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1.
Yılmaz Turgut Nadir Demirel Halil Hoşgören 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(1-2):29-33
New chiral diaza-18-crown-6 ether derivatives, 5 and 6 were synthesized from (R)-(-)-2-amino-1-bütanol. These chiral artificial receptors exhibit pronounced chiral recognition toward the enantiomers of
l- and d- amino acid derivatives. The highest enantioselectivity was observed in the case of Trp-OMe·HCl (KD/KL=12.5). 相似文献
2.
The syntheses of four aza-15-crown-5 ethers bearing phenyl and phenoxymethyl moieties attached to a stereogenic centre on the crown ring were achieved. Macrocycles have exhibited strong binding ability (Ka = 5364–12,969 M? 1) and modest enantiomeric discrimination towards the enantiomers of amino acid methyl ester salts by UV titration method in CHCl3 at 25°C. Computer modelling results supported experimental data providing a detailed understanding of the molecular recognition mode between hosts and guests and the likely binding sites involved. Macrocycles were used for chiral discrimination of amino acids in their zwitterionic forms or as potassium and sodium salts in transport experiments across a bulk chloroform membrane with satisfactory selectivity. 相似文献
3.
The stoichiometric protonation constants of some α-amino acid esters (glycine methyl ester, glycine t-butyl ester, l-valine methyl ester, l-valine ethyl ester, l-valine t-butyl ester, l-serine methyl ester, l-serine ethyl ester, l-leucine methyl ester, l-leucine ethyl ester, l-leucine t-butyl ester, l-alanine methyl ester, l-alanine benzyl ester, l-phenylalanine methyl ester, l-phenylalanine ethyl ester, and l-phenylalanine t-butyl ester) in water and 20%, 40%, and 60% (v/v) 1,4-dioxane–water mixtures have been determined at an ionic strength of
0.10 mol⋅L−1 NaCl and at 25.0±0.1 °C under a nitrogen atmosphere. A potentiometric method was used and the calculation of the protonation
constants has been carried out using the BEST computer program. The results were discussed in terms of macroscopic properties
of the mixed solvent. The stoichiometric protonation constants were influenced by changes in solvent composition and their
variations were discussed in terms of preferential solvation. Also, knowledge the protonation constant of α-amino acid esters will be helpful when determining the microscopic equilibrium constants of their corresponding amino acids. 相似文献
4.
Four novel C2-symmetric enantiomerically pure, chiral pyridine-18-crown-6 type macrocycles containing lipophilic chains at the stereogenic centers were prepared. The enantioselectivity of the new ligands toward the enantiomers of d-,l-amino acid methyl ester derivatives were also determined by 1H NMR titration method. These novel macrocycles have been showed to be strong complexing agents for d- and l-amino acid methyl ester hydrochloride salts (with Kass up to 13590 M−1 and ?G0 up to 23.3 kJ mol−1 and selectivity ratio: 80:20) by 1H NMR titration methods. These macrocyclic hosts exhibited enantioselective binding towards the d-enantiomer of valine methyl ester hydrochloride with Kd/Kl up to 5.08 in CDCl3 with 0.25% CD3OD. 相似文献
5.
Purvi B. Desai Rahul M. Kotkar Ashwini K. Srivastava 《Journal of Solid State Electrochemistry》2008,12(9):1067-1075
The electrochemical behaviour of pyridoxine hydrochloride (pyridoxine HCl) at the plain carbon paste electrode and the electrode
modified with oxa crown ether has been studied using voltammetric and impedance measurements. The macrocycles used as modifiers
were 18-crown-6, dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 and dibenzo-24-crown-8, out of which DB18C6 gave better
response for pyridoxine HCl. Tris buffer (pH 10.3) was chosen as an appropriate medium among the several supporting electrolytes
of varying pH studied. The characterization of the DB18C6-modified electrode (CME-DB18C6) using kinetic parameters such as
number of electrons (n) and electron transfer coefficient (α) is studied by cyclic voltammetry. Electrochemical impedance spectroscopic measurements obtained confirm the current enhancement
over the modified electrode. Analytical applications of this electrode have been studied for the determination of pyridoxine
HCl. A sensitive linear working range of 0.6 to 100 μg cm−3 with a detection limit of 0.4 μg cm−3 by differential pulse voltammetry was observed for pyridoxine HCl on CME-DB18C6. However, on decreasing the scan rate to
5 mV s−1, the detection limit lowered to 0.2 μg cm−3. Interference from some vitamins like thiamine hydrochloride, riboflavin, nicotinamide, para-aminobenzoic acid, cyanocobalamin, folic acid and d-biotin and amino acid l-tryptophan was studied, and simultaneously, riboflavin, thiamine hydrochloride and pyridoxine HCl were determined over the
modified electrode, CME-DB18C6. The modified electrode is successfully used for the determination of pyridoxine HCl in multivitamin
pharmaceutical preparations. 相似文献
6.
