Síntese de indanos: uma seleção de métodos gerais e eficientes

The indan ring system is present in several compounds with important pharmacological properties. In this account recent examples of selected methods (Friedel-Crafts acylation, cycloaddition reactions, ring contraction, cyclization and resolution) for the synthesis of indans are discussed.

Preparação de compostos lamelares: síntese do hidrogenofosfato de zircônio cristalino e sua intercalação com aminas. Um experimento para estudantes de graduação

The present paper describes the synthesis of crystalline zirconium hydrogen phosphate by direct precipitation and its intercalation with pyridine and n-butylamine. The simple experiment was tested in the undergraduate inorganic chemistry laboratory course for chemistry students at IQ-UNICAMP using inexpensive reagents. The materials were characterized by powder X-ray diffraction and infrared analyses in order to obtain detailed information of the solid structure changes as a result of the intercalation process. Pyridine and n-butylamine are focused in this work as clear and elucidative examples leading to acid-base interactive processes that result in the well-formed infinite sequence of inorganic lamellar structures.

Síntese de sulfadiazina e sulfadiazina de prata em escala semi-micro: prática experimental em síntese de fármacos

The total synthesis of sulfadiazine and silver sulfadiazine from readily available starting materials was adapted to semi-micro laboratory scale and is proposed as an experiment in drug synthesis for undergraduate courses.

Estudo da influência do solvente, carboidrato e ácido graxo na síntese enzimática de ésteres de açúcares

The aim of this work was to gain knowledge of enzymatic processes for the synthesis fatty acid esters of sugar, with the objective to develop an enzymatic process for the preparation of non-toxic biodegradable surface-active agents derived entirely from renewable resources. A wide range of data were collected for reaction conditions involving different sugars (glucose, fructose and sucrose), fatty acids (oleic, palmitic, lauric), solvents (hexane, heptane and t-butanol) and different sources of lipases in both free and immobilized forms. As a solvent t-butanol provided the best conditions to create a catalytic liquid phase in which the reaction occurs. Sugars were preferentially esterified in the following order: fructose > glucose > sucrose, depending on the enzyme preparation. For fructose no influence was found concerning de acyl donor and similar rates were achieved for all tested fatty acids. Ester synthesis was maximized for substrates containing fructose, lauric or oleic acids, t-butanol and lipase from porcine pancreas immobilized on polysiloxane-polyvinyl alcohol particles. Under such conditions molar conversions were higher than 50%.

Síntese e caracterização de novos complexos de platina (II) com ligantes derivados do furano e nitrofurano

Platinum (II) complexes, for example, cisplatin and carboplatin, have been used as chemotherapeutic agents for the treatment of various types of cancer. Several other complexes of this metallic ion are also under clinical evaluation. This work describes the synthesis of five new platinum (II) complexes having furan and 5-nitrofuran derivatives and chloride as ligands. The compounds were characterized by NMR, IR and elemental analysis.

Síntese e caracterização de nanocompósitos Ni: SiO2 processados na forma de filmes finos

We have produced nanocomposite films of Ni:SiO2 by an alternative polymeric precursor route. Films, with thickness of ~ 1000 nm, were characterized by several techniques including X-ray diffraction, scanning electron microscopy, atomic force microscopy, flame absorption atomic spectrometry, and dc magnetization. Results from the microstructural characterizations indicated that metallic Ni-nanoparticles with average diameter of ~ 3 nm are homogeneously distributed in an amorphous SiO2 matrix. Magnetization measurements revealed a blocking temperature T B ~ 7 K for the most diluted sample and the absence of an exchange bias suggesting that Ni nanoparticles are free from an oxide layer.

Síntese do monastrol e novos compostos de Biginelli promovida por In(OTf)3

In this paper, we describe a practical route for the synthesis of Biginelli compounds using In(OTf)3. To study the generality of this catalyst, several examples using aromatic aldehydes, 1,3-dicarbonyl compounds, urea, and thiourea were investigated. The present procedure provides an efficient modification of the classical Biginelli reaction, namely short reaction times and simple work-up, that not only preserves the simplicity of the original protocol but also produces excellent yields of 3,4-dihydropyridin-2(1H)-ones. Thiourea was used with similar success to provide the corresponding 3,4-dihydropyridin-2(1H)-thiones. In this case, the (+/-)-monastrol, antimitotic agent, was obtained in 92% yield and new thio analogues were synthesized.

