K. Duffy, R. Haltiwanger, A. Freyer, F. Li, J. Luengo, Hung‐Yuan Cheng
A series of novel, fluorescent pyrido[1,2-a]quinoxalines have been synthesized with crystal structures obtained for several analogues. These heterocycles exhibit characteristic pH-dependent UV-visible absorption and fluorescence properties that may be utilized for in-situ pH-sensing in biological experiments. The pKa values for this series of compounds, ranging from 4.5 to 7.5, can be systematically varied by manipulating the substitutions on the quinoxaline ring. These novel fluorescent pH indicators are readily available in one synthetic step from commercially available starting materials therefore being significantly more straightforward and less expensive to synthesize than the current standard fluorescent indicators.
{"title":"Pyrido[1,2-a]quinoxalines: synthesis, crystal structure determination and pH-dependent fluorescence","authors":"K. Duffy, R. Haltiwanger, A. Freyer, F. Li, J. Luengo, Hung‐Yuan Cheng","doi":"10.1039/B102755G","DOIUrl":"https://doi.org/10.1039/B102755G","url":null,"abstract":"A series of novel, fluorescent pyrido[1,2-a]quinoxalines have been synthesized with crystal structures obtained for several analogues. These heterocycles exhibit characteristic pH-dependent UV-visible absorption and fluorescence properties that may be utilized for in-situ pH-sensing in biological experiments. The pKa values for this series of compounds, ranging from 4.5 to 7.5, can be systematically varied by manipulating the substitutions on the quinoxaline ring. These novel fluorescent pH indicators are readily available in one synthetic step from commercially available starting materials therefore being significantly more straightforward and less expensive to synthesize than the current standard fluorescent indicators.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"29 1","pages":"181-185"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81371155","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}
C. Farren, S. FitzGerald, M. Bryce, A. Beeby, A. Batsanov
A range of axially substituted silicon phthalocyanines has been synthesised using various carboxylates as the ligands. 4-tert-Butylbenzoic acid gives rigid, orthogonal axial substituents, whilst a thiophene-containing bis-acetate was conformationally more flexible. Varying the aromatic substituents of phenylacetic acids gave phthalocyanines with altered spectroscopic properties, and changes in the alkyl chain length between the phthalocyanine and the aromatic nucleus of the ligand induced variations in the fluorescence lifetime and quantum yield. Three X-ray crystal structures of axially substituted silicon phthalocyanine bis-esters have been determined.
{"title":"Synthesis, structure and optical characterisation of silicon phthalocyanine bis-esters","authors":"C. Farren, S. FitzGerald, M. Bryce, A. Beeby, A. Batsanov","doi":"10.1039/B108778A","DOIUrl":"https://doi.org/10.1039/B108778A","url":null,"abstract":"A range of axially substituted silicon phthalocyanines has been synthesised using various carboxylates as the ligands. 4-tert-Butylbenzoic acid gives rigid, orthogonal axial substituents, whilst a thiophene-containing bis-acetate was conformationally more flexible. Varying the aromatic substituents of phenylacetic acids gave phthalocyanines with altered spectroscopic properties, and changes in the alkyl chain length between the phthalocyanine and the aromatic nucleus of the ligand induced variations in the fluorescence lifetime and quantum yield. Three X-ray crystal structures of axially substituted silicon phthalocyanine bis-esters have been determined.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"5 1","pages":"59-66"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82265317","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}
Helena McAlonan, James P. Murphy, M. Nieuwenhuyzen, K. Reynolds, P. K. Sarma, P. Stevenson, N. Thompson
Terminally N-substituted dienes derived from 3-methylisoindolin-1-one, 4-isopropyl- and 4-phenyloxazolidin-2-one undergo Diels–Alder reaction with a range of activated dienophiles. The reactions reported are completely regio- and endo-selective, with the diastereoisomeric excess with respect to the auxiliary good to excellent in most of the cases reported. A model has been developed for rationalising the stereochemical outcome of these reactions.
