Edson L. S. Lima

Synthesis and application of a functionalized resin for flow injection/F AAS copper determination in waters.

This paper reports the development of a new strategy for low-level determination of copper in water samples by using a flow-injection system coupled to solid-phase extraction (SPE) using flame atomic absorption spectrometry (F AAS) as detector. In order to preconcentrate copper from samples, a minicolumn packed with a styrene-divinylbenzene resin functionalized with (S)-2-[hydroxy-bis-(4-vinyl-phenyl)-methyl]-pyrrolidine-1-carboxylic acid ethyl ester was used and the synthesis procedure is described. System operation is based on the on-line retention of Cu(II) ions at pH 9.0+/-0.2 in a such minicolumn with posterior analyte elution with 2moll(-1) HCl directly to the F AAS nebulizer. The influence of several chemical (sample pH, buffer concentration, HCl eluent concentration and effect of the ionic strength) and flow (sample and eluent flow rates and preconcentration time) variables that could affect the performance of this system were investigated as well as the possible interferents. At optimized conditions, for 2min of preconcentration time (13.2ml of sample volume), the system achieved a detection limit of 1.1mugl(-1), a R.S.D. 1% at 20muggl(-1) and an analytical throughput of 25h(-1), whereas for 4min of preconcentration time (26.4ml of sample volume), a detection limit of 0.93mugl(-1), a R.S.D. 5.3% at 5mugl(-1) and a sampling frequency of 13h(-1) were reported.

Aromatic iodination in aqueous solution. A new lease of life for aqueous potassium dichloroiodate

Abstract A re-investigation of the use of aqueous potassium dichloroiodate (KICl 2 ) as an iodinating agent for aromatic compounds has found the reagent to be more generally applicable than previously known. The reagent has been found to give excellent yields of iodinated heterocyclic compounds, such as isatin, imidazole and pyrazole.

Synthesis of novel naphthoquinone-spermidine conjugates and their effects on DNA-topoisomerases I and II-alpha

Novos derivados do lapachol 2, nor-lapachol 3 e da lausona 4 foram sintetizados atraves do deslocamento nucleofilico das metoxinaftoquinonas 2a, 3a e 4a pela poliamina (PA) N1-Boc-N5-Bn-espermidina 1a. Os produtos, 2b, 3b e 4b, respectivamente, foram obtidos em bons rendimentos e caracterizados por metodos espectroscopicos e analiticos. Os ensaios preliminares de inibicao das enzimas topoisomerases (topo) I e II-a mostraram-se promissores: todos os compostos (1a 2b, 3b e 4b) inibiram a atividade catalitica da enzima topo II-a na dose de 2 µM. Considerando que somente a PA 1a nao inibiu a atividade da enzima na dose de 0,2 µM, as naftoquinonas apresentam-se como fragmentos em potencial para melhorar a atividade de PAs. Nenhum dos compostos inibiu a topo I na dose de 200 µM.

Synthesis of Dimethoxyfuranonaftoquinones

Abstract Recently some furanonaphthoquinones were isolated from Tabebuia species2,3,4. The structures la, lb2, and li4 were assigned to three of these compounds (those of la and lb being later confirmed by synthesis3,5,6). However, for the three other isolated compounds the spectroscopic data did not permit a decision to be made between the 2,3,4 - - - 4 isomeric pairs of structure lc and Id, le and lf 3, and lg and lh 4. Compounds la, lb, and le (or If), were tested in the KB cell culture assay and shown to be more active cytotoxic agents than lapachol2,3, the probable biogenetic precursor of all of them.

Reaction of 1,3-dimethyl-5-acetyl-barbituric acid (DAB) with primary amines. Access to intermediates for selectively protected spermidines

Abstract The ability of 1,3-dimethyl-5-acetyl-barbituric acid (DAB) to react with primary amines in a chemoselective fashion was applied to the synthesis of a selectively protected spermidine.

Leishmania amazonensis trypanothione reductase: Evaluation of the effect of glutathione analogs on parasite growth, infectivity and enzyme activity

Trypanothione reductase (TR) is a major enzyme in trypanosomatids. Its substrate, trypanothione is a molecule containing a tripeptide (L-glutamic acid-cysteine-glycine) coupled to a polyamine, spermidine. This redox system (TR/Trypanothione) is vital for parasite survival within the host cell and has been described as a good target for chemotherapy anti-Leishmania. The use of tripeptides analogs of glutathione would result in a decrease in trypanothione synthesis and as a consequence in TR activity. In this work, besides the enzyme potential inhibition, it also evaluated the influence of those analogs on parasite growth and on its infective capacity. The results showed a significant effect on parasite growth and infectivity and in addition TR activity was highly inhibited. These results are very promising, suggesting a potential use of those analogs as therapeutic drugs against experimental diseases caused by trypanosomatids.

An Efficient Protocol for Solution- and Solid-Phase End-Group Differentiation of Spermidine

The end-group differentiation of a selectively protected spermidine was achieved through a short sequence of steps. The functionalization of spermidine in solid-phase was monitored by FT-IR.

The use of Fukuyama's sulfonamide in the synthesis of selectively protected spermidines

A diferenciacao dos grupos amino terminais de poliaminas frequentemente envolve uma serie de etapas de protecao e desprotecao, resultando em rotas sinteticas longas e de baixo rendimento global. Tendo em vista o relevante papel biologico atribuido a estas substâncias, torna-se necessario o desenvolvimento de sinteses mais eficientes para poliaminas. Neste artigo descrevemos uma sintese de duas espermidinas seletivamente protegidas, empregando a sulfonamida de Fukuyama. As duas sinteses foram executadas em tres etapas a partir da 1,3-propanodiamina, com um rendimento global superior a 40%.

Synthesis of a bicyclo[6.3.0]undecene skeleton characteristic of some cyclooctanoids by an intramolecular reductive coupling of carbonyls promoted by low - valent titanium

A sintese do esqueleto biciclo[6.3.0]undeceno, caracteristico de um grande numero de ciclooctanoides naturais e descrita neste trabalho. A metodologia aplicada na construcao do sistema ciclooctanoide esta baseada na reacao intramolecular de acoplamento redutivo de dialdeidos promovida por titânio em baixa valencia (reacao de McMurry). O dialdeido 15, precursor do sistema biciclico [6.3.0]undeceno, foi preparado em 5 etapas com um rendimento global de 40% a partir da 2-metoxicarbonil-ciclopentanona como material de partida. O uso de C8K-TiCl3 como agente alternativo para efetuar o acoplamento redutivo intramolecular do dialdeido 15 tambem foi investigado. O acoplamento redutivo do dialdeido 15 para gerar o anel ciclooctânico ocorreu em baixos rendimentos (~10%) apesar de diversas alteracoes nas condicoes de reacao visando melhorar sua eficiencia.

Synthesis and characterization of a linker for primary amines used in the solid phase organic synthesis of spermidine

A linker resin for the synthesis of functionalized spermidine in good yield is described, along with its characterization by infrared (IR), 13C solid-state nuclear magnetic resonance with cross polarization and magic angle spinning (13C CPMAS NMR) and 1H high resolution magic angle spinning nuclear magnetic resonance (1H HRMAS NMR. This linker has been regenerated after cleavage of spermidine and re-used without loss of efficiency.