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Artificial photosynthesis enables the conversion and storage of solar energy into chemical energy, producing substances with high energy content. In this sense, the oxidation of water can provide the H+ ions and electrons needed for the energy conversion and storage processes. Since 2005, it has been known that single-site coordination compounds can act as water oxidation catalysts (WOC). Improvement of the catalytic activity, however, has occurred mainly by the choice of the redox-active metal matching with a series of compatible ligands, more specifically, paying attention to the electronic characteristics of the organic framework of the first coordination sphere. Recently, the use of dangling bases dramatically increased the catalytic activity of new species as WOC, taking advantage of what is called a second coordination sphere. With this assistance, some compounds were shown to reach turnover frequencies (TOF) of 104 s-1, while compounds with the first coordination sphere commonly exhibit TOF ca. 10-1 s-1. In this manuscript, we discuss the concept, together with a number of examples, of the use of controlled interactions between the first and second coordination spheres that have been wielded to improve the performance of ruthenium-centered complexes as WOC in water oxidation reactions.

A state-of-the-art method was developed for repurposing nitrone-containing compounds in the chemosensory field, the ability of the designed molecules to chelate metal cations was evaluated, and their unprecedented solubility in water was confirmed. A facile, rapid, and solvent-free method of synthesizing small molecular mass chemosensors was developed by using a modulative α-aryl-N-aryl nitrone template. α-(Z)-Imidazol-4-ylmethylen-N-phenyl nitrone (Nit1) and α-(Z)-2-pyridyl-N-phenyl nitrone (Nit2) were prepared in 15 min, isolated in less than 60 min with ca. 90% yield, and screened against nine metal cations. Nit1 is a small-molecular-mass compound (188 g mol−1) that is water-soluble and has specificity for sensing Cu2+ with an association constant of K = 1.53 x 1010 and a limit of detection (LOD) of 0.06 ppm. These properties make Nit1 a competitive chemosensor for the detection of Cu2+ in aqueous solution. The nitrone-containing template used in this study is a step forward for new and small chemosensory entities.

Made available in DSpace on 2018-11-27T07:08:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-02-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundacao de Amparo Pesquisa do Estado de Sao Paulo Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Budesonide (BUD) is a glucocorticoid widely used for the treatment of ulcerative colitis. In this work, we propose the study of the system BUD-HP-beta-CD inclusion complex incorporated into PL 407 and PL407-PL403 thermoreversible hydrogels, considering physico-chemical and pharmaceutical aspects. Complexation between BUD and HP-beta-CD was confirmed by phase solubility studies (1:1 stoichiometry, Kc = 8662.8 M-1), DSC, FTIR and microscopy analyzes. BUD solubility in simulated upper and lower colon fluids was improved in a dependence of HP-beta-CD and PL 407 or PL407-PL403 association. Micellar hydrodynamic diameter studies showed the interaction between HP-beta-CD and PL blocks, as well as the reorganization of the micellar system in the presence of BUD and its inclusion complex. Micellization temperature (T-m) was not shifted, but sol-gel phase transition studies showed that in the presence of BUD, HP-beta-CD or BUD:HP-beta-CD complex, the association PL407-PL403 favored the gel formation close to the physiological temperature. Physico-chemical and in vitro release assays studies revealed no competitive displacement of BUD from the HP-beta-CD cavity evoked by PL407 or PL407-PL403 addition. These findings point out the BUD-HP-beta-CD in PL-based hydrogels as strategies for future investigations on development of new pharmaceutical formulations for the treatment of ulcerative colitis. (C) 2015 Elsevier B.V. All rights reserved. Univ Fed Abc, Ctr Ciencias Nat & Humanas, BR-09210580 Santo Andre, SP, Brazil State Univ Julio de Mesquita Filho, Dept Enviroment Engn, Sorocaba, SP, Brazil Univ Estadual Campinas, Inst Biol, Dept Biochem, Campinas, SP, Brazil Fac Dent Sao Leopoldo Mand, Campinas, SP, Brazil State Univ Julio de Mesquita Filho, Dept Enviroment Engn, Sorocaba, SP, Brazil Fundacao de Amparo Pesquisa do Estado de Sao Paulo: FAPESP 2014/26200-9 Fundacao de Amparo Pesquisa do Estado de Sao Paulo: 2014/14457-5 CNPq: CNPq 487619/2012-9 CNPq: 309612/2013-6

