Racemic undecan-x-ols (x = 2,3) used as starting materials in a biocatalysed enzymatic acylation with vinyl acetate in the presence of Novozym 435®. As result enantiomerically pure alcohols and their acetates have been obtained. The odours of each of the enantiomers have been compared with those of the racemic mixtures. Enantiomerically pure undecan-2-ols as well as their acetates have intense odours which differ in type, since their intensity is similar, the odour of each racemate comprises the odours of both enantiomers. Racemic undecan-3-ol has the odour of the R enantiomer only, because the opposite enantiomer is almost odourless. The odour of the racemic undec-3-yl acetate is faint with a fatty-soapy note despite of the fact that both enantiomers exhibit pleasant floral odours.
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Lavandulol and its esters play a significant role in the perfume and cosmetics industry. Because of their biological activity they have recently become relevant in research on pheromones. Many natural sources of this important alcohol are known along with synthetic methods allowing to achieve either an optically pure product or a racemic mixture. The article presents a short overview on new natural resources of the alcohol, its sensory and pheromonal characteristics and synthesis of its racemic mixture and enantiomers.
Kinetic resolution of (R)- and (S)-mandelic acid by its transesterification with vinyl acetate catalysed by Burholderia cepacia lipase has been studied. The influence of the initial substrate concentration on the kinetics of process has been investigated. A modified ping-pong bi-bi model of enzymatic transesterification of (S)-mandelic acid including substrate inhibition has been developed. The values of kinetic parameters of the model have been estimated. We have shown that the inhibition effect revealed over a certain threshold limit value of the initial concentration of substrate.
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The high resolution NMR spectroscopy in liquids is a convenient tool for differentiating stereoisomers. Diastereomeric structures having different spatial distribution of electron density produce different magnetic environments for their nuclei and in consequence have, in general, different NMR spectra. The same concerns diastereotopic groups in a molecule. On the other hand, enantiomers or enantiotopic groups can be differentiated only when they are placed in a chiral environment. It can be accomplished by transforming enantiomers into their diastereomeric derivatives with the aid of chiral derivatising reagents, or by using chiral complexing or solvating agents. The most popular methods of practical realization of these approaches have been reviewed and illustrated with some examples. The spectroscopic differentiation of enantiomers provides a possibility of determining their absolute configurations.
W referacie przedstawiono znaczenie chiralności (izomerii optycznej) w związkach biologicznie czynnych, ze szczególnym uwzględnieniem agrochemikaliów (pestycydów). Omówiono zależność oddziaływania biologicznego od rodzaju enancjomeru.
EN
Chirality - one of the fundamental concepts in structural chemistry - belongs to the terms, which started to be commonly used in science from the beginning of 60-ties of the XXth century. The quickest progress on the area of chiral chemistry has been observed within the last few decades of XXth century, which was closely connected with research on the relationship between stereostructure and biological activity of many compounds. As practically each organism constitutes a chiral enviroment, the existence of a great deal of examples of enantiomeric selectivy seems to be fully justified. There is of big importance for pharmaceutical chemistry, but also still growing interest is notified on this area for the industry of plant protection agents, food flavours enhancers, syntetic fragrances, and many others. According to the data, concerning agrochemicals (pesticides) manufacturing, and published in 1996, market of chiral products in a global scale has attained the value of 9 billions, whereas the value of sales for those separated onto a single, pure enantiomers was higher than 2,6 billions USD. Knowledge of the fact that a desired activity, in general, is placed in only one of an enantiomeric pair, connected with technological and analytical possibilities, has led to legislative, ethical, ecological and commercial pressures to produce and apply only the active isomers. A difference between biological activity of indywidual enantiomers is particulary and clearly visible in the case of organophosphorous inhibitors of acetylcholinesterase.
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A method for the separation and the determination of enantiomers of four benzodiazepines: oxazepam, lorazepam, temazepam and lormetazepam by HPLC on the Chiralcel OD-R (Diacel-Chemical Industries) column is presented. When the Chiralcel OD (Diacel-Chemical Industries) column was used, only the resolution of oxazepam and lormetazepam could be successfully performed.
PL
Przedstawiono metodę rozdzielania i oznaczania enancjomerów czterech benzodiazepin: oksazepamu, lorazepamu, temazepamu i lormetazepamu metodą HPLC na kolumnie Chiralcel OD-R (Diacel-Chemical Industries). Na kolumnie Chiralcel OD (Diacel-Chemical Industries) udało się rozdzielić jedynie oksazepam i lormetazepam.
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The inclusion complexes of p-cyclodextrin with neutral and anionic forms of enantio-mers of 5-ethyl-l-methyl-5-phenyl-2-thiobarbituric acid (2-thioprominal) have been modeled and energetically optimised by the application of AMI method. The resulting difference in minimised energies of complexes of enantiomeric forms of 5-ethyl-l-methyl-5-phenyl-2-thiobarbituric acid with p-cyclodextrin confirm the ability of p-cyclodextrin to act as a mobile phase additive in reversed-phase HPLC, to separate en-antiomers of 5-ethyl-l-methyl-5-phenyl-2-thiobarbituric acid during chromatography and rationalize their order of elution.
PL
Kompleksy inkluzyjne p-cyklodekstryny z obojętnymi i anionowymi formami enan-cjomerów kwasu 5-etylo-l-metylo-5-fenylo-2-tiobarbiturowego (2-tioprominalu) były modelowane przy zastosowaniu metody AM1. Wyznaczona za pomocą tej metody różnica zminimalizowanych energii kompleksów potwierdza przydatność P-cyklodekstryny, jako dodatku do fazy ruchomej w systemach z odwróconymi fazami HPLC, do rozdziału enancej omerów kwasu 5-etylo-l-metylo-5-fenylo-2-tiobarbiturowego podczas rozdziału chromatograficznego oraz tłumaczy porządek ich wymywania z kolumny.
