Liquid chromatographic resolution of racemic ketones as their oxime 3,5-dinitrophenyl carbamates on a chiral stationary phase

Cyclic and acyclic chiral ketones have been resolved as their oxime 3,5-dinitrophenyl carbamates on a chiral stationary phase derived from (S)-1-(6,7-direthyl-1-naphthyl)isobutylamine.     

多糖类氨基甲酸酯衍生物的区域选择性合成及其手性识别

通过糖单元6-位羟基的保护和去保护,运用区域选择性方法合成了6种新型多糖类氨基甲酸酯衍生物,分别为纤维素/直链淀粉-[2,3-二(3,5-二甲基苯基)-6-环己基]氨基甲酸酯、[2,3-二(3,5-二氯苯基)-6-环己基]氨基甲酸酯及[2,3-二(4-氯苯基)-6-环己基]氨基甲酸酯,并将其涂敷在氨丙基硅胶的表面制备HPLC手性固定相.利用1H-NMR与FTIR光谱技术对所合成衍生物进行结构表征和分析,并应用HPLC法评价其对于9种手性化合物的手性识别能力.通过与以手性识别能力高而著称且含有单一取代基的纤维素/直链淀粉-三(3,5-二甲基苯基氨基甲酸酯)等手性固定相的对比分析表明,所合成新型手性固定相对于某些对映体显示出更优的手性识别能力.由进一步分析表明,糖单元2-、3-和6-位取代基的性能对于纤维素和直链淀粉氨基甲酸酯类衍生物的手性识别能力均具有较大影响.     

1-Arylethylamino-substituted s-triazine derivatives as chiral solvating agents for the determination of the enantiomeric composition of chiral compounds

The development of 2-[(R)-1-(9-anthryl)ethylamino]-4-chloro-6-methoxy-1,3,5-triazine, 2-[(R)-1-(9-anthryl)ethylamino]-4-chloro-6-[(R)-1-(1-naphthyl)ethylamino]-1,3,5-triazine and 2-[(R)-1-(9-anthryl)ethylamino]-4,6-bis-[(R)-1-(1-naphthyl)ethylamino]-1,3,5-triazine as chiral solvating agents (CSAs) for the determination of the enantiomeric composition of derivatized and underivatized chiral compounds is presented. The comparison between the efficiency of these chiral auxiliaries with the corresponding 1-(1-naphthyl)ethylamino substituted s-triazine derivatives is also discussed.     

Phenylcarbamate derivatives of cellulose and amylose immobilized onto silica gel as chiral stationary phases for high-performance liquid chromatography

Three polysaccharide phenylcarbamate derivatives [cellulose 2,3-bis(3,5-dimethylphenylcarbamate)-6-(3,5-dimethylphenylcarbamate)/(2-methacryloyloxyethylcarbamate), cellulose 2,3-bis(3,5-dichlorophenylcarbamate)-6-(3,5-dichlorophenylcarbamate)/(2-methacryloyloxyethylcarbamate), and amylose 2,3-bis(3, 5-dimethylphenylcarbamate)-6-(3,5-dimethylphenylcarbamate)/(2-methacryloyloxyethylcarbamate)] with vinyl groups were prepared and coated onto silica gel to immobilize them via radical copolymerization with 2,3-dimethylbutadiene. The copolymerization efficiently proceeded, and the coated polysaccharide derivatives were mostly immobilized on the surface of the silica gel. The immobilized polysaccharide derivatives showed high chiral recognition abilities similar to those of the corresponding coated polysaccharide derivatives. They could be used with an eluent containing chloroform, which dissolved the polysaccharide derivatives. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4704–4710, 2004     

纤维素-[2,3-(4-取代苯基)-6-(3,5-二氯苯基)]氨基甲酸酯的合成及作为HPLC手性固定相的手性识别

合成了3种新的纤维素苯基氨基甲酸酯类衍生物:纤维素-[2,3-二苯基-6(3,5-二氯苯基)]氨基甲酸酯、纤维素-[2,3-二(4-甲基苯基)-6-(3,5-二氯苯基)]氨基甲酸酯及[2,3-二(4-氯苯基)-6-(3,5-二氯苯基)]氨基甲酸酯,并将其涂敷在氨丙基硅胶表面制备 HPLC 手性固定相.利用<'1>H N...     

