Absolute Configuration
Mostrando 1-12 de 101 artigos, teses e dissertações.
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1. Absolute Configuration Reassignment of Natural Products: An Overview of the Last Decade
The assignment of absolute configuration (AC) is a crucial step in the structural characterization of natural products, especially for those subjected to biological assays. Methods such as X-ray crystallography, stereocontrolled organic synthesis, nuclear magnetic resonance (NMR), and chiroptical spectroscopies are commonly used to determine the AC of chiral
J. Braz. Chem. Soc.. Publicado em: 2021-08
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2. Absolute Configuration of (−)-Cubebin, a Classical Lignan with Pharmacological Potential, Defined by Means of Chiroptical Spectroscopy
This work describes the first determination of the absolute configuration (AC) of (−)-cubebin by means of electronic circular dichroism (ECD), supported by quantum chemical calculations. The comparison of experimental ECD with the corresponding quantum chemical prediction for the proper diastereoisomer resulted in the definitive assignment of the AC of the
J. Braz. Chem. Soc.. Publicado em: 2020-10
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3. Isolation, Absolute Configuration and Cytotoxic Activities of Alkaloids from Hippeastrum goianum (Ravenna) Meerow (Amaryllidaceae)
The phytochemical study of Hippeastrum goianum led to the identification of 13 compounds by means of gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR). Compounds 7-demethoxy-9-O-methylhostasine (1) and 7-deoxi-trans-dihydronarciclasine (2) had their absolute configurations determined by vibrational circular dichroism (VCD). Th
J. Braz. Chem. Soc.. Publicado em: 2020-10
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4. Structure and Absolute Configuration of Secondary Metabolites from Two Strains of Streptomyces chartreusis Associated with Attine Ants
The antibiotic streptazolin (1), its E-isomer (2), along with the stereoisomers strepchazolin A (3) and strepchazolin B (4) and the inorganic compound cyclooctasulfur (5) were produced in solid culture by Streptomyces chartreusis ICBG377, which was isolated from the fungal garden of the leaf-cutter ant Acromyrmex subterraneus brunneus. This is the first time
J. Braz. Chem. Soc.. Publicado em: 24/10/2019
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5. A New Cytotoxic Naphthoquinone and Other Chemical Constituents of Sinningia reitzii
Phytochemical study of Sinningia reitzii (Gesneriaceae) led to the isolation of three new naphtoquinones, 6,7-dimethoxydunnione, 7-hydroxy-6-methoxydunnione, and 5-hydroxy-6,7-dimethoxydunnione from the tubers, together with four known compounds, 7-hydroxydunnione, 8-hydroxydunnione, 5-hydroxy-6,7-dimethoxy-α-dunnione, and 8-hydroxydeydrodunnione. Aerial pa
J. Braz. Chem. Soc.. Publicado em: 21/10/2019
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6. Suicide risk configuration system in a clustered clinical sample: a generalized linear model obtained through the LASSO technique
Objective: To identify clinical and sociodemographic factors that increase or decrease suicidal risk in a clinical sample of subjects seeking mental health care. Method: A cross-sectional study was performed at three health centers in Santiago, Chile. The Parental Bonding Instrument (PBI), Depressive Experience Questionnaire (DEQ), Outcome Questionnaire (O
Braz. J. Psychiatry.. Publicado em: 11/10/2018
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7. (+)-BINOL and Pure Shift Experiment: A Bidirectional Approach for NMR Chiral Discrimination of Overcrowded Spectra of Primary Amines
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 pr
J. Braz. Chem. Soc.. Publicado em: 2018-08
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8. Absolute Configuration of Solenopsis Piperidines is a Tool to Classify Fire Ants (Formicidae:Myrmicinae)
Piperidine alkaloids are predominant in ant venom glands of S. invicta and S. saevissima. These ants are broadly sympatric in Southeastern Brazil, and potentially diagnostic compounds could assist in ant identification. We determined the absolute configuration of 2,6-dialkyl-piperidines of S. invicta and S. saevissima workers and used these data to group Sou
J. Braz. Chem. Soc.. Publicado em: 2018-02
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9. Is phototridachiahydropyrone a true natural product?
Abstract The occurrence of (−)-phototridachiahydropyrone (5) in nature has been proven. This compound has been now identified as minor component of the extract of marine sacoglossan mollusk Elysia crispata from which the main (−)-tridachiahydropyrone (4) was previously described. Synthetic (±)-5 was formerly obtained by Moses’ group by biomimetic phot
Rev. bras. farmacogn.. Publicado em: 2015-12
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10. Absolute configuration and enantiomeric composition of partially resolved mandelic, atrolactic and lactic acids by ¹H NMR of their (S)-2-methylbutyl esters
Ésteres dos ácidos mandélico, atrolático e lático com o (S)-2-metil-1-butanol foram examinados como derivados diastereoméricos para análise estereoquímica por ressonância nuclear magnética (NMR) de ¹H a 300 MHz dos ácidos mencionados. Diastereômeros destes ésteres apresentaram ressonâncias com diferenças evidentes na região de absorção do
J. Braz. Chem. Soc.. Publicado em: 2013-06
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11. Programa de controle da qualidade dosimétrico, validado com auxílio de filme radiocrômico, aplicado à radioterapia estereotáxica / Dosimetric quality assurance with the help of the radiochromic film, applied to stereotactic radiotherapy.
Radiation therapy of brain lesions near critical structures requires a highly accurate location and dose. The accuracy in dose delivery should be accompanied by an accurate quality control in devices involving the practice. The commissioning of the planning system is to ascertain and confirm the calculations performed by the system, but even with all quality
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 08/03/2012
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12. Avaliação do valor de predição de clivagem química de radicais hidroxila em regiões promotoras de genes ligados ao desenvolvimento craniofacial / Evaluation of predictive value for chemical cleavage of hydroxy radicals in the promoter regions of genes related to craniofacial developmentl
The initiation of the gene transcription is a very complex phenomenon, probably the principal stage where the control of the gene expression takes place. In general terms the transcription takes place with the connection of proteins called "transcription factors" with specific sequences of the DNA, called of regions or sequences "cis ". The interaction DNA -
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 28/02/2012