{"title":"4-Phenyloxazolidin-2-ones and isoindolin-1-ones; chiral auxiliaries for Diels-Alder reactions of N-substituted 1,3-dienes.","authors":"Helena McAlonan, James P. Murphy, M. Nieuwenhuyzen, K. Reynolds, P. K. Sarma, P. Stevenson, N. Thompson","doi":"10.1039/B108059H","DOIUrl":"https://doi.org/10.1039/B108059H","url":null,"abstract":"Terminally N-substituted dienes derived from 3-methylisoindolin-1-one, 4-isopropyl- and 4-phenyloxazolidin-2-one undergo Diels–Alder reaction with a range of activated dienophiles. The reactions reported are completely regio- and endo-selective, with the diastereoisomeric excess with respect to the auxiliary good to excellent in most of the cases reported. A model has been developed for rationalising the stereochemical outcome of these reactions.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"38 1","pages":"69-79"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73187863","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}
L. Frish, M. Vysotsky, S. E. Matthews, V. Böhmer, Y. Cohen
The interaction between tropylium salts and tetraurea calix[4]arene derivatives (such as 1 and 2) was studied in solution using 1D, 2D, diffusion, VT NMR and UV–visible spectroscopy. It was found that tropylium salts form charge transfer complexes with both the monomers and dimers of the tetraurea calix[4]arene derivatives depending on the experimental conditions. Compound 1 increases dramatically the solubility of tropylium salts in apolar solvents such as C2D4Cl2, CDCl3 and CD2Cl2 by forming the molecular capsule 1·C7H7+·1. In contrast to the benzene capsule of 1, in 1·C7H7+·1 the hydrogen bonds in the equatorial region that hold together the two parts of the dimer change their directionality faster than the NMR time scale (at 400 MHz) at temperatures higher than 298 K. Interestingly, the free energy barrier for this dynamic process at 298 K (ΔG‡298), depends on the nature of the counter-anion. Free energies of activation of 14.3 ± 0.2 kcal mol−1 and 12.6 ± 0.2 kcal mol−1 were found by total lineshape analysis for the dimeric capsules of C7H7+PF6− and C7H7+BF4−, respectively. The affinity of the tropylium cation toward the dimer's cavity is much higher than that of neutral organic guests. Although exact quantitative values are not available due to the low solubility of tropylium salts in apolar solvents, a rough estimation in CD2Cl2 shows that the tropylium cation affinity is several orders of magnitude higher than that of benzene, which is known to be a good guest. These results show that once the steric requirements are met, electronic effects may serve as an additional driving force for the formation of such molecular capsules demonstrating the importance of cation–π interactions in such systems.
利用一维、二维、扩散、VT NMR和紫外可见光谱等方法研究了tropyum盐与四脲杯[4]芳烃衍生物(如1和2)在溶液中的相互作用。研究发现，根据不同的实验条件，tropylium盐可以与四脲杯[4]芳烃衍生物的单体和二聚体形成电荷转移配合物。化合物1通过形成分子囊1·C7H7+·1，显著提高了tropylium盐在C2D4Cl2、CDCl3和CD2Cl2等极性溶剂中的溶解度。与苯囊体1相比，在1·C7H7+·1中，在温度高于298 K时，赤道区连接二聚体两部分的氢键改变方向的速度比核磁共振时间尺度(400 MHz)快。有趣的是，这个动态过程的自由能势垒在298 K (ΔG‡298)，取决于反阴离子的性质。C7H7+PF6−和C7H7+BF4−二聚体胶囊的激活自由能分别为14.3±0.2 kcal mol−1和12.6±0.2 kcal mol−1。tropylium阳离子对二聚体腔的亲和力远高于中性有机客体。虽然由于tropylium盐在极性溶剂中的溶解度低而无法获得精确的定量值，但在CD2Cl2中的粗略估计表明，tropylium阳离子的亲和力比苯高几个数量级，而苯是已知的好客体。这些结果表明，一旦空间要求得到满足，电子效应可能作为形成这种分子胶囊的额外驱动力，这表明阳离子-π相互作用在这种系统中的重要性。
