An environmentally benign method is described for the α-hydroxylation of malonates and cyclic analogues in aqueous medium at room temperature under mild conditions, based on the in situ generation of dimethyldioxirane through the combination of acetone and Oxone®. This procedure was found to be substrate-dependent and was successfully performed to provide α-hydroxylated γ-lactones. To demonstrate the synthetic potential of this mild α-hydroxylation, two different concise routes were developed to synthesize harzialactone A in the racemic form with a moderate (3:1) diastereomeric ratio.

We report a series of functionalized dienes as compounds of great potential in the treatment of Alzheimer’s disease due to their antioxidant activity and ability to inhibit the enzyme acetylcholinesterase. The dienes tested showed high enzymatic inhibition capacity and accentuated antioxidant activity, which are comparable to or higher than the standards tested. Molecular docking studies were performed to confirm the experimental results. We also describe the correlation values between the antioxidant activity and oxidation potentials. Predicted bioactivity scores and quantum studies were also determined.

The per-O-acetylation of D-ribono-1,4-lactone and representative carbohydrates through the combination of acetic anhydride and molecular sieves under solvent-free conditions is demonstrated. The use of 13X/KCl molecular sieves as the heterogeneous catalyst was found to be more efficient than the excess of pyridine normally employed in the conventional method, giving high yields of the expected peracetylated product after 3 h at 25 ºC or 1 h at 50 ºC. The transformation can be carried out in gram scale and in an open flask. Additionally, the catalyst is readily separated from the reaction medium and can be reutilized without significant loss of activity. This green procedure for acetylation was extended to D-ribonolactone derivatives and natural carbohydrates. To demonstrate the synthetic utility of the method, 2,3,5-tri-O-acetyl-D-ribonolactone was selected as the substrate for the regioselective alcoholysis of acetyl group catalyzed by Candida antarctica lipase B in EtOH to selectively produce 2,3-di-O-acetyl-D-ribonolactone in gram scale.

Copolímeros de anilina com ácido antranílico e seus ésteres metílico e etílico foram sintetizados utilizando uma variedade de ácidos dopantes e foram caracterizados por UV-Vis, espectroscopias no infravermelho com transformada de Fourier (FTIR) e Raman, e microscopia eletrônica de varredura. Os dados apóiam a existência de reações de acoplamento para- na construção da cadeia polimérica, embora a reação de acoplamento orto- seja competitiva e leve à formação de estruturas terminais do tipo fenazina. A condutividade elétrica e a solubilidade foram determinadas em uma diversidade de solventes e os resultados correlacionados com os dados espectrais. Observou-se que os copolímeros de anilina com ésteres antranílicos são mais solúveis do que as polianilinas correspondentes. Além disso, a condutividade do copolímero com antranilato de metila dopado com ácido trifluoroacético é da mesma ordem de magnitude que a observada para polianilinas comuns. Em geral, as condutividades mais elevadas foram obtidas para os polímeros e copolímeros dopados com os ácidos clorídrico e trifluoroacético.

Copolymers of aniline with anthranilic acid and two esters, ethyl and methyl anthranilate, were prepared through chemical synthesis using a variety of acids as the dopant. All polymers and copolymers were characterized by UV-Vis, Fourier transform infrared (FTIR) and Raman spectroscopies, as well as scanning electron microscopy. The data support the formation of variable amounts of phenazine-like structures due to ortho-coupling polymerization that competes with the para-coupling mode for the construction of the polymer backbone. The electrical conductivity and the solubility in a diversity of solvents were determined and correlated with the spectral data. The copolymers of aniline with anthranilic esters are more soluble than the corresponding polyanilines. In addition, the conductivity of the copolymer with methyl anthranilate doped with trifluoroacetic acid is of the same order of magnitude as that observed for the regular polyanilines. Overall, higher conductivities were obtained for all polymers and copolymers doped with hydrochloric acid and trifluoroacetic acid.

(Z)-2-(Bromometil)-2-alcenoatos são importantes intermediários sintéticos e foram preparados de forma simples e prática pelo tratamento de α-metileno-β-hidroxiésteres (produtos da reação de Morita-Baylis-Hillman) com LiBr/H2SO4 em acetonitrila à temperatura ambiente. Além de fornecer altos rendimentos e de tolerar a presença de diversos grupos funcionais, esta nova metodologia utiliza reagentes baratos e não faz uso de HBr.

