摘要:

Abstract6‐n‐Alkylchromone‐2‐carboxylic acids are metabolized solely by aliphatic oxidation. In the rabbit, the 6‐n‐propyl congener (PCCA) undergoes ω‐1 hydroxylation exclusively. Following administration of PCCA to female Dutch rabbits (500 μmol/kg), some 77% of the dose was excreted in the urine, 41% as PCCA and 36% as 6‐(2'‐hydroxy‐n‐propyl)chromone‐2‐carboxylic acid. Since this metabolite is chiral, we have examined the stereochemistry of the excreted material. Diastereoisomeric (as camphanate and α‐methoxy‐α‐(trifluoromethyl)phenylacetate esters) and direct chiral HPLC and chiral lanthanide shift NMR have each shown the S:R ratio of the excreted metabolite to be 76:24. When rabbits were dosed with the racemic metabolite, excretion of the compound was not stereoselective. The regio‐ and stereo‐selectivity of the aliphatic hydroxylation of PCCA are thus reflections of the selectivities of the enzyme systems responsible for its formation and suggest PCCA to be an appropriate probe compound for the s

ISSN:0899-0042    

DOI:10.1002/chir.530040103

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractTwo novel series, Ia,b and IIa,b, ofkappaopioid antinociceptive agents have recently been described.2a,b,3a,b,cThe biological activities of 16 racemic compounds and their corresponding (−) enantiomers are now compared in a battery of tests. Enantiomers of unsubstituted piperidinesIawere synthesized starting from S(−) pipecolic acid, whereas the enantiomerically pure substituted piperidines (Ib), tetrahydroisoquinolines (IIa), and thienopiperidines (IIb) were, in general, obtained after diastereomeric crystallization of the corresponding tartrate salts. The absolute stereochemistry of one representative enantiomer from seriesIIawas determined to be (1S) by X‐ray crystallographic analysis. Antinociceptive activity in the mouse abdominal constriction and tail‐flick tests following subcutaneous administration, and binding affinity for κ and μ receptors, were found to reside predominantly in the (−) enantiomers. Consequently, racemic compounds showed approximately half potency of the corresponding enantiomers. This potency difference was less clear after oral administration presumably due to small differences in bioavailability of the two corresponding enantiomers.For compounds with some affinity also for μ receptors (Ki<1,000 nM), the κ/μ selectivity was maintained within each enantiomeric pair, in contrast to results found for ot

ISSN:0899-0042    

DOI:10.1002/chir.530040104

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractWe present a chromatographic method for the separation and determination of the optical purity of the enantiomers of WB 4101 [(±)‐1], one of the most potent and selective α1‐adrenoreceptor antagonists. (±)‐1was converted into the amide ofN‐tosyl‐(S)‐proline. The two diastereoisomers were separated on silica gel and analysed by HPLC reversed phase. The analytical method described is both accurate and sensitive and allows the optical purity to be determined at very low concentrations and to obtain WB 4101 enantiomers with a purity of mo

ISSN:0899-0042    

DOI:10.1002/chir.530040105

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of phenprocoumon enantiomers on the stereoselective binding of 3‐substituted 1,4‐benzodiazepines to human serum albumin (HSA) was studied by chromatography on HSA‐Sepharose column. (S)‐Phenprocoumon exerts stereoselective allosteric interaction on the binding of benzodiazepines. The structural requirements of enhanced stereoselectivities are similar to those found previously with (S)

