases in the amastigote and trypomastigote numbers. Fe-SOD inhibition is noteworthy, whereas effect on human Cu/Zn-SOD is negligible.The authors thank the Spanish CICYT for the financial support

In vivo trypanosomicidal activity of imidazole- or pyrazole-based benzo[ g ]phthalazine derivatives against acute and chronic phases of chagas disease

The in vivo trypanosomicidal activity of the imidazole-based benzo[g]phthalazine derivatives 1−4 and of the new related pyrazole-based compounds 5 and 6 has been studied in both the acute and chronic phases of Chagas disease. As a rule, compounds 1−6 were more active and less toxic than benznidazole in the two stages of the disease, and the monosubstituted derivatives 2, 4, and 6 were more effective than their disubstituted analogs. Feasible mechanisms of action of compounds 1−6 against the parasite have been explored by considering their inhibitory effect on the Fe-SOD enzyme, the nature of the excreted metabolites and the ultrastructural alterations produced. A complementary histopathological analysis has confirmed that the monosubstituted derivatives are less toxic than the reference drug, with the behavior of the imidazole-based compound 4 being especially noteworthy.The authors thank the Santander-Universidad Complutense Research Program (Grant GR58/08-921371-891), the Spanish MEC Project (Grant CGL2008-03687-E/BOS), and the MCINN Projects (CTQ2009-14288-C04-01 and Consolider CSD2010-00065) for financial support

1,4-Bis(alkylamino)benzo[g]phthalazines able to form dinuclear complexes of Cu(II) which as free ligands behave as SOD inhibitors and show efficient in vitro activity against Trypanosoma cruzi

The synthesis of a new series of 1,4-bis(alkylamino)benzo[g]phthalazines 1–3 is reported, and their ability to form dinuclear complexes with Cu(II) assayed. The geometry of the complexes is dependent on the nature of the electron-donor sites at the sidechains. Compounds 1 and 2, that contain sp3 or sp2 nitrogens at the end of the alkylamino groups, originate monopodal dinuclear complexes which seem to include endogenous OH bridges, and the sidechains seem to actively participate in complexation. However, the substitution of nitrogen by oxygen in 3 leads to a tripodal dinuclear complex in which the sidechains are not involved. The in vitro antiparasitic activity on Trypanosoma cruzi epimastigotes and amastigotes and the SOD activity inhibition have been evaluated for compounds 1–3, and, as expected, 1 and 2 show in all cases relevant results, whereas 3 is always the less active among the three substrates tested.The authors thank the Spanish Comision Interministerial de Ciencia y Tecnologia for the economical support given to this work (SAF99-0066)

Hydrogen-bond-mediated self-assembly of 26-membered diaza tetraester crowns of 3,5-disubstituted 1 h -pyrazole. Dimerization study in the solid state and in CDCl3 solution

By using an improved synthetic method reported earlier, the cyclic stannoxanes obtained from RN-diethanolamine (R = Me, Bu) and dibutyltin oxide have been reacted with 1H-pyrazole-3,5-dicarbonyl dichloride to afford 26-membered diaza tetraester crowns (1, R = Me; 3, R = Bu) and 39-membered triaza hexaester crowns (2, R = Me; 4, R = Bu). The new structures were identified from their analytical and spectroscopic (1H and 13C NMR, FAB-MS, and/or ESI-MS) data. Both diaza tetraester crowns (1 and 3), containing two 1H-pyrazole units, self-assemble into dimeric species through the formation of four hydrogen bonds involving the two NH pyrazole groups and the two tertiary amine groups of both crowns, as proved by X-ray crystallography and NMR analysis. Preliminary NMR, ESI-MS, MALDI-TOF-MS, and molecular modeling studies suggest that, in CDCl3 solution, 1 interacts with ethyleneurea (ETU), affording 1:1, 2:1, and 2:2 1-ETU complexes. © 2011 American Chemical Society.Financial support from the Spanish Ministry of Science and Innovation (CTQ2009-14288-CO4-01 and CONSOLIDER INGENIO 2010 CSD2010-00065 Projects and Fondos FEDER) is gratefully acknowledged. ’Peer Reviewe

New 1H-pyrazole-containing polyamine receptors able to complex L-glutamate in water at physiological pH values

