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EN
The review is devoted to self-disproportionation of enantiomers (SDE) phenomenon which has been observed for many different classes of chiral organic compounds. The SDE phenomenon occurs when the fractionation of an enantioenriched sample due the application of a physicochemical process under achiral conditions results in the variation of the proportion of the enantiomers present across the fractions, though the overall composition in terms of the sample ee remains unchanged. The SDE process can be considered in terms of separating the excess enantiomer from the racemate. The basic terminology related to SDE was described. The formation of the SDE under chromatographic conditions is the result of an association process occurring in a solution of a chiral, non-racemic compound. Information on preferred interactions leading to homo-/heterochiral supramolecules can be provided by quantum chemical calculations, NMR spectroscopy and comparison of crystal structures of the racemic and enantiomeric crystals. Several examples of the chromatographic experiments with different classes of compounds were given in two purposes 1) to highlight the possibility of application SDE during column chromatography as the method for enantiopurification of the chiral, non-racemic compounds; 2) to demonstrate that a standard workup (chromatographic purification, evaporation) can alter the stereochemical outcome of asymmetric reactions.
EN
II Group-metals, like magnesium, are one of the most widespread elements in the environment. The abundance of II-group metals in the Earth’s crust is over 108 times greater than the precious metals. For the industrial applications, the important factors are the low costs of production and higher accessibility of their compounds. This puts the spotlight on alkaline-earth metals competing with transition elements as catalysts in organic synthesis. Features of their derivatives, like mild Lewis acidity and strong Brønsted basicity enabled them to catalyze reactions where Lewis-acidactivation of the substrate is essential. In this review the emphasis was put on magnesium-catalyzed pericyclic reactions, which are recognized as one of the most important methods of new carbon-carbon or carbon-heteroatom bonds formation. Using the catalysts based on II-group metal cations and chiral ligands, a highly stereoselective conversion of achiral substrates into enantioenriched products is possible. The Mg-based catalysts have been used in Diels-Alder, ene and 1,3-dipolar additions. Described synthesis methods were characterized by high efficiency (chemical yields and enantiomeric excesses). Where applicable, the relationships between the structure of catalyst/substrates, conditions and efficiency were discussed. Just now there are a few applications, for example in synthesis of alkaloid (–)-manzacidine or antibiotic of algal origin – (–)-malyngolide.
EN
We document an upper upper Albian (Mortoniceras rostratum Zone) cephalopod assemblage from Clansayes (Drôme, south-eastern France). Although fossils are rare in local exposures and in the single sampled level, a decade of intensive fossil collecting yielded 290 ammonite and 5 nautilid specimens. In total, we describe 1 species of nautilid and 24 species (within 17 genera) of ammonites, including 13 heteromorphs. Only two of these ammonite taxa were previously recorded from the upper upper Albian at Clansayes, which demonstrates the value of this fauna with regard to taxonomy, palaeobiology and palaeobiogeography. Based on morphological and biometric analyses performed on an extensive material (104 specimens), we discriminate two species for the heteromorphic ammonite genus Mariella Nowak, 1916 within the Mortoniceras rostratum Zone. In addition, we investigate shell chirality patterns in Mariella from the late Albian of southern France. Upon comparison of the Clansayes material with older material from the immediately underlying upper Albian Mortoniceras fallax Zone at the neighbouring Salazac locality, we identify an increase in the proportion of sinistral specimens. This observed increase in the frequency of sinistral Mariella specimens may hypothetically be part of a global evolutionary pattern, considering that nearly all documented younger Cenomanian Mariella (and more generally Cenomanian turrilitids) are sinistral.
EN
Macrocyclic complexes continue to attract considerable attention due to their significance in biological systems, catalysis, medical diagnostics and other fields. While the most intensively studied macrocycles containing donor nitrogen atoms are tetraazamacrocycles such as porphyrins or cyclen derivatives, larger macrocyclic ligands containing up to 18 (or even more) donor atoms are also known. Due to their enlarged size, these macrocycles can bind large metal ions such as lanthanide(III) ions or bind multiple metal ions. In this review a subclass of large macrocycles will be discussed i.e. macrocyclic amines and imines that can be generated in the condensation of diamines with dicarbonyl compounds, in particular with 2,6-diformylpyridine or 2,6-diformylphenols. These macrocycles of various sizes lead to a rich variety of structures of metal complexes, including polynuclear complexes. Moreover, macrocycles derived from enantiopure trans-1,2- diaminocylohexane form chiral metal complexes that exhibit unusual effects such as helicity inversion, enantioselective self-recognition or enantiodiscrimination of organic guest molecules.
