Fabiano T. Toledo

N-Functionalized organolithium compounds via tellurium/lithium exchange reaction

A set of tellurium amines have been evaluated in the tellurium/lithium exchange reaction. The nitrogen-containing organolithium compounds were efficiently prepared by using N-Bz tellurium amines and a mixture of n-butyllithium and lithium naphthalenide (LiNp) for performing the exchange reaction. The corresponding dianion intermediates were trapped with a wide range of electrophiles, furnishing the corresponding products in good to excellent yields. The reaction was also employed in the synthesis of phenethylamines.

Selenostannylation of Arynes Produced by Silylaryl Triflates under Mild Reaction Conditions

Tributil[(fenilselanil)aril]estananas foram preparadas em bons rendimentos por reacao entre tributil(fenilselanil)estanana e 2-(trimetilsilil)aril triflatos na presenca de fluoreto de potassio e eter 18-coroa-6 em THF a 0 o C. Tributyl[(phenylselanyl)aryl]stannanes were prepared in good yields by reaction between tributyl(phenylselanyl)stannane and 2-(trimethylsilyl)aryl triflates in the presence of potassium fluoride and18-crown-6 ether in THF at 0 o C.

Application of the Negishi reaction in the synthesis of thiophene-based lignans analogues with leishmanicidal effects

As lignanas tetraidrofurânicas sao metabolitos secundarios com reconhecida atividade antiprotozoaria. Na literatura, ha varios relatos sobre os efeitos anti-parasitarios de analogos sinteticos de lignanas contendo pontes de enxofre. Neste trabalho, foi realizada a sintese de analogos tiofenicos de lignanas com o uso de uma estrategia sintetica seletiva e de alto desempenho baseada na reacao de acoplamento cruzado de Negishi. Os derivados sinteticos foram obtidos de maneira rapida e apresentaram alto grau de pureza e baixa toxicidade para uma linhagem celular de mamifero e atividade leishmanicida com diferentes potencias. Lignans represent a well-known group of natural products with anti-protozoal activity. In the literature there are many examples of the anti-parasitic activity of synthetic analogues of lignans containing sulphur bridges. In this work, we have obtained thiophene-based analogues by using a selective and high performance synthetic strategy based on the Negishi cross-coupling reaction. The derivatives were quickly obtained and showed great purity, low toxicity toward a mammalian cell line, and leishmanicidal activity with different potencies.

Antiproliferative and ultrastructural effects of phenethylamine derivatives on promastigotes and amastigotes of Leishmania (Leishmania) infantum chagasi.

Leishmania (Leishmania) infantum chagasi is one of the agents that cause visceral leishmaniasis. This disease occurs more frequently in third world countries, such as Brazil. The treatment is arduous, and is dependent on just a few drugs like the antimonial derivatives and amphotericin B. Moreover, these drugs are not only expensive, but they can also cause severe side effects and require long-term treatment. Therefore, it is very important to find new compounds that are effective against leishmaniasis. In the present work we evaluated a new group of synthetic amides against the promastigote and amastigote forms of L. infantum chagasi. The results showed that one of these amides in particular, presented very effective activity against the promastigotes and amastigotes of L. infantum chagasi at low concentrations and it also presented low toxicity for mammal cells, which makes this synthetic amide a promising drug for combating leishmaniasis.

Synthetic Organotellurium Compounds Sensitize Drug-Resistant Candida albicans Clinical Isolates to Fluconazole

ABSTRACT Invasive Candida albicans infections are a serious health threat for immunocompromised individuals. Fluconazole is most commonly used to treat these infections, but resistance due to the overexpression of multidrug efflux pumps is of grave concern. This study evaluated the ability of five synthetic organotellurium compounds to reverse the fluconazole resistance of C. albicans clinical isolates. Compounds 1 to 4, at <10 μg/ml, ameliorated the fluconazole resistance of Saccharomyces cerevisiae strains overexpressing the major C. albicans multidrug efflux pumps Cdr1p and Mdr1p, whereas compound 5 only sensitized Mdr1p-overexpressing strains to fluconazole. Compounds 1 to 4 also inhibited efflux of the fluorescent substrate rhodamine 6G and the ATPase activity of Cdr1p, whereas all five of compounds 1 to 5 inhibited Nile red efflux by Mdr1p. Interestingly, all five compounds demonstrated synergy with fluconazole against efflux pump-overexpressing fluconazole-resistant C. albicans clinical isolates, isolate 95-142 overexpressing CDR1 and CDR2, isolate 96-25 overexpressing MDR1 and ERG11, and isolate 12-99 overexpressing CDR1, CDR2, MDR1, and ERG11. Overall, organotellurium compounds 1 and 2 were the most promising fluconazole chemosensitizers of fluconazole-resistant C. albicans isolates. Our data suggest that these novel organotellurium compounds inhibit pump efflux by two very important and distinct families of fungal multidrug efflux pumps: the ATP-binding cassette transporter Cdr1p and the major facilitator superfamily transporter Mdr1p.