In this work, enantiopure 1,1’-bi-2-naphthol (BINOL) derivatives and carboxylic acids were evaluated as chiral solvating agents (CSAs) in the nuclear magnetic resonance (NMR) chiral discrimination of primary amines. Among the CSAs screened, the readily available (+)-BINOL revealed a simple and rapid chiral auxiliary for 1H NMR chiral discrimination. The procedure required few minutes, assigning of the absolute configuration. The protocol was improved using the 1H pure shift pulse sequence for overcrowded alkyl primary amines due to the absence of JHH couplings. The 1H pure shift NMR experiment and the readily available (+)-BINOL chiral auxiliary can be used for routine chiral discrimination analysis of complex NMR spectra.

Lithium nbutylchalcogenolates are generated in situ by reacting the elements (S, Se, and Te) with nbutyllithium at 0 °C. Reaction of the lithium alkylchalcogenolates with activated alkenes and aldehydes gives the corresponding aldol adducts. The selenium-containing products give Morita–Baylis–Hillman adducts after the oxidation/elimination of the selenoxide. The whole sequence can be performed in a one-pot procedure.

The mechanism of the addition reaction of TeCl 4 to alkynes was indirectly established by the detection of TeCl 3 centered radicals using EPR spin trapping, ESI-MS and ESI-MS/MS characterization.

The use of whole cells of micro-organisms to bring about the biotransformation of an organic compound offers a number of advantages, but problems caused by enzymatic promiscuity may be encountered upon with substrates bearing more than one functional group. A one-pot screening method, in which whole fungal cells were incubated with a mixture of 4-methylcyclohexanone 1 and phenyl methyl sulfide 2 , has been employed to determine the chemoselectivity of various biocatalysts. The hyphomycetes, Aspergillus terreus CCT 3320 and A. terreus URM 3571, catalysed the oxidation of 2 accompanied by the reduction of 1 to 4-methylcyclohexanol 1a and, for strain A. terreus CCT 3320, the Baeyer-Villiger oxidation of 1 . The Basidiomycetes, Trametes versicolor CCB 202, Pycnoporus sanguineus CCB 501 and Trichaptum byssogenum CCB 203, catalysed the oxidation of 2 and the reduction 1 , but no Baeyer–Villiger reaction products were detected. In contrast, Trametes rigida CCB 285 catalysed the biotransformation of 1 to 1a , exclusively, in the absence of any detectable sulfide oxidation reactions. The chemoselective reduction of (±)-2-(phenylthio)cyclohexanone 3 by T. rigida CCB 285 afforded exclusively the (+)- cis -(1 R , 2 S) and (+)- trans -(1 S ,2 S ) diastereoisomers of 2-(phenylthio)cyclohexan-1-ol 3a in moderate yields (13% and 27%, respectively) and high enantiomeric excesses (>98%). Chemoselective screening for the reduction of a ketone and/or the oxidation of a sulfide group in one pot by whole cells of micro-organisms represents an attractive technique with applications in the development of synthesis of complex molecule bearing different functional groups.

