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    Wyświetlanie 1-15 z 15
    Tytuł:
    Study of the Thermoluminescence of CVD Diamond
    Autorzy:
    Karczmarska, A.
    Mitura-Nowak, M.
    Nowak, T.
    Marszałek, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1490194.pdf
    Data publikacji:
    2012-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.10.Bk
    81.05.ug
    78.60.Kn
    Opis:
    This work reports some thermoluminescent properties of chemical vapour deposition diamond film grown by 5 kW microwave assisted plasma chemical vapour deposition. The 2" diamond sample with the thickness of 32 μm was exposed to gamma radiation in the dose range 0.6-55 Gy. The thermoluminescent glow curve of diamond sample displayed a peak with the maximum centered at 240°C. The linearity of the detector response in the range of 10-55 Gy was observed. The bleaching effect, seen as fading of the thermoluminescent signal when the device was exposed to light in the visible range, was also noticed. Two-dimensional dose distribution was measured using 2D thermoluminescent reader equipped with a sensitive 640 × 480 pixels charge coupled device camera. The surface morphology of the diamond film was observed with scanning electron microscope and atomic force microscope. The grain size was estimated as about 15 μm. The Raman spectroscopy was used to characterize phase purity. The width and position of the diamond Raman band around 1332 $cm^{-1}$ indicated that the coating is crystalline and of good quality. It is concluded that good quality chemical vapour deposition diamond coating could be promising material for thermoluminescent dosimetry.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 2; 510-513
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Antyoksydacyjne właściwości i przeciwmiażdżycowe działanie paraoksonazy 1
    Antioxidant and antiatherosclerotic properties of paraoxonase 1
    Autorzy:
    Kupczyk, D.
    Karczmarska-Wódzka, A.
    Studzińska, R.
    Sikora, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/172751.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    paraoksonaza 1
    stres oksydacyjny
    miażdżyca
    paraoxonase 1
    oxidative stress
    atherosclerosis
    Opis:
    This overview will discuss the Paraoxonase 1 (PON1) in arteriosclerosis diseases. Atherosclerosis is one of lifestyle diseases and affects greater number of people. Ischemic heart disease, acute coronary syndromes or stroke are the clinical symptoms of atherosclerosis and are the most common cause of morbidity especially in middle and old age people. In atherosclerosis, in the space between the endothelium and the muscular layer in the wall of a blood vessel, accumulates deposits consisting of macrophages, lipoprotein, low density foam cells and extracellular concentrations of cholesterol. In this way fatty streaks are formed which are early stage atherosclerotic lesions. With the passage of time they are joined by elements of fibrous connective tissue that undergo hypertrophy. They begin to surround primarily created the fireplace of inflammation and separate them from the rest of the blood vessel [1]. Further research if needed to better understanding the mechanisms related to atherosclerosis development and plaque instability because it may have important clinical implications for the identification of high-risk patients. The present review tries to summarize the current knowledge on the role of PON1 in the formation of atherosclerotic plaque is the goal of current research [2].
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 1-2; 3-36
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Asymetryczne przeniesienie wodoru do ketonów katalizowane związkami Rutenu(II) i Rodu(III)
    Asymmetric transfer hydrogenation of ketones catalyzed by Ruthenium(II) and Rhodium(III) complexes
    Autorzy:
    Karczmarska-Wódzka, A.
    Kołodziejska, R.
    Studzińska, R.
    Wróblewski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172550.pdf
    Data publikacji:
    2012
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    transfer wodoru asymetryczny
    związki kompleksowe Ru(II) i Rh(III)
    chiralne ligandy
    prochiralne związki karbonylowe
    asymmetric transfer hydrogenation
    Ru(II) and Rh(III) complexes
    chiral ligands
    prochiral carbonyl compounds
    Opis:
    Asymmetric hydrogen transfer (ATH) is one of the methods of stereoselective reduction of prochiral carbonyl compounds (Scheme 6). Complexes of the platinum group metals (Noyori catalysts) are the most common catalysts for AT H reactions. The specific structure of the Noyori catalyst allows to activate two hydrogen atoms. These atoms are transferred from donor to acceptor in the form of hydride ion and proton (Scheme 1). Depending on the used catalyst the transfer hydrogenation of ketons can proceed by direct and indirect transfer mechanism. The direct hydride transfer from a donor to an acceptor proceeds via a six-membered transition state (3) (Scheme 2). The indirect hydride transfer proceeds through the formation of an intermediate metal hydride. A monohydride (HLnMH) and or a dihydride (LnMH2) can be formed depending on the catalyst that is used (Scheme 3). In the