ISSN:0899-0042    

DOI:10.1002/chir.530040106

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractAlthough chiral anionic compounds, notably a large number of organic acids, have been found to be readily separated into enantiomers on BSA‐based columns, the structural requirements for an efficient enantiomer discrimination by the protein is still not very well known. Since it is often observed that very hydrophobic acids, like many of the antiinflammatory “profens,” can be resolved with large separation factors for the enantiomers, a systematic study of a series of racemic α‐substituted alkanoic acids was made. The series of analytes was prepared from α‐amino acids, RCH(NH2)CO2H (where R = C1‐C6), by reaction with N‐(chloroformyl)‐carbazole. A rapid increase in the capacity ratios of both enantiomers was found with increasing length of R. The effect, however, was larger for the last eluted enantiomer, leading to a substantial increase in the separation factor; this being 7.3 for R = C6in 20 mM phosphate buffer (pH 8.0) with 30% of acetonitrile. Further, the separation factor also increased with decreasing organic modifier content. Thus when the R = C6‐analyte was run at a mobile phase concentration of 20% acetonitrile and a flow rate of 1.5 ml/min, the time difference between the two eluted enantiomers exceeded 20 hr.A reasonable interpretation of our results seems to be that enantioselectivity is promoted by increased hydrophobic interaction. Since the anionic charge of the analyte is also taking part in the retention mechanism, a tight binding of the analyte will result from simultaneous electrostatic and hydrophobic interaction. When the latter is increased, less conformational freedom will be left for the analyte and the steric configuration at the α‐carbon atom will become more and more important. Steric hindrance by the α‐substituent in the first eluted enantiomer will counteract the tight binding caused by the combined binding interactions and lead to a smaller incre

ISSN:0899-0042    

DOI:10.1002/chir.530040107

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of mobile phase pH and dimethyloctylamine (DMOA) on the retention (k') and stereoselectivity (α) of antimalarial agents mefloquine, enpiroline, and chloroquine on the α1‐acid glycoprotein chiral stationary phase (AGP‐CSP) was investigated. An increase of k' with increasing pH was observed while the effect on α was a function of the solute. The magnitude and direction of changes induced by DMOA depended on pH and the structure of the solute.The results of this study are consistent with a change of the conformation of the AGP between pH 5 and 7. At pH 7, the effect of DMOA on mefloquine was relatively well described by a competitive displacement from one enantioselective site. The effect on chloroquine and enpiroline suggests a multiple‐site mechanism in which both competitive and allosteric interactions are

ISSN:0899-0042    

DOI:10.1002/chir.530040108

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractA novel chiral stationary phase (CSP) derived from tyrosine is evaluated with regard to the first generation commercially available (S)‐ChyRoSine‐A CSP, under normalphase or reversed‐phase liquid chromatographic (NPLC or RPLC) and subcritical fluid chromatographic (SubFC) conditions. The complete scope of application of these CSPs is reviewed. The novel CSP, which bears a bulkier functional group, displays a higher enantiorecognition ability than previously described (S)‐ChyRoSine‐A toward about 15 families of racemates, whatever the mobile phase conditions.The direct enantiomeric separation of 1,2‐amino‐alcohols (β‐blockers) is carried out on both CSPs. Facile separations are achieved within short analysis times using SubFC mode, whereas very poor separations are obtained using NPLC mode. These results disagree with previous theories (interchangeability between NPLC

ISSN:0899-0042    

DOI:10.1002/chir.530040109

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

ISSN:0899-0042    

DOI:10.1002/chir.530040110

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe simultaneous stereodifferentiation of all aromarelevant 4(5) alkylsubstituted γ(δ)‐lactones is described, using enantioselective multidimensional gas chromatography (MDG), and the column combination OV 1701/octakis(3‐O‐butyryl‐2,6‐di‐O‐pentyl)‐γ‐cyclodextrin. The method is applicated to the lactone flavour compounds of fruits, indicating the advance to the analytical differentiation between “natural” and “nature‐identical” aromas. Modified cyclodextrins are also proved to be powerful tools in the chirospecific CGC analysis of monoterpenoid constituents of essential oils. Optical purity control is discussed as an indi

ISSN:0899-0042    

DOI:10.1002/chir.530040111

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn this study capillary zone electrophoresis has been used for the separation of racemic tryptophan derivatives in their enantiomers. The effect of cyclodextrins with different shape, added to the background electrolyte, on the migration time of 10 compounds, including methyl tryptophan, hydroxy tryptophan, and tryptophan ester derivatives, has been studied. Furthermore, the effect of cyclodextrins with different shape and that of the composition of the background electrolyte on the enantiomer resolution are discussed. Among different cyclodextrins used α‐cyclodextrin and heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin were found to possess the best complexing capacity and thus the resolution power toward analy

ISSN:0899-0042    

DOI:10.1002/chir.530040112

出版商:Alan R. Liss, Inc.    

年代:1992

数据来源: WILEY