The first experimental evidence for the formation of an organic tellurium-centered radical (RTe•, R = Ph or nBu groups) during the hydrotelluration of alkenes and alkynes is provided. The radicals were detected by electronic paramagnetic ressonance (EPR), using DBNBS (3,5-dibromo-4-nitrosobenzenesulfonate) as the spin trap. The radical adducts (DBNBS/•TenBu and DBNBS/•TePh) presented an EPR spectrum characterized by a triplet of triplets due to one nitrogen and two equivalent hydrogen atoms (aN = 21.6 G and aH = 0.7 G) and a g value of 2.0060. The presence of tellurium radical adducts was confirmed by isotopic substitution (125Te) and by electrospray and chemical ionization mass spectrometry and MS/MS analysis. The products showed isotopic patterns expected for compounds containing Br and Te. These results provide evidence for organic tellurium-centered radical formation and suggest that the hydrotelluration reactions occur by a free radical mechanism.

The potential of different Aspergillus strains in carrying out the biotransformation of cyclic ketones was investigated. All the strains employed showed alcohol dehydrogenase and Baeyer–Villiger monooxygenase activities. trans -2-Methylcyclohexanol and trans -4-methylcyclohexanol were prepared in a single isomeric form by the use of Aspergillus terreus SSP 1498 and the corresponding ketones. Baeyer–Villiger oxidation of cyclic ketones by all the fungi Aspergillus led to chiral lactones in good enantioselectivity.

Experimental conditions using whole cells to select fungal strains for specific bioreduction of ketones and formation of Baeyer–Villiger oxidation products were studied. Epicoccum nigrum SSP 1498 was effective in the bioreduction leading to the chiral alcohols in up to 98% enantiomeric excess. High acetophenone monooxygenase activity was observed by the use of the fungus Emericella nidulans CCT 3119 as biocatalyst.

Lithium nbutylchalcogenolates are generated in situ by reacting the elements (S, Se, and Te) with nbutyllithium at 0 °C. Reaction of the lithium alkylchalcogenolates with activated alkenes and aldehydes gives the corresponding aldol adducts. The selenium-containing products give Morita–Baylis–Hillman adducts after the oxidation/elimination of the selenoxide. The whole sequence can be performed in a one-pot procedure.

Through direct transmetalation reaction of Z-vinylic tellurides with nBuLi was observed the unexpected isomerization of double bonds leading to potassium E-vinyltrifluoroborates salts in low to moderate yields. Using EPR spin trapping experiments the radical species that promoted the stereoinversion of Z-vinylic organometallic species during the preparation of potassium vinyltrifluoroborate salts was identified. The experiments support the proposed mechanism, which is based on the homolytic cleavage of the TenBu bond.

Nesse trabalho avaliamos o potencial enzimático de diferentes linhagens de fungos, visando determinar a presença de mono-oxigenases capazes de oxidar cetonas aromáticas e cíclicas. Todas as linhagens empregadas apresentaram atividade de álcool desidrogenase e Baeyer-Villiger mono-oxigenases. Adicionalmente foram sintetizadas oito moléculas bi-funcionalizadas com grupos sulfeto, seleneto e carbonila (cetona). Os produtos das reações biocatalisadas foram isolados e caracterizados. In this work, we evaluated the enzymatic potential of different Aspergillus strains, through the biotransformations of two substrates: 2- and 4-methylcyclohexanone (1a e 1b). All the strains employed showed alcohol dehydrogenase and Baeyer-Villiger monooxygenase (CPMO and CHMO) activities. These enzymes can perform ketone biorreduction and oxidation. Using the A. terreus SSP 1498 selected from the screening study, we prepared alcohols and lactones in good enantiosselectivity. In this way, other fungal strains were studied aiming to determine the presence of monooxygenase activity by means of the biotransformation of aromatic ketones. Like the Aspergillus, we observed that all strains used in this study showed alcohol dehydrogenase and Baeyer-Villiger monooxygenase (APMO) activities. We selected 1-phenyl-etanone and its para substituted derivates as substrates. Additionally, we synthesized eight examples of bi-functionalized compounds with sulfide, selenide and ketone groups. These compounds were submitted to the action of enzymatic system of different fungi which were selected from the initial screening. The products from the biotransformation were isolated and characterized.