Enantiomeric analysis of phenylpropanolamine in plasma via resolution of dinitrophenylurea derivatives on a high performance liquid chromatographic chiral stationary phase.

Racemic phenylpropanolamine was resolved on a high performance liquid chromatographic (HPLC) chiral stationary phase (CSP) as the 3,5-dinitrophenyl ureide derivative. The CSP was prepared by a simple in situ procedure in which (R)-(1-naphthyl)ethyl isocyanate was bound to aminopropyl silanized silica through a urea linkage. The enantiomeric ureides were prepared by a room-temperature, 60-second procedure, accomplishing simultaneous extraction and derivatization and utilizing achiral 3,5-dinitrophenyl isocyanate as reagent. Baseline resolution was readily achieved under normal phase conditions, with a separation factor (alpha) of 1.16 and a resolution factor (RS) of 2.2. Elution was complete within 10 min. A limit of detection, by UV at 235 nm, of 250 pg per isomer was established. Feasibility of the procedure for plasma determinations was demonstrated by assay of samples from a canine subject.     

新型直链淀粉类手性固定相的制备与手性拆分性能

通过对糖单元2-位进行选择性酯化以及6-位保护与去保护,运用区域选择性方法合成了5种新型直链淀粉类衍生物,分别为直链淀粉-2-苯甲酸酯-3-(4-氯苯基氨基甲酸酯)-6-(3,5-二甲基苯基氨基甲酸酯)、直链淀粉-2-苯甲酸酯-3-(4-氯苯基氨基甲酸酯)-6-(3,5-二氯苯基氨基甲酸酯)、直链淀粉-2-苯甲酸酯-3,6-二(4-氯苯基氨基甲酸酯)、直链淀粉-2-(4-氯苯甲酸酯)-3,6-二(3,5-二氯苯基氨基甲酸酯)和直链淀粉-2-(4-氯苯甲酸酯)-3,6-二(环己基氨基甲酸酯),并将其涂覆在氨丙基硅胶表面制备了HPLC手性固定相。利用核磁共振-氢谱(¹H-NMR)和傅里叶变换红外光谱(FT-IR)技术对所合成衍生物的结构进行了表征和分析,并用HPLC法评价所合成衍生物的手性识别能力。与具有单一取代基直链淀粉类手性固定相的对比分析表明,所合成的新型直链淀粉类手性固定相对于某些对映体具有更为优异的拆分结果。进一步分析表明,2-、3-和6-位取代基的性能和引入位置对直链淀粉衍生物的手性识别能力均有较大的影响。     

Novel highly fluorescent dendritic chiral amines: synthesis and optical properties

An efficient approach to dendritic chiral amines through the allylation of optically active imines bearing chiral auxiliaries were developed. The addition of allylic zinc catalyzed by CeC1₃·7H₂O to chiral imines derived from 2-thiophenecarboxaldehyde and α-amino acid esters conveniently and efficiently afforded the corresponding homoallylic amines with excellent diastereoselectivity. Such addition reactions employing diimines or triimines of the polycyclic aromatic derivatives also produced the chrial multiallylic dendritic amines with the similar diastereoselectivity. The investigation of their photophysical properties including UV-vis absorption and fluorescence spectra as well as circular dichroism (CD) indicated that it did not affect the absorption of the precursors to induce the chiral auxiliaries; however, that the whole molecules exhibited the obvious CD behaviors.     