EN
Reactions involving carbonyl groups are one of the most important transformations in organic chemistry. The nucleophilic properties of carbonyl compounds, when they are in the form of enolate ions, offer many possibilities for creating new carbon-carbon bonds in reactions with electrophiles. In the case of cyclic ketones, enolate formation can be stereocontrolled by deprotonation with the use of chiral lithium amides. Stereoselective formation of the chiral lithium enolate determines the stereochemistry of the product of the subsequent reaction with the electrophile. The induction of chirality in the reaction of enolate ions with electrophiles can also be achieved by using metals other than lithium, i.e. magnesium. When other alkali metals are used, an organometallic catalyst containing a chiral ligand must be present in the reaction. The presence of particular structural elements allow distinguishing the chiral lithium amides between eight major classes. Due to the high reactivity of lithium enolates, they are often converted into the silyl enol ether. This is done in two ways: internal quench (in situ reaction with TMSCl) or external quench. Due to aggregation of the chiral lithium amides and, thus, a decrease in asymmetric induction, the addition of LiCl is necessary for reactions run in external quench conditions. Although there are known examples of the use of chiral lithium amides in a catalytic amount in the deprotonation of epoxides, there is only one example of using less than stoichiometric amounts of chiral lithium amides in the deprotonation of ketones. There are many reports in the literature on the use of chiral lithium amides in total syntheses. The chiral lithium amides were used to form chiral enol silyl ether intermediates, e.g. in synthesis of chlortetaine or (+)-ibogamine. They are also used to form chiral lithium enolates which reacts directly with electrophiles, e.g. in synthesis of lasonolide A.
EN
Over the last 20 years asymmetric aminocatalysis has emerged as highly useful and reliable method of asymmetric synthesis. It involves the use of primary or secondary amines as catalysts of various stereoselective transformations of carbonyl substrates. Owing to the diverse activation strategies available in asymmetric aminocatalysis, it became a method of choice when the functionalization of prochiral aldehydes and ketones is considered. As a consequence, a direct and straightforward access to various chiral building blocks is possible that is of relevance to modern stereocontrolled organic synthesis. In the manuscript, the development of various aminocatalytic activation concepts is described and recent, selected contributions to this field of chemistry discussed. Main advantages of these strategies are highlighted providing an overview of this fascinating area of research.
EN
Two-dimensional deformations induced by electric field in twisted nematic cells filled with liquid crystal possessing flexoelectric properties were simulated numerically. The influence of chiral dopants on the occurrence and structure of the spatially periodic patterns was investigated. It was found that the chirality influences mainly the direction of the periodic patterns whereas the threshold voltage for deformation and the width of the stripes are weakly affected
PL
Dwuwymiarowe deformacje indukowane polem elektrycznym w warstwach ciekłych kryształów nematycznych posiadających właściwości fleksoelektryczne były symulowane numerycznie. Zbadano wpływ chiralnych domieszek na strukturę tych odkształceń i ich rozwój pod wpływem pola elektrycznego. Stwierdzono, że chiralność wpływa głównie na kierunek odkształceń, podczas gdy napięcie progowe na odkształcenie i przestrzenny okres odkształceń słabo zależą od chiralności nematyka. Stwierdzono, że chiralność wpływa głównie na kierunek odkształceń, podczas gdy jej wpływ na napięcie progowe i na przestrzenny okres odkształceń jest nieznaczny.
EN
An enantiopure trans-1,2-diaminocyclohexane is one of the most widely used chiral diamines in modern organic chemistry. This chiral building block, readily available from waste industrial products, emerges as a major figure in the field of asymmetric synthesis. The unique structural and conformational properties of trans-1,2-diaminocyclohexane make it very useful for the development of new synthetic strategies, taking advantage of its geometrical pre-organization. In this short article, we will highlight the utility of enantiomerically pure trans-1,2-diaminocyclohexane derivatives as broad-range chiral reagents and ligands for catalytic cycles. A brief overview of the aspects of applications in the field of molecular recognition will also be given.
