Indole ring oxidation by activated leukocytes prevents the production of hypochlorous acid

Hypochlorous acid (HOCl) released by activated leukocytes has been implicated in the tissue damage that characterizes chronic inflammatory diseases. In this investigation, 14 indole derivatives, including metabolites such as melatonin, tryptophan and indole-3-acetic acid, were screened for their ability to inhibit the generation of this endogenous oxidant by stimulated leukocytes. The release of HOCl was measured by the production of taurine-chloramine when the leukocytes (2 x 10(6) cells/mL) were incubated at 37ºC in 10 mM phosphate-buffered saline, pH 7.4, for 30 min with 5 mM taurine and stimulated with 100 nM phorbol-12-myristate acetate. Irrespective of the group substituted in the indole ring, all the compounds tested including indole, 2-methylindole, 3-methylindole, 2,3-dimethylindole, 2,5-dimethylindole, 2-phenylindole, 5-methoxyindole, 6-methoxyindole, 5-methoxy-2-methylindole, melatonin, tryptophan, indole-3-acetic acid, 5-methoxy-2-methyl-3-indole-acetic acid, and indomethacin (10 µM) inhibited the chlorinating activity of myeloperoxidase (MPO) in the 23-72% range. The compounds 3-methylindole and indole-3-acetic acid were chosen as representative of indole derivatives in a dose-response study using purified MPO. The IC50 obtained were 0.10 ± 0.03 and 5.0 ± 1.0 µM (N = 13), respectively. These compounds did not affect the peroxidation activity of MPO or the production of superoxide anion by stimulated leukocytes. By following the spectral change of MPO during the enzyme turnover, the inhibition of HOCl production can be explained on the basis of the accumulation of the redox form compound-II (MPO-II), which is an inactive chlorinating species. These results show that indole derivatives are effective and selective inhibitors of MPO-chlorinating activity.

Ethyl 1-(2-cyanoethyl)-3,5-dimethyl-1H-indole-2-carboxylate

The title compound, C16H18N2O2, is an important precursor in the synthesis of 1,2,3,4-tetrahydropyrazinoindoles, which show excellent antihistamine, antihypertensive and central nervous system depressant properties. The carbethoxy group attached to C2 and the planar cyanoethyl group attached to N1 make dihedral angles of 11.0(4) and 75.0(3)degrees, respectively, with the mean plane of the indole ring, The C-C=N chain is linear with a bond angle of 179.3 (4)degrees.

2-[(3,3-Dimethylindolin-2-ylidene)methyl]-4-[(3,3-dimethyl-3H-indol-1-ium-2-yl)methylidene]-3-oxocyclobut-1-en-1-olate chloroform disolvate

In the title squaraine dye solvate, C26H24N2O2·2CHCl3, the dye molecule is essentially planar, except for the methyl groups, having a maximum deviation over the 26-membered delocalized bond system of 0.060 (2) Å. It possesses crystallographic twofold rotational symmetry with the indole ring systems adopting a syn conformation. The molecular structure features intramolecular N-HO hydrogen bonds enclosing conjoint S7 ring motifs about one of the dioxocyclobutene O atoms, while the two chloroform solvent molecules are linked to the second O atom through C-HO hydrogen bonds.

DNA cleavage in red light promoted by copper(II) complexes of -amino acids and photoactive phenanthroline bases