2,4,6-Tri[(S)-1′-methylbenzylamino]-1,3,5-triazine: a new NMR chiral solvating agent for 3,5-dinitrophenyl derivatives; an attempt at a chiral discrimination rationale

The use of 2,4,6-tri[(S)-1′-methylbenzylamino]-1,3,5-triazine as a chiral solvating agent for the NMR evaluation of the enantiomeric excess of 3,5-dinitrophenyl derivatives is reported along with an investigation into the origin of the enantiodiscrimination process.     

纤维素2,3-位和2,3,6-位苯基氨基甲酸酯手性固定相的选择性研究

合成了纤维素-2,3,6-三苯基氨基甲酸酯、纤维素-2,3-二苯基氨基甲酸酯、纤维素-2,3,6-三(3,5-二甲基苯基氨基甲酸酯)和纤维素-2,3-二(3,5-二甲基苯基氨基甲酸酯)4种纤维素衍生物手性固定相,用正己烷-异丙醇（体积比为9∶1）混合液作流动相,对9种手性化合物进行了高效液相色谱拆分。实验结果表明:对所测的9个样品,纤维素-2,3-二苯基氨基甲酸酯的手性选择性大大好于纤维素-2,3,6-三苯基氨基甲酸酯;而纤维素-2,3-二(3,5-二甲基苯基氨基甲酸酯)与纤维素-2,3,6-三(3,5-二甲基苯基氨基甲酸酯)的分离因子针对不同的对映体各有优点,但前者通常具有更小的保留因子,可以缩短一定的分析时间。     

Enantiodiscrimination by inclusion phenomena inside a bis(ethyl lactate) p-tert-butylcalix[4]arene derivative

An ethyl lactate derivative of p-tert-butylcalix[4]arene is able to differentiate the NMR spectra of 3,5-dinitrobenzoyl derivatives of amino acids methyl esters. The origin of enantiodiscrimination in solution was investigated by NMR spectroscopy and comparison with model chiral auxiliaries.     

Temperature dependence of helical structures of poly(phenylacetylene) derivatives bearing an optically active substituent

The temperature dependence of the helical conformations for the homopolymers of phenylacetylene derivatives bearing an optically active substituent, such as the (R)-((1-phenylethyl)carbamoyl)oxy and (R)-((1-(1-naphthyl)ethyl)carbamoyl)oxy groups at the phenyl group, and their copolymers with achiral phenylacetylenes were investigated in solution using circular dichroism (CD) and absorption spectroscopies. The magnitude of the induced CD (ICD) of the optically active homopolymers increased with decreasing temperature and was accompanied by a blueshift in their absorption maxima. On the other hand, the copolymers with achiral phenylacetylenes exhibited interesting ICD changes with temperature, depending on the bulkiness of the achiral comonomers. The copolymers with a less bulky phenylacetylene had a very intense ICD at low temperatures, the ICD pattern was almost opposite to those of the chiral homopolymers, while the copolymers with the most bulky phenylacetylene bearing a tert-butyldiphenylsiloxy group at the para position showed an ICD change similar to that of the optically active homopolymers. However, the copolymers with the phenylacetylene bearing a tert-butyldimethylsiloxy group with intermediate bulkiness at the para position showed no ICD change with temperature. These results indicate that the prevailing helix-sense of the chiral-achiral random copolymers of the phenylacetylenes is determined by a delicate interaction between the chiral and achiral side chains. The thermodynamic stability parameters for the helical conformations of the homopolymers and copolymers of the phenylacetylenes were estimated from the temperature dependence of the ICDs.     