monohydride route, the reduction proceeds in the inner sphere of the metal (four-membered transition state (4)) or in the outer sphere of the metal (six-membered transition state (5)) (Scheme 4). The proposed reduction of carbonyl compounds in the AT H reaction by Noyori catalysts uses the mechanism of the hydride ion and proton transfer from the donor to the catalyst and the formation of the monohydride. In the indirect transfer hydrogenation the hydride ion and proton are transferred from the monohydride to the acceptor (Scheme 5, 7). AT H reactions that lead to chiral alcohols are conducted in organic solvents or in water. Hydrogen donors most often used in organic solvent reactions are propan-2-ol or an azeotropic mixture of formic acid and triethylamine (Tab. 1, 6). Sodium formate is usually used as hydrogen donor in the reactions conducted in water. Yield and enantioselectivity of the reaction depend on many factors the most important of which are: the structure of a substrate, hydrogen donor and solvent that were used, the reaction time, substrate concentration, and the S/C ratio [2]. In the case of asymmetric reduction conducted in water the solvent pH is also of great importance [3, 7, 8]. An optimal pH range depends on the type of a catalyst [7, 8]. AT H reactions conducted in water are distinguished by a shorter reaction time and higher enantioselectivity than the reactions conducted in organic solvents. In addition, catalysts used in the AT H reactions are more stable in water allowing reuse of the catalyst without loss of its activity. This paper presented examples of the use of specific catalysts in asymmetric reactions of hydrogen transfer. In particular, I drew attention to the reactions running in the aquatic environment due to the above-mentioned advantages of this solvent. The authors focused specifically on bifunctional catalysts based on Ru(II) and Rh(III) on the account of wide usage of the catalysts of that type in AT H reactions in water and their good performance [8, 9, 15, 16, 17, 19, 20, 21, 22]. p-Cymene is the most common aromatic ligand in catalysts based on Ru(II) while in the case of catalysts with Rh(III) the most common is anionic pentamethylcyclopentadienyl ligand. In both cases the second most common ligands are diamines or amino alcohols (Scheme 8). There are better performance and enantioselectivity when diamines are used as ligands. Attempts to replace diamines and amino alcohols by Schiff bases (Scheme 13) in the catalysts containing Rh(III) proved poor results due to a very low enantioselectivity of conducted reactions (Tab. 7).
    Źródło:
    Wiadomości Chemiczne; 2012, 66, 3-4; 273-295
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Rozdzielenie mieszanin racemicznych za pomocą krystalizacji. Część 2, Rozdzielenie racematów z utworzeniem diastereoizomerycznych soli
    Separation of the racemic mixtures by crystallization. Part 2, Resolution by formation of diastereomeric salts
    Autorzy:
    Kołodziejska, R.
    Studzińska, R.
    Kopkowska, E.
    Karczmarska-Wódzka, A.
    Augustyńska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/171666.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    krystalizacja
    mieszanina racemiczna
    rozdzielenie racemicznych amin
    rozdzielenie racemicznych kwasów
    diastereoizomeryczne sole
    crystallization
    racemic mixture
    resolution of racemic mixture
    resolution of rac-amines
    resolution of rac-acids
    diastereoisomeric salts
    Opis:
    The enantioseparation of a racemate through diastereomeric salt formation with a resolving agent is one of the most attractive methods for obtaining an enantiopure compound, with advantages such as its simplicity in operation, recyclability of the chiral source, and applicability on an industrial scale. In this method the enantiomers are converted into a diastereomeric salt pair by reaction with a single enantiomer of resolving agent. The diastereomers are then separated by crystallization taking advantage of the different solubility of the two compounds [1–3]. The formation of diastereomers, to be separated afterward, usually consists of salt formation with a resolving agent of opposite acide-base character (Scheme 1, 9). In this process, the molecules of opposite character (amine and acid) recognize each other by various interactions on the basis of their molecular structures and functional groups [3]. Using this method can be obtained a series of enantiomerically pure amines (Scheme 2–8) [4–26] and acids (Scheme 10–17) [27–41] which may be valuable substrates for asymmetric synthesis. The conditions for enantioseparation play an important role. On the efficiency of the enantioseparation has an effect the resolving agent, nature of the solvent or just its dielectric constant and the character and amount of some supplementary additives.
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 1-2; 89-110
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prolina : pospolity aminokwas wyjątkowy katalizator. Część IV, Reakcja Michaela
    Proline as a common amino acid and an exceptional catalyst. Part IV, Michael reaction
    Autorzy:
    Karczmarska-Wódzka, A.
    Studzińska, R.
    Kołodziejska, R.
    Wróblewski, M.