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It is well known that living organisms show strong enantiometric selectivity on their molecular level. The enantiomorphic discrimination is sometimes manifested in the shape of an animal or plant. It was Pasteur who in 1857 discovered that the chemistry of life had a preferred handedness. 'Life is manifested to us as a function of the dyssymmetry of the universe' he wrote. Pasteur's work was carried out before the recognition of the quadrivalence of the carbon by Kekuléand Couper (1858). He did far more than simply discover the underlying theory of molecular asymmetry, he foresaw most of the consequences of that theory, he understood the principle of a transference of the asymmetric property from one set of molecules to another. Finally he clearly understood the biological implications of the discovery of asymmetry. The theory of organic stereochemistry has been established independently by Van't Hoff and Le Bell in 1874. Now, very frequently we have the question why there is no 'mirror life'. Would not biochemistry like ours with every configuration inverted be just as good? Was our way better or lucky? In 1957 it was found that mirror symmetry is broken on the subatomic level. Some elementary particles, like neutrino, exist only as left-handed objects. Thus, in fact, there are no exact enantiomers in our world. They are rather diastereoisomers of different energy. Thus, our mirror images friends living on the other side of the looking glass, with all the biological molecules with opposite configurations would not be as perfect as we are.
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The enantiomers; series mainly of 2-amirio-I-butánol derivatives, were investigateď by reversed phase high performance, thin-layer and column chromatography. The chiral selector ß-cyclodextrin (ßCD) was used as a mobile phase additive. The effecis of bCD, and bis (2-ethylhexyl) orthophosphoric acid on retention and enantioselectivity were investigated. The resolution of the enantiomers was dependent on the type of the stationary phase and on the type and concentration of modifier and ß-cyclodextrin in the mobile phase. High separation factors (a) have been obtained for most investigated optical isomers.
PL
Badano enancjomery, głównie pochodne 2-amino-1-butanolu, metodą cienkowarstwowej i kolumnowej chromatograf i w odwróconym układzie faz. ß-Cyklodekstrynę (ßCD) dodawano do fazy ruchomej: Badano wpływ ß-cyklodekstryny i kwasu bis(2-etylobeksylo)-fosforowego (HDEHP) na retencję i enancjoselektywność. Rozdzielenie enancjomerów było uzależnione od rodzaju fazy stacjonarnej oraz od rodzaju i stężenia organicznego modyfikatora i ß-cyklodekstryny w fazie ruchomej. (a) Dla większości badanych optycznych izomerów otrzymano wysokie współczynniki rozdzielenia (a).
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The enantiomeric separntion of several 2-arylpropionic acids has been studied by capillary isotachophoresis using two chiral selectors added to the leading electrolyte with the aim to find the optimum experimental conditions for qualitative purpose. Enantiomeric resolution was recorded for fenoprofen, flurbiprofen, ibuprofen and ketoprofen, when heptnkis(2,3,6-tri-O-methyl)-ß-cyclodextrin was used as additive in the leading electrolyte.
PL
Badano rozdzielnie ennncjomerów szeregu kwasów 2-arylopropionowych za pomocą kapilarnej isotachoforezy. W celu ustalenia optymalnych warunków doświadczalnych analizy jakościowej, do elektrolitu podstawowego dodawano dwa związki chirałne różnicujące selektywność. Zaobserwowano , iż w przypadku dodania do elektrolitu podstawowego heptakis/2,3,6-tri-O-methyl/-ß-cyklodekstryny zachodzi rozdzielenie enancjomerów fenoprofenu, flurbiprofenu; ibuprofenu i keptoprofenu.
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The Snyder-Soczewiński model of adsorption chromatography was applied to investigate the stoichiometry of enantiomers adsorption mechanism of some amino acids derivatives on (R)-3,5-(dinitrobenzoyl)phenylglycine chiral stationary phase (CSP)using nonaqueous organic mobile phases. The investigations of relationship between retentipn factors of amino acids derivatives and composition of binary mobile phase have shown that the log k vs log X, plots are linear in aceordance with the Snyder-Soczewiński competitive adsorption model. The expcrimental results confirm the earlier suggestions that in this case the separation process of enantiomers on (R)-3,5-(dinitrobenzoyl)phenylglycine CSPS' of the Pirkle type occurs as a result of competitive adsorption of enantiomers and solvent molccules on the surface of CSP. In some cases the log k vs log Xs plots, for givcn pairs of ennntiomers are not parallel to each other what indicates that the separation factor a depends also on the type and composition of the mobile phase.
PL
Zastosowano równanie Snydera-Soczewiáskiego do badania mechanizmu adsorpcji pochodnych aminokwasów na kolumnie z (R)-3,5-(dinitrobenzoilo)fenyloglicyną jako chiralną fazą stacjonarną (CSP) oraz niewodnymi rozpuszczalnikami organicznymi jako fazą ruchomą. Zgodnie z wnioskami wypływającymi z równania Snydcra-Soczewińskiego otrzymano liniowe zależności log k vs log Xz. Otrzymane wyniki potwierdzają wcześniejsze sugestie, tc proces rozdzielania enancjometrów na CSP typu Pirkle'a jest wynikiem konkurencyjnej adsorpcji cząsteczek enancjomerów i modyfikatora na powierzchni CSP. W kilku przypadkach linie zależności log k vs log X: nie są do siebie równolegle, co świadczy o tym, że współczynnik rozdzielenia a zależy także od rodzaju i stężenia modyfikatora w fazie ruchomej
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