Immobilization of lipases and assay in continuous fixed bed reactor

Lipases are versatile enzymes regarding the range of reactions they catalyse and substrates on which they act. They are as well important as catalyst in organic synthesis. Their immobilization on appropriate supports confer them greater stability besides the possibility of operating in continuous reactors. In order to explore these abilities, the reactions involving hydrolysis of p-nitrophenyl acetate (PNPA) and transesterification of PNPA with n-butanol were chosen. Lipases from two different sources were assayed, namely: microbial (Candida rugosa, CRL, Sigma Type VII) and pancreatic (PPL, Sigma, Type 11). Two immobilization methods were also used, namely: 1) adsorption, using as support the following silica derivatives (150-300μm e 450μ): phenyl, epoxy, amino and without derivation, and 2) covalent binding, using glutaraldehyde as binding agent and silica amino as support. This later method led to better results. Hydrolytic activity was 6.1 U/gsupport for CRL and 0.97U/gsupport for PPL, and of transesterification, 2,8U/gsupport for CRL and 1,9U/gsupport for PPL. Stability of the immobilized enzyme as a function of temperature was evaluated for CRL at 40°C and 50°C and for PPL at 32°C and 40°C. The assays were initially carried out batchwise, both for soluble and immobilized enzymes, aiming to the obtention of parameters for the continues reactor. Lipases immobilized by covalent binding were used in the assays of operacional stability in continuos reactors. For PPL in aqueous medium, at 32°C, and CRL in organic medium at 40°C, both operating continuously, no significant loss of activity was detected along the analysis period of 17 days. In the case of CRL in aqueous medium at 40°C there was a loss of activity around 40% after 18 days. For PPL in organic medium at 40°C the loss was 33% after 20 days. Compairing both sources with each other, very different results were obtained. Higher activitiy was found for CRL, both for hydrolysis and for transesterification reactions, with higher stability in organic medium. PPL showed lower activity as well as higher stability in aqueous medium. The immobilization method by covalent binding showed to be the most appropriate. Immobilized lipases are therefore relatively stable both in aqueous and organic medium.

Microondas doméstico na síntese de derivados ftalimídicos

Microwaves have been used in organic synthesis, since 1986, and have proved advantageous in several respects: the possibility of higher yields, greater selectivity and less thermal decomposition. Phthalimide and its derivatives constitute an important class of compounds for use in synthetic organic chemistry; in medicinal chemistry, it is considered an important biophore, acting as a pharmacophoric structural subunit for the synthesis of a number of compounds with different pharmacological uses, such as against sickle-cell disease. The purpose of the work reported here was to develop an alternative method for the synthesis of phthalimide derivatives by exploiting the condensation of phthalic anhydride with amino groups under microwave radiation. The results showed that phthalimide derivatives were obtained in shorter reaction times (5-10 min) and higher yields (60-89%) than by with conventional heating (reflux), demonstrating the potential use of microwaves in the synthesis of this class of molecules.

Preparação e caracterização estrutural de complexos quirais de nióbio, utilizando álcoois terpênicos quirais como ligantes

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Desenvolvimento de compostos potencialmente ativos contra Helicobacter Pylori

Pós-graduação em Ciências Farmacêuticas - FCFAR

Espectroscopia de infravermelho e suas aplicações

Infrared spectroscopy (IR spectroscopy) explores the infrared region of the electromagnetic spectrum. Like any other spectroscopic technique, it can be used to identify a compound or the composition of investigate a sample. Spectroscopy (IR) is a very important technique in qualitative chemical analysis, widely used in the chemistry of natural products, organic synthesis and transformations. In this work we study of the theoretical foundations of infrared spectroscopy, the different vibration modes, experimental techniques, and the identification and characterization of solids. Were studied as applications: their use in thermograph and remote sensing satellites

Lipases microbianas: produção, propriedades e aplicações biotecnológicas

Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)

Recent advances in nanoparticle carriers for coordination complexes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Síntese e caracterização de monômeros azo-carbonatos para a preparação de poli(azo-carbonato)s e poli)azo-uretana)s

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Metallic chalcogenolates mediated modular Michael-aldol cascade reaction: an easy route to multi-functionalized chalcogenides and Morita-Baylis-Hillman adducts

Chalcogenolate mediated Michael-aldol cascade reactions consists of a very efficient route to multi-functionalized gamma-hydroxichalcogenides. Although, when selenolates are employed, these gamma-hydroxichalcogenides can be readily converted into the corresponding Morita-Baylis-Hillman adducts by oxidative elimination of the selenium moiety. In this context, herein we present a complete study on the scope and limitations of this reaction. (C) 2012 Elsevier Ltd. All rights reserved.