{"title":"Tropylium cation capsule of hydrogen-bonded tetraurea calix 4 arene dimers","authors":"L. Frish, M. Vysotsky, S. E. Matthews, V. Böhmer, Y. Cohen","doi":"10.1039/B108043A","DOIUrl":"https://doi.org/10.1039/B108043A","url":null,"abstract":"The interaction between tropylium salts and tetraurea calix[4]arene derivatives (such as 1 and 2) was studied in solution using 1D, 2D, diffusion, VT NMR and UV–visible spectroscopy. It was found that tropylium salts form charge transfer complexes with both the monomers and dimers of the tetraurea calix[4]arene derivatives depending on the experimental conditions. Compound 1 increases dramatically the solubility of tropylium salts in apolar solvents such as C2D4Cl2, CDCl3 and CD2Cl2 by forming the molecular capsule 1·C7H7+·1. In contrast to the benzene capsule of 1, in 1·C7H7+·1 the hydrogen bonds in the equatorial region that hold together the two parts of the dimer change their directionality faster than the NMR time scale (at 400 MHz) at temperatures higher than 298 K. Interestingly, the free energy barrier for this dynamic process at 298 K (ΔG‡298), depends on the nature of the counter-anion. Free energies of activation of 14.3 ± 0.2 kcal mol−1 and 12.6 ± 0.2 kcal mol−1 were found by total lineshape analysis for the dimeric capsules of C7H7+PF6− and C7H7+BF4−, respectively. The affinity of the tropylium cation toward the dimer's cavity is much higher than that of neutral organic guests. Although exact quantitative values are not available due to the low solubility of tropylium salts in apolar solvents, \u0000a rough estimation in CD2Cl2 shows that the tropylium cation affinity is several orders of magnitude higher than that of benzene, which is known to be a good guest. These results show that once the steric requirements are met, electronic effects may serve as an additional driving force for the formation of such molecular capsules demonstrating the importance of cation–π interactions in such systems.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"6 1","pages":"88-93"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75408625","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 equilibrium constants for the association of a fluorinated alcohol, 1,1,1,3,3,3-hexafluoropropanol with amino acid and peptide derivatives dissolved in methylene chloride were calculated. The mathematical approach for the determination of the equilibrium constant KOH is based on the decrease of the integral intensity of the OH stretching signal in the infrared spectrum. Alternatively, the decrease of the intensities of the acceptor signals can be used for the calculation of individual equilibrium constants KZ, KPeptide and KEster, for the association of the alcohol on the urethane, peptide and ester function, respectively. The equilibrium constants obtained with both approaches for a number of amino acid, di- and tripeptide derivatives will be discussed. Generally, in no case was the ester function involved in a complex formation with the fluorinated alcohol. For most examples the association constant for the peptide function was larger than for the urethane group. The investigation of the effect of the variation of the concentration on the equilibrium constant shows that up to a ratio cA0/cB0 of the initial concentrations of the alcohol, cA0, and the acceptor compound, cB0, equal to 10, no formation of 1 ∶ 2 or 1 ∶ 3 associates need to be considered.
