For chiral deriv of amino acids

Wang, H. et al.Sodium maleopimaric add as pseudostationary phase for chiral separations of amino acid derivatives by capillary micellar electrokinetic chromatography. J. Sep. Sci. 2007, 30, 2748-2753. 

He X, Cui X, Li M et al (2009) Highly enantioselective fluorescent sensor for chiral recognition of amino acid derivatives. Tetrahedron Lett 50 5853-5856... 

Diamide Chiral Separations. The first chiral stationary phase for gas chromatography was reported by GH-Av and co-workers in 1966 (113) and was based on A/-trifluoroacetyl (A/-TFA) L-isoleucine lauryl ester coated on an inert packing material. It was used to resolve the tritiuoroacetylated derivatives of amino acids. Related chiral selectors used by other workers included -dodecanoyl-L-valine-/-butylamide and... 

For the separation of amino acids, the applicability of this principle has been explored. For the separation of racemic phenylalanine, an amphiphilic amino acid derivative, 1-5-cholesteryl glutamate (14) has been used as a chiral co-surfactant in micelles of the nonionic surfactant Serdox NNP 10. Copper(II) ions are added for the formation of ternary complexes between phenylalanine and the amino acid cosurfactant. The basis for the separation is the difference in stability between the ternary complexes formed with d- or 1-phenylalanine, respectively. The basic principle of this process is shown in Fig. 5-17 [72]. 

Possible racemisation of imines, derivatives of amino acids and R(—)-myrtenal, has been examined by Dufrasne et al.1 After 72 h, no significant effect on chiral purity was observed. For imines being derivatives of chiral primary amines and the a-substituted 8-keto-aldehydes, no evidence of epimerisation has been indicated by the NMR measurements.3 For a series of imines, being derivatives of amino acids or amino acid esters and (R)-BINOL reagents, Chin et al.5 have tested the possibility of epimerization under experiment conditions. It was shown that R S ratio has changed only slightly, and after 24 h, the difference was lower than 10%. 

General procedures for the synthesis of the imidazole core have been published in 2000. Solvent-free microwave assisted synthesis of 2,4,5-substituted imidazoles 64 from aldehydes 62 and 1,2-dicarbonyl compounds 63 in the presence of ammonium acetate and alumina has been reported <00TL5031>. V-protected a-amino glyoxals 65 were utilized as potential chiral educts for the synthesis of amino acid-derived imidazoles 66 <00TL1275>. 

An approach, similar to that employed in the analysis of tartrate mixtures, has been used for the chiral discrimination of amino acid (M/j/s) mixtures, using an amino acid of defined configuration as reference (S). The proton-bound trimers [S2-M H]+ form [S M H]+ and [S2H]+ fragments upon CID or MIKE decay (equations (9)-(12)). With two independent measurements of the fragmentation ratio [S-M-H] /[S2H] from either [S2-M -H] and [52-M5-H]" , the differences in binding energies can be determined. The relative gas phase basicities (GB) of the molecular pairs [S-M] and [S2] can be derived from equations (13) and (14). 

These enantioselective capillary columns showed extremely good performance in the CEC mode. Plate numbers in excess of 100,000 m could be easily achieved for a variety of amino acid derivatives (with chromophoric and fluorophoric labels) (Eigure 1.34a) as well as other chiral acids such as 2-aryloxycarboxylic acids. 

An experimental design approach was also used in Reference 26 for the chiral analysis of amino acid derivatives. The screening and optimization schedule followed... 

Perrin, C., Vargas, M.G, Vander Heyden, Y., Maftonh, M., Massarf D.L. Fast development of separation methods for the chiral analysis of amino acid derivatives using capillary electrophoresis and experimental designs. J. Chromatogr. A 2000, 883, 249-265. 

Amino acid enantiomers can be separated on a chiral stationary phase after derivatization with chloroformates (Abe et al., 1996). The derivatization procedure is quite simple and rapid, but the derivatizing reagent must be synthesized, which complicates the assay. Another method for the analysis of amino acid enantiomers uses N,0-pentafluoropropionyl isopropyl derivatives and a chiral column with NPD detection (Hashimoto et al., 1992). 

Alkylation of a-amino esters with 9-bromo-9-phenylfluorene serves as the principal step in the preparation of N-(9-phenylfluoren-9-yl)-a-amino carbonyl compounds which are useful chiral educts for asymmetric synthesis. A discussion of the synthetic utility of N-9-phenylfluoren-9-yl derivatives of amino acids and amino acid esters appears in the procedure following. 

Armstrong et al. [54] resolved the enantiomers of some amino acids and their derivatives on x-CD-based CSPs using 1% aqueous triethylammonium acetate (pH 5.1). The same authors also tested a /LCD CSP for the chiral resolution of amino acids [55]. In addition, they evaluated a y-CD phase for the enantiomeric resolution of some dansyl amino acids and other drugs. The mobile phase was 38% methanol with 1% triethylammonium acetate [58]. In another study, the same authors reported the chiral resolution of 25 pairs of amino acids in less than 30 min [63]. The enantiomers of some /i-adrcncrgic blockers were resolved on a /LCD stationary phase, with 1% aqueous triethylammonium acetate, containing methanol, as the mobile phase [9,48]. 

The application of antibiotics as chiral selectors has resulted in the successful resolution of almost all types of neutral, acidic, and basic racemic molecule. These antibiotics have been used for the enantiomeric resolution of amino acids, their derivatives, peptides, alcohols, and other pharmaceuticals. The selectivities of the most commonly used antibiotic-based (vancomycin, teicoplanin, and ristocetin A) CSPs varied from one racemate to another and are given in Table 1. Vancomycin was used for the chiral resolution of amino acids, amines, amides, imides, cyclic amines, amino alcohols, hydantoins, barbiturates, oxazolidinones, acids, profens, and other pharmaceuticals. Teicoplanin was found to be excellent chiral selector for the enantiomeric resolution of amino acids, amino alcohols, imides, peptides, hydantoins, a-hydroxy and halo acids, and oxazolidinones, whereas ristocetin A is capable of chiral resolution of amino acids, imides, amino... 

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