Chirality
An aqueous solution of enantiomerically pure tryptophan (Trp), namely, D‐Trp or L‐Trp (100 mg/kg), was administered intraperitoneally to male Sprague‐Dawley rats. The time‐course profiles of the rat plasma concentrations of D‐kynurenine (KYN), L‐KYN, and kynurenic acid (KYNA), which are metabolites of D‐ or L‐Trp, were investigated using high‐performance liquid chromatography (HPLC) systems that were...
The racemic hemicryptophane molecular cage 2 was resolved by semipreparative HPLC on Whelk‐O1 column. The absolute configuration of each isolated enantiomer was established from the analysis of their circular dichroism spectra and assigned as P‐(+)‐2 and M‐(−)‐2. Chirality, 2010. © 2010 Wiley‐Liss, Inc.
The chiral octahedral bimetallic assemblies [(bpy)2Ru(o‐LIr)][CF3SO3]2 (2), [(ppy)2Rh(o‐LIr)][NO3] (7) and [(ppy)2Ir(o‐LIr)][NO3] (8) featuring chelating organometallic linker [Cp*Ir(η4‐o‐benzoquinone)] (o‐LIr) have been prepared and fully characterized. Anion metathesis following a convenient procedure allowed the preparation of the related diastereomers [Δ‐(bpy)2Ru(o‐LIr)][Δ‐TRISPHAT]2 (2a) and...
Parity violation (PV) effects in chiral molecules have so far never been experimentally observed. To take up this challenge, a consortium of physicists, chemists, theoreticians, and spectroscopists has been established and aims at measuring PV energy differences between two enantiomers by using high‐resolution laser spectroscopy. In this article, we present our common strategy to reach this goal,...
This review deals with the preparation of chiral, nonracemic α‐aminoorganostannanes and their applications in asymmetric synthesis. The pioneering works in this field date back almost 20 years ago and since then extensive research has been carried out to develop efficient and selective routes to highly enantioenriched α‐aminoorganostannanes. The facile Sn/Li transmetalation of these compounds by n...
A novel single isomer of positively charged β‐cyclodextrin, mono‐6‐deoxy‐6‐((2S,3S)‐(+)‐2,3‐O‐isopropylidene‐1,4‐tetramethylenediamine)‐β‐CD (MIPTACD) was designed and synthesized in seven steps starting from commercially available (2R,3R)‐tartaric acid. The chiral resolution abilities of the new cationic chiral selector were studied by capillary electrophoresis using 10 different dansyl (Dns)‐amino...
The use of phase appropriate technologies is critical for efficiently moving drug candidates forward in the early stages of drug discovery and development. Phase appropriate purification technology develops the analytical method and subsequently scales up the method and turns the sample around quickly (Kennedy et al., J Chromatogr A 2004; 1046:55). In this article, separation results and conditions...
Two new chiral dinuclear Mn(III)‐Salen complexes with inherent phase‐transfer capability have been synthesized, which serve as catalysts in the asymmetric epoxidation of nonfunctionalized alkenes. Experimental results show these complexes are effective catalysts for the asymmetric epoxidation of some cyclic alkenes and the catalysts have certain inherent phase‐transfer capability during the epoxidation...
The active catalysts for the enantioselective ring opening (ARO) of meso‐stilbene oxide, cis‐butene oxide, cyclohexene oxide, cyclopentene oxide, and cyclooctene oxide with various substituted anilines were generated in situ by the reaction of Ti(OiPr)4 with poly‐[(R,R)‐N,N′‐bis‐{3‐(1,1‐dimethylethyl)‐5‐methylene salicylidene} cyclohexane‐1,2‐diamine]‐1 and (1R,2R)‐N,N′‐bis[3,5‐di(tert‐butyl)salicylidene]...
The effect of solvent systems on previously‐reported ESI‐MS based proton‐assisted enantioselective molecular recognition phenomena of tartar emetic, L‐antimony(III)‐tartrate, was evaluated. This was achieved by carrying out a series of competitive binding experiments using chiral selectors, bis(sodium) D‐ and ‐L‐antimony(III)‐tartrates with chiral selectands, neutral side‐chain amino acid enantiomeric...
