29 research outputs found
Nem lineáris összefĂĽggĂ©sek a királis vegyĂĽletek szelektĂv kölcsönhatásaiban = Non-linear relationships in selective interactions between chiral compounds.
MĂłdszeresen vizsgáltuk a rokon molekulaszerkezetű racĂ©m vegyĂĽletek, illetve reszolválóágensek viselkedĂ©sĂ©t a diasztereomerek elválasztásai során. Az enantiomer keverĂ©kek elválasztásainál a kapott nem lineáris lefutásĂş ee0-ee görbĂ©k Ă©s az olvadási biner fázisdiagramjaik közötti hasonlĂłságot, (pl. az eutektikus összetĂ©telek egyezĂ©sĂ©t) tapasztaltunk. MegállapĂtottuk, hogy a diasztereomer sĂłk olvadási biner fázisdiagramjainak a nem lineáris lefutása a racĂ©m vegyĂĽlet enantiomer keverĂ©keinek a viselkedĂ©sĂ©nek a fĂĽggvĂ©nye. A rokon molekulaszerkezetű vegyĂĽleteink körĂ©ben számos aminosav (N-acil-, vagy Ă©szter-) származĂ©kát vizsgáltuk. MegállapĂtottuk, hogy önmagukban, vagy szabad állapotban is felhasználhatĂłak enantiomerek elválasztására racĂ©m vegyĂĽlet, vagy reszolválóágenskĂ©nt. MegállapĂtottuk, hogy az alfa- Ă©s gamma-aminosavak enantiomerjei, pĂ©ldául „királis báziskĂ©nt” jĂł enantiomer elválasztást eredmĂ©nyeznek. Ugyanakkor a diasztereomerek kristályosodásánál a kinetikus kontroll fellĂ©pĂ©sĂ©t is megfigyeltĂĽk. A vĂ©gzett elválasztások során a kristályos fázis kialakulásainak az azonosságai azt bizonyĂtják, hogy az enantiomer keverĂ©kek viselkedĂ©se meghatározza a diasztereomer keverĂ©kek viselkedĂ©sĂ©t is. A vĂ©gzett enantiomer Ă©s diasztereomer keverĂ©kek elválasztásai során szinte kivĂ©tel nĂ©lkĂĽl környezetbarát eljárásokat dolgoztunk ki, melyeknĂ©l oldĂłszerkĂ©nt vizet alkalmaztunk. További P-kiralitáscentrumot tartalmazĂł heterociklusos racĂ©m vegyĂĽletek enantiomer elválasztásait oldottuk meg. | We have systematically studied the behaviour of structurally related racemic compounds and resolving agents during the separation of diastereoisomers. As it was assumed earlier, correlation between the non-linear ee0-ee curves and melting point phase diagrams was found during these separations, as similarities of eutectical compositions on the two diagrams were observed. Among the investigated compounds with related molecular structure, several (N-acylated, or ester-) derivatives of amino acids were examined. We established, that they can be applied for separation of enantiomers both as a racemic compound or resolving agent, in free state or as a derivative. We established that alpha- and gamma-amino acids, for example as „chiral base”, result in good enantiomeric enrichment. At the same time the kinetic control at the crystallisation of diastereomers was observed. On the basis of our own experimental results we can declare that the similarities of the crystalline phases prove that the behaviour of enantiomeric mixture also determines the behaviour of diastereomeric mixtures. Almost without exception, during the separation of all the enantiomeric and diastereomeric mixtures we worked out environmentally friendly methods, applying water as solvent. We successfully extended our resolution methods to the separation of further cyclic racemic compounds containing P-chiral centre unknown in literature in enantiopure form
New Opportunities to Improve the Enantiomeric and Diastereomeric Separations
The preparation of single enantiomers (ee ~100%) is one of the most important demands both for industrial practice and research. Actually, the resolution of the racemic compounds still remains the most common method for producing pure enantiomers on a large scale. To obtain the pure enantiomers, it is necessary to find the appropriate conditions and resolving agents. During the separation of diastereomeric mixtures, similar trends can be observed as in course of the distribution of enantiomeric mixtures between phases, because just the presence of one-third chiral compound (namely the resolving agent) is the difference. This chapter presents new observations and establishments about the new opportunities to optimize the separation of chiral mixtures, especially the diastereomeric mixtures
Separation of Chiral Compounds: Enantiomeric and Diastereomeric Mixtures
Despite the dramatic development of enantioselective synthesis and chromatographic separation methods, optical resolution still remains the cheapest and operationally simplest method for producing pure enantiomers on a larger scale. No extreme conditions or expensive reagents are required, and the eventually expensive resolving agents can be recovered. This chapter is based mainly on the authors’ long experience in the resolution of industrially important molecules, and it presents new observations and establishments as well. Several methods for separation of chiral mixtures, enantiomeric and diastereomeric mixtures, are shown, and possibilities for predicting the efficiency of resolution based on the analysis of physico-chemical properties of the reactants are also described
Prediction of the efficiency of diastereoisomer separation on the basis of the behaviour of enantiomeric mixtures
The composition of a crystalline diastereoisomer (eeDIA) is determined either by the eutectic composition of the racemic compound (eeEuRac) or that of resolving agent (eeEuRes) and the higher ee value has the more dominant effect.</p
Influence of Helical Structured Supramolecular Asso ciates and that of Eutectic Composition on the Distribution of Enantio meric and Diastereomeric Mixtures between Phases
Crystalline Forms of 4,4'-Methylenediantipyrine: Crystallographic Unit Cell for the Anhydrous Form, from Laboratory Powder XRD Pattern by DASH Program Package
Crystalline unit cell structure of anhydrous title compound, diantipyrinylmethane (CAS Registry No. 1251-85-0), a substance usually obtained as a by-product in Mannich type reactions of antipyrine, has been modelled by the help of powder X-ray diffraction, applying the DASH software package and crystal coordinates coming from former single crystal X-ray structure determinations (CSD codes FADDIY and FADDIY01) of its monohydrate. The unit cell of the anhydrate compound belongs to the monoclinic space group P21/a, with unit cell parameters of a = 14.604, b = 9.858, c = 14.509 Å, β = 95.56 °, V = 2078.9 Å3, Z = 4, Z ' = 1. Comparisons of FT-IR spectrum and thermal behavior of the anhydrous and monohydrated forms confirm differences in degree of hydration and solid state structure, while those of 1H- and 13C NMR-spectra show their molecular identity