Chirality is of primary importance in many areas of chemistry and has been extensively investigated since its discovery. We introduce here a description of central chirality for tetrahedral molecules using a geometrical approach based on complex numbers. According to this representation, for a molecule having n chiral centers it is possible to define an "index of chirality chi." Consequently, a...

A new spectroscopic method of triple resonance is proposed for studying chirality of a molecule of C₁ symmetry. Each enantiomer of such a molecule is of mixed parity and thus exhibits all three a-, b-, and c-types of rotational spectra. The present study concludes, by using time-dependent perturbation theory, that the transition probability between two of the three rotational levels under tripl...

BACKGROUND Malathion (R,S)-diethyl-2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate is a chiral organophosphorus compound used widely as pesticide for suppression of harmful insects such as mosquitoes. It is well known that in biological systems (R)-malathion is the active enantiomer, therefore a sustainable approach could be the use of only the biologically active enantiomer. The resolution ...

Microwave three-wave mixing allows for enantiomer-selective excitation of randomly oriented chiral molecules into rotational states with different energy. The random orientation is reflected in the degeneracy spectrum respect to orientational quantum number M and reduces, if not accounted for, enantiomer-selectivity. Here, we show how design pulse sequences maximal enantiomer-selectivity from a...

mefloquine (mfq), as a racemic mixture is used for the prophylaxis and treatment of malaria. stereoselective pharmacodynamic and pharmacokinetic differences have been observed for mfq. in the present study, the human blood was spiked with racemic mfq. the concentration of mfq enantiomers in various blood fractions including packed erythrocyte layer, platelet rich plasma and platelet poor plasma...

The (R)-enantiomer of racemic albuterol produces bronchodilation, whereas the (S)-enantiomer may increase airway reactivity. After oral or intravenous administration of racemic albuterol, the (R)- enantiomer is metabolized several times faster than the (S)-enantiomer; however, enantiomer disposition after inhaling racemic albuterol with a metered-dose inhaler (MDI) is not known. Accordingly, 10...

The 5-HT (5-hydroxytryptamine, serotonin) transporter (SERT) mediates the reuptake of 5-HT from the synaptic cleft into the neuron, and inhibition of this uptake is the target of selective serotonin reuptake inhibitors (SSRIs). Escitalopram (S-citalopram) is the most selective SSRI available, whereas the other enantiomer, R-citalopram, is approximately 30-40 times less potent than the S-enantio...

Life did not emerge in a single step. In chemical evolution, the first formation of a self-replicating molecule was probably one of the most critical bottlenecks, which was overcome only with a very low probability. If only one such event was successful, present-day life originates from a single molecule. In this case, homochirality in DNA and RNA is explained almost without further assumptions...

Over the past fifteen to twenty years, the stereochemistry is gaining prime importance in pharmaceutical practice. As a result of advancement in chemical technologies associated with the synthesis, separation, identification and analysis of single enantiomer present in racemic compound, several chiral drugs are presented as single enantiomer for approval to regulatory authorities. Rather to int...

Escitalopram the S-enantiomer of the racemate citalopram, is clinically more effective than citalopram in the treatment of major depressive disorder. However, the precise mechanism by which escitalopram achieves superiority over citalopram is yet to be determined. It has been hypothesized that the therapeutically inactive R-enantiomer competes with the serotonin-enhancing S-enantiomer at a low-...