Four chiral derivatizing reagents (CDR 1–4), namely, FDNP-l-Ala, FDNP-l-Val, FDNP-l-Phe, and FDNP-l-Leu, were synthesized using microwave (MW) irradiation by substituting one of the fluorine atoms in difluoro dinitro benzene
(DFDNB) with l-Ala, l-Val, l-Phe, and l-Leu (CDR 1–4). The other set of CDRs, namely, FDNP-l-Phe-NH2, FDNP-l-Val-NH2, and FDNP-l-Leu-NH2, was also prepared. These reagents were used for synthesis of diastereomers of 18 proteinogenic and 08 non-proteinogenic
amino acids, which were resolved by reversed-phase high-performance liquid chromatography using C18 column and gradient eluting
mixture of aq.TFA and acetonitrile with UV detection at 340 nm. The reagents were used for resolution of a complex mixture
of 18 racemic proteinogenic amino acids in a single chromatographic run of 65 min and to determine concentration of the d-amino acid in a solution of dl-amino acid. The resolution (R
S) and selectivity (α) obtained for the two sets of diastereomers were compared among themselves and among the two groups. The method was validated
for accuracy, precision, limit of detection (LOD), and limit of quantification. LOD is 0.001% impurity of d-enantiomer. 相似文献
7.
Summary Mixed ligand complexes (1)-(18) of composition [RuL-(PPh3)Y] and [RuL(PPh3)(H2O)Y]- (L = chiral Schiff bases derived from l-alanine, l-valine, l-serine, l-cystein, l-arginine or l-aspartic acid with salicylaldehyde; Y = azide, 2,2-bipyridyl or 1,10-phenanthroline) have been prepared and characterized by microanalysis, spectroscopy and polarography. The conformational aspects regarding the relationship of the asymmetric carbon atom to the nitrogen donors around the RuII are discussed. All complexes showed quasi-reversible c.v. behaviour and the redox potentials of the RuII/RuI couple lie in the -0.31 to-0.16 V range. 相似文献
8.
Hasegawa H Fukushima T Lee JA Tsukamoto K Moriya K Ono Y Imai K 《Analytical and bioanalytical chemistry》2003,377(5):886-891
d-Lactic and l-lactic acids were simultaneously determined by means of a column-switching high-performance liquid chromatography (HPLC) with fluorescence detection. As a fluorescence reagent, 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ) was employed for the fluorescence derivatization of lactic acid. The proposed HPLC system adopted both octylsilica (Cadenza CD-C8) and amylose-based chiral columns (CHIRALPAK AD-RH), which proved to give a sufficient enantiomeric separation of the lactic acid derivatives with a separation factor () of 1.32 and a resolution (Rs) of 1.98. Moreover, the features of the first elution of d-lactic acid peak in the proposed HPLC were convenient for the determination of trace amount of serum d-lactic acid, which is known to increase under diabetes. Intra-day and inter-day accuracies were in the range of 90.5–101.2 and 89.0–100.7%, and the intra-day and inter-day precisions were 0.3–1.2 and 0.4–4.8%, respectively. The proposed method was applied to determine d-lactic and l-lactic acids in human serum of normal subjects and diabetic patients, showing that both d-lactic and l-lactic acid concentrations were significantly increased in the serum of diabetic patients (n=31) as compared with normal subjects (n=21). This fact was found for the first time owing to the development of the proposed HPLC method which is able to determine d-lactic and l-lactic acid simultaneously. Finally, serum d-lactic acid concentrations determined by the proposed HPLC method were compared with those from a reported enzymatic assay, and the smaller p value between normal subjects and diabetic patients was shown by the proposed HPLC method. 相似文献
9.