Representative (Z)-2-(bromomethyl)-2-alkenoates were easily prepared in high yield by treating α-methylene-β-hydroxyesters (Morita-Baylis-Hillman adducts) with LiBr/H2SO4 in acetonitrile at room temperature. Besides the tolerance to many diverse functional groups, this new methodology employs inexpensive reagents and avoids the use of HBr.

Este trabalho apresenta um método simples para a caracterização estrutural de 3,4-O-benzilideno-D-ribono-1,5-lactonas e análogos, fundamentado em técnicas convencionais de RMN e experimentos de NOESY em solução. 2-O-Acil-3,4-O-benzilideno-D-ribono-1,5-lactonas foram preparadas em bons rendimentos a partir da acilação das lactonas de Zinner empregando cloretos de ácido sob condições básicas. A estrutura de 2-O-(4-nitrobenzoil)-3,4-O-benzilideno-D-ribono-1,5-lactona foi determinada por difração de raios-X e confirmou, de forma inequívoca, os dados espectroscópicos obtidos.

A practical method for the structural assignment of 3,4-O-benzylidene-D-ribono-1,5-lactones and analogues using conventional NMR techniques and NOESY measurements in solution is described. 2-O-Acyl-3,4-O-benzylidene-D-ribono-1,5-lactones were prepared in good yields by acylation of Zinner’s lactone with acyl chlorides under mildly basic conditions. Structural determination of 2-O-(4-nitrobenzoyl)-3,4-O-benzylidene-D-ribono-1,5-lactone was achieved by single crystal x-ray diffraction, which supports the results based on spectroscopic data.

Este trabalho descreve a preparação de ésteres e amidas derivados do ácido caurenóico e a avaliação da atividade antifúngica frente a cepas padronizadas de fungos patogênicos. Ésteres alquílicos e benzílicos foram obtidos com bons rendimentos, sob condições brandas, a partir da esterificação do ácido caurenóico com haletos de alquila em KOH-acetona. Todos os compostos sintetizados foram submetidos aos testes de inibição contra leveduras, hifomicetos e dermatófitos, mas somente o ácido caurenóico e os derivados contendo um grupo carboxilato livre apresentaram atividade moderada frente a dermatófitos.

Representative esters derived from kaurenoic acid were prepared in order to evaluate their antifungal properties. Alkyl and substituted benzyl esters were obtained in good yield under mild conditions by esterification of kaurenoic acid with the corresponding alkyl halide in KOH-acetone. All synthesized compounds were tested for antifungal properties against pathogenic yeasts, hialohyphomycetes and dermatophytes. Kaurenoic acid and derivatives containing a free carboxyl group were moderately active against dermatophytes.

Neste trabalho foi investigado o comportamento de alil azidas e alil iminas polifuncionais em reações de ciclização intramolecular, buscando desenvolver novas metodologias para a síntese de heterociclos nitrogenados. (E)-3-Aril-2-(azidometil)propenoatos reagem com trifenilfosfina na presença de aldeídos em uma reação tandem Staudinger/aza-Wittig, fornecendo N-alil iminas em bons rendimentos. A estereoquímica (E) para as ligações C=C e C=N foi determinada por NOESY. Também é apresentada a formação de 3-carbometoxiquinolina a partir da ciclização de (E)-2-(azidometil)-3-fenilpropenoato de metila promovida por AlCl3.

The synthetic potential of multifunctional allylic azides and imines in attempted intramolecular cyclizations to nitrogen-containing heterocycles was investigated. Tandem Staudinger/aza-Wittig reaction of (E)-3-aryl-2-(azidomethyl)propenoates with triphenylphosphine and aldehydes yielded N-allylic imines in good yield. The (E)-stereochemistry of C=C and C=N bonds was assigned based on NOESY experiments. AlCl3 mediated formation of 3-carbomethoxyquinoline from methyl (E)-2-(azidomethyl)-3-phenylpropenoate is also described.