Origin(s) of biological chirality appear(s) to be intimately connected to origin(s) of life. Prebiotic evolution toward these important turning points can be traced back to single chiral molecules. These can be small (monomeric) units as amino acids or monosaccharides or oligomers as oligo‐RNA type molecules. Earlier speculations about these two kinds of entries to biological chirality are critically...
Louis Pasteur resolved sodium ammonium (±)‐tartrate in 1848, thereby discovering molecular chirality. Although hindered by the primitive state of organic chemistry, he introduced new terminology and nomenclature for his new science of molecular and crystal chirality. He was well prepared for this task by his rigorous education and innate abilities, and his linguistic achievements eventually earned...
The web site, http://www.csm.huji.ac.il/, uses the Continuous Chirality Measure to evaluate quantitatively the degree of chirality of a molecule, a structure, a fragment. The value of this measure ranges from zero, the molecule is achiral, to higher values (the upper limit is 100); the higher the chirality value, the more chiral the molecule is. The measure is based on the distance between the chiral...
We report that 3,3′‐diaryl‐BINOL phosphoric acids are effective enantioselective extractants in chiral separation methods based on reactive liquid–liquid extraction. These new extractants are capable of separating racemic benzylic primary amine substrates. The effect of the nature of the substituents at the 3,3′‐positions of the host were examined as well as the structure of the substrate, together...
A tetradentate tripodal ligand containing a chiral center and three different coordinating arms was designed and synthesized. Its complexation properties with ZnII and CuI were studied by NMR and optical spectroscopy. NMR experiments demonstrated the formation of two diastereomers, indicating the stabilization of the central tertiary amine configuration by metal coordination. The inversion of pyramidalization...
Dobutamine is a cardiotonic agent, developed as a racemate more than 30 years ago. The compound soon got the label “the β1‐selective adrenoceptor agonist”. However, a closer examination of the enantiomers showed that (+)‐dobutamine is predominantly a β1‐ and β2‐adrenoceptor agonist with modest selectivity whereas (−)‐dobutamine is predominantly an α1‐adrenoceptor agonist. Nevertheless, rac dobutamine...
Antimalarial drugs have shown potential in suppressing the role of glycosaminoglycans (GAGs) in the pathology of prion protein conformational disorders (e.g. “Mad Cow” disease) by competing for sites of electrostatic interaction. In this study, circular dichroism (CD) and UV/Visible (UV/Vis) absorption spectroscopy techniques were used to investigate the interactions between N‐methyl‐N′‐(7‐chloro‐4‐quinolyl)‐1,3‐diaminopropane...
We report the synthesis of a series of novel structurally related protic chiral ionic liquids (PCILs) derived from ephedrines. Enantiopure norephedrine, ephedrine, and methylephedrine were neutralized by use of fluorinated acids, bis(trifluoromethanesulfonyl)imide, and bis(pentafluoroethanesulfonyl)imide to afford six PCILs with protonated primary, secondary, and tertiary amines. The goal of this...
Kynurenic acid (KYNA), an endogenous antagonist of N‐methyl‐D‐aspartate and α7 nicotinic acetylcholine receptors, is one of the L‐tryptophan (Trp) metabolites. To compare the level of KYNA produced in the striatum of rats after independent administration of L‐Trp and D‐Trp, rats were intraperitoneally administered L‐Trp and/or D‐Trp (100 mg/kg), and a microdialysis (MD) probe was implanted in the...
Pericosines are carbasugar‐type metabolites of Periconia byssoides OUPS‐N133, a fungus that was originally separated from the sea hare Aplysia kurodai. It has been reported that pericosines C and E are enantiomeric mixtures. The difference in specific rotation between natural pericosine C and the synthetic one led to the conclusion that natural pericosine C is an enantiomeric mixture. Meanwhile, the...