RESUMO

Alpha-lipoic acid is a natural product that possesses distinct pharmacological properties. Lipoic acid is a short-chain fatty acid containing an asymmetric carbon at five bonds of distance to the organic function. Herein, we developed a nuclear magnetic resonance protocol to access the chiral recognition of lipoic acid in a simple and rapid procedure employing cinchonidine as a cheap chiral solvation agent in deuterated chloroform. To optimize this method, a statistical design of the experimental model was performed to produce a clear understanding of the optimal concentration, temperature, and molar ratio parameters. Based on the obtained spectra, the cinchonidine H8 -H9 scalar coupling indicated a conformational preference in the chiral discrimination procedure. Density functional theory calculations established a proximity between the asymmetric center of lipoic acid and the aromatic moiety of cinchonidine, clarifying possible conformations in this ion-pair interaction. The described protocol demonstrates how far is far enough to chiral discrimination using a chiral solvation agent, expanding the method to compounds that contain a remote stereocenter.

Assuntos

RESUMO

A green methodology to synthesize 2-organoselanyl-naphthalenes based on the reaction of alkynols with diaryl diselenides is described. The electrophilic species of selenium were generated in situ, by the oxidative cleavage of the Se-Se bond of diaryl diselenides by Oxone® using water as the solvent. The reactions proceeded efficiently under ultrasonic irradiation as an alternative energy source, using a range of alkynols and diorganyl diselenides as starting materials. Through this methodology, the corresponding 2-organoselanyl-naphthalenes were obtained in moderate to good yields (56-94%) and in short reaction times (0.25-2.3 h).

RESUMO

The beet culture has great economic and food importance in the world, especially with respect to energy generation. In Brazil the culture is still little studied, lacking studies in all stages of production of culture, mainly in the management of fertilization. This study aimed to evaluate the effect of organo-mineral fertilization on growth, gas exchanges and production of beet, cv. Katrina. The experiment was conducted under field conditions in the municipality of Pombal-PB, Brazil, from September to December 2015, in a randomized block design. The treatments were arranged in a 4 x 2 factorial scheme and corresponded to four periods of fermentation of the biofertilizer (10, 20, 30 and 40 days) applied in soils with and without mineral fertilization, with four replicates and 18 plants evaluated per plot. Plants were conducted for 70 days after transplanting, in 15-cm-high, 1-m-wide beds. During this period, plant growth, gas exchanges and production components were evaluated. The application of mineral biofertilizer fermented for 20 to 30 days, associated with mineral fertilization with 36 g m-2 of P2O5, 18.0 g m-2 of K2O and 14 g m-2 of N at planting, promoted better performance of growth, gas exchanges and production of beet plants. In the soil without mineral fertilization, it is recommended to use the longest biofertilizer fermentation periods, 30 to 40 days, for beet cultivation.

A cultura da beterraba tem grande importância econômica e alimentar no mundo, especialmente no que diz respeito à geração de energia. No Brasil, a cultura ainda é pouco estudada, faltando estudos em todos os estágios de produção da cultura, principalmente no manejo da adubação. Objetivou-se no presente trabalho, avaliar a adubação organomineral no crescimento, trocas gasosas e produção da beterraba cv. Katrina. O experimento foi conduzido em condições de campo, no município de Pombal, PB, no período de setembro a dezembro de 2015. O delineamento experimental utilizado foi o de blocos ao acaso, com tratamentos arranjados em esquema fatorial 4 x 2, relativos a quatro períodos de fermentação do biofertilizante (10, 20, 30 e 40 dias) aplicados em solos com e sem adubação mineral, com quatro repetições e 18 plantas úteis por parcela. As plantas foram conduzidas durante 70 dias após o transplantio, em canteiros de 15 cm de altura, com 1 m de largura. Durante esse período, avaliou-se o crescimento, trocas gasosas e os componentes de produção. A adubação com biofertilizante mineral fermentado no período entre 20 e 30 dias associado à adubação mineral com 36 g m-2 de P2O5, 18,0 g m-2 de K2O e 14 g m-2 de N no plantio, proporcionou melhor desempenho no crescimento, trocas gasosas e produção da beterraba. No solo sem adubação mineral, recomenda-se a utilização dos maiores períodos de fermentação do biofertilizante, 30 a 40 dias, para o cultivo da beterraba.

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