{"title":"Quantitative characterisation of the hydrogen bonding behaviour on the acceptor functions in oligopeptide derivatives with a fluorinated alcohol","authors":"M. Plass, I. Schaller","doi":"10.1039/B008747P","DOIUrl":"https://doi.org/10.1039/B008747P","url":null,"abstract":"The equilibrium constants for the association of a fluorinated alcohol, 1,1,1,3,3,3-hexafluoropropanol with amino acid and peptide derivatives dissolved in methylene chloride were calculated. The mathematical approach for the determination of the equilibrium constant KOH is based on the decrease of the integral intensity of the OH stretching signal in the infrared spectrum. Alternatively, the decrease of the intensities of the acceptor signals can be used for the calculation of individual equilibrium constants KZ, KPeptide and KEster, for the association of the alcohol on the urethane, peptide and ester function, respectively. The equilibrium constants obtained with both approaches for a number of amino acid, di- and tripeptide derivatives will be discussed. Generally, in no case was the ester function involved in a complex formation with the fluorinated alcohol. For most examples the association \u0000constant for the peptide function was larger than for the urethane group. The investigation of the effect of the variation of the concentration on the equilibrium constant shows that up to a ratio cA0/cB0 of the initial concentrations of the alcohol, cA0, and the acceptor compound, cB0, equal to 10, no formation of 1 ∶ 2 or 1 ∶ 3 associates need to be considered.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"102 1","pages":"186-191"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75436204","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}
T. Gunnlaugsson, M. Nieuwenhuyzen, L. Richard, V. Thoss
The anthracene based fluorescent PET chemosensor 1 and the azo-dye based chemosensor 2 show high selectivity for Na+ over other alkali and alkaline-earth metal cations in the 12–300 mM concentration range in 50 ∶ 50 MeOH–H2O at pH 7.4. Chemosensor 1 shows fluorescence ‘off-on’ switching upon Na+ complexation with λFmax of 440 nm and a log βNa of 2.5 (±0.05) and a pKa of 5.3 with no concomitant changes in the absorption spectra. Conversely, 2 displays only a weak fluorescent emission at around 520–640 nm, and large changes in its absorption spectra upon addition of Na+, with a log βNa of 1.25 (±0.05) and a pKa of 3.9. In 100% water the sensitivity of 2 for Na+ was somewhat lower with a log βNa of 0.8 (±0.05). The crystal structure of 2, and its corresponding protonated form (2·H+) were obtained, showing 2 in its trans conformation with the crown ether moiety at a 75° angle to the plane of the chromophore. These results, in conjunction with 1H NMR measurements of 2, and UV–VIS measurements of the ion receptor 3, suggest that upon complexation of Na+, the 2′-methoxy group of the crown receptor participates in the Na+ complexation through chelation to the Na+ ion. We propose that this interaction forces the amine moiety of the crown ether to twist out of the plane of the chromophore, inducing loss of conjugation which gives rise to large Na+-induced spectral changes in the absorption spectra, which are most noticeable for 2.
{"title":"Novel sodium-selective fluorescent PET and optically based chemosensors: towards Na+ determination in serum","authors":"T. Gunnlaugsson, M. Nieuwenhuyzen, L. Richard, V. Thoss","doi":"10.1039/B106474F","DOIUrl":"https://doi.org/10.1039/B106474F","url":null,"abstract":"The anthracene based fluorescent PET chemosensor 1 and the azo-dye based chemosensor 2 show high selectivity for Na+ over other alkali and alkaline-earth metal cations in the 12–300 mM concentration range in 50 ∶ 50 MeOH–H2O at pH 7.4. Chemosensor 1 shows fluorescence ‘off-on’ switching upon Na+ complexation with λFmax of 440 nm and a log βNa of 2.5 (±0.05) and a pKa of 5.3 with no concomitant changes in the absorption spectra. Conversely, 2 displays only a weak fluorescent emission at around 520–640 nm, and large changes in its absorption spectra upon addition of Na+, with a log βNa of 1.25 (±0.05) and a pKa \u0000of 3.9. In 100% water the sensitivity of 2 for Na+ was somewhat lower with a log βNa of 0.8 (±0.05). The crystal structure of 2, and its corresponding protonated form (2·H+) were obtained, showing 2 in its trans conformation with the crown ether moiety at a 75° angle to the plane of the chromophore. These results, in conjunction with 1H NMR measurements of 2, and UV–VIS measurements of the ion receptor 3, suggest that upon complexation of Na+, the 2′-methoxy group of the crown receptor participates in the Na+ complexation through chelation to the Na+ ion. We propose that this interaction \u0000forces the amine moiety of the crown ether to twist out of the plane of the chromophore, inducing loss of conjugation which gives rise to large Na+-induced spectral changes in the absorption spectra, which are most noticeable for 2.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"275 1","pages":"141-150"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76394061","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}
Julian S. Northen, F. Boyle, W. Clegg, N. Curtin, Andrew J. Edwards, R. Griffin, B. Golding
For the rational synthesis of 2,4,6,8-tetrasubstituted pyrimido[5,4-d]pyrimidines, required as purine mimetics, sequential nucleophilic substitutions of 2,4,6,8-tetrachloropyrimido[5,4-d]pyrimidine have been investigated. Reaction conditions have been devised leading to 2,4,6,8-tetrasubstituted pyrimido[5,4-d]pyrimidines with patterns of substitution denoted as abab (reaction with nucleophile 1 at C-4 and C-8, followed by nucleophile 2 at C-2 and C-6) or abac (reaction with nucleophile 1 at C-4 and C-8, nucleophile 2 at C-2 and nucleophile 3 at C-6) or abcd (reaction with nucleophile 1 at C-4, nucleophile 2 at C-8, nucleophile 3 at C-2 and nucleophile 4 at C-6). The use of low temperature, relatively dilute solution and careful addition of the amine nucleophile can control the critical first step. The third step in the production of the abcd pattern leads to two regioisomers, which have been structurally characterised by 1H NMR and a crystal structure analysis. Selected 2,4,6,8-tetrasubstituted pyrimido[5,4-d]pyrimidines were tested as inhibitors of the cyclin-dependent kinase 1 complex (cyclin B/CDK1), but none of the compounds showed significant activity.
