Introduction to Enantiomeric Excess

1% enantiomeric excess (e.

Moreover, chiral analysis accuracy of these hosts was evaluated through relationship between enantiomeric excess values of 4-chloromandelic acid provided by NMR and gravimetry, respectively.

The chiral nature of the host also leads to clear differences in the NMR spectra of ternary complexes involving corannulene and one or the other enantiomer of a chiral guest, which enables the determination of enantiomeric excess by NMR.

Incorporation of aromatic chiral species with axial, helical, or propeller chirality in surapmolecular chiral motifs would potentially facilitate the chiroptical applications such as enantiomeric excess detection, chiral sensing, and displays, which however suffer from inevitable competition between supramolecular chirality and molecular chirality and remain major challenges.

In asymmetric catalysis the enantiomeric excess (e.

Parameters such as conversion, enantiomeric excess, and enantioselectivity were considered.

The enantiomeric excess (ee) was almost 100%.

The enzymatic activity of the immobilized enzyme was three times more than that of free PCL in enantioselective hydrolysis system, and the enantiomeric excess was maintained above 99 %.

Most of these reactions are accompanied by high yields and enantiomeric excesses.

Further, enzymatic kinetic resolution (EKR) and chemoenzymatic dynamic kinetic resolution (DKR) protocols were developed using geminal diacetate as an acylating agent, resulting in chiral acetates in high yields up to 94% with enantiomeric excesses exceeding 99%.

As reported previously, the as-received catalyst provided an enantiomeric excess of ~ 40%(R).

The precise design of a catalyst for a given reaction is extremely difficult, often requiring a significant empirical screening campaign to afford products in high yields and enantiomeric excess.

Enantioselective decarboxylative protonation of tetralone-derived β-ketocarboxylic acids was achieved with up to 89% enantiomeric excess (ee)-in the presence of a chiral primary amine catalyst.

Furthermore, when chiral β-substituted nitro compounds were reacted, the stereochemical integrity of the stereocenter was maintained and α-functionalized nitriles were obtained with no loss in enantiomeric excess.

This work describes a formulation of ionic gradient liposomes (IGL) containing S75BVC, an enantiomeric excess mixture of 75% S(-) and 25% R(+) bupivacaine.

However, there lacks a protocol that could be used to couple a wide range of chiral amines and aryl halides, without erosion of the enantiomeric excess (ee).

Following optimization of the reaction conditions, NHC, and amino acid ligands, high enantioselectivity was achieved when employing the Ir(IMe)2(l-Pro)(H)(I) catalyst (IMe = 1,3-dimethylimidazol-2-ylidene), which asymmetrically reduces a range of acetophenone derivatives in up to 95% enantiomeric excess.

Using this protocol, the radiotracer can be produced in a 20 ± 5% (decay corrected at the end of synthesis, n > 20) radiochemical yield, with both radiochemical purity and enantiomeric excess of over 95%.

In addition, the chiral separation of (±)-MA racemic solution was successfully executed by the S-MAPR separation column with 55% and 82% enantiomeric excess of R- and S-MA within both the initial loading and recovery eluant solutions, respectively.

In biocatalytic reduction reactions, the conversion of the substrate and the enantiomeric excess (ee) of the product are significantly affected by optimization parameters such as temperature, agitation rate, pH, and incubation time.

Application of only 10 mol% of salan allows to obtain the title ketone with high yield and enantiomeric excess up to 75%.

The strain 2a1-2b produced optically active 5R-hexahydrocurcumin (enantiomeric excess (e.

The non-covalently linked [Pd(phen)(OAc)2] with st-DNA catalysed the Markonicov hydroamination of β-nitrostyrene with methoxyamine for the first time with >75% enantiomeric excess (ee) in an aqueous buffer (pH 7.

This provides a potential way to detect the enantiomeric excess of chiral mixture by monitoring the output field of the cavity.

The best hydrolysis results of dimethyl 1-butyryloxy-1-carboxymethylphosphonate were obtained with the use of lipases from Candida rugosa, Candida antarctica, and Aspergillus niger, leading to optically active dimethyl 1-carboxy-1-hydroxymethylphosphonate (58%–98% enantiomeric excess) with high enantiomeric ratio (reaching up to 126).

In addition, there is a linear relationship between the experimental and observed values of enantiomeric excess of G1 in the presence of L-PCSA, which indicated that L-PCSA can be used to rapidly and reliably analyze the enantiomeric purity of various naphthylethylamine samples.

