Chirality enantiomers

Murakami H (2007) From Racemates to Single Enantiomers - Chiral Synthetic Drugs over the last 20 Years. 269. 273-299 Mutule I, see Sima E (2006) 266 49-101... 

Itoh, T., et al. Stereoselectivity of the folate transporter in rabbit small intestine studies with amethopterin enantiomers. Chirality 2001, 13, 164-169. 

Another cooperativity effect, dubbed majority rule has also been noted. Where opposite enantiomer chiral groups are both present in side chains, such as (S) and (l )2-methylbutyl groups, the overall helicity is determined in a non-linear manner by the ee only, as is evident in Figure 42. 

CE has been established as a very efficient technique for the separation of drug enantiomers. Chiral separations in CE are also based on the formation of diastereomeric complexes between the enantiomers and a chiral selector. The main advantages of the technique are its high efficiency, short analysis times, versatility due to the great variety of chiral selectors that can be added to the BGE, short equilibration times required when changing the chiral selector and low consumption of selector. °... 

From the method development and robustness point of view, the temperature is a parameter that controls equilibria such as pK and enantiomer—chiral selector complexation, or induces structural changes in, e.g., proteins.For chiral separations, generally a lower temperature results in better enantioseparation, but even the opposite has been observed. Sometimes a raise in temperature does not so much affect the enantiomeric separation, but increases the resolution between an enantiomer and a matrix component. ... 

The future is fascinating for pharmaceuticals. A big trend now for many drugs is manufacture of the pure enantiomer. Chiral drugs can be made... 

Key Words Principal axes symmetry asymmetry enantiomers chirality QSAR. 

Chromatography may be used for the direct separation of enantiomers ( chiral chromatography ) and also for the normal separation of diastereomeric pairs. 

Takacs, J.M., Hrvatin, P.M., Atkins, J.M., Reddy, D.S. and Clark, J.L. (2005) The selective formation of neutral, heteroleptic zinc(ll) complexes via self-discrimination of chiral bisoxazoline racemates and pseudoracemates. New J. Chem., 29, 263—265 Atkins, J.M., Moteki, S.A., DiMagno, S.G. and Takacs, J.M. (2006) Single enantiomer, chiral donor—acceptor metal complexes from bisoxazoline pseudoracemates. Org. Lett., 8 (13), 2759-2762. 

Many other methods utilizing a three-carbon-chain segment have been employed in the syntheses of the fluoxetine enantiomers. Chirality has been established by enzymatic reduction,lipase mediated enzymatic resolution, " oxidative kinetic... 

Asymmetric catalysis, shown by equation 5 is an ideal method for synthesizing optically active compounds (2,3). The chemical approach, which uses a small amount of a chiral man-made catalyst, produces naturally occurring and nonnaturally occurring chiral materials in large quantities. The efficiency of chirality multiplication, defined as [(major enantiomer - minor enantiomer)/chiral source], can be infinite for asymmetric catalysis. Recent advances in this area are turning chemists dreams into reality at both academic and industrial levels. 

Drugs classified as either natural or semisynthetic in origin accounted for - 22% of the market share in 1991. Nearly 94% of the agents are chiral compounds and are sold as single enantiomers. Chiral synthetic... 

The importance of this mode of separation lies in the shear scale of the market for optically pure molecules. The sales of single enantiomer chiral drugs is currently U 180 billion per annum and —65% of active pharmaceutical ingredients (APIs) currently in development have at least one chiral centre. Apart... 

S. P. Mendez, E. B. Gonzalez, A. Sanz-Medel, Hybridation of different chiral separation techniques with ICP-MS detection for the separation and determination of selenomethionine enantiomers chiral speciation of selenized yeast, Biomed. Chromatogr., 15 (2001), 181D188. 

The FITC labeling method was also applied to chiral separations of amino acids on a microchip to determine the enantiomeric ratios of amino acids found on a meteorite [27], Since biotic amino acids are normally single enantiomers, chiral separations of amino acids are not truly clinical in nature, but illustrate the potential for chiral separations of small molecules of clinical interest. Ma-thies and co-workers used this technique to search for evidence of life in extraterrestrial environments. Enantiomeric forms of Val, Ala, Glu, and Asp could be discriminated by addition of a-, (3-, or y-cyclodextrin (CD) to the run buffer. Improved resolution with faster separations was found with respect to conventional CE. This method has been modified, by addition of SDS to the buffer, to perform cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) [28]. Increasing the SDS concentration decreased the magnitude of elec-troosmotic flow (EOF), increasing the effective migration distance, and therefore the resolution on the microchips. 

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