{"title":"Controlled stepwise conversion of 2,4,6,8-tetrachloropyrimido[5,4-d]pyrimidine into 2,4,6,8-tetrasubstituted pyrimido[5,4-d]pyrimidines","authors":"Julian S. Northen, F. Boyle, W. Clegg, N. Curtin, Andrew J. Edwards, R. Griffin, B. Golding","doi":"10.1039/B102224P","DOIUrl":"https://doi.org/10.1039/B102224P","url":null,"abstract":"For the rational synthesis of 2,4,6,8-tetrasubstituted pyrimido[5,4-d]pyrimidines, required as purine mimetics, sequential nucleophilic substitutions of 2,4,6,8-tetrachloropyrimido[5,4-d]pyrimidine have been investigated. Reaction conditions have been devised leading to 2,4,6,8-tetrasubstituted pyrimido[5,4-d]pyrimidines with patterns of substitution denoted as abab (reaction with nucleophile 1 at C-4 and C-8, followed by nucleophile 2 at C-2 and C-6) or abac (reaction with nucleophile 1 at C-4 and C-8, nucleophile 2 at C-2 and nucleophile 3 at C-6) or abcd (reaction with nucleophile 1 at C-4, nucleophile 2 at C-8, nucleophile 3 at C-2 and nucleophile 4 at C-6). The use of low temperature, relatively dilute solution and careful addition of the amine nucleophile can control the critical first step. The third step in the production of the abcd pattern leads to two regioisomers, which have been structurally characterised \u0000by 1H NMR and a crystal structure analysis. Selected 2,4,6,8-tetrasubstituted pyrimido[5,4-d]pyrimidines were tested as inhibitors of the cyclin-dependent kinase 1 complex (cyclin B/CDK1), but none of the compounds showed significant activity.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"1 1","pages":"108-115"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77797168","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}
1H NMR measurements of a series of ortho-phenyl substituted 3-aryl-2-cyano-5,5-bis(alkylthio)- (3h), 3-aryl-2-cyano-5-alkylthio-5-dialkylamino- (4h, 5) and 3-aryl-2-cyano-5,5-bis(dialkylamino)penta-2,4-dienenitriles (6) with prochiral groups showed the rotation about the C-3–C-aryl bond to be hindered within the NMR timescale. The activation parameters of this atropisomerization process are discussed with respect to steric effects of substituents. The rotation barriers correlate with bond lengths and angles as determined by X-ray structure analyses.
