排序方式: 共有36条查询结果,搜索用时 453 毫秒
11.
Enantiomers in solution have a tendency to form associations of various compositions. This phenomenon is used to separate partially resolved mixtures of enantiomers.Possibilities for improving separation by changing various parameters have been investigated. A new method for determination of optical purity is described. 相似文献
12.
R. Illés Cs. Kassai Gy. Pokol J. Madarász E. Fogassy D. Kozma 《Journal of Thermal Analysis and Calorimetry》2000,61(3):745-755
Thermal behaviour of O,O'-dibenzoyl-(2R,3R)-tartaric acid (DBTA), its monohydrate, and its potential supramolecular compounds
with achiral alcohols and phenols were investigated with TG, DSC, EGD. The structural differences among the anhydrous DBTA,
its monohydrate, and the supramolecular derivatives were investigated with X-ray powder diffraction. The thermal behaviour
of DBTA-supramoleculars with isopropyl, tert-butyl, and 5-cyclohexyl alcohols is found to be similar to each other but essentially different from that of both DBTA and
its monohydrate. On heating they melt and decompose between 60–180°C while they loose in one or two steps the bound alcohol.
The thermal stability of the supramolecular compounds increases with the boiling point of the alcohol component. According
to the X-ray powder diffraction patterns each supramolecular substance has different structure, that may also result in the
different thermal stability of the compounds. The molar ratio of DBTA:achiral alcohol samples is 1:1.01–1:1.57 estimated from
the corresponding mass losses. The XRD patterns of the prepared two DBTA-phenol materials are different from those of DBTA-achiral
alcohol samples. The phenol compounds melt with slow mass losses and give an endothermic peak between 73–83°C but the melting
point of the anhydrous DBTA cannot be observed. DBTA:phenol molar ratio is estimated to be 1:0.41 and 1:0.65 for phenol and
2-methylphenol, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Tibor Novk Viktria Ujj Jzsef Schindler Mtys Czugler Mikls Kubinyi Zsuzsa A. Mayer Elemr Fogassy Gyrgy Keglevich 《Tetrahedron: Asymmetry》2007,18(24):2965-2972
The antipodes of 1-aryl-, 1-alkyl- and 1-alkoxy-3-methyl-3-phospholene 1-oxides 1a–h and 1-phenyl-3-methyl-3-phospholene 1-sulfide 1i were separated in good yields and high enantiomeric excesses (up to >99% ee) by resolution via formation of diastereomeric complexes with either (−)-(4R,5R)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane 2 (TADDOL) or (−)-(2R,3R)-,,′,′-tetraphenyl-1,4-dioxaspiro[4.5]decan-2,3-dimethanol 3. The stereostructure of the supramolecular formations and the absolute configurations of the 3-phospholene oxides 1a, 1e and 1f were elucidated by single crystal X-ray crystallography. CD spectroscopy was also useful in determining the absolute configurations of some phospholene oxides 1b, 1c, 1g and 1h. 相似文献
14.
Emese Pálovics József Schindler Ferenc Faigl Elemér Fogassy 《Tetrahedron: Asymmetry》2010,21(19):2429-2434
Reciprocal resolutions between compounds (racemates and enantiomers) with similar structures have been examined. Amongst structurally similar compounds (so called relative structures) several N-acyl amino acids and amino acid esters were investigated. A part of the resolving agent or the racemic compound could be replaced by an achiral compound with a relative structure and an additive could occasionally improve significantly the efficiency of the resolution. Both the kinetic and the thermodynamic controls were observed as governing factors of the reciprocal resolutions. 相似文献
15.
Dorottya Fruzsina Bnhegyi Elemr Fogassy Jnos Madarsz Emese Plovics 《Molecules (Basel, Switzerland)》2022,27(10)
The optically active dibenzoyltartaric acid, tartaric acid, and its sodium salts were successfully applied to the optical resolution of (1R,2S)(1S,2R)-2-(methylamino)-1-phenylpropan-1-ol (EPH) and (1R,2R)(1S,2S)-2-amino-1-(4-nitrophenyl)propane-1,3-diol (AD) as resolving agents. It was observed that both compounds’ resolution using a mixture of salts of quasi-racemic resolving agents showed a change in chiral recognition under the same conditions compared to the result of the use of the single enantiomeric resolving agent. The changes are followed by detailed analytical (XRD, FTIR, and DSC) studies. Meanwhile, the DASH indexing software package was also tested on powder XRD patterns of pure initial materials and intermediate salt samples of high diastereomeric excess. 相似文献
16.
Jzsef Blint Gabriella Egri Violetta Kiss Antal Gajry Zoltn Juvancz Elemr Fogassy 《Tetrahedron: Asymmetry》2002,12(24):369-3439
6-Fluoro-2-methyl-1,2,3,4-tetrahydroquinoline (FTHQ) was resolved in several different solvents by tartaric acid derivatives as the most common acidic resolving agents available in industrial quantities. Strong reaction kinetics and solvent dependence were observed, curiously without solvation. In possession of these findings, an economic resolution process is proposed, which is completed by the incorporation of a racemization step. 相似文献
17.
D. Kozma Klára Tomor C. Novák G. Pokol E. Fogassy 《Journal of Thermal Analysis and Calorimetry》1996,46(6):1613-1623
Racemic malic acid (I) was resolved by R-α-phenylethylamine(II). The S-(?)-I.R-(+)-II diastereoisomer was in excess in the precipitated salt. DSC curves and X-ray powder diffractograms proved that the diastereoisomeric salt mixture precipitated during the resolution was isomorphous with the optically pure S-(?)-I.R-(+)-II salt. The diastereoisomeric salt mixture containing the R-(?)-I.R-(+)-II salt in abundance bound crystal solvate (water or methanol) when produced by the total evaporation of the mother liquor, while the optically pure R-(?)-I.R-(+)-II salt crystallized without solvate. It is generally assumed that solid solution formation takes place when the two diastereoisomers are alike and the high similarity results in less efficient enantiomer separation. This paper demonstrates that efficient resolution can be accomplished in case of solid solution formation too. The diastereoisomeric salt mixtures can crystallize in isomorphic form even when the physico-chemical properties of the optically pure diastereoisomeric salts are quite different. 相似文献
18.
Optical resolution of racemic 2-(3-chloro-phenyl)-3.4a. 5.6.7.7a-hexahydrocyclopentapyrimidin-4-one with O.O′-dibenzoyl-2R,3R-tartaric acid in an unusual solvent combination, in water-chloroform two phase solvent system was accomplished. During enantiomeric enrichment of the resulted raw base the optically active base can be recovered from the ethanolic mother liquor. 相似文献
19.
D. Kozma C. Novák G. Pokol E. Fogassy 《Journal of Thermal Analysis and Calorimetry》1996,47(3):727-733
The products obtained in the optical resolution of the N-methylamphetamine by the Pope-Peachy method, using half equivalent R, R-tartaric acid and half equivalent hydrochloric acid in absolute ethanol were investigated by thermoanalytical methods. The DSC measurements of the precipitated salts provide sufficient information for following the progress of the resolution. In this way, the results of the resolution can be estimated with the precision of about 5% optical purity. 相似文献
20.
Elemér Fogassy Antal Lopata Ferenc Faigl Ferenc Darvas Mária Ács László Tõke 《Tetrahedron letters》1980,21(7):647-650
Significant statistical relationships have been found between the parameters characterizing the results and circumstances of the resolutions of seventeen phenylglycine derivatives. The successful predictions given for the results of six independent resolutions prove the utility of these relationships. 相似文献