90 research outputs found
Otimização da síntese de ésteres usados na indústria de sabores e aromas
No full textTCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Físicas e Matemáticas. Curso de Química.Ésteres constituem uma das classes de substâncias químicas largamente encontradas na natureza. Alguns ésteres, de baixo peso molecular, tendem a apresentar sabor e aroma agradáveis e, por isso, são bastante usados em alimentos e bebidas industrializadas. Os ésteres podem ser sintetizados através da reação entre um ânion carboxilato e um haleto de alquila, ou ainda, pela reação de esterificação de Fischer, que é a esterificação de um ácido carboxílico com um álcool, catalisada por ácido. Esta última tem maior ênfase devido à viabilidade de aplicação industrial, e foi a utilizada no presente trabalho. Neste trabalho foram sintetizados o butirato de isoamila e o butirato de etila. Objetivando deslocar o equilíbrio da reação para a formação de produtos foram realizados experimentos como: retirada da fase aquosa, uso de agentes secantes (MgSO4 e CaCl2) e uso de meio heterogêneo (hexano e óleo mineral). Os parâmetros avaliados foram a temperatura, estequiometria dos reagentes e quantidade e tipo de catalisador. As conversões, de ácido butírico em butirato de etila, obtidas foram de 65 a 75%, tendo como melhor método a utilização do secante MgSO4 e para o butirato de isoamila ficou na faixa de 90 a 95% usando método extrativo da água da reação. Os resultados obtidos mostram a viabilidade da técnica do uso de MgSO4 e retirada de fase aquosa na síntese de butirato de etila. Para a o éster butirato de isoamila os resultados mostraram a alta viabilidade de utilização do Dean Stark para ésteres que derivem de alcoóis insolúveis em água e/ou alto ponto de ebulição
Molecular Physiology in Molluscs of Economic or Ecological Importance
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
The Total Synthesis of Dragmacidins D and F
No full textThe dragmacidins are an emerging class of bis(indole) natural products isolated from deep-water marine organisms. Although there has been a substantial effort to prepare the simple piperazine dragmacidins, little synthetic work has been done in the area of the pyrazinone-containing family members, dragmacidins D, E, and F. These compounds are particularly interesting due to their complex structures and broad range of biological activity.
A highly convergent strategy to access dragmacidin D has been developed. In this approach, sequential halogen-selective Suzuki couplings were used to assemble the carbon scaffold of the natural product. After executing a highly optimized sequence of final events, the first completed total synthesis of dragmacidin D was achieved.
An enantiodivergent strategy for the total chemical synthesis of both (+)- and (-)-dragmacidin F from a single enantiomer of quinic acid has been developed and successfully implemented. Although unique, the synthetic routes to these antipodes share a number of key features, including novel reductive isomerization reactions, Pd(II)-mediated oxidative carbocyclization reactions, halogen-selective Suzuki couplings, and high-yielding late-stage Neber rearrangements.
The formal total syntheses of dragmacidin B, trans-dragmacidin C, and dihydrohamacanthin A are described. In addition, preliminary studies involving a novel approach for the preparation of dragmacidin E are reported.</p
Architecture for children
No full textCelem naukowym jest zbadanie wpływu przestrzeni kreatywnych na kształtowanie architektury adresowanej do dzieci na przykładzie realizacji japońskiej pracowni HIBINOSEKKEI + Youji no Shiro. Studium przypadku trzech wyselekcjonowanych przedszkoli, reprezentatywnych w ocenie autorki w kontekście przestrzeni kreatywnych, pozwoliło na wyciągnięcie wniosków dotyczących pozytywnego wpływu tak kształtowanych przestrzeni na wieloaspektowy rozwój dziecka.For the following study, the scientific goal adopted is to investigate the impact creative space exerts on shaping architecture addressed to children. The study is based on the example of the project implementation of the Japanese HIBINOSEKKEI + Youji no Shiro studio. A case study of three selected pre-schools that, according to the author, are representative in the context of creative spaces, made it possible to draw conclusions regarding the positive impact that spaces shaped in such as way have on the multi-faceted development of the child
Genistein inhibits placental choriocarcinoma cell line JAR invasion through ERβ/MTA3/Snail/E-cadherin pathway
No full textRe-expression of estrogen receptor β inhibits the proliferation and migration of ovarian clear cell adenocarcinoma cells
No full textMalay narratives in Nanyang travel