{"title":"NMR studies on the axial chirality of ortho-substituted push–pull phenyl butadienes","authors":"M. Michalik, T. Freier, H. Reinke, K. Peseke","doi":"10.1039/B107402B","DOIUrl":"https://doi.org/10.1039/B107402B","url":null,"abstract":"1H NMR measurements of a series of ortho-phenyl substituted 3-aryl-2-cyano-5,5-bis(alkylthio)- (3h), 3-aryl-2-cyano-5-alkylthio-5-dialkylamino- (4h, 5) and 3-aryl-2-cyano-5,5-bis(dialkylamino)penta-2,4-dienenitriles (6) with prochiral groups showed the rotation about the C-3–C-aryl bond to be hindered within the NMR timescale. The activation parameters of this atropisomerization process are discussed with respect to steric effects of substituents. The rotation barriers correlate with bond lengths and angles as determined by X-ray structure analyses.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"46 1","pages":"114-119"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84803370","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}
Bernhard J. Rausch, D. Werz, S. Rittinger, R. Gleiter, T. Oeser, F. Rominger
The syntheses of three cyclic dithiatetraynes 4–6 with the sulfur atoms in propargylic positions are reported. Their structural features have been studied by means of X-ray analysis on single crystals. Additionally, six cyclic octathiatetraynes 15–20 with sulfur atoms in α,α′-positions to the triple bond have been prepared. The structures of 15 and 17 have been elucidated by means of X-ray analysis. These macrocycles exhibit an ellipsoidal geometry dominated by the stiff triple bond moieties. In the case of 4 a three-dimensional columnar structure is found, demonstrating the unique features of the potential cavities.
{"title":"Cyclic thiatetraynes: syntheses and structural properties","authors":"Bernhard J. Rausch, D. Werz, S. Rittinger, R. Gleiter, T. Oeser, F. Rominger","doi":"10.1039/B108403H","DOIUrl":"https://doi.org/10.1039/B108403H","url":null,"abstract":"The syntheses of three cyclic dithiatetraynes 4–6 with the sulfur atoms in propargylic positions are reported. Their structural features have been studied by means of X-ray analysis on single crystals. Additionally, six cyclic octathiatetraynes 15–20 with sulfur atoms in α,α′-positions to the triple bond have been prepared. The structures of 15 and 17 have been elucidated by means of X-ray analysis. These macrocycles exhibit an ellipsoidal geometry dominated by the stiff triple bond moieties. In the case of 4 a three-dimensional columnar structure is found, demonstrating the unique features of the potential cavities.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"1 1","pages":"72-76"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88202943","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 formation of inclusion complexes of di[(R)-3-hydroxybutanoate] (Dimer 1) and the methyl ester of di[(R)-3-hydroxybutanoate] (Dimer 2) with β-cyclodextrin (β-CD) was studied by NMR spectroscopy. The stoichiometry of the complexation was 1 ∶ 1 (host ∶ guest). Thermodynamic analysis revealed that the complex formation is enthalpically favorable, but entropically unfavorable. Dimer 1 forms hydrogen bonds with β-CD more frequently than Dimer 2 because 1 has two hydroxy groups. Conformational analysis of the 3HB (3-hydroxybutanoate) dimers in the complexes indicates that they have extended (trans) forms. In contrast, in solution without β-CD, the end of both Dimers 1 and 2 takes a sickle (gauche) shape due to formation of intermolecular hydrogen bonds.
{"title":"Formation of inclusion complexes between dimers of (R)-3-hydroxybutanoic acid and β-cyclodextrin: thermodynamic study of the complexation and conformational analysis of the complexed dimers","authors":"Jun Li, K. Toh","doi":"10.1039/B104984B","DOIUrl":"https://doi.org/10.1039/B104984B","url":null,"abstract":"The formation of inclusion complexes of di[(R)-3-hydroxybutanoate] (Dimer 1) and the methyl ester of di[(R)-3-hydroxybutanoate] (Dimer 2) with β-cyclodextrin (β-CD) was studied by NMR spectroscopy. The stoichiometry of the complexation was 1 ∶ 1 (host ∶ guest). Thermodynamic analysis revealed that the complex formation is enthalpically favorable, but entropically unfavorable. Dimer 1 forms hydrogen bonds with β-CD more frequently than Dimer 2 because 1 has two hydroxy groups. Conformational analysis of the 3HB (3-hydroxybutanoate) dimers in the complexes indicates that they have extended (trans) forms. In contrast, in solution without β-CD, the end of both Dimers 1 and 2 takes a sickle (gauche) shape due to formation of intermolecular hydrogen bonds.","PeriodicalId":17267,"journal":{"name":"Journal of The Chemical Society-perkin Transactions 1","volume":"20 1","pages":"35-40"},"PeriodicalIF":0.0,"publicationDate":"2002-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79895956","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：