Comparison between cellulose and amylose tris(3,5‐dimethylphenylcarbamate) chiral stationary phases for enantiomeric separation of 17 amidotetralins

Abstract

Direct enantiomeric separations of 17 chiral amidotetralins by means of high performance liquid chromatography were performed on stationary phases composed of tris(3,5-dimethylphenylcarbamate) derivatives of cellulose and amylose, coated on silica gel. The enantiomers of 15 out of 17 amidotetralins were resolved with a resolution of more than 1.5 by at least one of the chiral stationary phases. The stationary phases showed complementary results with regard to the separation of the amidotetralins, that is, pairs that did not separate on the cellulose-type column were well separated on the amylose-type column, and vice versa. There was no significant correlation between the chromatographic properties of the chiral stationary phases. o 1993 Wiley-Liss, Inc.KEY WORDS: cellulose, amylose, silica gel, high performance liquid chromatography, direct separationsHigh performance liquid chromatography (HPLC) has been the fastest developing chromatographic technique during the last two decades in the area of chiral applications. For direct separations with chiral HPLC, much work has been done with straight phase systems and water-free eluents. With these systems analyses from biological matrices can only be performed after a good sample pretreatment, since some commercially available stationary phases are easily ruined by small amounts of biological material (e.g., proteins).In 1980 Blaschke4 described the use of cellulose, starch, and cellulose acetate as chiral sorbents. Later, Okamoto et al. published promising results on stationary phases containing cellulose triesters coated on macroporous silica. These stationary phases belong to the general category of polysaccharide sorbents, and the formation of diastereoisomeric complexes involves hydrogen bonding, n-n complexes, and dipole interactions. Different cellulose derivatives were studied by Okamoto et aL6 They found that the dimethylphenyl-and dichlorophenyl-carbamates, substituted at the 3,4 or 3,5 positions, showed better chiral recognition for most enantiomers studied compared to the monosubstituted carbamates. The mobile phases used in combination with these columns were nonpolar, that is, hexane modified with an alcohol, for example, ethanol. Compounds separated successfully on these phases contain combinations of phenyl, carbonyl, nitro, cyano, sulfonyl, and hydroxyl groups. A commercially available cellulose derivative is tris(3,5-dimethylphenylcarbamate). In mixed with acetonitrile. At the moment, cellulose-based chiral stationary phases (CSPs) are commercially available for both reversed and straight phase modes, but the majority of these phases are still to be used with water-free eluents.In addition to cellulose-type columns, amylose-type stationary phases were developed.*910*" Cellulose and amylose differ only in the configuration on the 1-4 position of the D-glucose units being 1-4p-in the cellulose unit while it is 1-4a-in the amylose unit, as can be seen in Figure 1. This results in a different spatial arrangement between cellulose, being rigid and...

Enantioseparation of amfepramone (rac-diethylpropion): Preparative separation of the enantiomers and enantioselective analysis

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Enantioselective recognition of 2,3-benzodiazepin-4-one derivatives with anticonvulsant activity on several polysaccharide chiral stationary phases

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Chiral separation of nucleoside analogues of d4T and acyclovir, by liquid chromatography, of amylose stationary phases and determination of enantiomeric purity

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