No full text“Nanyang” 南洋was a general term used by the Chinese for Southeast Asia before World War II. After the 19th century, the Chinese moved to Nanyang in succession. Located at the centre of “Nanyang”, the Malay Peninsula and Singapore became the gathering place of the Chinese at that time and they unexpectedly encountered the indigenous Malay civilisation, thus arousing cultural interaction and immersion. In the 1920s and 1930s, a large number of Chinese literati came to the south for various purposes such as seeking relatives and friends, travelling, investigating, or settling down for a long time, and they recorded the experiences
of what they saw and heard in Nanyang in travel records or books. The “Nanyang Youji” 南洋游记 (Nanyang Travels) mainly recorded the customs and anecdotes of the Nanyang society. It is rich in content, diverse in subject matter, and large in volume. It also has a
unique writing style, with great literary, historical, and even cultural anthropology value. Although the content of “Nanyang Youji” is mainly based on Chinese society and culture, many of them also contain records of the Malay customs and culture that the author personally witnessed which are thus, very precious. This article reviews several “Nanyang Youji” travel records to gain an insight into the Malay society and the Chinese-Malay cultural interaction from the perspective of the early Nanyang travellers
Asymmetric methodologies for the construction of 5,7,5- and 6,6,6-tricyclic sesquiterpene lactones towards the synthesis of Arglabin
No full textMany naturally extracted guaianolides (i.e. GLs) and pseudoguaianolides are based on the 5,7,5-fused ring skeleton and they show a broad biological profile. Among them, Arglabin has attracted special attention due to its promising antitumor and cytotoxic activity as an inhibitor of Farnesyltransferase. In the present work the asymmetric synthesis towards Arglabin was investigated via gamma-butyrolactone carbaldehyde (i.e. GBL) as key intermediate. For the synthesis of GBL, the enantiomerically pure cyclopropane carbaldehyde (i.e. CPC) and enantiomerically pure cyclopentenyl allylsilane are necessary. Asymmetric cyclopropanation of furancarboxylate using an asymmetric BOX ligand, subsequent ozonolysis, and recrystallization afforded CPC. The synthesis of enantiomerically enriched cyclopentenyl allylsilane was achieved from fufuryl alcohol via enzymatic kinetic resolution using lipase, conjugate addition leading to silyl enol ether, and coupling reaction with the silyl enol ether and Grignard reagent under Ni(acac)2 catalyst as key steps. Sakurai allylation and retro-aldol lactonization under basic condition afforded 2,3-anti-substituted GBL. Diastereoselectivity was studied during the Sakurai allylation and retro-aldol lactonization sequence. Further transformations of GBL were carried out subsequently, such as Sakurai allylation, ring closing metathesis, desoxygenation, epoxidation, debenzylation, formation of olefin via syn-elimination of hydrate, and alpha-dimethylaminomethylation using Eschenmoser�s salt. The directing effect of homoallylic alcohol during an epoxidation and the regioselectivity of syn-elimination reactions depending on reaction temperature were investigated in detail
An Empirical Study on Evolution of the Connectivity for VANETs Based on Taxi GPS Traces
No full textNetwork connectivity is a fundamental requirement for intervehicle communication and services in VANETs. The fast movement of the vehicles results in rapid changes in network topology generating dynamic variation in network connectivity, which causes dynamic variation in network connectivity. In this paper, we analyze the evolution of the VANETs connectivity based on the realistic data collected by the GPS devices installed on taxis in Shanghai. The study of the evolution characteristics shows that the number of connected components, the size of the giant component, and the connectivity length time series possess strong temporal correlation and long-range dependence. As a result, the short-range dependent processes such as the exponential, normal, or Poisson distributions cannot capture the statistical distribution characteristics. Moreover, all connectivity parameters cannot be described by unimodal distributions. We also conclude that although the whole topology of the VANETs is broken into a large number of small-sized connected components under small transmission radius, the size of the giant component keeps stable when transmission radius reaches the threshold. These results will be helpful to optimize the RSUs deployment and transmission radius to keep the giant component stable and design more efficient strategies to forward the information in VANETs
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