Luo Mei Sun Jie Zhou Shi-Ming Yin Hao Hu Ke-Liang 《Research on Chemical Intermediates》2010,36(9):1049-1054
Two opposite configuration (R/S) of chiral complexes (C8H11N)2·CuCl2 were obtained from the reaction of chiral d(+)/l(−)-α-ethylphenyl amine with copper chloride (II) in dry ethanol. The crystal structures of 1a and 1b were characterized by
IR, elemental analysis and X-ray crystallography. 相似文献
10.
Katleen Verleysen Jos Vandijck Mark Schelfaut Pat Sandra 《Journal of separation science》1998,21(6):323-331
An overview is presented of the applicability of the crown ether 18-crown-6-tetracarboxylic acid (18C6H4) as buffer additive in capillary electrophoresis (CE) for the separation of enantiomers. The chiral selector 18C6H4 is particularly useful for the separation of racemates having a primary amino function. Unfortunately, the crown ether is no longer commercially available. The synthesis and spectroscopic characterization are therefore described in detail. Moreover, a method is presented for the regeneration of the crown ether after CE application. Some new enantiomeric separations of amino acids i.e. NORLEU, ARG, GLU, m-TYR, and o-TYR are listed and the influence of the pH and temperature of the separation buffer is discussed. An intermediate in the synthetic pathway, namely 18-crown-6-tetracarboxamide, did not exhibit any enantioselectivity in CE. 相似文献
11.
Chiral recognition of phenylalanine (Phe) was achieved in the gas phase by electrospray ionization Q-TOF tandem mass spectrometry.
In this method, two central ions, i.e. proton and divalent copper, were used and chiral crown ether, (+)-2,3,11,12-tetracarboxylic
acid-18-crown-6 (18-C-6-TCA), was used as a chiral host. Dimeric complexes were readily formed by electrospray ionization
of a methanol/water (50/50, V/V) solution containing central ions, Phe and 18-C-6-TCA. The dimeric complex included proton-bound (18-C-6-TCA)(Phe)H+ and
copper-bound deprotonated [Cu2+(18-C-6-TCA)(Phe)-H]+ ions were mass selected and then collided with Ar in the CID experiments. The chiral recognition capability of these complexes
was evaluated using the relative abundance of daughter ion to parent ion. A higher degree of chiral recognition ability was
observed with Cu2+ compared to that of H+. Different central ions exhibited distinctive dissociation pathways and unique chiral recognition characteristics. The chiral
recognition mechanism was also discussed in detail with the help of the structure of copper-bound complex predicted by theoretical
calculation. 相似文献
12.
Ming‐Hua Piao Jaeyoung Hwang Mi‐Sook Won Myung Ho Hyun Yoon‐Bo Shim 《Electroanalysis》2008,20(12):1293-1299
All solid‐state enantioselective electrode (ASESE) based on a newly synthesized chiral crown ether derivative ((R)‐(?)‐(3,3′‐diphenyl‐1,1′‐binaphthyl)‐23‐crown‐6 incorporating 1,4‐dimethoxybenzene) was prepared and characterized by potentiometry. The ASESE clearly showed enantiomer discrimination for methyl esters of alanine, leucine, valine, phenylalanine, and phenylglycine, where the enantioselectivity for phenylglycine methyl ester was the highest (KR,S=8.5±7.1%). Experimental parameters of ASESE for the analysis of (R)‐(?)‐phenylglycine methyl ester were optimized. The optimized ASESE showed a slope of 55.3±0.2 mV/dec for (R)‐(?)‐phenylglycine methyl ester in the concentration range of 1.0×10?5–1.0×10?2 M and the detection limit was 9.0×10?6 M. The ASESE showed good selectivity for (R)‐(?)‐phenylglycine methyl ester against inorganic cations and various amino acid methyl esters. The concentration of (R)‐(?)‐phenylglycine methyl ester was determined in the mixture of (R)‐(?) and (S)‐(+)‐phenylglycine methyl ester, which ratios varied from 2 : 1 to 1 : 9. The lifespan of the electrode was alleged to be 30 days. 相似文献
13.
