Search results for "enantioselective synthesis"
showing 10 items of 418 documents
Determination of fluoxetine enantiomers in pharmaceutical formulations by electrokinetic chromatography-counter current technique
2012
In this work, an electrokinetic chromatography–counter current procedure for the separation of fluoxetine enantiomers using highly sulfated β-cyclodextrin was optimized and applied to the determination of the enantiomers in three pharmaceutical formulations according to the matrix features. Quality criteria were applied to facilitate its transferability to testing laboratories. Fluoxetine was used therapeutically as the racemate, although a stereospecificity associated with its interactions with the neuronal serotonin-uptake carrier was demonstrated. In this context, the development of enantioselective methods for the chiral analysis of pharmaceuticals allowing stereoisomer ratio estimation…
Organic carbonates as alternative solvents for asymmetric hydrogenation
2009
Organic carbonates like propylene carbonate (PC) or butylene carbonate (BC) belong to the class of aprotic, highly dipolar solvents (AHD). Interestingly, their potential as solvents for asymmetric catalysis has been overlooked for a long time. The aim of this work is to evaluate organic carbonates and other organic solvents like THF, CH2Cl2, and acetonitrile as well as members of the AHD-family (DMF, DMSO, etc.) as media for homogeneous asymmetric hydrogenation. For this reason cationic Rh-complexes based on chiral phosphine ligands were tested in the hydrogenation of typical benchmark substrates. In several trials, significant advantages of organic carbonates were found. In contrast to DMS…
Enantioselective copper-aminopyridine-catalyzed aza-Henry reaction with chelating N-(2-pyridyl)sulfonyl imines
2012
This article describes a copper-catalyzed aza-Henry reaction. Copper complexes of camphor-derived aminopyridines catalyze the addition of nitromethane to N-(2-pyridyl)sulfonyl aldimines to give the corresponding β-nitrosulfonamides with good yields and variable enantiomeric excesses (up to 83%). An example of transformation of these compounds into N-(2-pyridyl)sulfonyl-α-amino acids and deprotection of the sulfonamide with Mg–MeOH is provided. Chirality 24:441–450, 2012. © 2012 Wiley Periodicals, Inc.
Enantioselective Hydrogenation Catalysis Aided by a σ-Bonded Calix[4]arene to a P-Chirogenic Aminophosphane Phosphinite Rhodium Complex
2010
The first P-chirogenic aminophosphane−phosphinite (AMP*P) ligand (4a) supported on the upper rim of a calix[4]arene moiety was synthesized in two steps using the ephedrine methodology. Ligand 4a wa...
3.17 Synthetically Derived Auxiliaries: Phosphorus Derivatives
2012
This chapter aims to give an overall view of chiral-pool based asymmetric synthesis of organophosphorus compounds more particularly bearing the chirality on the phosphorus atom (P-stereogenic). The enantiomerically pure organophosphorus compounds can be obtained either by resolution of the racemate or by stereoselective synthesis using particularly ephedrine or sparteine as the main chiral auxiliaries and borane as a P(III)-protecting group.
Enantioselective Total Syntheses of (+)-Hippolachnin A, (+)-Gracilioether A, (-)-Gracilioether E, and (-)-Gracilioether F.
2018
The Plakortin polyketides represent a structurally and biologically fascinating class of marine natural products. Herein, we report a unified strategy that enables the divergent syntheses of various Plakortin polyketides with high step-economy and overall efficiency. As proof-of-concept cases, the enantioselective total syntheses of (+)-hippolachnin A, (+)-gracilioether A, (-)-gracilioether E, and (-)-gracilioether F have been accomplished based on a series of bio-inspired, rationally designed, or serendipitously discovered transformations, which include (1) an organocatalytic asymmetric 1,4-conjugate addition to assemble the common chiral γ-butenolide intermediate enroute to all of the afo…
On the zopiclone enantioselective binding to human albumin and plasma proteins. An electrokinetic chromatography approach
2011
In this work, a methodology for the chiral separation of zopiclone (ZPC) by electrokinetic chromatography (EKC) using carboxymethylated-β-cyclodextrin as chiral selector has been developed and applied to the evaluation of the enantioselective binding of ZPC enantiomers to HSA and total plasma proteins. Two mathematical approaches were used to estimate protein binding (PB), affinity constants (K(1)) and enantioselectivity (ES) for both enantiomers of ZPC. Contradictory results in the literature, mainly related to plasma protein binding reported data, suggest that this is an unresolved matter and that more information is needed. Discrepancies and coincidences with previous data are highlighte…
Enantioselective alkynylation of benzo[e][1,2,3]-oxathiazine 2,2-dioxides catalysed by (R)-VAPOL-Zn complexes: synthesis of chiral propargylic cyclic…
2015
[EN] (R)-VAPOL-Zn(II) complexes catalysed the enantioselective addition of terminal alkynes to cyclic benzoxathiazine 2,2-dioxides, providing the corresponding chiral propargylic sulfamidates with high yields (up to 93%) and good enantiomeric excesses (up to 87%).
ChemInform Abstract: Auxiliary-Controlled Stereoselective Enolate Protonation: Enantioselective Synthesis of cis and trans Annulated Decahydroquinoli…
2010
Abstract The diastereoselective synthesis of the octahydroquinoline enone precursor of pumiliotoxin C is achieved via tandem Mannich-Michael reaction on N-galactosyl imines. Conjugate cuprate addition to the bicyclic enone stereoselectively forms the trans annulated 4a- epi -pumiliotoxin C skeleton in the presence of the carbohydrate auxiliary, and the cis annulated pumiliotoxin C skeleton in its absence.
2-Alkenoyl Pyridine N-Oxides, Highly Efficient Dienophiles for the Enantioselective Cu(II)−Bis(oxazoline) Catalyzed Diels−Alder Reaction
2007
2-Alkenoyl pyridine N-oxides are introduced as a new kind of efficient dienophiles for the Cu(II)−bis(oxazoline) (BOX) catalyzed enantioselective Diels−Alder reaction affording higher reactivity and enantioselectivity (ee's up to 96%) than the corresponding nonoxidized 2-alkenoyl pyridines.