7% enantiomeric excess (ee) for R-MA.

Using Novozyme 435, reaction conditions were optimized and hydroxyesters (3S) or (3R) were achieved with enantiomeric excesses up to ≥99% ee and maximum overall yields of 80%.

To test their practical application in the determination of enantiomeric excess, 1H NMR spectra of chiral amides (G16) with different optical purities were measured in the presence of CSAs 7 and 8, respectively.

In one case successful discrimination is also observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios.

The (S)- and (R)-enantiomers of 2-(1-naphthyloxy)- and 2-(2-iodophenoxy)propionic acids with enantiomeric excess ee >99% were isolated using preparative chiral HPLC.

A lack of information regarding the optical purity (enantiomeric excess) of the single stereogenic centre of PF74 has resulted in ambiguity as to the potency of different samples of this compound.

This assay can be used to determine the enantiomeric excess of L-Trp in the range from 0 to + 100%.

Such non-covalently bound chiral contact pairs are the foundation of chiral-tag rotational spectroscopy, an exciting new analytical application of rotational spectroscopy for determination of enantiomeric excess.

The enantioselective analysis, carried out on a β-cyclodextrin-based column, showed four scalemic mixtures in which (1R,5R)-(+)-α-pinene, (1S,5S)-(−)-β-pinene, (S)-(−)-limonene, and (1R,2S,6S,7S,8S)-(−)-α-copaene were the major enantiomers, with enantiomeric excesses of 28.

6% enantiomeric excess (ee) values.

The products of the studied reactions were formed in up to 99% yield, with syn diastereoselectivity (dr) >20: 1 and enantiomeric excess of up to 93% ee for syn-isomer.

For these operating conditions, it was estimated that the product could be obtained with 94% enantiomeric excess (ee) and 95% conversion rate (cr).

Summary The enantiomeric excess phenomenon in spontaneous chiral symmetry breaking (SCSB) is a crucial issue in the origin of homochirality in nature, whereas chiral inorganic compounds have long been reckoned as racemates.

Given the diurnal variations in enantiomeric excess of biogenic emissions, possible contributions of such a link to biosphere:atmosphere feedbacks as well as aerosol particle viscosity and phase separation are discussed.

The observed (R)-enantiomeric excess (ee) of styrene epoxidation is up to 99% with a turnover number (TON) of 918 by the best enantioselective mutant F87A/T268I/L181Q, while the best active mutant F87A/T268I/V78A/A184L (with 98% ee) gave a catalytic TON of 4350, representing the best activity of a P450 peroxygenase towards styrene epoxidation to date.

Comparative catalytic studies with various UiO‐MOFs indicate different outcomes in terms of enantiomeric excess, handedness distribution of the product and reaction rate, when compared to pristine solid Soai aldehyde, while the crystalline MOF remains highly stable to action of Zn(iPr)2 vapour.

The outcome of the chemometric analysis highlighted the quantification of the enantiomeric excess of l-DOPA in enantiomeric mixtures in the solid state, which was possible by coupling NIR and PLS, and, to a lesser extent, by using MIR.

The conversion of rac-ibuprofen reached 46%, with an enantiomeric excess towards the S-enantiomer of 42%.

Among the examined chiral catalysts, divalent tin porphyrin was the most effective, and the product yield and enantiomeric excess were 98% and 91.

A molecular rotational resonance spectroscopy method for measuring the enantiomeric excess of pantolactone, an intermediate in the synthesis of panthenol and pantothenic acid, is presented.

The reduction is strictly (R)‐selective (enantiomeric excess >99 %).

Results show that β-CD displays a much stronger enantioselective affinity toward l -enantiomer than d -enantiomer, so that such β-CD modified GO membrane (β-CD-GOM) exhibits a retarded transport mechanism, having exceptional enantioselectivities with the enantiomeric excess value of nearly 100%.

Under optimal separation conditions, the enantiomeric excess value (e.

This atom-economical catalytic process that associates IPrAu(MeCN)BF4 and an alcohol demonstrated remarkable selectivity in accessing functionalized 3,4-dihydro-1H-[1,4]oxazino[4,3-a]indole derivatives of high synthetic utility (21 examples, yields of ≤96%) and could be optimized under asymmetric conditions with an enantiomeric excess of ≤86%.

