A. Yamamoto, S. Kodama, A. Matsunaga, H. Nakazawa, K. Hayakawa
A novel device is described that permits fluorescence-detected circular dichroism (FDCD) detection in a conventional fluorescence spectrophotometer. FDCD is a phenomenon in which the emission intensity of a chiral analyte depends on the polarization state of the excitations. Although FDCD is a sensitive chiral detection technique, measurement of FDCD by using a special CD spectrometer has involved many difficulties. The proposed device consists of a polarizing prism and a retardation plate that fit on the excitation light side in the sample compartment of the fluorescence spectrophotometer. In this method, a FDCD wave superimposed on the fluorescence excitation spectrum of a chiral analyte was detected. We have also demonstrated the possibility of the enantiomeric purity determination of chiral analytes in real samples.
{"title":"Fluorescence-detected circular dichroism by modulated beam in the wavelength axial direction.","authors":"A. Yamamoto, S. Kodama, A. Matsunaga, H. Nakazawa, K. Hayakawa","doi":"10.1080/10242430212875","DOIUrl":"https://doi.org/10.1080/10242430212875","url":null,"abstract":"A novel device is described that permits fluorescence-detected circular dichroism (FDCD) detection in a conventional fluorescence spectrophotometer. FDCD is a phenomenon in which the emission intensity of a chiral analyte depends on the polarization state of the excitations. Although FDCD is a sensitive chiral detection technique, measurement of FDCD by using a special CD spectrometer has involved many difficulties. The proposed device consists of a polarizing prism and a retardation plate that fit on the excitation light side in the sample compartment of the fluorescence spectrophotometer. In this method, a FDCD wave superimposed on the fluorescence excitation spectrum of a chiral analyte was detected. We have also demonstrated the possibility of the enantiomeric purity determination of chiral analytes in real samples.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"25 1","pages":"225-9"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85316788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Circular dichroism (CD) spectra of sublimated films of alanine and alanine dipeptide were measured in UV-VUV region. When a film has some linear anisotropy, the apparent CD signal is known to be strongly distributed by linear anisotropy. In order to obtain the true CD spectra, we examined this disturbance for L-alanine films. We measured linear dichroism spectra and CD spectra as a function of the sample rotation angle, turning the sample over. On the basis of these measurements, we concluded that the linear anisotropy contribution to CD was sufficiently small for carefully prepared films. In addition, we revealed that it is essential for accurate measurement to prepare thin film of which thickness is smaller than 100 nm for the case of alanine films. CD of amino acid films was compared with that of aqueous solution. Sign of CD signal of solid films was observed to be the same for aspartic acid, but it was reversed from that of aqueous solution for alanine and alanine dipeptide.
{"title":"Circular dichroism of amino acid films in UV-VUV region.","authors":"Masahito Tanaka, Y. Kodama, K. Nakagawa","doi":"10.1080/10242430212884","DOIUrl":"https://doi.org/10.1080/10242430212884","url":null,"abstract":"Circular dichroism (CD) spectra of sublimated films of alanine and alanine dipeptide were measured in UV-VUV region. When a film has some linear anisotropy, the apparent CD signal is known to be strongly distributed by linear anisotropy. In order to obtain the true CD spectra, we examined this disturbance for L-alanine films. We measured linear dichroism spectra and CD spectra as a function of the sample rotation angle, turning the sample over. On the basis of these measurements, we concluded that the linear anisotropy contribution to CD was sufficiently small for carefully prepared films. In addition, we revealed that it is essential for accurate measurement to prepare thin film of which thickness is smaller than 100 nm for the case of alanine films. CD of amino acid films was compared with that of aqueous solution. Sign of CD signal of solid films was observed to be the same for aspartic acid, but it was reversed from that of aqueous solution for alanine and alanine dipeptide.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"14 1","pages":"185-90"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84328231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Kosaka, S. Kuwahara, Masataka Watanabe, N. Harada, Gabriel E. Job, W. H. Pirkle
Enantiopure (2,6-dimethylphenyl)phenylmethanol (+)-(3) and analog (+)-(4) were prepared and their CD spectra were found opposite to that of (2-methylphenyl)phenylmethanol (R)-(-)-(2), the absolute configuration of which was previously established by X-ray crystallography. Therefore the S absolute configuration was once assigned to (+)-3 and (+)-4. After that we have succeeded in the X-ray analyses of chiral dichlorophthalate esters of (+)-3 and (+)4, which clearly indicated R absolute configuration. It is thus evident that comparison of the CD spectra of alcohols 2, 3, and 4 leads to erroneous absolute configurations.