EN
Cinchona alkaloids comprising quinine, quinidine, cinchonidine and cinchonine as the major members constitute a unique class of quinoline alkaloids with tremendous impact on human civilization (Section 1). The odyssey of Cinchona alkaloids began with the discovery of their antimalarial properties followed by antiarrhytmic action of quinidine. Currently medicinal chemistry of Cinchona alkaloids derivatives develops rapidly and many other activities such as cytotoxic, multidrug resistance inhibitory have been demonstrated (Section 5) [5]. Beside medicine Cinchona alkaloids gave also the fundaments of stereochemistry and asymmetric synthesis. An extraordinary catalytic potency of parent and modified Cinchona alkaloids (deserving privileged catalyst classification) include more than 50 types of diverse stereoselective reactions, with few spectacular such as asymmetric dihydroxylation of alkenes or heterogeneous α-ketoesters hydrogenation (Section 3) [3]. Last but not least the portfolio of applications of Cinchona alkaloids includes resolution of racemates by diastereomeric crystallization or by the use of Cinchona- -based chiral stationary phases for ion-exchange enantioselective chromatography and other recognition or sensing systems (Section 4) [166]. Easy transformation of Cinchona alkaloids (for example by click chemistry) into other chiral and modular building blocks together with current pressure on a more intense exploration of sustainable products make cinchona alkaloids of primary importance for modern synthetic, catalytic and medicinal chemistry. The aim of this review which covers over 200 references is to briefly summarize all aspects of Cinchona alkaloid chemistry and biology with the special emphasis on new applications.
10
Content available remote Wpływ chiralności na aktywność biologiczną cieczy jonowych
PL
Przedstawiono syntezę nowych chlorków 1-[(±)-mentoksymetylo]-X-dimetyloamino- pirydyniowych (X=3 lub 4) oraz ich aktywność mikrobiologiczną. Dla otrzymanych racemicznych soli wyznaczono temperatury topnienia, a strukturę soli potwierdzono za pomocą protonowego i węglowego magnetycznego rezonansu jądrowego. Ponadto określono wpływ chiralności cieczy jonowych na ich właściwości przeciwdrobnoustrojowe. Aktywność form optycznie czynnych przewyższa w sile działania nawet stukrotnie aktywność racemicznych odpowiedników.
EN
1-[(±)-Menthoxymethyl]-X-(dimethylamino)pyridinium chlorides (X=3 or 4) were synthetized and studied for microbiol. activity. The resulting salts were analyzed for purity (thin layer chromatog.), content of cationic active substance (titrn.), mp. and chem. structure (NMR). The chirality impact of the ionic liqs. on their antimicrobial activities was obsd. The racemic counterparts were much less effective than the optically active chlorides.
EN
In this part selenuranes (10-Se-4 and 10-Se-5) and perselenuranes 12-Se-6 as well as telluranes 10-Te-4 and pertelluranes 12-Te-6 will be presented. The main goal is to describe recent reports on the synthesis, chemical, physical, spectral and conformational behavior, stereochemistry, stability and biological activity of these compounds. Their occurrence as reaction intermediates will also be shown.
EN
In this part of the review one of the most famous 10-S-4 sulfurane called Martin sulfurane together with sulfuranes 10-S-5 and persulfuranes 12-S-6 will be presented. Martin sulfurane has been well known for a relatively long time but it is still useful in organic synthesis as a dehydrating, coupling and oxidizing agent. Its use in selected substitution reactions will be also described. Next, synthesis and selected properties of sulfuranes 10-S-5, mainly sulfurane oxides, and persulfuranes 12-S-6, will be shown. Besides synthetic methods, the review is focused on the investigations of the stability and isomerization of these types of compounds, which is particularly interesting for persulfuranes, because of the presence of three 3c-4e bonds.