New insights on reaction pathway selectivity promoted by crown ether phase-transfer catalysis: Model ab initio calculations of nucleophilic fluorination

Crown ethers have the ability of solubilizing inorganic salts in apolar solvents and to promote chemical reactions by phase-transfer catalysis. However, details on how crown ethers catalyze ionic S(N)2 reactions and control selectivity are not well understood. In this work, we have used high level theoretical calculations to shed light on the details of phase-transfer catalysis mechanism of KF reaction with alkyl halides promoted by 18-crown-6. A complete analysis of the of the model reaction between KF(18-crown-6) and ethyl bromide reveals that the calculations can accurately predict the product ratio and the overall kinetics. Our results point out the importance of the K* ion and of the crown ether ring in determining product selectivity. While the K* ion favors the S(N)2 over the E2 anti pathway, the crown ether ring favors the S(N)2 over E2 syn route. The combination effects lead to a predicted 94% for the S(N)2 pathway in excellent agreement with the experimental value of 92%. A detailed analysis of the overall mechanism of the reaction under phase-transfer conditions also reveals that the KBr product generated in the nucleophilic fluorination acts as an inhibitor of the 18-crown-6 catalyst and it is responsible for the observed slow reaction rate. (C) 2012 Elsevier B.V. All rights reserved.

Novel cross-coupling reactions between organotellurides and Grignard reagents employing a MnCl2/CuI catalytic system

We present a general protocol for the cross-coupling reaction of Grignard reagents and organic tellurides. Aryl Grignard reagents react stereospecifically with vinyl tellurides in the presence of a catalytic amount of manganese (II) chloride and copper (I) iodide to produce good yields of the corresponding cross-coupling products. (C) 2012 Published by Elsevier Ltd.

Metabolic engineering of beta-oxidation in Penicillium chrysogenum for improved semi-synthetic cephalosporin biosynthesis

Industrial production of semi-synthetic cephalosporins by Penicillium chrysogenum requires supplementation of the growth media with the side-chain precursor adipic acid. In glucose-limited chemostat cultures of P. chrysogenum, up to 88% of the consumed adipic acid was not recovered in cephalosporinrelated products, but used as an additional carbon and energy source for growth. This low efficiency of side-chain precursor incorporation provides an economic incentive for studying and engineering the metabolism of adipic acid in P. cluysogenum. Chemostat-based transcriptome analysis in the presence and absence of adipic acid confirmed that adipic acid metabolism in this fungus occurs via beta-oxidation. A set of 52 adipate-responsive genes included six putative genes for acyl-CoA oxidases and dehydrogenases, enzymes responsible for the first step of beta-oxidation. Subcellular localization of the differentially expressed acyl-CoA oxidases and dehydrogenases revealed that the oxidases were exclusively targeted to peroxisomes, while the dehydrogenases were found either in peroxisomes or in mitochondria. Deletion of the genes encoding the peroxisomal acyl-CoA oxidase Pc20g01800 and the mitochondrial acyl-CoA dehydrogenase Pc20g07920 resulted in a 1.6- and 3.7-fold increase in the production of the semi-synthetic cephalosporin intermediate adipoyl-6-APA, respectively. The deletion strains also showed reduced adipate consumption compared to the reference strain, indicating that engineering of the first step of beta-oxidation successfully redirected a larger fraction of adipic acid towards cephalosporin biosynthesis. (C) 2012 Elsevier Inc. All rights reserved.