Ternary copper(II) complexes [Cu(L-trp)(B)(H2O)](NO3) ( 1–3) and [Cu(L-phe)(B)(H2O)](NO3) ( 4–6) of L-tryptophan (L-trp) and L-phenylalanine (L-phe) having phenanthroline bases (B), viz. 1,10-phenanthroline (phen, 1 and 4), dipyrido[3,2-d:2,3-f]quinoxaline (dpq, 2 and 5) and dipyrido[3,2-a:2,3-c]phenazine (dppz, 3 and 6), were prepared and characterized by physico-chemical techniques. Complexes 3 and 6 were structurally characterized by X-ray crystallography and show the presence of a square pyramidal (4 + 1) CuN3O2 coordination geometry in which the N,O-donor amino acid (L-trp or L-phe) and N,N-donor phenanthroline base bind at the equatorial plane with an aqua ligand coordinated at the elongated axial site. Complex 3 shows significant distortion from the square pyramidal geometry and a strong intramolecular – stacking interaction between the pendant indole ring of L-trp and the planar dppz aromatic moiety. All the complexes display good binding propensity to the calf thymus DNA giving an order: 3, 6 (dppz) > 2, 5 (dpq) > 1, 4 (phen). The binding constant (Kb) values are in the range of 2.1 × 104–1.1 × 106 mol-1 with the binding site size (s) values of 0.17–0.63. The phen and dpq complexes are minor groove binders while the dppz analogues bind at the DNA major groove. Theoretical DNA docking studies on 2 and 3 show the close proximity of two photosensitizers, viz. the indole moiety of L-trp and the quinoxaline/phenazine of the dpq/dppz bases, to the complementary DNA strands. Complexes 2 and 3 show oxidative DNA double strand breaks (dsb) of supercoiled (SC) DNA forming a significant quantity of linear DNA along with the nicked circular (NC) form on photoexposure to UV-A light of 365 nm and red light of 647.1 nm (Ar–Kr laser). Complexes 1, 5 and 6 show only single strand breaks (ssb) forming NC DNA. The red light induced DNA cleavage involves metal-assisted photosensitization of L-trp and dpq/dppz base resulting in the formation of a reactive singlet oxygen (1O2) species.

Simultaneous observation of positive and negative nuclear Overhauser effects in oligopeptides due to segmental motio

Nuclear Overhauser effect (NOE) studies of the symmetrical cystine peptides (Formula: see text) (n = 1-3) in dimethylsulfoxide, have resulted in the simultaneous observation of both positive and negative NOEs. Positive NOEs are observed on the Trp C2H and C4H protons of the indole ring upon irradiation of Trp C alpha H and C beta H2 resonances in the peptides where n = 1 and 2. Negative NOEs are observed between backbone NH and C alpha H protons. The magnitudes of the observed NOEs are sensitive to changes in molecular size and solvent viscosity. The results demonstrate that NOEs may be a useful probe of sidechain segmental motion in oligopeptides.

Tryptophan photooxidation promoted by new hybrid materials prepared by condensation of naphthalene imides with silicate by the sol-gel process

Three novel hybrid organic/inorganic materials were synthesized from 4-substituted (NO(2), Br, H) 1,8-naphthalene imide-N-propyltriethoxysilane by the sol-gel process. These materials were obtained as a xerogel and partially characterized. The ability to photosensitize the oxidation and degradation of tryptophan indole ring by these materials was studied through photophysical and photochemical techniques. Although the derivatives containing Br and NO(2) as substituent do not cause efficient tryptophan photodamage, the hybrid material obtained from 1,8-naphthalic anhydride is very efficient to promote tryptophan photooxidation. By using laser flash photolysis it was possible to verify the presence of naphthalene imide transient radical species. The presence of oxygen causes an increase of the yield of radical formation. These results suggest that the mechanism of photodegradation of tryptophan occurs by type I, i.e. the transient radical (TrpH(center dot+)) formed by the direct reaction of the triplet state of the naphthalene imide moiety with tryptophan. Thus a inorganic-organic hybrid material that can be used to promote the oxidation of biomolecules was obtained. (C) 2009 Elsevier B.V. All rights reserved.

Study of the binding of Eu3+ and Tb3+ to L-phenylalanine and L-tryptophan

Trivalent europium and terbium ions have ionic radii similar to that of Ca2+. So they are employed as probes of calcium binding sites in biological molecules. These ions exhibit very useful spectroscopic characteristics, chiefly a pronounced luminescence. In protein bound lanthanide, visible light emission from the lanthanide excited states can be observed when UV light is absorbed by aromatic amino acids. Subsequently, the energy is transferred to the lanthanide ion. The present work was carried out to define the binding sites of Eu3+ and Tb3+ in complexes with the aromatic amino acids L-phenylalanine and L-tryptophan. The techniques utilized were infrared and C nuclear magnetic resonance spectroscopies. It was found that trivalent europium and terbium interact with the carboxylate group of both amino acids. With L-tryptophan, the imino group of the indole ring is also involved representing another coordination site.