Enhancement of diastereoselectivity in photodimerization of alkyl 2-naphthoates with chiral auxiliaries via inclusion within γ-cyclodextrin cavities

Irradiations of alkyl 2-naphthoates are known to result in four isomeric "cubane-like" photodimers: anti(HH)-2, syn(HH)-2, anti(HT)-2, and syn(HT)-2 where the anti(HH)-2, anti(HT)-2, and syn(HT)-2 consist of pairs of diastereomers. Here, chiral auxiliary and chiral microreactor strategies have been combined to achieve high diastereoselectivity in photodimerizations of an enantiomeric pair of 2-naphthoates with (R)- and (S)-1-methoxycarbonylethyl esters as chiral auxiliaries (1R and 1S). Thus, irradiations of their γ-cyclodextrin (γ-CD) complexes have been conducted. Fluorescence, IR, and NMR spectra of both enantiomers of 1 demonstrate that their γ-CD complexes are mainly 2:2 with the molecules of 1 in head-to-head orientations. Irradiation of the complexes in the solid state mainly resulted in anti(HH)-2. The absolute configuration of each diastereomer of anti(HH)-2 has been established for the first time here. The diastereomeric excesses (de's) of anti(HH)-2 from 1R and 1S were 94% and 86%, respectively. These de's are much higher than those found from irradiations in solution (55% for 1R and 1S), where the opposite diastereomeric form is in excess! Calculations of the energies of various conformations of the head-to-head 2:2 inclusion complexes were performed using the PM3 approach. The predicted major diastereomers based on the calculation are consistent with those found experimentally.     

Circular dichroism of N-2,4-dinitrophenyl derivatives of chiral 1-alkyl-2-propynylamines and 1-alkyl-2-propenylamines

The sign of the Cotton effects near 320 and 400 nm in the CD spectra of the N-2,4-dinitrophenyl derivatives of chiral 1-alkyl-2-propynylamines and 1-alkyl-2-propenylamines correlates with their absolute configurations. The Cotton effects are generated by the coupled oscillator methanism and their sign is the same as the chirality (right-handed screw for positive chirality) of the interaction of the dominant oscillators of the 2,4-dinitrophenylamino chromophore with that of the amine moiety, the chirality of the interaction being deduced by conformational analysis.     

Preparation of two new [2]rotaxanes based on the pillar[5]arene/alkane recognition motif

Based on the pillar[5]arene/alkane recognition motif, two [2]rotaxanes were successfully prepared. Their formation was confirmed by NMR spectroscopy and ESI mass spectrometry. We also demonstrated that 3,5-dinitrophenyl group and 3,5-bis(trifluoromethyl)phenyl group are big enough to work as stoppers for DPPillar[5]arene, which lays a foundation for the preparation of more complex and functional supramolecular structures.     

Conformation‐Specific Circular Dichroism Spectroscopy of Cold,Isolated Chiral Molecules

The CD spectroscopy of a chiral compound in solution yields an average CD value derived from all of the conformations of a chiral molecule. By contrast, CD spectroscopy of cold chiral molecules in the gas phase distinguishes specific conformers of a chiral molecule, but the weak CD effect has limited the practical application of this technique. Reported herein is the first resonant two‐photon ionization CD spectra of ephedrines in a supersonic jet using circularly polarized laser pulses, which were generated by synchronizing the oscillation of the photoelastic modulator with the laser firing. The spectra exhibited well‐resolved CD bands which were specific for the conformations and vibrational modes of each enantiomer. The CD signs and magnitudes of the jet‐cooled chiral molecules were very sensitive to their conformations and thus offered crucial information for determining the three‐dimensional structures of chiral species, as conducted in combination with quantum chemical calculations.     

Conformation‐Specific Circular Dichroism Spectroscopy of Cold,Isolated Chiral Molecules

The CD spectroscopy of a chiral compound in solution yields an average CD value derived from all of the conformations of a chiral molecule. By contrast, CD spectroscopy of cold chiral molecules in the gas phase distinguishes specific conformers of a chiral molecule, but the weak CD effect has limited the practical application of this technique. Reported herein is the first resonant two‐photon ionization CD spectra of ephedrines in a supersonic jet using circularly polarized laser pulses, which were generated by synchronizing the oscillation of the photoelastic modulator with the laser firing. The spectra exhibited well‐resolved CD bands which were specific for the conformations and vibrational modes of each enantiomer. The CD signs and magnitudes of the jet‐cooled chiral molecules were very sensitive to their conformations and thus offered crucial information for determining the three‐dimensional structures of chiral species, as conducted in combination with quantum chemical calculations.     