{"title":"Comparison of CD spectra of (2-methylphenyl)- and (2,6-dimethylphenyl)-phenylmethanols leads to erroneous absolute configurations.","authors":"M. Kosaka, S. Kuwahara, Masataka Watanabe, N. Harada, Gabriel E. Job, W. H. Pirkle","doi":"10.1080/10242430212878","DOIUrl":"https://doi.org/10.1080/10242430212878","url":null,"abstract":"Enantiopure (2,6-dimethylphenyl)phenylmethanol (+)-(3) and analog (+)-(4) were prepared and their CD spectra were found opposite to that of (2-methylphenyl)phenylmethanol (R)-(-)-(2), the absolute configuration of which was previously established by X-ray crystallography. Therefore the S absolute configuration was once assigned to (+)-3 and (+)-4. After that we have succeeded in the X-ray analyses of chiral dichlorophthalate esters of (+)-3 and (+)4, which clearly indicated R absolute configuration. It is thus evident that comparison of the CD spectra of alcohols 2, 3, and 4 leads to erroneous absolute configurations.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"39 1","pages":"213-7"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81545904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Racemic g - and n -hydroxy sulfides were resolved by Humicola lanuginosa lipase catalyzed transesterification using vinyl acetate both as acyl donor and solvent. The effect of substituents and spacer length on rate of reaction and enantioselectivity is observed.
{"title":"Kinetic Resolution of β- and γ-Hydroxy Sulfides by Fungal Lipase from Humicola lanuginosa","authors":"Satwinder Singh, Subodh Kumar, S. Chimni","doi":"10.1080/10242430212883","DOIUrl":"https://doi.org/10.1080/10242430212883","url":null,"abstract":"Racemic g - and n -hydroxy sulfides were resolved by Humicola lanuginosa lipase catalyzed transesterification using vinyl acetate both as acyl donor and solvent. The effect of substituents and spacer length on rate of reaction and enantioselectivity is observed.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"9 1","pages":"231-240"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81684262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A high-performance photoelastic modulator (PEM) has been built. It consists of a home-made PEM head and a home-built PEM driver that is based on the principle of the phase-locked loop (PLL) (PLL PEM driver). It was installed in our new type circular dichroism (CD) spectrometer for visible light region and its performance was evaluated. With the phase angle being set exactly to zero, the PEM is found to be about eight times more efficient than commercially available one. The efficiency of PEM depends not only on the efficiency of PEM driver but also on the quality of PEM head. The latter can be estimated from admittance-parameter measurements without installing it into a spectrometer. With substituting the PLL PEM driver for a conventional one, the PEM drive voltage can be reduced from one-half to one-third and the baseline shift for air blank that is a measure of the total performance of polarization modulation spectrometers becomes quite small.
{"title":"High-performance photoelastic modulator for polarization modulation spectrometer.","authors":"S. Maeda, K. Nakae, Y. Shindo","doi":"10.1080/10242430212885","DOIUrl":"https://doi.org/10.1080/10242430212885","url":null,"abstract":"A high-performance photoelastic modulator (PEM) has been built. It consists of a home-made PEM head and a home-built PEM driver that is based on the principle of the phase-locked loop (PLL) (PLL PEM driver). It was installed in our new type circular dichroism (CD) spectrometer for visible light region and its performance was evaluated. With the phase angle being set exactly to zero, the PEM is found to be about eight times more efficient than commercially available one. The efficiency of PEM depends not only on the efficiency of PEM driver but also on the quality of PEM head. The latter can be estimated from admittance-parameter measurements without installing it into a spectrometer. With substituting the PLL PEM driver for a conventional one, the PEM drive voltage can be reduced from one-half to one-third and the baseline shift for air blank that is a measure of the total performance of polarization modulation spectrometers becomes quite small.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"82 1","pages":"175-83"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75632749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Near infrared vibrational circular dichroism spectra in the region of 1300 to 800 nm were recorded for 12 enantiomeric pairs of molecules with a home-made dispersive apparatus. With respect to earlier measurements, a better signal-to-noise ratio was obtained, thus allowing a more precise determination of molecular parameters. A detailed examination of the spectra between 1300 and 1100 nm allowed us to correlate the data of the different molecules, based on local properties of given molecular moieties. The relevance of this correlation in configurational and/or conformational studies is discussed.
