The effect of climate change on electricity planning

The literature is vast in what regards the relationship between climate change (CC) and energy, especially in the sense of pointing this sector as an inducer of greenhouse gases (GHG) and demonstrating the importance of Renewable Energy Sources (RES) in mitigating these impacts. The relationships in the opposite direction, i.e. the way how CC could affect energy systems, are now being recognized as increasingly important by some international organizations and authors. This is precisely the focus of this paper, aiming to demonstrate how CC can affect RES and future electricity scenarios. The work addresses the particular case of Portugal and departed from the assessment of the impact of CC upon parameters of interest to hydro, wind and solar power production, according to international studies. This information was used as input of an optimization model for a long term power planning, resulting in the proposal of trajectories of the Portuguese electricity system under different CC assumptions.This research was supported by a Marie Curie International Research Staff Exchange Scheme Fellowship within the 7th European Union Framework Programme, under project NETEP- European Brazilian Network on Energy Planning (PIRSES-GA-2013-612263

N,N-Diprotected dehydroamino acid derivatives: versatile substrates for the synthesis of novel amino acids

Non-proteinogenic amino acids are an important class of organic compounds that can have intrinsic biological activity or can be found in peptides with antiviral, antitumor, anti-inflammatory or immunosuppressive activities. This type of compounds is also important in drug development, in the elucidation of biochemical pathways and in conformational studies. Therefore, research towards efficient methods that allow the synthesis of these compounds constitutes an important area of peptide chemistry. In our laboratories we have developed a new and high yielding method for the synthesis of N,N-diprotected dehydroamino acid derivatives using tert-butyl pyrocarbonate and 4-dimethylaminopyridine. These compounds were used as substrates in several types of reactions, allowing the synthesis of a variety of new amino acid derivatives. Some of these new compounds are heterocyclic systems or contain heterocyclic moieties such as pyrazole, indole, or imidazole. Thus, several nitrogen heterocycles were reacted with N,N-diprotected dehydroalanine to give new beta-substituted alanines and dehydroalanines. Furanic amino acids were obtained treating the methyl ester of N-(4-toluenesulfonyl), N-(tert-butoxycarbonyl) dehydroalanine with carbon nucleophiles of the beta-dicarbonyl type having at least one methyl group attached to one of the carbonyl groups. Treatment of these furanic amino acids with trifluoracetic acid afforded pyrrole derivatives in good to high yields. A N,N-diprotected 1,4-dihydropyrazine was obtained reacting the methyl ester of N-(4-toluenesulfonyl), N-(tert-butoxycarbonyl)dehydroalanine with 4-dimethylaminopyridine and an excess of potassium carbonate. Tetrahydropyrazines were synthesized by reaction of this 1,4-dihydropyrazine derivative with nucleophiles or by electrochemical reduction. Cleavage of the N-protecting groups from the 1,4-dihydropyrazine gave a disubstituted pyrazine. This review covers the synthesis of N,N-diprotected dehydroamino acids and their application as precursors for the synthesis of newFEDER - Federación Española de Enfermedades Raras (POCI/QUI/59407/2004

Synthesis of new beta-amidodehydroaminobutyric acid derivatives and of new tyrosine derivatives using copper catalyzed C-N and C-O coupling reactions

Several beta-amidodehydroaminobutyric acid derivatives were prepared from N,C-diprotected beta-bromodehydroaminobutyric acids and amides by a copper catalyzed C-N coupling reaction. The best reaction conditions include the use of a catalytic amount of CuI, N,N’-dimethylethylenediamine as ligand and K2CO3 as base in toluene at 110 ºC. The stereochemistry of the products was determined using NOE difference experiments and the results obtained are in agreement with an E-stereochemistry. Thus, the stereochemistry is maintained in the case of the E-isomers of beta-bromodehydroaminobutyric acid dervatives, but when the Z-isomers were used as substrates the reaction proceeds with inversion of configuration. The use of beta-bromodehydrodipeptides as substrates was also tested. It was found that the reaction outcome depend on the stereochemistry of the beta-bromodehydrodipeptide and on the nature of the first amino acid residue. The products isolated were the beta-amidodehydrodipeptide derivatives and/or the corresponding dihydropyrazines. The same catalytic system (CuI/N,N’-dimethylethylene diamine) was used in the C-O coupling reactions between a tyrosine derivative and aryl bromides. The new O-aryltyrosine derivatives were isolated in moderate to good yields. The photophysical properties of two of these compounds were studied in four solvents of different polarity. The results show that these compounds after deprotection can used as fluorescence markers.This work was financed by FEDER through "Programa Operacional Factores de Competitividade"-COMPETE and by FCT-"Fundacao para a Ciencia e Tecnologia" through project "Projecto Estrategico-UI 686-2011-2012" Ref: PEst-C/QUI/UI0686/2011. The NMR spectrometer is part of the National NMR Network (RNRMN) and was purchased in the framework of the National Programme for Scientific Re-equipment, contract REDE/1517/RMN/2005, with funds from POCI 2010 (FEDER) and Fundacao para a Ciencia e a Tecnologia (FCT) and is supported with funds from FCT. G. P. acknowledges FCT for a PhD grant SFRH/BD/38766/2007. H. V. acknowledges FCT for a PhD grant SFRH/BD/7265/2010

Synthesis and reactivity of a 1,4-dihydropyrazine derivative

N,N-Bis-(tert-butoxycarbonyl)-2,5-bis-methoxycarbonyl-1,4-dihydropyrazine can be obtained in high yield by treatment of the methyl ester of N-(4-toluenesulfonyl)-N-(tert-butoxycarbonyl)-alpha,beta-didehydroalanine with dimethylaminopyridine and potassium carbonate. This compound was used as substrate in Michael addition reactions with several types of nucleophiles. The electrochemical behaviour of this pyrazine derivative was also studied by cyclic voltammetry and by controlled potential electrolysis.We wish to thank the Fundação para a Ciência e a Tecnologia for financial support (project no. POCTI/1999/QUI/32689)