EN
The compounds presented herein are sulfuranes 10-S-3 and 10-S-4 containing hypervalent sulfur atom. They have been known for a relatively long time. Nevertheless, they, and especially 10-S-4 species, are still of great interest due to their unique properties. The review presents recent approaches to the synthesis of these compounds, their selected structural, physical, chemical, stereochemical and electronic properties and their use as reagents and catalysts in several reaction types. The presence of structures of these types as intermediates, which explains selected reaction mechanisms, will also be shown.
EN
The goal of this four-part review is a presentation of the results of recent studies on the properties and chemistry of hypervalent sulfur, selenium and tellurium compounds. The term “hypervalency” has been known since 1969 when Musher used it to describe molecules bearing heteroatoms which formally did not fulfill the octet rule. This violation was explained by the postulate concerning the existence of a 3-center 4-electron bond between a hypervalent heteroatom and two axial electronegative ligands. The bond is the a combination of two ligand orbitals and a pz orbital of a central heteroatom which results in the formation of three molecular orbitals. The distances between the central atom and these two ligands are longer than the length of the typical sp2 bonds, such as equatorial ones. Moreover, the effective electron density is shifted from the central atom towards the axial ligands what results in the fulfillment of the octet rule of this atom. The geometry of this system is trigonal bipyramid (Fig. 2), except from compounds having three 3-center 4-electron (3c-4e) bonds which have tetragonal bipyramid geometry (Fig. 3). The term “geometry” includes positions of ligands and lone electron pairs. The stability of hypervalent compounds is affected by a few factors: electronegativity of ligands, formation of five-membered cyclic structures involving the central atom and the number of electron shells of the central atom. Martin proposed three-symbol notation N-X-L for these structures, which was further modified (Tab. 1). Hypervalent compounds can isomerize according to various mechanisms: Berry pseudorotation (Scheme 1), turnstile rotation (Scheme 2), cuneal inversion (Scheme 3), lever mechanism (Scheme 4), or Bailar twist (Scheme 5). Furthermore, hypervalent structures of 10-X-4 and 10-X-5 type with trigonal bipyramid geometry, C1 or C2 symmetry and at least three different ligands can exist as optically active species (Tab. 2, Fig. 5–7, Scheme 6), especially the "spiro" ones, which are resistant to isomerization. In 1977 Martin and Balthazor proposed extended Cahn-Ingold-Prelog convention for description of the absolute configuration of chiral hypervalent compounds (Fig. 5).
EN
Chirality is of paramount importance in chemistry and life sciences. Electronic circular dichroism (ECD) as well as optical rotation (OR) are fundamental properties of chiral molecules. These chiroptical properties provide rich information about conformation and configuration of the molecules. Although empirical correlations between chiroptical phenomena, mostly ECD, and molecular stereochemistry have existed for some time, the development of new accurate theoretical methods opened new opportunities for correlation of chiroptical properties with structure. Computational chemistry has made an amazing progress during the past two decades, moving this highly specialized discipline into the mainstream, and making a renaissance in chiroptical methods. This short review is meant as an introduction to the modern approach to optical activity of chiral molecules. Some illustrative applications will put the emphasis on practical applications of the theoretical/experimental analysis of complex molecules including highly flexible bistramide C and noncovalently bonded donor-acceptor dyad. The importance of the solvent effect is briefly discussed and a typical methodology is described and its strengths and weak points are commented.
16
Content available remote NMR spectroscopy in studies of new chiral ionic liquids
PL
Przedstawione w pracy chiralne ciecze jonowe [CILs, wzory (I)—(IV)] badano by ocenić możliwość ich zastosowania w roli katalizatorów, reagentów oraz rozpuszczalników w syntezie asymetrycznej, jak również w polimeryzacji stereoselektywnej. Omówiono szczegółowo wykorzystanie spektroskopii NMR do badań nowych CILs. Analizując widma NMR czwartorzędowych soli amoniowych z podstawnikiem (1R,2S,5R)-(–)-mentoksymetylowym zwrócono uwagę na charakterystyczne dwa dublety pochodzące od diasteretopowych protonów grupy metylenowej (układ spinowy AB) znajdującej się między czwartorzędowym atomem azotu i tlenem (rys. 1). W celu precyzyjnego określenia położenia każdego protonu i węgla części mentolowej oraz szczegółowego przypisania rodzaju sygnałów wykonano i omówiono widma dwuwymiarowe 2D NMR (rys. 2). Analiza widm 1H NMR i 13C NMR badanych CILs wykazała przesunięcia sygnałów chemicznych, w stosunku do położenia analogicznych sygnałów grup atomów wodoru (widma 1H NMR) oraz grup atomów węgla (widma 13C NMR) w chlorkach. Uszeregowano zarówno aniony, jak i syntezowane związki (w zależności od rodzaju aminy będącej częścią strukturalną czwartorzędowej soli amoniowej), pod względem zdolności ekranujących.