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Methyl 6-O-allyl-2,3-di-O-benzyl-4-deoxy-4-(2 -iodobenzoylamine)-alpha-D-glucopyranoside was synthesized in nine conventional steps from methyl alpha-D-glucopyranoside. Its Bu3SnH-mediated aryl radical cyclization provided a benzomacrolactam, resulting from 11-endo aryl radical cyclization and the reduced uncyclized product methyl 6-O-allyl-4-benzoylamine-2,3-di-O-benzyl-4-deoxy- alpha-D-glucopyranoside. The structures of the three new products were supported by ¹H and 13C NMR spectroscopy and DEPT, COSY and HMQC experiments.

Cloreto isocianúrico e cloreto cianúrico: aspectos gerais e aplicações em síntese orgânica

The aromatic six-membered heterocycles having three nitrogen atoms are denominated triazines. Among these heterocycles, isocyanuric chloride and cyanuric chloride are inexpensive and readily available 1,3,5-triazine derivatives, which have been attracting significant attention of organic chemists due to their different kinds of applications, which vary from pharmaceuticals to explosives. This short overview explores their uses in synthetic methods, as chlorinating and oxidating agents and some procedures for their preparation.

Efeito da composição do solvente sobre a estabilidade de proteínas em soluções aquosas

A protein presents a native (N) macro state, which is functionally active, in equilibrium with the denatured (D) macro state, which is devoid of biological activity. An ensemble of microstates forms each macrostate. The denatured state comprises a greater ensemble of microstates than the native macrostate. The N-D equilibrium can be affected by several factors, that comprise the purity of the water, temperature, pH and solute concentration. This work discusses the influence of osmolytes and chaotropics on the N-D equilibrium in aqueous solutions.

Oxidação de proteínas por oxigênio singlete: mecanismos de dano, estratégias para detecção e implicações biológicas

Proteins are potential targets for singlet molecular oxygen (¹O2) oxidation. Damages occur only at tryptophan, tyrosine, histidine, methionine, and cysteine residues at physiological pH, generating oxidized compounds such as hydroperoxides. Therefore, it is important to understand the mechanisms by which ¹O2, hydroperoxides and other oxidized products can trigger further damage. The improvement and development of new tools, such as clean sources of ¹O2 and isotopic labeling approaches in association with HPLC/mass spectrometry detection will allow one to elucidate mechanistic features involving ¹O2-mediated protein oxidation.

Síntese e emprego do ciclometalado [Pd(dmba)(N3)(PPh3)] em processos catalíticos envolvendo a n-carbonilação redutiva de nitroarenos a carbamatos e na síntese de derivados da uréia

This work deals with the use of the cyclometallated compound [Pd(dmba)(N3)(PPh3)] in homogeneous catalytic processes comprising the reductive N-carbonylation of nitrobenzene and p-nitrotoluene to ethyl-phenylcarbamate and ethyl-4-methylphenylcarbamate, respectively. The cyclopalladated compound was also employed in the synthesis of urea derivatives by reacting p-nitrotoluene and m-nitrotoluene, respectively, with p-toluidine and and m-chloroaniline.

Síntese e reatividade de complexos platina-trifenilestibina: uma revisão bibliográfica

This article deals with synthesis and reactivity of complexes with triphenylstibine (SbPh3) as the ligand. A comparative study of analogous complexes of triphenylphosphine (PPh3) and triphenylarsine (AsPh3) with platinum in the oxidation states zero, two and four is included. The bibliographic revision includes publications since 1936, when the first Pt(II) complex with triphenylstibine was described.

A reação de ciclização de prins: uma estratégia eficiente para síntese estereosseletiva de anéis tetraidropirânicos substituídos

The Prins cyclization reaction has significantly advanced in the last years as demonstrated by a number of applications described in the literature. The objective of this report is to introduce this powerful synthetic methodology to the undergraduate and graduated student, since it is rarely presented in an organic synthesis formal course. This reaction is, in some cases, the methodology of choice for the preparation of natural products or drugs that present the tetrahydropyrane moiety in their structures. In this report we show some aspects of this reaction, including mechanism, scope and limitations.

N-halossacarinas: reagentes úteis (e alternativos) em síntese orgânica

N-halosaccharins proved to be useful and alternative reagents for diverse organic transformations, such as halogenation of aromatic compounds, benzylic and alpha-carbonylic positions, cohalogenation of alkenes, oxidation of secondary alcohols, etc. Their preparation from saccharin, a cheap and readly available starting material, is simple.