High-pressure liquid chromatography enantiomers

Once again, the ratio of diastereomers is the same as that of the original enantiomers. High-pressure liquid chromatography has been used in a similar manner and has wider applicability. The direct separation of enantiomers by gas or liquid chromatography on a chiral column has also been used to determine optical purity. " Other methods... 

Peyton, A.L. Carpenter, R. Rutkowski, K. The stereospecific determination of fluoxetine and norfluoxetine enantiomers in human plasma by high-pressure liquid chromatography (HPLC) with fluorescence detection. Pharm.Res., 1991, 8, 1528-1532... 

About at the same time, enantiomers of ofloxacin have been described and synthetized through optical resolution of a racemic intermediate of ofloxacin by high-pressure liquid chromatography [57]. 

Acid catalyzed hydrolysis followed by the identification of D-amino acids in the hydrolysate is equally useful. To make this possible the amino acids in the mixture are acylated with an enantiomerically pure amino acid, for instance with the N-carboxyanhydride of L-leucine. In the resulting mixture of dipeptides any racemized residue is revealed by the formation of two dipeptides that are diastereoisomers of each other, for instance L-leucyl-L-phenylalanine and L-leucyl-D-phenylalanine. Since these are compounds with different physical properties they are separable and appear as a doublet on recordings of an amino acid analzyer. In recent years the conversion to diastereoisomers became unnecessary because the availability of chiral supports now permits separation of enantiomers by high pressure liquid chromatography (HPLC) and also by thin layer chromatography on plates covered with a chiral layer. 

Brucine is used in a similar manner and the carboxyl unit of the amino acid is coordinated to the tertiary amine unit in brucine rather than the poorly basic amide nitrogen. Selective crystallization of these salts leads to their separation, and basic hydrolysis leads to an enantiopure amino acid. It is now possible to separate many racemic mixtures into their enantiomeric components by using high-pressure liquid chromatography (HPLC) fitted with a column that contains a chiral compound bound to an adsorbent (known as chiral HPLC columns). Such columns have been developed by William H. Pirkle (United States 1934-). The chiral HPLC column is prepared by coating a chiral chemical compound on an inert material when a solution of the racemic mixture passes through this column, one enantiomer is adsorbed to the column material better than the other. These are sometimes called Pirkle columns. 

The second Litaudon report described the methods required to separate each of the racemic compounds from the others as well as the specifications for a chiral high-pressure liquid chromatography (HPLQ method that separated some pairs of enantiomers. 

The diastereomeric /1-hydroxysulfoximines derived from prostereogenic ketones are generally separable by medium-pressure liquid chromatography (WLC) on silica gel. Subsequent desulfurization of the separated adducts affords both enantiomers of the tertiary alcohols with high optical purity58,59. 

Desai,M.J., Armstrong, D.W. (2004). Analysis of native amino acid and peptide enantiomers by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry. J. Mass. Spec. 39, 177-187. 

A series of planar chiral pyridine-fused ferrocene analogs (366) have been prepared and the enantiomers are resolved by chiral High performance (pressure) liquid chromatography (HPLC) see High Performance Liquid... 

C. R. Lei, Liquid high-pressure carbon dioxide chromatography of P-blockers. Resolution of the enantiomers of Nadolol, J. Chromatogr., 539(1991)55. 

May be analytical or preparative. Fractions of the analyte may be passed directly into other spectroscopic techniques for structure determination. Can be used, with an appropriate chiral stationary phase, to separate enantiomers (see Chapter 7). Usually takes place under high pressures, hence ftPLC, which is used to indicate both high-pressure and higher-performance liquid chromatography. 

---