Estudo da oxidação da melatonina e de seus produtos por radicais peroxila

Melatonin is an endoleamine that has anti-inflammatory, immunomodulating and antioxidants properties. But there is a contradiction between the antioxidant effects of melatonin and glutathione (GSH). Therefore, the main objective of this work was to study the effect of melatonin on the oxidation of GSH and the effect of GSH on the oxidation of melatonin by peroxyl radicals generated by thermolysis of 2,2 -Azobis(2- amino-propane)-dihydrochloride (AAPH). The influence of the reaction conditions and the identity of the products of oxidation were also studied. The main products obtained during the oxidation of melatonin were its monohydroxylated derivative and N1-acetyl- N2-formyl-5-methoxykynuramine (AFMK), which is the product obtained by oxidative cleavage of the melatonin indole ring. By studying the buffer type, pH and the presence or absence of dissolved oxygen in the reaction system, it was observed that, the yield of AFMK was higher when the pH or the concentration of oxygen was increased. Comparing the reactivity of both molecules GSH and melatonin, it can be seen that intermediates radicals generated during the oxidation of melatonin are able to oxidize GSH itself. We propose that this chemical property could justify the recent reports that demonstrated the inability of melatonin to inhibit the oxidation of GSH in cells

Synthese von Carbolinen durch übergangsmetall-katalysierte [2+2+2]-Cycloaddition von Alkinen und Nitrilen: Ein neuer Weg zur Totalsynthese von Lavendamycin

Carboline sind eine große Gruppe von natürlich vorkommenden Alkaloiden, die eine tricyclische Pyrido[b]indol-Ringstruktur gemeinsam habe. Das breite Spektrum biologischer Eigenschaften dieser Verbindungsklasse macht sie zu einem interessanten Syntheseziel. Die größte Herausforderung in der Darstellung von Carbolinen ist die regioselektive Funktionalisierung an den aromatischen Positionen. Im Rahmen dieser Arbeit konnte ein A ABC-Zugang zu beta- und gamma-Carbolinen entwickelt werden, dessen Schlüsselschritt der Aufbau des Carbolin-Gerüsts durch eine übergangsmetall-katalysierte [2+2+2]-Cycloaddition von 1,6-Diin-Einheiten und Nitrilen ist. Die benötigten Diin-Einheiten wurden in wenigen Schritten ausgehend von 2-Iodanilin durch eine Reaktionssequenz aus Sonogashira-Reaktion mit terminalen Alkinen, N-Tosylierung und N-Ethinylierung mit Alkinyliodonium-Salzen synthetisiert. Eine flexible Funktionalisierung dieser Diine wurde durch palladium-katalysierte sp2-sp-Kreuzkupplungsreaktionen der terminalen Alkine mit Aryl- und Alkenylhalogeniden erreicht. Cp*RuCl- und [Rh(cod)2]BF4/BINAP-katalysierte [2+2+2]-Cycloadditionen der 1,6-Diine mit elektronenarmen Nitrilen lieferte in hoher Regioselektivität beta- oder gamma-Carboline. In Übereinstimmung mit literaturbekannten übergangsmetall-katalysierten [2+2+2]-Cycloadditionen konnte dabei eine starke Abhängigkeit von sterischen und elektronischen Faktoren beobachtet werden. Um das Potential dieser Methode zu demonstrieren, wurde der Einsatz der [2+2+2]-Cycloaddition in Totalsynthese von Lavendamycin untersucht. Lavendamycin, ein aus Bakterien stammendes Chinochinolin-substituiertes beta-Carbolin mit antimikrobieller und signifikanter Antitumor-Aktivität, wurde ausgehend von Hydrochinon und 2-Iodanilin in 14 Schritten und in einer Gesamtausbeute von 29% dargestellt.

Bioconjugation and synthetic approach towards enantioenriched gem-difluoromethylene compounds through carbenium ions

Bioconjugation of peptides and asymmetric synthesis of gem-difluoromethylene compounds are areas of the modern organic chemistry for which mild and selective methods continue to be developed. This thesis reports new methodologies for these two areas based on the use of stabilized carbenium ions. The reaction that makes the bioconjugation of peptides possible takes place via the direct nucleophilic substitution of alcohols and is driven by the spontaneous formation of stabilized carbenium ions in water. By reacting with the thiol group of cysteine in very mild conditions and with a high selectivity, these carbenium ions allow the site-specific ligation of polypeptides containing cysteine and their covalent derivatization with functionalized probes. The ligation of the indole ring of tryptophan, an emerging target in bioconjugation, is also shown and takes place in the same conditions. The second area investigated is the challenging access to optically active gem-difluoromethylene compounds. We describe a methodology relying on the synthesis of enantioenriched 1,3-benzodithioles intermediates that are shown to be precursors of the corresponding gem-difluoromethylene analogues by oxidative desulfurization-fluorination. This synthesis takes advantage of the highly enantioselective organocatalytic α-alkylation of aldehydes with the benzodithiolylium ion and of the wide possibilities of synthetic transformations offered by the 1,3-benzodithiole group. This approach allows the asymmetric access to complex gem-difluoromethylene compounds through a late-stage fluorination step, thus avoiding the use of fluorinated building blocks.

