1.New method for the resolution of the enantiomers of 5,6-dihydroxy-2-methyl-aminotetralin by selective derivatization and HPLC analysis: application to biological fluids.
Rondelli I1, Corsaletti R, Redenti E, Acerbi D, Delcanale M, Amari G, Ventura P. Chirality. 1996;8(5):381-9.
A new chiral derivatization procedure for the HPLC resolution of chiral catecholamines and structurally related compounds is described. The homochiral reagent, (+)-(R)-1-phenylethyl isocyanate (RPEIC), was added to separate and quantitate the enantiomers of rac-5,6-dihydroxy-2-methyl-aminotetralin, the main metabolite of rac-5, 6-diisobutyryl-2-methyl-aminotetralin, a potent dopamine agonist, by reversed-phase HPLC analysis. To avoid catecholamine degradation in the basic reaction medium and to obtain the selective and quantitative derivatization of the amino group of the compound, the reversible complex formation between diphenylborinic acid (DPBA) and the catechol group, in alkaline medium, was performed before homochiral isocyanate addition. The RPEIC derivatization was completed in 30 min and then the DPBA complex was dissociated by adding dilute acid. The structure of intermediates and urea derivatives was confirmed by mass spectometry.
2.Gas-chromatographic resolution of enantiomeric secondary alcohols. Stereoselective reductive metabolism of ketones in rabbit-liver cytosol.
Gal J, DeVito D, Harper TW. Drug Metab Dispos. 1981 Nov-Dec;9(6):557-60.
Chiral secondary alcohols were treated with (S)-(-)-1-phenylethyl isocyanate. For each racemic alcohol, the resulting diastereomeric urethane derivatives were resolved on flexible fused-silica capillary GLC columns with retention times of 15 min or less. Derivatization of individual enantiomers showed that the urethane derivatives of (R)-(-)-2-octanol, (R)-(+)-1-phenylethyl alcohol, and (S)-(+)-2,2,2-trifluoro-1-phenylethanol are eluted before the corresponding diastereomers. The procedure is simple and rapid, and is suitable for the determination of the enantiomeric composition of chiral alcohols extracted from biological media. A series of aliphatic alcohols, aryl alkyl carbinols, and arylalkyl alkyl carbinols were resolved with the procedure, and the degree of resolution varied from good to excellent. Eight achiral ketones were incubated, individually, with rabbit-liver 90,000 g supernatant fractions, and the enantiomeric composition of the alcohol metabolites was determined with the GLC procedure.
3.Multiple inverse isotope dilution assay for the stereospecific determination of R(+)- and S(-)-oxprenolol in biological fluids.
Dieterle W, Faigle JW. J Chromatogr. 1983 Apr 1;259(2):311-8.
An isotope dilution assay has been developed for the determination of both oxprenolol enantiomers in biological samples after administration of the racemic 14C-labelled mixture. The enantiomers were reacted with optically pure S(-)-1-phenylethyl isocyanate and the diastereoisomeric urea derivatives formed were separated by normal-phase high-performance liquid chromatography. Quantitation was performed by on-line ultraviolet detection at 275 nm and off-line radiometry. Endogenous compounds and oxprenolol metabolites did not interfere with the assay. Analysis of water and blood, plasma and urine samples of rats and dogs spiked with [14C]oxprenolol hydrochloride showed mean recoveries for R(+)-oxprenolol hydrochloride of 99.2% (water), 99.3% (blood), 99.1% (plasma) and 97.9% (urine), and for S(-)-oxprenolol hydrochloride of 99.7% (water), 98.1% (blood), 98.6% (plasma) and 96.9% (urine). In a pilot study, the presented method was used to investigate the metabolic fate of the enantiomers in two dogs dosed orally with racemic [14C]oxprenolol hydrochloride (3 mg/kg).
4.High-performance liquid chromatographic resolution of enantiomers of 1-phenyl-2-aminopropanes (amphetamines) with four chiral reagents.
Miller KJ, Gal J, Ames MM. J Chromatogr. 1984 May 11;307(2):335-42.
High-performance liquid chromatography (HPLC) was employed for resolution of enantiomers of chiral ring-substituted 1-phenyl-2- aminopropanes (amphetamines) and 1-phenylethylamine following derivatization with four chiral reagents: (R)-(+)-1-phenylethyl isocyanate ( PEIC ), (-)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride ( MTPA X Cl), 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate ( GITC ), and 2,3,4-tri-O-acetyl-alpha-D- arabinopyranosyl isothiocyanate ( AITC ). Reactions were accomplished under mild conditions (25-70 degrees C) and were complete for all substrates within 60 min. Derivatization with the sugar isothiocyanates ( GITC and AITC ) and the acyl chloride ( MTPA . Cl) was carried out in methylene chloride or acetonitrile in the presence of a base catalyst while derivatization with the isocyanate ( PEIC ) was performed in methylene chloride. The diastereomeric derivatives were separated by reversed-phase HPLC (C18) with a methanol-water mobile phase.