The interaction of the pyrazole-containing macrocyclic receptors 3,6,9,12,13,16,19,22,25,26- decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 1[L1], 13,26-dibenzyl-3,6,9,12,13,16,- 19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 2[L2], 3,9,12,13,16,22,- 25,26-octaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 3[L3], 6,19-dibenzyl-3,6,9,12,13,- 16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 4[L4], 6,19-diphenethyl- 3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 5[L5], and 6,19-dioctyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 6[L6] with L-glutamate in aqueous solution has been studied by potentiometric techniques. The synthesis of receptors 3-6[L3-L6] is described for the first time. The potentiometric results show that 4[L4] containing benzyl groups in the central nitrogens of the polyamine side chains is the receptor displaying the larger interaction at pH 7.4 (Keff ) 2.04 104). The presence of phenethyl 5[L5] or octyl groups 6[L6] instead of benzyl groups 4[L4] in the central nitrogens of the chains produces a drastic decrease in the stability [Keff ) 3.51 102 (5), Keff ) 3.64 102 (6)]. The studies show the relevance of the central polyaminic nitrogen in the interaction with glutamate. 1[L1] and 2[L2] with secondary nitrogens in this position present significantly larger interactions than 3[L3], which lacks an amino group in the center of the chains. The NMR and modeling studies suggest the important contribution of hydrogen bonding and ð-cation interaction to adduct formation.This work is devoted to the memory of Prof. Manuel Lora-Tamayo. Financial support by the Spanish “Comisio´n Interministerial de Ciencia y Tecnologı´a” (CICYT, Proyects SAF-99-0063, and BQU2003-09215-CO3-01) is gratefully acknowledged.Peer reviewe

CuII and ZnII coordination chemistry of pyrazole-containing polyamine receptors - Influence of the hydrocarbon side chain length on the metal coordination

The synthesis of a new macrocyclic receptor (L4) containing two 3,5-dimethylpyrazole units connected by dipropylenetriamine bridges is reported for the first time; pH-metric titrations indicate that L4 shows six protonation steps in the pH range 2−11. In the absence of metal ions, the pyrazole moieties are not involved in acid-base processes in this pH range. Addition of CuII and ZnII results in deprotonation of the pyrazole moieties which act as bis(monodentate) η1:η1 ligands. This induced deprotonation occurs at higher pH values than in the complexes of the analogous ligand containing diethylenetriamine bridges (L1). The crystal structures of [Cu2(H−2L4)](ClO4)2 and [Zn2(H−2L4)](ClO4)2 obtained by treatment of Na2[H−2L4] with either Cu(ClO4)2·6H2O or Zn(ClO4)2·6H2O in methanol followed by recrystallisation from water/methanol also show the deprotonation of the pyrazole moieties. The coordination geometry around each metal ion is square-pyramidal and involves all nitrogen atoms of the macrocycle. The crystal structure of [Zn2(H−2L1)](ClO4)2 shows full involvement of all the nitrogen atoms of the macrocycle in the coordination to the metal ions. The coordination geometry can be defined as midway between a square pyramid and an irregular trigonal bipyramid. Treatment of neutral L4 in methanol with Cu(ClO4)2·6H2O yields a blue complex which, after heating in boiling water, crystallises as a red compound. Elemental microanalyses, ESI-MS and FAB-MS data of both forms of this complex are consistent with the formula [Cu2L4](ClO4)4·2H2O. Furthermore, these data along with the paramagnetic 1H NMR spectrum of the red form of the compound suggest a structure in which the pyrazole rings are deprotonated while the central nitrogen atoms of the bridging chains are protonated and consequently uncoordinated. The change from the blue (square-pyramidal) to the red form (square-planar) can be ascribed to dissociation of the water molecules which occupy the axial positions in the CuII coordination spheres of the blue form. The variation of the magnetic susceptibility of the red complex [Cu2L4](ClO4)4·2H2O and the complex [Cu2(H−2L4)](ClO4)2 with temperature has been studied in the 2−300 K temperature range. Fitting of the experimental data provides J values which are among the highest found for doubly pyrazolate-bridged dicopper(II) complexes {J = −299 cm−1 for red-[Cu2L4](ClO4)4·2H2O and J = −286 cm−1 for [Cu2(H−2L4)](ClO4)2}. A trinuclear CuII complex of formula [Cu3(H−2L4)](ClO4)4·2MeOH was also isolated after treatment of L4 with Cu(ClO4)2·6H2O solutions of higher concentration.Financial support by the Spanish “Comisión Interministerial de Ciencia y Tecnología” (CICYT, SAF-99-0063 and BQU2003-09215-CO3-01) and Generalitat Valenciana (CTIDIB/2002/244 and Grupos03/196) is gratefully acknowledged