Transition metal ion activation of DNA binding by the diphtheria tox repressor requires the formation of stable homodimers.

The diphtheria tox repressor (DtxR) is a transition metal ion-dependent regulatory element that controls the expression of diphtheria toxin and several genes involved in the synthesis of siderophores in Corynebacterium diphtheriae. In the presence of transition metal ions apo-DtxR becomes activated and specifically binds to its target DNA sequences. We demonstrate by glutaraldehyde cross-linking that monomeric apo-DtxR is in weak equilibrium with a dimeric form and that upon addition of activating metal ions to the reaction mixture a dimeric complex is stabilized. Addition of the DNA-binding-defective mutant apo-DtxR(delta 1-47) to apo-DtxR in the absence of transition metal ions inhibits conversion of the apo-repressor to its activated DNA-binding form. We also show that the binding of Ni2+ to both apo-DtxR and apo-DtxR(delta 1-47) is cooperative and that upon ion binding there is a conformational change in the environment of the indole ring moiety of Trp-104. For the wild-type repressor the consequences of this conformational change include a shift in equilibrium toward dimer formation and activation of target DNA binding by the repressor. We conclude that the formation of DtxR homodimers is mediated through a protein-protein interaction domain that is also activated on metal ion binding.

Non-substituted B-ring flavonoids and an indole alkaloid from Piper aleyreanum (Piperaceae)

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)

A Diastereoselective Total Synthesis of trans-Trikentrin A: A Ring Contraction Approach

A new route to obtain the polyalkylated indole (+/-)-trans-trikentrin A was developed. The synthesis of this natural alkaloid features a thallium(III)mediated ring contraction reaction to obtain the trans-1,3-disubstituted five-membered ring in a diastereoselective manner. Thallium(III) is chemoselective in this rearrangement, reacting with the olefin without oxidation of the indole moiety. Other key transformations are the Bartoli`s reaction to construct the heterocyclic ring and a Heck coupling to add the carbons atom that will originate the nonaromatic cycle.

Au(I) Catalyzed Manipulation of Propargylic Alcohols: A New Route Towards the Synthesis of Indole Alkaloids

In this work we presented several aspects regarding the possibility to use readily available propargylic alcohols as acyclic precursors to develop new stereoselective [Au(I)]-catalyzed cascade reactions for the synthesis of highly complex indole architectures. The use of indole-based propargylic alcohols of type 1 in a stereoselective [Au(I)]-catalyzed hydroindolynation/immiun trapping reactive sequence opened access to a new class of tetracyclic indolines, dihydropyranylindolines A and furoindolines B. An enantioselective protocol was futher explored in order to synthesize this molecules with high yields and ee. The suitability of propargylic alcohols in [Au(I)]-catalyzed cascade reactions was deeply investigated by developing cascade reactions in which was possible not only to synthesize the indole core but also to achieve a second functionalization. Aniline based propargylic alcohols 2 were found to be modular acyclic precursors for the synthesis of [1,2-a] azepinoindoles C. In describing this reactivity we additionally reported experimental evidences for an unprecedented NHCAu(I)-vinyl specie which in a chemoselective fashion, led to the annulation step, synthesizing the N1-C2-connected seven membered ring. The chemical flexibility of propargylic alcohols was further explored by changing the nature of the chemical surrounding with different preinstalled N-alkyl moiety in propargylic alcohols of type 3. Particularly, in the case of a primary alcohol, [Au(I)] catalysis was found to be prominent in the synthesis of a new class of [4,3-a]-oxazinoindoles D while the use of an allylic alcohol led to the first example of [Au(I)] catalyzed synthesis and enantioselective functionalization of this class of molecules (D*). With this work we established propargylic alcohols as excellent acyclic precursor to developed new [Au(I)]-catalyzed cascade reaction and providing new catalytic synthetic tools for the stereoselective synthesis of complex indole/indoline architectures.

Merovingian ring-fort

One could argue that there are many approaches to site specifically as there are specific sites. Each site has a variety of influences such as visibility and natural and cultural histories. Human impositions that endure do so because of some canniness, some appreciation of how the current will live with the past.