EN
Chiral ionic liquids (CILs) were discussed as new potential media for enantioselective organic synthesis, including enantioselective polymer synthesis. NMR spectra of new CILs, whose structures are shown in formulas (I)—(IV), were investigated in detail. In the case of 1H NMR analysis of those compounds two characteristic doublets were observed — diasterotopic protons (AB spin system). In order to precisely determine the spectral position of each proton and carbon, but also to attribute in a detailed way the type of their signals, two-dimensional spectra were obtained. Additionally, 1H NMR and 13C NMR spectra indicated notable differences in the chemical shifts depending on the anion used. Comparing the differences between values of the chemical shifts, the anions, but also the quaternary ammonium salts, depending on the amine used, were ordered according to their increasing shielding capacities.
18
Content available remote Kronika
PL
Tytuły profesorskie. Sukces polskich fizyków jądrowych. Nagroda EPS dla fizyków jądrowych. Michio Sorai honorowym profesorem IFJ PAN. Po milionie euro dla młodych naukowców. ERC zaczyna działać. A jednak 118. Z Genewy do Gran Sasso. Międzynarodowa Olimpiada Fizyczna. Wykorzystanie energii słonecznej w Portugalii. Kapitan z Kopenick w fizyce fal grawitacyjnych. Prace Darwina on line. Filantrop łoży na wielkie podziemne laboratorium. Raymond Davis (1914-2006).
PL
Przedstawiono zagadnienia dotyczące wykorzystania w syntezie związków biologicznie aktywnych bicyklicznego węglowodoru monoterpenowego, (+)-3-karenu, taniego i łatwo dostępnego naturalnego surowca, składnika terpentyn pozyskiwanych z niektórych gatunków sosny (w Polsce z Pinus syhestris L.). Bazę substratową w opisanych syntezach stanowiły otrzymane z (+)-3-karenu tlenowe pochodne o ściśle określonej strukturze przestrzennej z zachowanym układem bicyklo[4.1.0]heptanu lub gem-dimetylobicyklo[3.1.0]heksanu i gem-dimetylocykloheksanu. Zaprojektowano i opracowano metody syntezy trzech klas związków biologicznie aktywnych: substancji o właściwościach zapachowych, będących potencjalnymi komponentami w przemyśle kosmetyczno-perfumeryjnym oraz spożywczym, połączeń o aktywności insektycydowej, będących analogami pyretroidów i juwenoidów oraz preparatów posiadających aktywność farmakologiczną, zwłaszcza specyfików o działaniu znieczulającym, kardiotropowym 1 neuromodulatorowym. Łącznie zsyntetyzowano ponad 150 nowych, dotychczas nieopisanych w literaturze związków pośrednich i końcowych, stosując nowoczesne, stereokontrolowane metody syntez oraz rozdziału izomerycznych mieszanin. Otrzymane związki poddano testom biologicznym (sensorycznym, insektycydowym i farmakologicznym). W grupie związków o właściwościach zapachowych szczególnie interesujące okazały się pochodne z zachowanym układem karanu (224-232), związki w układzie 6,6-dimetylobicyklo[3.1.0]heksanu (263-266) oraz pochodne będące cyklicznymi analogami z układem dihydronerylowyn i dihydrogerany-lowym (282-285). W grupie związków o aktywności insektycydowej pochodne będące analogami acyklicznych juwenoidów (300-307) wykazywały aktywność wobec szkodnika bawełny (Disdercus cingulatus). Nowe spirolaktony w układzie karanu (311-317), będące mimetykami naturalnych deterentów pokarmowych owadów okazały się natomiast aktywnymi antyfidantami wobec szkodnika magazynów zbożowych (Trogoderma granarium). Badzo interesującą grupę stanowiły analogi anestetyków lokalnych, leków kardiotropowych i neuromodulatorowych. Najbardziej cennym preparatem okazała się pochodna aminohydroksyiminokaranu (R,S)-332, która wykazała silne działanie miejscowo znieczulające. Hydrolityczny rozdział kinetyczny (HKR) doprowadził do uzyskania pojedynczych diastereoizomerów (R)-332 i (S)-332 o bardzo dużej czystości enancjomerycznej. Dla tych dwóch pochodnych przeprowadzono badania interdyscyplinarne, obejmujące testy farmakologiczne, analizę krystalograficzną oraz modelowania molekularne oddziaływania tych połączeń z błoną fosfolipidową.
