Chiral speciation

Chiral speciation—determination of the enantiomers of the given compound... 

Mendez, S.P., Bayon, M.M., Gonzalez, E.B., and Sanz-Medel, A. 1999. Selenomethionine chiral speciation in yeast and parenteral solutions by chiral phase capillary gas chromatography-ICP-MS. J. Anal. At. Spectrom. 14(9), 1333-1337. 

C. A. Ponce de Leon, K. L. Sutton, J. A. Caruso, P. C. Uden, Chiral speciation of selenoamino acids and selenium enriched samples using HPLC coupled to ICP-MS, J. Anal. Atom. Spectrom, 15 (2000), 1103-1107. 

A. Sanz-Medel, E. Blanco-Gonzalez, Chiral speciation of trace elements approaches to the speciation of selenoaminoacid enantiomers in biological samples, J. Anal. Atom. Spectrom., 16 (2001), 957-963. 

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. 

J. A. Day, S. S. Kannamkumarath, E. G. Yanes, M. M. Bayon, J. A. Caruso, Chiral speciation of Marfey s derivatized DL-selenomethionine using capillary electrophoresis with UV and ICP-MS detection, J. Anal. Atom. Spectrom., 17 (2002), 27D31. 

Mendez, S. P., Gonzalez, E. B., Medel, A. S. Chiral speciation and determination of selenomethionine enantiomers in selenized yeast by HPLC-ICP-MS using a teicoplanin-based chiral stationary phase. J Anal At Spectrom 2000, 15, 1109-1114. 

The study of biochemical natural products has also been aided through the application of two-dimensional GC. In many studies, it has been observed that volatile organic compounds from plants (for example, in fruits) show species-specific distributions in chiral abundances. Observations have shown that related species produce similar compounds, but at differing ratios, and the study of such distributions yields information on speciation and plant genetics. In particular, the determination of hydroxyl fatty acid adducts produced from bacterial processes has been a successful application. In the reported applications, enantiomeric determination of polyhydroxyl alkanoic acids extracted from intracellular regions has been enabled (45). 

The simultaneous presence of a chiral selector and a charged non-chiral IPR was studied successfully [129]. The presence of a non-chiral IPR dramatically improved the separation of oppositely charged compounds on a chiral column, probably because the IPR increased retention and hence interactions with the chiral packing, as in the speciation of selenium-containing amino acids, on a crown ether column... 

The chromatographic modes typically used in speciation analysis are size-exclusion, ion-exchange, ion-pair reversed-phase, reversed-phase and, to a lesser extent, micellar, vesicular, chiral and affinity LC. Detailed descriptions of their capabilities and limitations can be found in a number of comprehensive reviews.i>2,9-ii,i4... 

HPLC. " Different perfluorinated carboxylic acids have been examined as the ion-pairing agents (pH 2.5. 5) in the analyses of enriched yeast and vegetable extracts Alkylsulfonic acids have been successfully used in speciation analysis carried out on nuts, onion leaves and yeast " " Owing to their different biological activities, optical enantiomers of Se-amino acids were analyzed by several chiral separation techniques - ... 

CD can be a versatile tool in speciation analyses of aqueous solutions containing vanadate or VO + and chiral ligands.P l and for assigning a chiral compound the correct configuration. Figure 3.19 illustrates the latter situation for the optical antipodes of the complex [VO(naph-tyr)], where naph-tyr is the Schiff base formed from o-hydroxynaphthaldehyde and tyrosine. 

Catalytic symmetric synthesis of P-stereogenic phosphines by cross-coupling of secondary phosphines with benzyl or other alkyl halides was promoted by chiral ft and Ru complexes [112-114]. The key step is believed to be the nucleophilic attack of a metal-phosphido complex on a free electrophile the background reaction of the unactivated nucleophilic substrate is much slower. The origin of enantioselec-tivity, as in the Pd-catalyzed asymmetric cross-couplings described above, is the interconversion of diastereomeric phosphido complexes, whose speciation and relative rates of nucleophilic attack determine the product ratio. In the case of ft ((R./ )-Me-DuPhos)(Ph)(PMels), as with the Pd analog in Scheme 43 above, the major product phosphine was formed from the major diastereomeric phosphido complex (Scheme 63) [112-113]. 

Sanz-Medel a. and Bianco-Gonzalez E. (2002) Chiral trace-element speciation in biological samples present importance and applications to speciation for seleno-amino acids, Trends Anal. Chem. 21 709-716. 

The enantiomeric composition of several insect pheromones has been determined by employing a chiral derivative and chiral lanthanide shift reagents (45). The amount of material required was of the order of 5—500 ig of substrate. As the enantiomeric composition of chiral pheromones is of fundamental importance to their efficacy and appears to play a role in speciation, one can expect its determination to become a standard procedure. 

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