A utilização do safrol, principal componente químico do óleo de sassafráz, na síntese de substâncias bioativas na cascata do ácido araquidônico: antiinflamatórios, analgésicos e anti-trombóticos

In this paper we describe the results of a research effort developed in Laboratório de Avaliação e Síntese de Substancias Bioativas (LASSBio, UFRJ) in the utilization of Brazilian abundant natural product, safrole (1), the principal chemical constituent of Sassafras oil (Ocotea pretiosa), as an attractive synthon to access different chemical class of bioactive compounds, as prostaglandins analogues, non-steroidal antiinflammatory agents and antithrombotic compounds.

Reações de inserção intramolecular de diazo compostos polifuncionais catalisadas por ródio(II): síntese de oxetan-3-ona-2-carboxilato e outros heterociclos funcionalizados

gamma-Hydroxy-alpha-diazo-beta-ketoesters are key intermediates in the chemistry of penicilin-based antibiotics and natural products. The method developed here for the synthesis of ethyl 2-diazo-4-hydroxy-3-oxo-butanoate 17 (in two steps from the diazo mercurial 2) compares very favorably with those reported in the literature for similar compounds. The Rh2(OAc)4-mediated intramolecular OH-insertion reaction of the diazo hydroxy ester 17 was investigated, furnishing the oxetan-3-one-2-carboxilate 18 in good yield. When the diazo ester lacks a free hydroxyl group as in the case of the phenoxy diazo ester 11 an intramolecular CH-insertion takes place, affording the 2H-chromene 20 in almost quantitative yield. The behavior of other functionalized diazo esters towards Rh2(OAc)4 was also investigated.

Síntese de poli(p-xililenos)

Poly(p-xylylenes), PPX, are a class of high performance insulating materials with many applications in the electronic component industry. We review herewith the most important synthetic routes to these polymers, described in the literature, since 1904.

O emprego de lipases como agentes de resolução cinética de enantiômeros em síntese orgânica: aspectos gerais sobre a influência do solvente

In organic synthesis, lipases are the most frequently used biocatalysts. They are efficient stereoselective catalysts in the kinetic resolution of a wide variety of chiral compounds. The discovery that enzymes possess catalytic activity in organic solvents has made it possible to address the question of reaction medium influence on enzymatic specificity. Perhaps the most exciting and significant development in this emerging area is the discovery that enzyme specificity, in particular enantioselectivity, can be affected by changing from one organic solvent to another. This article discusses the scope and possible mechanistic models of this phenomenon in hydrolases, specially lipases, as well as directions of future research in the area.

Síntese de 1,3,5-triazinas substituídas e avaliação da toxicidade frente a Artemia Salina leach

The synthesis of ten symmetrically and unsymmetrically substituted 1,3,5-triazines by Phase Transfer Catalysis (PTC) method is described. Their toxicities were determined against Artemia salina Leach. The LD50 values have also been obtained for these compounds.

Síntese de aminoglicosídeos, precursores de pseudo-dissacarídeos potencialmente ativos

This work describes the syntheses of O-protected aminoglycosides as an important block building for the preparation of potential bioactive pseudodisaccharide. The new O-protected methyl 3-amino-3-deoxy-alpha-D-glycopyranoside 4 and methyl 2-amino-2-deoxy-alpha-D-glycopyranoside 5 were prepared, respectively, in five and four steps. All compounds were obtained in good yield and characterized by spectral data (¹H and 13C NMR, MS, IR) and elemental analysis.

Síntese e reatividade de sílica lamelar

An overview of the experimental procedures to prepare lamellar samples of silica, as well as the reactivity and possible applications of this kind of material is presented. Special attention is focused on the obtained materials by using neutral dialkylamine route through sol-gel process.

Reação de Baylis-Hillman: uma estratégia para a preparação de intermediários multifuncionalizados para síntese orgânica

The Baylis-Hillman reaction has significantly advanced in the last ten years as demonstrated by a number of applications described in the literature. In this report we show some aspects of this reaction, including scope, limitations and perspectives.

Síntese orgânica limpa

An introduction to the fundamental concepts and main aspects of organic clean synthesis is given, and relevant industrial examples which have implemented the philosophy of cleaner synthesis are also presented. Recent trends in organic synthesis which are environmentally friendly are also discussed.

Síntese de polímeros condutores em matrizes sólidas hospedeiras

This review discusses the methods used to prepare conductive polymers in confined environments. This spatial restriction causes formation of defect-free polymer chains in the interlayer as porous cavities of inorganic hosts. The properties of the different composites obtained are a synergist combination of the characteristics of the inorganic host and the polymer. This opens new perspectives for the preparation of these materials and widens its potential applications.

Ambergris: perfume e síntese

Rules for the occurence of the ambergris odor is presented and discussed in terms of the relationship between chemical structure and odor. A general overview of the major approaches in the synthesis of Ambrox® , the key ambergris-type compound, is also presented.

Safrol e eugenol: estudo da reatividade química e uso em síntese de produtos naturais biologicamente ativos e seus derivados

The chemical reactivity of safrole, eugenol, piperonal, vanillin and derivates toward ozone, aluminium chloride, brominating agents and butyl lithium was investigated. The synthesis of naturally occuring anthraquinones, furonaphthoquinones, naphthoquinones, lignans and pterocarpans from these easily available staring materials is also discussed.

Síntese e atividade fitotóxica de 2-fenil-6,7-exo-isopropilidenodioxi-8-oxabiciclo [3.2.1]oct-2-eno

The [3+4] cycloaddition between furan and the oxyallyl cation generated from 1-bromo-1-phenylpropan-2-one (4), resulted in the formation of 2-phenyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (5) in 30% yield. This compound was further converted into 2-phenyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]oct-2-ene (13) in 35.4% yield. The selective effect of compound (13) and its isomer 3-phenyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]oct -2-ene (1a) on the radicle growth of Sorghum bicolor L. (sorghum) and Cucumis sativus L. (cucumber) were evaluated. For both plants, compound 13 showed to be more potent than its isomer 1a.

Uma rota alternativa para a síntese de PPh2Si(CH3)3 segundo Appel; preparação e purificação dePPh2H (Ph = fenila)

The unexpected low yield in the Appel's synthesis of PPh2Si(CH3)3 can be attributed to the presence of phenyllithium and its interfering reactions. The method was carried out with hydrolysis of the products formed by the reaction of PPh3 with metallic lithium, phenyllithium and lithiumdiphenylphosphide. PPh2Si(CH3)3 was obtained by subsequent reaction of the resulting diphenylphosphin with elemental lithium and ClSi(CH3)3.

Estratégias para a síntese de desoxinucluosídeos

The number of agents available for the treatment of viral infections has increased dramatically during the past decade most of them belonging to the nucleoside class. The accomplishment of many syntheses for these nucleosides in recent years offers evidence that the field is very important for the organic synthesis. The discussion of several approaches for preparing deoxy and dehydronucleosides is reviewed in a simplified way.