Diazatetraester 1H-pyrazole crowns as fluorescent chemosensors for AMPH, METH, MDMA (Ecstasy), and dopamine

The synthesis and steady-state fluorescence studies on the interaction with AMPH, METH, MDMA, and DA of two diazatetraester pyrazole crowns containing appended N-(9H-fluoren-9-yl) and N-(naphth-2-ylmethyl) functions, in a water/ethanol 70:30 mixture at physiological pH, are described.This work was supported by the Spanish Ministry of Science and Innovation (CTQ2006-15672-CO5-01, CTQ2006-15672-CO5-05, CTQ2006-14987-CO2-O2, CSD2007-000101) and the Generalitat Valenciana (GV/2007/141 and GVAINF 2007-051) and European FEDER funds. J.C.F. and M.T.A. thank “Carmen y Severo Ochoa” and “Juan de la Cierva” Programmes for their respective grants

Synthesis and evaluation of in vitro and in vivo trypanocidal properties of a new imidazole-containing nitrophthalazine derivative

A series of new phthalazine derivatives (1-4) containing imidazole rings and functionalized with nitro groups in the benzene ring of the phthalazine moiety were prepared and identified on the basis of their MS, elemental analyses and bidimensional H and C NMR data, and their trypanocidal activity was tested. The 8-nitrosubstituted compound (3) was more active in vitro against Trypanosoma cruzi and less toxic against Vero cells than the reference drug benznidazole, and showed a SI value that was 47-fold better than the reference drug in amastigote forms. It also remarkably reduced the infectivity rate in Vero cells and decreased the reactivation of parasitemia in immunodeficient mice. Ultrastructural alterations found in epimastigotes treated with 3 confirmed extensive cytoplasm destruction in the parasites, whereas histopathological analysis of the hearts of mice infected and treated with 3 resulted in a decrease in cardiac damage. Biochemical markers showed that livers, hearts, and kidneys of treated mice were substantially unaffected by the administration of 3, despite the presence of the potentially toxic nitro group. It was also found that this compound selectively inhibited the antioxidant parasite enzyme Fe-superoxide dismutase (Fe-SOD) in comparison with human CuZn-SOD, and molecular modeling suggested interaction with the H-bonding system of the iron-based moiety as a feasible mechanism of action against the enzyme.The authors thank the MCINN Projects Consolider Ingenio CSD2010-00065 and CTQ2009-14288-C04-01 for financial support. F.O. is grateful for a FPU grant from the Ministry of Education of Spain

Phthalazine derivatives containing imidazole rings behave as Fe-SOD inhibitors and show remarkable anti-T. cruzi activity in immunodeficient-mouse mode of infection

A series of new phthalazine derivatives 1-4 containing imidazole rings were prepared. The monoalkylamino substituted derivatives 2 and 4 were more active in vitro against T. cruzi and less toxic against Vero cells than both their disubstituted analogues and the reference drug benznidazole. Compounds 2 and 4 highly inhibited the antioxidant parasite enzyme Fe-SOD, and molecular modeling suggested that they interact with the H-bonding system of the iron atom moiety. In vivo tests on the acute phase of Chagas disease gave parasitemia inhibition values twice those of benznidazole, and a remarkable decrease in the reactivation of parasitemia was found in the chronic phase for immunodeficient mice. Glucose metabolism studies showed that compounds 1-4 did not affect the succinate pathway but originated important changes in the excretion of pyruvate metabolites. The morphological alterations found in epimastigotes treated with 1-4 confirmed extensive cytoplasm damage and a high mortality rate of parasites. © 2012 American Chemical Society.The authors thank the MCINN Projects: Consolider Ingenio CSD2010-00065 and CTQ2009-14288-C04-01 for financial support