Enantiomeric discrimination of pyrethroic acid esters on polysaccharide derived chiral stationary phases

Abstract

Enantiomeric separation of pyrethroic acid methyl and ethyl esters was examined on cellulose-based chiral stationary phases (CSPs): chiralcel OD (cellulose tris(3,5-dimethylphenyl carbamate)) and chiralcel OF (cellulose tris(4-chlorophenyl carbamate)). The good resolution of pyrethroic acid esters was achieved on chiralcel OD and OF. Separation factors ranged from 1.19-5.12 for Chiralcel OD and 1.00-1.59 for chiralcel OF. Hexane/2-propanol (100:0.15, v/v %) was used as the eluent. The resolution capability of CSPs was greater chiralcel OD than chiralcel OF in the case of the pyrethroic acid esters. The flow rate was 0.8 ml/min and detection was set at 230 nm. The results of the chromatographic data and molecular mechanics suggest that steric effect was a major factor in the enantioseparation. Furthermore, the hydrogen bond between analytes and CSP played an important role in the chiral recognition. Chirality 15: 276-283, 2003. © 2003 KEY WORDS: chiral discrimination; pyrethroic acid ester; HPLC; enantioseparation; molecular mechanics; cellulose tris(3,5-dimethylphenyl carbamate); chiralcel OD; cellulose tris(4-chlorophenyl carbamate); chiralcel OF The natural insecticidal compound pyrethrin was available in the form of dried flowers of Chrysanthemum roseum as early as the beginning of the 19th century. The active insecticidal component of pyrethrum extract is a mixture of six related compounds, known as pyrethrins, of which the most potent are pyrethrins I and II. Pyrethroids are important in agriculture and household usage because of their high insecticidal activity and very low mammalian toxicity. Pyrethroid insecticides with greater stability were sought to replace the increasing insect resistance to organophosphates.1 Most pyrethroids contain a mixture of isomers, both inactive and active isomers. Many are now being sold as the resolved form of the original product, containing only the active isomers or a higher ratio of active isomers. Therefore, enantiomer separation of pyrethroids and their intermediates is a very important task. As shown in Figure 1, pyrethroic acid esters show that two asymmetric carbon atoms give rise to four isomers, two pairs of which have geometric isomer cis-and trans-configuration with respect to the plane of the cyclopropane ring. Micellar electrokinetic capillary chromatographic (MECC) methods using types of cyclodextrin and their derivatives in phosphate buffer containing several surfactants as chiral selector have been reported to separate the enantiomers of cypermethrin, alphamethrin, permethrin, and fenpropathrin. 2 (1R,3R)-trans-Chrysanthemic acid and its amide derived chiral stationary phases (CSPs) have been employed for enantiomer separation of trans-chrysanthemic acid 3,5-dinitroanilide.3 Gas chromatographic separation of chrysanthemic acid ester enantiomers has been reported. In that article, a novel amide phase derived from (1R,3R)-trans-chrysanthemic acid with (S)-mandelic acid (R)-1-(␣-naphthyl)-ethyl amide shown good stereoselectivity for chrysanthemic aci...

Chiral Recognition of N‐Phthaloyl, N‐Tetrachlorophthaloyl, and N‐Naphthaloyl α‐Amino Acids and Their Esters on Polysaccharide‐Derived Chiral Stationary Phases

“…1,2 Among them, N-phthaloyl (PHT) group has been widely used in organic and peptide synthesis. 12,[15][16][17][18] The investigation of chiral recognition is hardly difficult in polysaccharide CSPs, because a number of structural peculiarities exist due to the presence of several stereogenic centers of the glucopyranose units and their helical structures of the polymer backbone. 6 And also, N-naphthaloyl (NPHT) group has been usefully used in the determination of enantiomeric excess as a chiral solvating agent.…”

“…[3][4][5] N-tetrachlorophthaloyl (TCPHT) group has been applied to solid-phase synthesis of C-terminal peptide amides. 19 The chiral discrimination mechanisms in polysaccharide CSPs have been examined using spectroscopic methods, [20][21][22] computer-aided methods, 17,18,20,23 and quantitative structure-retention relationship studies. [7][8][9] In order to utilize these useful N-protected a-amino acid derivatives, it is necessary to establish adequate analytical method diversely for the enantiomer separation.…”

“…[7][8][9] In order to utilize these useful N-protected a-amino acid derivatives, it is necessary to establish adequate analytical method diversely for the enantiomer separation. 17,18 In this study, we present liquid chromatographic results for the enantiomer separation of N-PHT, N-TCPHT, and N-NPHT a-amino acids and their esters with polysaccharide-derived CSPs. [10][11][12][13][14] Liquid chromatographic enantiomer separation has been frequently employed in evaluation of the enantiomeric purity with polysaccharide-derived chiral stationary phases (CSPs) that can separate a wide range of racemic compounds.…”

“…[10][11][12][13][14] Liquid chromatographic enantiomer separation has been frequently employed in evaluation of the enantiomeric purity with polysaccharide-derived chiral stationary phases (CSPs) that can separate a wide range of racemic compounds. 12,[15][16][17][18] The investigation of chiral recognition is hardly difficult in polysaccharide CSPs, because a number of structural peculiarities exist due to the presence of several stereogenic centers of the glucopyranose units and their helical structures of the polymer backbone. 19 The chiral discrimination mechanisms in polysaccharide CSPs have been examined using spectroscopic methods, [20][21][22] computer-aided methods, 17,18,20,23 and quantitative structure-retention relationship studies.…”

Separation of Racemic Chiral Drugs Using Immobilized CHIRALPAK IA: Methodology for Preparative Scale Development

“…Generally, the selection of the mobile phase plays the main role in chiral resolution and therefore the mobile phase is selected according to compatibility with CSPs as well as solubility and structure of the racemic mixture (13)(14)(15)(16).…”