1H and 13C NMR spectral study of some 3,5-bis[(E)-thienylmethylene]piperidin-4-ones

(1)H and (13)C NMR spectra have been recorded for 3,5-bis[(E)-thienylmethylene]piperidin-4-one (1a), 3',3″-dimethyl-3,5-bis[(E)-thienylmethylene]piperidin-4-one (1b), 5',5″-dibromo-3,5-bis[(E)-thienylmethylene]piperidin-4-one (1c), their 1-methyl derivatives 2a-c and 3,5-bis[(E)-thienylmethylene]-2r,6c-diphenylpiperidin-4-one (3a). For selected compounds 2D spectra have been recorded. The spectral data are used to study the configuration and conformation of these molecules. The chemical shifts are discussed in light of steric, electronic and magnetic anisotropic effects. The magnetic anisotropic effects of thiophene ring and phenyl group are noteworthy. (1)H-(1)H COSY spectrum of 2b suggests that long-range (1)H-(1)H coupling, up to seven bonds, is possible in it. HMBC spectrum of 2b displays the magnetic nonequivalence of C-2 and C-6 and protons at these carbons.     

新型2,6-双(3,5-二取代吡唑基-1-羰基)吡啶的合成

报道了四种吡唑衍生物和它们四种新型的杂环酰胺衍生物的合成 ,它们是 3 ,5 二甲基吡唑 (1) ,5 甲基 3 苯基吡唑(2 ) ,3 ,5 二苯基吡唑 (3 ) ,5 甲基 3 二茂铁基吡唑 (4 ) ,2 ,6 双 (3 ,5 二甲基吡唑基 1 羰基 )吡啶 (5 ) ,2 ,6 双 (5 甲基 3 苯基吡唑基 1 羰基 )吡啶 (6) ,2 ,6 双 (3 ,5 二苯基吡唑基 1 羰基 )吡啶 (7)和 2 ,6 双 (5 甲基 3 二茂铁基吡唑基 1 羰基 )吡啶 (8) .并对它们进行了元素分析 ,FT IR ,1HNMR和13 CNMR等波谱分析 .     

Stereochemistry of phenyl alpha-nitronyl nitroxide radicals

An extensive investigation of the conformations adopted by the family of phenyl alpha-nitronyl nitroxides has been carried out. A database containing 110 crystal structures was used in a statistical study of the solid-state geometries and conformations of these radicals. This study revealed that the favoured conformations involve a twisted distortion in the imidazolyl rings and a twist between the aromatic and heterocyclic rings in the molecules. As a consequence, these radicals show two types of preferred conformations in the solid state: the pseudo-anti enantiomeric pair and the pseudo-eclipsed pair, the latter type being the most statistically probable. A new chiral member of this group of radicals that bears a lactate moiety, (R)-1, and its corresponding racemic compound, (R,S)-1, have been prepared in order to study the influence of chiral induction from the stereogenic centre on the torsion angle between the aromatic and heterocyclic rings of the alpha-nitronyl nitroxides. The X-ray crystal structures of the enantiopure and racemic compounds, which both reveal chains of molecules sustained by strong O-H...O hydrogen bonds between the carboxylic acid group and the ON group of the radical in the solid, as well as their magnetic properties have been determined. Remarkably, the molecules with a given stereogenic centre have a single helical sense between their component rings, even in the racemic crystal. Chiral induction from the stereogenic centre to the radical unit has also been proved by CD spectroscopy in the solid state. The results of these experiments have been rationalised by ab initio calculations of the spectra.