Estratégias para a obtenção de compostos farmacologicamente ativos a partir de plantas medicinais: conceitos sobre modificação estrutural para otimização da atividade

In the present paper we discuss, based in our experience, some experimental procedures which may be employed for isolation of active compounds from medicinal plants. We have also emphasized some insights about the way to obtain more active and selective compounds from natural products through structural modifications oriented for analysis of structure-activity relationships.

Unsaturated Oxazolopiperidone Lactams: an Unexpected Domino-type Double Conjugate Additioncyclization Process

Reactions of 2-acetylindole enolate with unsaturated oxazolopiperidones 3, 4 and 10 unexpectedly gives pentacyclic dilactams 6, 7 and 11, respectively, resulting from a domino-type process involving two successive conjugate additions and a final cyclization.

Mecanismo de fotodegradação de compostos orgânicos catalisada por TiO2

Conventional technology used in the treatment of wastewater has been pointed as a major environmental problem for sustainable development, since minimization is not addressed accordingly. Advanced oxidation processes (AOP), based on the formation of hydroxyl radical (•OH), a powerful oxidant agent, have been considered to be a potential technology for the destruction of many toxic compounds. Photocatalysis using solar light, an AOP, has been studied for nearly 20 years and recently attracted great interest as a clean-up technology. However, solar detoxification processes have not yet achieved commercial success. This article presents an overview of reaction mechanisms at the surface of semiconductors used as photocatalysts (specially TiO2), when heterogeneous photocatalysis is used to remove hazardous compounds from contaminated sites.

Isolamento e caracterização de acil-tiossemicarbazidas como intermediários na síntese de compostos mesoiônicos

1,3,4-thiadiazolium-2-aminides and their isomers 1,3,4-triazolium-2-thiolates have been synthesized via anhydroacylation reactions. This work presents a study by infrared monitoring of the reaction between substituted aroyl acid chlorides and 1,4-diphenylthiosemcarbazide. The intermediates and products were isolated, purified and charaterized by IR and 13C NMR spectroscopy. The increasing or decreasing in intensity of characteristic stretching bands indicated the rate dependence on the electronic nature of substituents. The results also demonstrate that 1,3,4-triazolium-2-thiolates are obtained in anhydrous conditions whereas presence of water leads to a mixture of the isomers.

Utilização de uma interface do tipo "particle beam" para a obtenção de espectros de massas de compostos pouco voláteis em solução

Due to source contamination and wearing of instrument components problems caused by the direct insertion probe technique, a new way of introduction of low volatile compounds into mass spectrometer was tested. This new scheme comprises the introduction of the low volatile compounds solutions via a six port valve connected to a particle beam interface. Solutions of isatin were injected into this system and the best results were obtained with CH2Cl2, CH3OH and CH3CN. The solution inlet system has shown to be advantageous over the conventional way of direct insertion probe introduction.

Potencialidades da utilização de compostos de ródio na confecção de sensores eletroquímicos: uma breve revisão

The electrochemistry field has increased in recent years, specially in the search for new sensors to monitor specific analyte in complex samples. In order to improve electrodes, many rhodium compounds have been used as electron mediators for novel sensors development. The most used compounds for this purpose are metal, metal complexes and some organic dyes. Rhodium complexes are known by their good catalytic properties and it could be useful in the sensor field. However, there are only a few reports, on the use of rhodium complexes in sensors and biosensors. A brief review of the electrochemistry of rhodium complexes and some discription of their properties which make those compounds suitable for development of sensor and biosensor.

Dimetildioxirano. 1. Oxidação de compostos de enxofre

A brief review of the chemistry of dimethyldioxirane is presented. This article specifically foccus on the preparation of dimethyldioxirane, its chemical reactivity, and specially on the oxidation of sulfur compounds.

Síntese e caracterização de compostos organometálicos de estanho (IV)

Organotin(IV) derivatives containing bulky R groups have been synthesized and characterized. It is discussed how their syntheses depend on the reaction conditions, such as stoichiometry of starting materials, bulkiness of the organo group attached to the Sn centre as well as temperature in which the reaction is carried out. Finally the molecular structure of Sn2Ph6, determined by X-ray diffraction is reviewed.