{"title":"Vibrational circular dichroism in the near infrared: instrumental developments and applications.","authors":"E. Castiglioni, F. Lebon, G. Longhi, S. Abbate","doi":"10.1080/10242430212877","DOIUrl":"https://doi.org/10.1080/10242430212877","url":null,"abstract":"Near infrared vibrational circular dichroism spectra in the region of 1300 to 800 nm were recorded for 12 enantiomeric pairs of molecules with a home-made dispersive apparatus. With respect to earlier measurements, a better signal-to-noise ratio was obtained, thus allowing a more precise determination of molecular parameters. A detailed examination of the spectra between 1300 and 1100 nm allowed us to correlate the data of the different molecules, based on local properties of given molecular moieties. The relevance of this correlation in configurational and/or conformational studies is discussed.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"48 1","pages":"161-73"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86749534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Achiral molecules of tetrakis(p-bromophenyl)ethylene and 2,3,6,7,10,11-hexahydroxy triphenylene were found to arrange in a chiral form in their inclusion crystal with an achiral guest molecule. The chiral arrangement of these achiral molecules was studied by X-ray analysis and CD spectral measurement in the solid state.
{"title":"Chiral inclusion crystals constructed with achiral host and achiral guest molecules.","authors":"F. Toda","doi":"10.1080/10242430212198","DOIUrl":"https://doi.org/10.1080/10242430212198","url":null,"abstract":"Achiral molecules of tetrakis(p-bromophenyl)ethylene and 2,3,6,7,10,11-hexahydroxy triphenylene were found to arrange in a chiral form in their inclusion crystal with an achiral guest molecule. The chiral arrangement of these achiral molecules was studied by X-ray analysis and CD spectral measurement in the solid state.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"7 1","pages":"59-65"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80963217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The benzamide chromophore is widely used as a Cottonogenic derivative of primary amines for stereochemical studies by circular dichroism. The assignments based on the exciton chirality method are reliable since the benzamide group has well-defined geometry and conformation. A recent report (J.D. Chisholm, J. Golik, B. Krishnan, J.A. Matson, D.L. Van Vranken, J. Am. Chem. Soc. 1999, 121: 3801-3802) claimed a caveat in the application of the exciton chirality method to benzamides derived from secondary amines. By the use of benzoyl derivatives of amino alcohols (1-4) and diamines (5, 6) of known absolute configuration we demonstrate that the 250-210 nm range exciton Cotton effects due to secondary and tertiary benzamides are generally of opposite sign. The origin of such disparity is traced to different conformational equilibria of the amide C-N bond in secondary and tertiary benzamides, as shown by semiempirical molecular modelling and NMR data. This feature can be useful in the determination of absolute configuration by analysis of the CD spectra due to exciton coupling of tertiary benzamides.
苯酰胺发色团作为伯胺的致棉衍生物被广泛应用于圆二色性立体化学研究。基于激子手性方法的指派是可靠的，因为苯甲酰胺基团具有明确的几何和构象。最近的一份报告(J.D. Chisholm, J. Golik, B. Krishnan, J.A. Matson, D.L. Van Vranken, J. Am。化学。应用激子手性方法研究仲胺类苯酰胺的研究进展。化学学报，1999,21:381 - 382。通过使用已知绝对构型的氨基醇(1-4)和二胺(5,6)的苯甲酰衍生物，我们证明了由仲苯酰胺和叔苯酰胺引起的250-210 nm范围内激子棉效应通常是相反的符号。半经验分子模型和核磁共振数据表明，这种差异的来源可以追溯到仲、叔苯酰胺中酰胺C-N键的不同构象平衡。这一特征可用于通过分析叔苯酰胺激子耦合引起的CD光谱来确定绝对构型。
{"title":"The use of benzamide derivatives of secondary amines for stereochemical studies by circular dichroism.","authors":"J. Gawroński, Halina Kołbon, M. Kwit","doi":"10.1080/10242430212196","DOIUrl":"https://doi.org/10.1080/10242430212196","url":null,"abstract":"The benzamide chromophore is widely used as a Cottonogenic derivative of primary amines for stereochemical studies by circular dichroism. The assignments based on the exciton chirality method are reliable since the benzamide group has well-defined geometry and conformation. A recent report (J.D. Chisholm, J. Golik, B. Krishnan, J.A. Matson, D.L. Van Vranken, J. Am. Chem. Soc. 1999, 121: 3801-3802) claimed a caveat in the application of the exciton chirality method to benzamides derived from secondary amines. By the use of benzoyl derivatives of amino alcohols (1-4) and diamines (5, 6) of known absolute configuration we demonstrate that the 250-210 nm range exciton Cotton effects due to secondary and tertiary benzamides are generally of opposite sign. The origin of such disparity is traced to different conformational equilibria of the amide C-N bond in secondary and tertiary benzamides, as shown by semiempirical molecular modelling and NMR data. This feature can be useful in the determination of absolute configuration by analysis of the CD spectra due to exciton coupling of tertiary benzamides.