Gekreuzt konjugierte Oligomere aus Benzolringen und Heterocyclen

Gekreuzt konjugierte Oligomere aus Benzolringen und Heterocyclen Oligomere aus Arylen- oder/und Hetarylen-Bausteinen stellenein aktuelles Arbeitsgebiet in der organischen Synthese undder Materialwissenschaft dar. Die Enoneinheit der Chalkonerepräsentiert ein bifunktionelles Elektrophil, das für denAufbau von unterschiedlichen Heterocyclen hervorragendgeeignet ist. Im Rahmen der vorliegenden Arbeit wurden dreineue Reihen von heterocyclischen Oligomeren hergestellt:1H-Pyrrole, 1H-Pyrazole und Pyridine, die über eine alter-nierende Sequenz von Phenylen- oder Benzoylen-Einheitenverbunden sind. Ihre Herstellung basierte auf Michael-Additionen von den kettenförmigen, gekreuzt konjugiertenOligochalkonen und den jeweiligen geeigneten N-haltigenBausteinen: Tosylmethylisocyanid, Methylhydrazin undPhenacylpyridiniumbromid in der Reihe der Pyrrole, Pyrazoleund Pyridine. Die UV/Vis-Untersuchung aller Reihen der Oligoheterocyclenzeigte als allgemeinen Trend im Vergleich mit dem UV/Vis-Verhalten der Oliogochalkone eine ausgeprägte hypsochromeVerschiebung der langwelligen Absorption. Dieser beobachtetehypsochrome Shift geht auf die veränderten Chromophore zurück und deutet außerdem darauf hin, dass die effektiveKonjugation bei wachsender Moleküllänge geringer sein sollte. In den einzelnen Reihen der Oligoheterocyclenerkennt man jeweils bei Vergrößerung der Chromophore einenkleinen bathochromen Shift der langwelligen Absorption.

Development of Organocatalytic stereoselective SN1 type reactions

The proposal in my thesis has been the study of Stereoselective α-alkylation through SN1 type reaction. SN1 type reaction involves a stabilized and reactive carbocation intermediate By taking advantages of stability of particular carbocations, the use of carbocations in selective reactions has been important. In this work has been necessary to know the stability and reactivity of carbocations. And the work of Mayr group has helped to rationalize the behaviour and reactivity between the carbocations and nucleophiles by the use of Mayr’s scale of reactivity. The use of alcohols to performed the stable and reactive carbocations have been the key in my thesis. The direct nucleophilic substitution of alcohols has been a crucial scope in the field of organic synthesis, because offer a wide range of intermediates for the synthesis of natural products and pharmaceutics synthesis. In particular the catalytic nucleophilic direct substitution of alcohols represents a novel methodology for the preparation of a variety of derivatives, and water only as the sub-product in the reaction. The stereochemical control of the transformation C-H bond into stereogenic C-C bond adjacent to carbonyl functionalized has been studied for asymmetric catalysis. And the field of organocatalysis has introduced the use of small organic molecule as catalyst for stereoselective transformations. Merging these two concepts Organocatalysis and Mayr’s scale, my thesis has developed a new approach for the α-alkylation of aldehydes and ketones through SN1 type reaction.

Oxidative properties of the Iron - Thymine-1-acetic acid - Hydrogen peroxide catalytic system

The oxidation of alcohols and olefins is a pivotal reaction in organic synthesis. However, traditional oxidants are toxic and they often release a considerable amounts of by-products. Here, two IronIII-based systems are shown as oxidative catalyst, working in mild conditions with hydrogen peroxide as primary oxidant. An efficient catalytic system for the selective oxidation of several alcohols to their corresponding aldehydes and ketones was developed and characterized, [Fe(phen)2Cl2]NO3 (phen=1,10-Phenantroline). It was demonstrated that the adoption of a buffered aqueous solution is of crucial importance to ensure both considerable activity and selectivity.The Iron - Thymine-1-acetic acid in-situ complex was studied as catalyst in alcohol oxidations and C-H oxidative functionalization, involving hydrogen peroxide as primary oxidant in mild reaction conditions. The catalytic ability in alcohol oxidations was investigated by Density Functional Theory calculations, however the catalyst still has uncertain structure. The system shows satisfactory activity in alcohol oxidation and aliphatic rings functionalization. The Fe-THA system was studied in cyclohexene oxidation and oxidative halogenations. Halide salts such as NBu4X and NH4X were introduced in the catalytic system as halogens source to obtain cyclohexene derivatives such as halohydrins, important synthetic intermediates.The purpose of this dissertation is to contribute in testing new catalytic systems for alcohol oxidations and C-H functionalization. In particular, most of the efforts in this work focus on studying the Iron - Thymine-1-acetic acid (THA) systems as non-heme oxidative model, which present: •an iron metal centre(s) as a coordinative active site, •hydrogen peroxide as a primary oxidant, •THA as an eco-friendly, biocompatible, low cost coordinating ligand.