Lu-zhi Liu Chun-huan He Lin Yang Yan Huang Qiang Wu Wen-gui Duan Heng-shan Wang Ying-ming Pan 《Tetrahedron》2014
Four types of novel C1-symmetric chiral crown ethers including 28-crown-8, 20-crown-6, 17-crown-5 and 14-crown-3 (9a–m) were synthesized and their enantiodiscriminating abilities with protonated primary amines (10–14) were examined by 1H NMR spectroscopy. 20-crown-6 crown ethers exhibited good chiral recognition properties toward these guests and showed different complementarity to some chiral guests, indicating that 20-crown-6 crown ethers could be used as a chiral NMR solvating agent to determine the enantiopurity of these guests. In addition, the binding model and binding site between the hosts and guests were also studied by the computational modeling and experimental calculation. 相似文献
14.
Chevela V. V. Vul'fson S. G. Matveev S. N. Salnikov Yu. I. Semyonov V. E. Bezryadin S. G. 《Russian Chemical Bulletin》1994,43(6):964-967
The molar constants of paramagnetic birefringence (PBR) for the dimeric dysprosium(iii)d- anddl-tartrates, Dy2(d-Tart)(l-Tart)2– (1) and Dy2(d-Tart)2
2– (2) have been determined by means of pH-metric and PBR measurements. The simulation of the structure of the ligand and solvate environment has been carried out using the method of molecular mechanics (Dashevsky-Plyamovaty model, the MIND program). In addition to the four oxygen atoms from the ligand, each DyIII ion coordinates four molecules of water and a Na+ ion.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1029–1032, June, 1994. 相似文献
15.
W. Zielenkiewicz A. Marcinowicz J. Poznański S. Cherenok V. Kalchenko 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):11-19
The stability constants, enthalpy ΔH
0, entropy ΔS
0, and Gibbs energy ΔG
0 were determined for the host–guest complexes (1:1) of calix[4]arene bis-hydroxymethylphosphous acid with glycine, l-alanine, l-valine, l-leucine, l-isoleucine residues in methanol solution with the aid of the titration experiments followed by calorimetric and spectroscopic (1H NMR, UV) methods. The experimental data indicated that the host–guest complexation was under control of the direct electrostatic interaction between negatively charged calixarene phosphoryl group and amino acid residue NH
3
+
group, modulated by the hydrophobic interaction, which drive the inclusion of the residue alkyl side-chain into the calixarene cavity. The stability of the inclusion complexes was found correlated with the size of the aliphatic amino acid’s side-chain. The experimental data were additionally analyzed in the terms of the three state model corresponding to coexistence of 2:1 and 1:1 complexation equilibria. 相似文献
16.
Lucia Mutihac Radu Mutihac Hans-Jürgen Buschmann 《Journal of inclusion phenomena and macrocyclic chemistry》1995,23(3):167-174
The transport of some amines in protonated form was studied (viz. methylamine, dimethylamine, diethylamine andn-propylamine) and -amino acids (l-leucine,l-methionine,l-isoleucine,l-phenylalanine,l-valine,l--alanine andl-cysteine). The following macrocyclic ligands were used as carriers throughout the experiments: 15-crown-5 (15C5), 18-crown-6 (18C6), benzo-18-crown-6 (B18C6), dibenzo-18-crown-6 (DB18C6), diazacrown ether [2.2] (1,7,10,16-tetraoxa-4,13-diazacyclooctadecane) and cryptand [2.2.2] (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo [8.8.8] hexacosane). The active transport, assisted by pH gradient, of amino acids and amines in protonated form as ion pairs in the presence of picrate anion was performed. The experiments suggested the influence of the ligand size, the donor atom type, and the substituents on the transport phenomena. 相似文献
17.
