61 research outputs found
Cytotoxic and Antimicrobial Activity of Pseudopterosins and seco-Pseudopterosins Isolated from the Octocoral Pseudopterogorgia elisabethae of San Andrés and Providencia Islands (Southwest Caribbean Sea)
To expand the potential of pseudopterosins and seco-pseudopterosins isolated from the octocoral Pseudopterogorgia elisabethae of San AndrĂ©s and Providencia islands (southwest Caribbean Sea), we report the anti-microbial profile against four pathogenic microorganisms (Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans) and report a more complete cytotoxic profile against five human cells lines (HeLa, PC-3, HCT116, MCF-7 and BJ) for the compounds PsG, PsP, PsQ, PsS, PsT, PsU, 3-O-acetyl-PsU, seco-PsJ, seco-PsK and IMNGD. For the cytotoxic profiles, all compounds evaluated showed moderate and non-selective activity against both tumor and normal cell lines, where PsQ and PsG were the most active compounds (GI50 values between 5.8 ÎŒM to 12.0 ÎŒM). With respect to their anti-microbial activity the compounds showed good and selective activity against the Gram-positive bacteria, while they did not show activity against the Gram-negative bacterium or yeast. PsU, PsQ, PsS, seco-PsK and PsG were the most active compounds (IC50 2.9â4.5 ÎŒM) against S. aureus and PsG, PsU and seco-PsK showed good activity (IC50 3.1â3.8 ÎŒM) against E. faecalis, comparable to the reference drug vancomycin (4.2 ÎŒM)
Quinones as dienophiles in the Diels-Alder reaction: history and applications in total synthesis
In the canon of reactions available to the organic chemist engaged in total synthesis, the DielsâAlder reaction is among the most powerful and well understood. Its ability to rapidly generate molecular complexity through the simultaneous formation of two carboncarbon bonds is almost unrivalled, and this is reflected in the great number of reported applications of this reaction. Historically, the use of quinones as dienophiles is highly significant, being the very first example investigated by Diels and Alder. Herein, we review the application of the DielsâAlder reaction of quinones in the total synthesis of natural products. The highlighted examples span some 60â
years from the landmark syntheses of morphine (1952) and reserpine (1956) by Gates and Woodward, respectively, through to the present day examples, such as the tetracyclines
Nuclear magnetic resonance spectroscopy for structural characterization of bioactive compounds
The structural assignment of a new natural product molecule is not only to establish
the 3D structure of a compound, but potentially to provide the basis for
research in a multitude of disciplines, ultimately generating new therapeutic
agents and/or new understanding of disease biology. The development of modern
spectroscopic techniques has transformed the structure assignment process,
which previously was essentially based on chemical degradation or derivatization
followed by partial or total synthesis. Notably, it was only in the specialization
era of the spectroscopic structural assignment of natural products that the
field of marine natural products chemistry took shape.
Today the processes of marine and terrestrial natural product isolation and
structural determination are frequently streamlined and expeditious due to the spectacular advances in chromatographic and spectroscopic technologies as
well as chemical synthesis.
The NMR spectroscopy is a powerful tool in structure elucidation because
the properties it displays can be related to the molecular structure. The chemical
environment of a particular nucleus is associated with the chemical shift (d,
ppm), and the area of a resonance, usually presented as its relative integral, is
related to the number of nuclei giving rise to the NMR signal. The interactions
between individual nuclei, mediated by electrons in a chemical bond, determine
the coupling constant (J, Hz). In this chapter we will present the techniques
commonly used, basic concepts, and how they are useful for chemists in the
structural elucidation of mainly bioactive marine natural products. Its complex
planar structure is determined by 1H and 13C NMR analysis strongly supported
by other 1D (DEPT) and 2D (COSY, TOCSY, HSQC/HMQC, HMBC) NMR
techniques. The stereochemistry is generally based on NOE experiments (NOE
difference, NOESY, and ROESY), 1Hâ1H and 1Hâ13C coupling constants, chiral
derivatizing agents, and also in empirical procedures comparing the chemical
shifts of unknown vicinal and proximal centers with libraries of configurationally
known stereomodels. However, the most reliable option to assign all the 3D
structure of a marine natural product still is their total synthesis.
The use of NMR hyphenated with other chromatographic and spectroscopic
techniques and microcoil probes and narrow diameter tube probes for the structural
elucidation of bioactive marine natural products, mainly associated with
the quantitative NMR determinations, will be also briefly described.
The chapter will finish with a description of the structural characterization of
several types of marine natural products using all the referred NMR techniques
followed by a small reference to the misassignments that still are very common
Catalytic Asymmetric Crotylation of Aldehydes: Application in Total Synthesis of (â)-Elisabethadione
This is the peer reviewed version of the following article: O'HORA, P. ... et al, 2015. Catalytic asymmetric crotylation of aldehydes: application in total synthesis of (- )-elisabethadione. Chemistry - A European Journal, 21(12), pp.4551-4555, which has been published in final form at http://dx.doi.org/10.1002/chem.201500176. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.A new, highly efficient Lewis base catalyst for
a practical enantio- and diastereoselective crotylation of
unsaturated aldehydes with E- and Z-crotyltrichlorosilanes
has been developed. The method was employed as a key
step in a novel asymmetric synthesis of bioactive serrulatane diterpene (Ă)-elisabethadione. Other strategic reactions for setting up the stereogenic centers included
anionic oxy-Cope rearrangement and cationic cyclization.
The synthetic route relies on simple, high yielding reactions and avoids use of protecting groups or chiral auxiliaries
ChemInform Abstract: General Route for the Preparation of Diverse 17-Membered Macrocycles Based on RCM and Examination of the E/Z Selectivity.
Rentenantragsteller in der psychosomatischen Rehabilitation : Therapiemotivation und -ergebnisse
Total Synthesis of Elisabethin A: Intramolecular DielsâAlder Reaction under Biomimetic Conditions  [ J. Am. Chem. Soc
Highly Variable Bacterial Communities Associated with the Octocoral Antillogorgia elisabethae
Solargebaeude Leinefelde - Demonstration energiesparender Techniken bei der Altbausanierung Abschlussbericht
An industrially prefabricated nursery school building at Leinefelde, Thuringia, was modernized and extended to ensure maximum ecological awareness. Consumption data will fall far below the 1999 WSVO (Thermal Insulation Ordinance), and high user comfort will be ensured. The low residual energy demand will be covered preferably by renewable energy sources. The building will be a demonstration project for drastic reduction of carbon dioxide emissions.Ein in Plattenbauweise errichtetes, nicht mehr genutztes Kindergartengebaeude in Leinefelde/Thuer. soll in energetisch und oekologisch vorbildlicher Weise saniert und erweitert werden. Das so geschaffene energieoptimierte Gebaeude soll die Anforderungen der fuer 1999 in Aussicht gestellten WSVO weit unterbieten und minimalen Energiebedarf mit hohem Nutzerkomfort verbinden. Der geringe Restheizwaermebedarf soll ueberwiegend durch regenerative Energiequellen gedeckt werden. Das Gebaeude soll als Demonstrationsprojekt fuer die drastische Senkung des CO_2-Ausstosses dienen. (orig.)Available from TIB Hannover: F01B1060 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDeutsche Bundesstiftung Umwelt, Osnabrueck (Germany)DEGerman
Enantioselective Total Synthesis and Determination of the Absolute Configuration of the 4,6,8,10,16,18-Hexamethyldocosane fromAntitrogus parvulus
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