Search results for " Synthesis"
showing 10 items of 1625 documents
Carbohydrate Auxiliaries in Stereoselective Syntheses of Decahydroquinoline Alkaloids
2002
Using tetra-O-pivaloyl-β-D-galactopyranosylamine as the chiral auxiliary, both trans- and cis-annelated decahydroquinoline alkaloids can be synthesized stereoselectively. This methodology of asymmetric synthesis is based on the effect that both enantiomers of 2,6-disubstituted piperidin-4-ones are selectively and alternatively accessible using the auxiliary as the identical stereodifferentiating tool. In addition, the carbohydrate auxiliary controls the stereoselective protonation of enolates formed by conjugate addition of cuprates to N-galactosyl octahydroquinolin-4-ones. The syntheses of trans-4a-epi-pumiliotoxin C and cis-4a-epi-perhydro-219A illustrate this concept of asymmetric synthe…
Total Synthesis of (±)-Oxalicumone C and Chiral Resolution and Elucidation of Its Absolute Configuration
2014
The racemic total synthesis, the chiral resolution, and the elucidation of the absolute configuration of the natural product oxalicumone C were investigated. The goal was achieved by a synthetic strategy beginning with the synthesis of a 5-hydroxy-7-methylchromone precursor. Further modification possibilities were achieved by introduction of a vinyl moiety into the chromone, which was based on a selective iodination step in the 3-position. Further transformations furnished the racemic natural product. To determinate the absolute configuration of naturally occurring oxalicumone C, both enantiomers were separated by chiral HPLC. Comparison of the calculated and experimental vibrational circul…
Ligands P-stéréogéniques dérivés du calix[4]arène. Synthèses et applications en catalyse asymétrique
2010
We were interested in synthesis of P-stereogenic ligands derived from calix[4]arene and in their application in asymmetric catalysis. Mono et diphosphines were prepared on the upper rim of the macrocyle starting from the mono or dianion of the calix[4]arene and chlorophosphines borane or the oxazaphospholidine borane complex. The best selectivity was obtained by reaction of the dianion with the oxazaphospholidine borane complex leading to a bisaminophosphine borane. After acidolysis with HCl giving the corresponding bischlorophosphine and reaction with organolithium reagents, diphosphines diborane were obtained with good yields (40 à 60 %). X-ray structures of the prepared ligands confirmed…
Making natural products from renewable feedstocks: back to the roots?
2019
Covering: up to mid-2019 This review highlights the utilization of biomass-derived building blocks in the total synthesis of natural products. An overview over several renewable feedstock classes, namely wood/lignin, cellulose, chitin and chitosan, fats and oils, as well as terpenes, is given, covering the time span from the initial beginning of natural product synthesis until today. The focus is put on the origin of the employed carbon atoms and on the nature of the complex structures that were assembled therefrom. The emerging trend of turning away from petrochemically derived starting materials back to bio-based resources, just as seen in the early days of total synthesis, shall be demon…
Synthèses optimisées et caractérisations avancées de nanotubes de titanate et de leurs fonctionnalisations : vers l'élaboration de nanovecteurs de mo…
2017
The aim of this PhD thesis is to develop new nanohybrids based on titanate nanotubes (TiONts) in order to use them as nanocarrier of a therapeutic molecule: a stilbene phenol, 4'-hydroxy-4-(3-aminopropoxy)-trans-stilbene (HAPtS), which is a transresveratrol derivative.TiONts are synthesized by a hydrothermal treatment from a precursor of rutile titanium dioxide. Two methods of hydrothermal synthesis have been studied (the static and dynamic ones): the second approach uses an original hydrothermal device which provides a vigorous mechanical stirring during the hydrothermal process with controllable stirring time par hour. A parametric study was carried out to evaluate the effect of reaction …
Iron-Catalyzed C(sp2)–C(sp3) Cross-Coupling of Aryl Chlorobenzoates with Alkyl Grignard Reagents
2020
Aryl benzoates are compounds of high importance in organic synthesis. Herein, we report the iron-catalyzed C(sp2)&ndash
Plasma non-cholesterol sterols: a useful diagnostic tool in pediatric hypercholesterolemia.
2010
Current guidelines strongly recommend the identification of genetic forms of hypercholesterolemia (HC) during childhood. The usefulness of non–cholesterol sterols (NCS) in the diagnosis of genetic HC has not been fully explored. Plasma NCS were measured by gas chromatography/mass spectrometry (GC/MS) in 113 children with hypercholesterolemia affected by: autosomal dominant hypercholesterolemia (ADH), familial combined hyperlipidemia (FCHL), polygenic hypercholesterolemia (PHC), and in 79 controls to evaluate: i) plasma NCS profile in different genetic HC and ii) the usefulness of NCS for the diagnosis of HC beyond current clinical criteria. ADH was characterized by raised lathosterol/total …
Method development for the determination of 1,1-dimethylhydrazine by the high-performance liquid chromatography-mass spectrometry technique.
2018
Unsymmetrical dimethyl hydrazine is highly toxic, carcinogenic compound, widely used for organic synthesis and drug development. Therefore, due to its high reactivity, direct analysis is problematic. Current study proposes to use derivatization reaction to increase selectivity and sensitivity of high-performance liquid chromatography–mass spectrometry method. Different derivatization agents were tested and optimal reaction media was found. Derivatization was performed by using small amounts of reagents to lower the cost of analysis. The full validation of the method was performed and it can be used in a routine control in pharmaceutical analysis. Method sensitivity is 0.15 ppm, and lineari…
Homochiral Metal-Organic Frameworks for Enantioselective Separations in Liquid Chromatography
2020
Selective separation of enantiomers is a substantial challenge for the pharmaceutical industry. Chromatography on chiral stationary phases is the standard method, but at a very high cost for industrial-scale purification due to the high cost of the chiral stationary phases. Typically, these materials are poorly robust, expensive to manufacture, and often too specific for a single desired substrate, lacking desirable versatility across different chiral analytes. Here, we disclose a porous, robust homochiral metal–organic framework (MOF), TAMOF-1, built from copper(II) and an affordable linker prepared from natural l-histidine. TAMOF-1 has shown to be able to separate a variety of model…
In-line capillary electrophoretic evaluation of the enantioselective metabolism of verapamil by cytochrome P3A4
2013
Abstract In this paper a methodology for the in-line evaluation of enantioselective metabolism by capillary electrophoresis has been developed and applied to the study of verapamil metabolism by cytochrome P3A4. The developed methodology comprises an in-capillary reaction step carried out by electrophoretically mediated microanalysis and a separation step in which highly sulfated β-cyclodextrin with partial filling technique has been employed as chiral selector for verapamil and norverapamil enantiomers resolution, joining the advantages of both methodologies in a unique assay. Kinetic parameters of the enzymatic reaction (Km and Vmax) have been evaluated for both verapamil enantiomers by n…