Kinga Suwińska Janusz Lipkowski 《Journal of inclusion phenomena and macrocyclic chemistry》1988,6(3):237-248
The crystal structure of α-d-mannosido-benzo-18-crown-6·KSCN (1) was solved by X-ray single crystal diffractometry. C28H36O10·KSCN is orthorhombic, space groupP212121 withZ=4,a=8.035(4),b=9.960(2),c=38.83(2) Å,M r =629.8,V=3103.6 Å3,D x =1.347 g cm?3, μ(CuKα)=2.53 mm?1, λ=1.54178 Å,F(000)=1324. FinalR=0.043 for 1139 unique observed reflections measured at room temperature. The potassium ion is surrounded by a nearly planar hexagon of oxygen atoms of the macrocyclic ring and lies on the plane formed by those atoms. Hexagonal pyramidal coordination is completed by the nitrogen atom of the thiocyanate anion. The SCN ion was found on the face of the macrocyclic ring opposite that for the chiral mannopyranoside moiety. The molecular structure of α-d-mannosido-18-crown-6 (2) and the structure of molecular complexes of2 and α-d-glucosido-benzo-18-crown-6 (3) were studied by molecular mechanics methods. The results suggest enthalpy driven selectivity of complexation of the phenylalanine methyl ester (4) by2 and both enthalpy and entropy effects in selective complexation of4 by3. 相似文献
18.
Hengshan Wang Chunhuan He Yingming Pan Guiyang Yao Qiang Wu Honggui Deng 《Journal of inclusion phenomena and macrocyclic chemistry》2012,73(1-4):177-183
Novel chiral 22-crown-6 ethers (5a–b) bearing methoxycarbonyl side groups derived from rosin acid and 2,2′-dihydroxy-1,1′-binaphthyl (BINOL) were prepared in optically pure forms, and their enantiodiscriminating abilities toward protonated primary amines and amino acid methyl ester salts were examined by the UV–vis titration method. These receptors exhibit good chiral recognition towards the isomers (up to KL/KD?=?5.23, ΔΔG0?=?4.10?kJ?mol?1) in CHCl3:MeOH?=?2:1 at 25?°C. 相似文献
19.
Alexander Y. Nazarenko Peter Huszthy Jerald S. Bradshaw John D. Lamb Reed M. Izatt 《Journal of inclusion phenomena and macrocyclic chemistry》1994,20(1):13-22
A solvent extraction technique was used to determine equilibrium constants for the reactions occurring when an aqueous phase containing [-(1-naphthyl)ethyl]ammonium ions [(R)- and (S-isomers] is equilibrated with a chloroform phase containing chiral substituted pyridino-18-crown-6 ligands. Selectivity coefficients and equilibrium constants for the interactions in chloroform solutions were calculated. The existence of two different types of ion pairs separated by the macrocycle molecule was detected from the UV spectra. One ion pair has a nearly complete separation of the picrate anion from the protonated amine by the ligand. The other has the picrate ion only partly separated from the cation by the macrocycle. 相似文献
20.
A chiral liquid chromatographic method for determination of the enantiomeric purity of both l-carnitine and acetyl-l-carnitine is described. Separation of the enantiomers of dl-carnitine and acetyl-dl-carnitine was achieved on a commercial chiral column (Chiralcel OD-R) after derivatization with (alpha-bromo)methyl phenyl ketone. Introduction of this lipophilic UV chromophoric group to the carnitine and acetylcarnitine molecules improved their retention, resolution, and UV detection. The mobile phase was 74:26 (v/v) 0.5 mol L-1 sodium perchlorate–acetonitrile, pH 3.8, and the flow rate was 0.4 mL min-1. Detection was performed at 235 nm. The method is selective and reliable for determination of the enantiomeric purity of bulk drug substances l-carnitine and acetyl-l-carnitine. 相似文献