EN
Applications of naturally occurring (+)-3-carene for synthesis of biologically active compounds are presented. This bicyclic monoterpene hydrocarbon is an inexpensive, little explored and readily available natural component of turpentine obtained from some species of pine (in Poland from Pinus sylvestris L.) My investigations were focused on three classes of biologically active compounds: (i) odoriferous substances exploited as components in perfume and food industry, (ii) analogues of pyrethroids, juvenoids and feeding deterrents as potent biorational insecticides and (iii) derivatives possessing pharmacological activity as potent local anaesthetic, cardiovascular and neuromodulatory drugs. Oxoderivatives with preserved bicyclo[4.1.0]heptane skeleton, as well as gem-dimethylbicyclo[3.1.0]hexane and gem-dimethylcyclohexane system were chiral substrates in designed and elaborated synthetic methods for these analogues. Finally, over 150 new compounds were synthesized, using novel stereocontrolled methods of synthesis and resolution of isomeric mixtures. All compounds obtained were subjected to biological tests (olfactory, insecticidal and pharmacological). In the group of odoriferous compounds, derivatives with preserved carane skeleton (224-232), 6,6-dimethylbicyclo[3.10]hexane moiety (263-266) and cyclic analogues of dihydroneryl and dihydro-geranyl system (282-285) possessed very interesting and valuable odour characteristics. Analogues of acyclic juvenoids (300-307) were morphogenetically active against pest of cotton (Disdercus cingulatus). New spirolactones with carane backbone (311-317) exhibited good feeding deterrent activity against storage pest insect, khapra beetle (Throgoderma granarium Ev. lervea and adults). Pharmacologically active compounds were the most interesting group. Among all synthesized analogues (318-342), the aminohydroxyiminocarane derivative (R,S)-332 proved to be most valuable. Hydrochloride salt of (R,S)-332 possessed the strongest local anaesthetic activity in corneal infiltration anaesthesia tests. It is very promising that this salt does not evoke any toxicodermal effects and does not induce any allergic reaction in response to topical application. Hydrolytic kinetic resolution (HKR) process led to separate diastereoisomers (R)-332 and (S)-332 with high enantiopurity (over 98% cc). Interdisciplinary investigations including comparative pharmacological tests, X-ray crystallography and phos-pholipid bilayer study by molecular dynamic stimulation were carried out. In summary, (+)-3-carene proved to be valuable and uncommonly useful chiral substrate in synthesis of structurally various compounds with broad spectrum of biological activity. General accessibility of this hydrocarbon, component of many kinds of turpentines including the very cheap sulfate turpentine (0.5 USD per gallon as a waste during cellulose production) creates large technological perspectives for this natural product.
20
EN
Commonly available hydrolytic enyzymes are capuble of recognizing heteroatom stereogenic centres. A review of the application of these enzymes in the preparation of optically active sulfur and phosphorus compounds, based on the results from the authors' Laboratory, is presented.
PL
Powszechnie dostępne enzymy hydrolityczne są w stanie rozpoznać stereogenne centra heteroatmowe. Niniejszy przegląd przedstawia zastosowanie tego typu enzymów w syntezie optycznie czynnych połączeń siarki i fosforu ze szczególnym uwzględnieniem wyników badań pochodzących z Laboratorium autorów.
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