Bioreduction of 1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfonyl)ethanone (2), using ketoreductase KRED-P2-D12, led to (R)-3 with 48% conversion and 93% enantiomeric excess (ee).

In the racemate separation experiments under isobaric conditions, the enantiomeric excess (ee) values of alanine (Ala), threonine (Thr), tyrosine (Tyr), and penicillamine (Pen) racemates in the permeation solution were 43.

The -blocker (S)-practolol ((S)-N-(4-(2-hydroxy(isopropylamino)propoxy)phenyl)acetamide) was synthesized with 96% enantiomeric excess (ee) from the chlorohydrin (R)-N-(4-(3chloro-2 hydroxypropoxy)phenyl)acetamide, which was produced in 97% ee and with 27% yield.

This capability has been exploited to develop molecular systems able to report the enantiomeric excess and composition of (a)chiral dicarboxylic acids in fruit juices and wines using 1H-NMR.

The method, which relies on an iridium(I)/bisphosphine chiral catalyst, is particularly efficient for the synthesis of five‐, six‐ and seven‐membered fused indole and pyrrole products, bearing one and two stereocenters, with enantiomeric excesses of up to >99 %.

By directly employing the pH adjusted supernatant as a biocatalyst, we were able to almost completely transform 10 g/L of pyrmetazole into the corresponding (S)-sulfoxide, with >99% enantiomeric excess.

(S)-1-(4-methoxyphenyl) ethanol, which can be used for the synthesis of antihistamines, including diphenhydramine hydrochloride and loratadine cycloalkyl [b] indoles that have the treatment function for an allergic response, was obtained in > 99% conversion, > 99% enantiomeric excess and 96% yield with whole cells of L.

2O3 (La7Sr3Fe8Ni2) catalyst is more active for asymmetric electrocarboxylation of acetophenone with 95% enantiomeric excess and 85% yield.

Triglycine sulfate (TGS) acts as a chiral trigger for asymmetric autocatalysis with amplification of enantiomeric excess, i.

Enantiocomplementary synthesis of ( R )- and ( S )-3A5HEF was implemented with the yields of up to  >  99% and the enantiomeric excess (ee) values of  >  99%.

Helical polymer–based molecular systems allow naked-eye determination of chirality and enantiomeric excess of chiral amines.

α,β-Butenolides with ≥96% enantiomeric excess are synthesized from β,γ-butenolides via a novel Cu(I)-ligand cooperative catalysis.

Determining the relative configuration or enantiomeric excess of a substance may be achieved using NMR spectroscopy by employing chiral shift reagents (CSRs).

Recent analyses of meteoritic hydroxycarboxylic acids (HCAs) – potential co-building blocks of ancestral proto-peptides – showed an enantiomeric excess in l-lactic acid.

Cu2+ , Zn2+ and Tween 80 strongly inhibited the enzyme activity, but the optical purity of the product R-mandelic acid (R-MA) was stable, with practically 100% enantiomeric excess (ee).

Dynamic covalent chemistry-based sensors have recently emerged as powerful tools to rapidly determine the enantiomeric excess of organic small molecules.

In each library, the vast majority of the variants displayed the desired activity, and of the 40 different designs, 38 produced the target amine in good yield with >99% enantiomeric excess.

coli BL21(DE3)-pET28a(+) - LXCAR-S154Y variant affording carbonyl reductase was adopted for the reduction of 3'-(trifluoromethyl)acetophenone to ( R )-MTF-PEL with enantiomeric excess (ee) > 99.

Under optimal preparation conditions, enantiomeric excess value (ee) of 7.

The obtained chiral electrodes were also used for the determination of the enantiomeric excess (ee) for Trp, and a good linear relationship between peak currents and ee% of Trp was obtained.

The racemic naproxen sample was separated via the chiral antiport process, with an enantiomeric excess of 71.

A novel screening protocol was developed using a combination of a fluorescent indicator displacement assay and a circular dichroism (CD) active Fe(II) complex to determine concentration and enantiomeric excess (ee) of α-chiral amines, respectively.

By directly employing the pH adjusted supernatant as a biocatalyst, we were able to almost completely transform 10 g/L of pyrmetazole into the corresponding ( S )-sulfoxide, with  >  99% enantiomeric excess.

Furthermore, transformations of the obtained allylation products are demonstrated without a significant loss of enantiomeric excess.