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"25 1","pages":"85-92"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82913792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Šinko, P. Novak, Dinko Žiher, V. Vinković, V. Sunjic, V. Simeon-Rudolf
Enantiomers of ethopropazine x HCl (10-(2-diethylaminopropyl)phenothiazine hydrochloride) were prepared by fractional crystallization of diastereomeric dibenzoyltartaric acid salts, and their optical purity (enantiomeric excess, ee) determined by HPLC on Chiralcel OJ column. With a solvent mixture n-hexane/t-butanol/triethylamine (100:3:0.5) as eluent a very good enantioseparation (alpha = 1.68) for racemic ethopropazine was obtained. Enantiomeric purity for (-)-enantiomer was 99.1% and for (+)-enantiomer 97.9%. Combined data from NMR and CD spectra of both enantiomers, along with previously reported X-ray structure analyses of racemic ethopropazine, revealed skewed conformation of tricyclic system in solution, and (S)-configuration on the stereogenic center for (-)-enantiomer, and (R)-configuration for (+)-enantiomer.
{"title":"Separation, conformation in solution and absolute configuration of ethopropazine enantiomers.","authors":"G. Šinko, P. Novak, Dinko Žiher, V. Vinković, V. Sunjic, V. Simeon-Rudolf","doi":"10.1080/10242430212188","DOIUrl":"https://doi.org/10.1080/10242430212188","url":null,"abstract":"Enantiomers of ethopropazine x HCl (10-(2-diethylaminopropyl)phenothiazine hydrochloride) were prepared by fractional crystallization of diastereomeric dibenzoyltartaric acid salts, and their optical purity (enantiomeric excess, ee) determined by HPLC on Chiralcel OJ column. With a solvent mixture n-hexane/t-butanol/triethylamine (100:3:0.5) as eluent a very good enantioseparation (alpha = 1.68) for racemic ethopropazine was obtained. Enantiomeric purity for (-)-enantiomer was 99.1% and for (+)-enantiomer 97.9%. Combined data from NMR and CD spectra of both enantiomers, along with previously reported X-ray structure analyses of racemic ethopropazine, revealed skewed conformation of tricyclic system in solution, and (S)-configuration on the stereogenic center for (-)-enantiomer, and (R)-configuration for (+)-enantiomer.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"14 1","pages":"149-56"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89799067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tadashi Mori, Junya Shinkuma, Masafumi Sato, H. Saito, T. Wada, Y. Inoue
The first unequivocal circular dichroism spectra were obtained for organic radical cations, which were prepared from p-(1S,2S,5R)-neomenthyloxyanisole (1) and p-(1S,2S,4S)-isobornyloxyanisole (2) by single electron oxidation with triethyloxonium hexachloroantimonate in dichloromethane. The chiroptical properties of the radical cations 1*+ and 2*+ were discussed in comparison with those of neutral species 1 and 2.
{"title":"The first circular dichroism observation for organic radical cations: chiroptical properties of neomenthyloxy- and isobornyloxyanisole radical cations.","authors":"Tadashi Mori, Junya Shinkuma, Masafumi Sato, H. Saito, T. Wada, Y. Inoue","doi":"10.1080/10242430212199","DOIUrl":"https://doi.org/10.1080/10242430212199","url":null,"abstract":"The first unequivocal circular dichroism spectra were obtained for organic radical cations, which were prepared from p-(1S,2S,5R)-neomenthyloxyanisole (1) and p-(1S,2S,4S)-isobornyloxyanisole (2) by single electron oxidation with triethyloxonium hexachloroantimonate in dichloromethane. The chiroptical properties of the radical cations 1*+ and 2*+ were discussed in comparison with those of neutral species 1 and 2.","PeriodicalId":11752,"journal":{"name":"Enantiomer","volume":"54 1","pages":"115-8"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75053931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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