Limitations of thermal power plants to solar and wind development in Brazil

Some three fourths of electricity generation in Brazil come from renewables. Most of it is supplied by hydro, complemented by biomass-fueled thermal power plants and wind, while solar is still irrelevant. However, in the medium and long terms, a strong growth is expected for wind and solar in the country. Solar and wind resources are variable in time, partially unpredictable and cannot be dispatched to meet the load. These characteristics require system flexibility, which is the capacity of the power grid to adapt to different supply and demand patterns. Given that most thermal plants are not designed for a large frequency of operating cycles, renewables penetration may result in higher maintenance and operating costs, increased fuel consumption and reduced lifetime. Furthermore, some units might be called out-off-merit to maintain voltage and frequency levels. This paper presents preliminary results on the ability of thermal units to provide flexibility to the country´s grid, through an analysis for the Northeast region bounded by transmission constraints among 65 nodes (out of 196 nodes along the country). Results show that the power sector in Brazil might not be well equipped to deal with high penetration rates of variable renewable energy sources, with impacts on the capacity factor, and on the efficiency, of thermal power plants in the country. They also reveal that while wind energy increases the need of ramping capabilities, solar has greater impacts on the number of starts and shutdowns of conventional units.This research was supported by a Marie Curie International Research Staff Exchange Scheme Fellowship within the 7th European Union Framework Programme, under project NETEP- European Brazilian Network on Energy Planning (PIRSES-GA-2013-612263). The authors would also like to express their gratitude to the Coordination for the Improvement of Higher Education Personnel (CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for the essential support given for this work to be carried out

Supramolecular dehydropeptide hydrogels: synthesis, properties and biomedical applications

Self-assembled low molecular weight peptide hydrogels have emerged in recent years as the new paradigm in biomaterials research due to their high water content; fully organic struc-ture; intrinsic nontoxicity and biocompatibility and fibrillar nanostructure indicative of the ex-tracellular matrix.1 The properties of peptide hydrogels can be tuned by design and there is a large variety of possible hydrogelator structures using proteinogenic and non proteinogenic aminoacids. Our research group has recently described a series of self-assembled hydrogels based on dehydrodipeptides N-protected with an aromatic moiety. The C-terminal dehy-droaminoacid residue (dehydrophenylalanine, dehydroaminobutyric acid and dehydroalanine) is prone to make the peptide resistant to prote-olysis and restrains the conformational freedom of the peptide.2 In this work the preparation and characterization of the new hydrogelators as well as the corresponding hydrogels will be presented together with some biomedical appli-cations of the new biomaterials prepared name-ly as drug delivery systems or as plataforms for theragnostics.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding of CQUM (UID/QUI/00686/2016) and CF-UM-UP (UID/FIS/04650/2013 and UID/FIS/04650/ 2019), FEDER, PORTUGAL2020 and COMPETE2020 are also acknowledged for funding under the research projects PTDC/QUI-QFI/28020/2017 (POCI-01-0145-FEDER-028020) and PTDC/QUI-QOR/29015/ 2017 (POCI-01-0145-FEDER-029015)

Supramolecular ultra-short dehydropeptide-based hydrogels as potential affordable nanocarriers

A library of Cbz-protected dehydrodipeptides was synthesised and evaluated as minimalist hydrogels. The molecular aggregation, self-assembly, gelation and biocompatibility were thoroughly studied through fluorescence spectroscopy, and the mechanical properties were assessed. The compounds that afforded hydrogels were evaluated as drug delivery systems for curcumin and doxorubicin using biomembrane models.UIDB/04650/2020; UIDB/00686/2020; PTDC/QUI-QFI/28020/2017; PTDC/QUI-QOR/29015/2017; SFRH/BD/144017/201

Supramolecular plasmonic magnetic gels for controlled drug delivery

In this work, two different magnetic/plasmonic nanoparticle architectures were developed, characterized and combined with a naproxen N-capped dehydropeptide-based hydrogel. Spectroscopic techniques and rheologic assays were used were used to assess the gel physicochemical properties, the incorporation of a model drug (curcumin), drug transport towards model membranes and controlled drug release

Electrochemical synthesis of diaminodicarboxylic acid derivatives

Diaminoadipic acid derivatives were synthesized in good yields by electrolysis of N,N-diacyidehydroalanines. Cyclic voltammetry measurements on the precursors are presented and interpreted as supporting formation of a nucleophilic intermediate generated by electrochemical reduction. (C) 2003 Elsevier Science Ltd. All rights reserved.- Fundação para a Ciência e a Tecnologia (project no. POCTI/1999/QUI/32689)

Synthesis of 2,6-bis-(oxazolyl)pyridine ligands for luminescent Ln(III) complexes

Submitted to the European Journal of Organic ChemistryNew bis-(oxazolyl)pyridine ligands for Ln(III) ions were prepared using a expeditious methodology from threonine and dipicolinic acid chloride. The synthetic strategy includes a dehydration step to give a bis-dehydroaminobutyric acid derivative followed by bromination and cyclization with DBU. Photophysical studies of Eu(III) and Tb(III) complexes of these ligands showed that the 2,6-bis-(oxazolyl)pyridine moiety acts as an effective sensitizer for lanthanide luminescence and indicate the formation of 3:1 complexes [Ln-(bis-(oxazole)pyridine)3]3+.Fundação para a Ciência e Tecnologia (FCT), QREN, FEDER/E