Preparation of penta-azole containing cyclopeptides: challenges in macrocyclization

Herein is described the synthesis of several analogs of the natural product IB-01211 from concatenated azoles, via a biomimetic pathway based on cyclization-oxidation of serine containing peptides combined with the Hantzsch synthesis. The macrocyclization of rigid peptide compounds 1 and 2 to give IB-01211 and its epimer 12b was explored, and the results are compared here to those previously obtained for the macrocyclization of more flexible structures in the syntheses of YM-216391, telomestatin, and IB-01211. Lastly, the preliminary results of anti-tumor activity screening of the synthesized analogs are discussed.

Synthesis and antitumor activity of mechercharmycin A analogues

Several analogs of the cytotoxic thiopeptide IB-01211 or Mechercharmycin A (1) have been synthetized. The cytotoxicity of 1 and the synthetized analogs was evaluated against a panel of three human tumor cell lines. Thiopeptide 1 and the most active derivatives, 2 and 3c, were chosen for further studies like effects on cell cycle progression and induction of apoptosis. Interestingly, the inhibition of cell division and activation of a programmed cell death by apoptosis was detected.

Componentes voláteis do café torrado. Parte I: compostos heterocíclicos

A review of heterocyclic compounds in roasted coffee is presented. The contents, precursors and sensorial properties of furans, pyrroles, oxazoles, thiazoles, thiophenes, pyrazines and pyridines are discussed. The impact heterocyclic compounds of coffee aroma are described.

Compostos fosfatados ricos em energia

The chemical and biological properties of energy-rich phosphate compounds, e.g. ATP and acetyl phosphate, were revised. The role of water in the formation of this class of energy-rich compounds in biological systems is also discussed.

Reações de Diels-Alder entre compostos carbonílicos a,b-insaturados e ciclopentadieno

We review herewith the use of solids such as activated alumina and other modern Lewis acid catalysts, as well as the influence of different solvents, including water, on the title reactions, described in the last seven years.

Presença de compostos carbonílicos no ar em ambientes internos na cidade de São Paulo

The presence of low carbonyl compounds (C1-C4) and glutaraldehyde was observed in 14 work-locations in São Paulo city, Brazil, during January to July 1997 period. The quantification of other carbonyls was not possible due to a sampling artifact caused probably by undesirable reactions between the ambient ozone and the organic substract of C18 cartridge used to collect carbonyls. High indoor concentrations, compared to outdoor levels, were observed for all compounds. Formaldehyde was the most abundant species (29 ppb) followed by acetone and acetaldehyde (25 and 17 ppb) with a small contribution of propanal, crotonaldehyde and C4 isomers (0.7 to 1.5 ppb) when related to the total indoor carbonyls level. Glutaraldehyde was observed only in two different occupational locations in a hospital at high concentrations (121 ppb). In general, high individual carbonyl levels as well as total carbonyls levels found in several locations indicated an unpropitious air quality for the occupants of these non-industrial sites.

Estudi i disseny d'un sistema de modificació tímbrica en instruments determinats a través d'anàlisi, filtratge i síntesi de senyal d'àudio digital

Aquest treball final de carrera sorgeix doncs d'una idea molt ambiciosa: crear un sistema de processat de senyal digital que permetés, a temps real, convertir un timbre d'un instrument determinat a un altre, és a dir, a través d'un micròfon que capti el so d'un instrument, com ara el clarinet, analitzar i processar mitjançant programari d'ordinador aquest so d'entrada. Conseqüentment, convertir-lo per poder percebre'l a través dels altaveus com a so d'un altre instrument. D'aquesta manera, un músic amb habilitats per tocar el clarinet, mitjançant aquesta eina podria simular so de saxo, trompeta, etc., sense haver de recórrer a un sintetitzador ni a altres instruments MIDI.