    Dramiński, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/171840.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    prolina
    reakcja Michaela
    synteza asymetryczna
    proline
    Michael reaction
    asymmetric synthesis
    Opis:
    In recent years there has been a dynamic development of asymmetric synthesis. Groups of researchers, particularly the one led by Benjamin List and Carlos Barbas, carried out a number of reactions and showed the effectiveness of the use of small organic molecules such as proline as catalysts. Michael addition catalyzed with proline is a particularly interesting reaction because it can be carried out in two aminocatalytic pathways. The analysis of Michael reaction reveals potential for both forms of aminocatalysis: enamine and iminium catalysis (Scheme 1) [1–14]. Presumably Michael reaction proceeds mainly according to enamine mechanism. The use of proline in Michael reaction with imine activated acceptor is slightly effective. So far the researches have shown that the modification of proline molecule or addition of other catalyst is necessary for condensation to appear. Enamine catalysis concerns the activation of carbonyl compound in situ being a donor. There is no need for enolase anion to be created earlier [2, 15–17]. When, as a result of the reaction of a,b-unsaturated carbonyl compound with proline, Michael acceptor activation appears it means that it is enamine mechanism reaction (Scheme 1) [2, 24]. One of the first examples of direct Michael reaction proceeding through enamine transition state is the reaction of cyclopentanone with nitrostyrene (Scheme 6) [20–23]. Other examples of Michael addition of ketone with nitro olefin catalysed by proline are shown in table 2 and 3 [10, 23, 30]. Nitroketones obtained in that way are useful as precursors for different organic compounds [33], also pyrrolidines [34]. Pyrrolidines are pharmacologically active and they selectively block presynaptic dopamine receptors [34] (Scheme 7). Except for Michael intermolecular reaction, intramolecular condensation adducts were also obtained. Michael intramolecular proline-catalyzed condensation in which inactive ketones transform into α,β-unsaturated carbonyl compounds was described (Scheme 9) [35, 36]. These reactions require a stoichiometric amount of a catalyst and a long time of reaction and they give as a result a little enantiomeric excess [11, 24, 35]. In 1991, Yamaguchi and co-workers carried out malonates Michael addition to α, β-unsaturated aldehydes catalyzed by L-proline [24, 39]. The reaction proceeded according to enamine mechanism, for example dimethyl malonate was reacted with hex- 2-enal in the presence of proline to give Michael adduct in 44% yield. To improve the yield an attempt of a slight modification of a proline molecule was made transforming it into proper salt. Proline lithium salt enabled to obtain the condensation product in 93% yield (Tab. 4). Regardless of a used catalyst the products in the form of racemates were obtained. In order to improve enantioselective properties of a catalyst, Michael addition of diisopropyl malonate to cycloheptenone was carried out in chloroform in the presence of different proline salts. Optimal enantioselectivity and yield was obtained by using rubidium salt (Tab. 5–7) [40, 41]. Rubidium prolinate-catalyzed Michael additions are used in industry e.g. for enantioselective synthesis of the selective serotonine reuptake inhibitior (SSRI) (–)-paroxetine (antidepressant) (Scheme 12) [24].
    Źródło:
    Wiadomości Chemiczne; 2014, 68, 1-2; 49-65
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prolina : pospolity aminokwas wyjątkowy katalizator. Część III, Reakcja Mannicha
    Proline as a common amino acid and an exceptional catalyst. Part III, Mannich reaction
    Autorzy:
    Studzińska, R.
    Karczmarska-Wódzka, A.
    Wróblewski, M.
    Kołodziejska, R.
    Dramiński, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172649.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    prolina
    reakcja Mannicha
    synteza asymetryczna
    proline
    Mannich reaction
    asymmetric synthesis
    Opis:
    Mannich reaction occuring among ketone, aldehyde, and amine is one of the ways of a synthesis of biologically active compounds. Reactions of this type were carried out in the presence of different catalysts [3–10], however in recent years a lot of attention has been paid to enantioselective Mannich reaction catalyzed with proline. Such reactions were carried out with the use of different compounds containing carbonyl group and the most frequently used amine was p-anisidine. The advantage of the use of p-anisidine is a possibility of conducting the direct Mannich reaction (Scheme 3). In this way β-amino ketones (Tab. 1, 2, 4) [15, 18–20, 23, 24], α-hydroxy-β-amino ketones (Tab. 3) [15, 22], and β-amino alcohols (Tab. 5, 6) [25, 26] were obtained. A possibility of syntheses of β-amino sugars and α-amino acids with their derivatives (Tab. 7) [28, 29] is worth noticing. In a great number of described reactions, the products were obtained with satisfactory yield and enantiomeric excess. Taking into consideration the difficulty of a removal of p-hydroxyphenyl group which protects amine group in the resulting products, the attempts of using different amine compounds in Mannich reactions catalyzed with proline were undertaken. The use of amines blocked by tert-butoxycarbonyl group (Boc) enabled to obtain the products with high yield and ee values (Tab. 12–15) [35–38]. However in the case of the use of Boc the reaction must be carried out in an indirect way (it is necessary to prepare imine blocked by Boc earlier).
    Źródło:
    Wiadomości Chemiczne; 2014, 68, 1-2; 21-48
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prolina – pospolity aminokwas wyjątkowy katalizator. Część II, Międzycząsteczkowa kondensacja aldolowa
    Proline as a common amino acid and an exceptional catalyst. Part II, Intermolecular aldol reaction
    Autorzy:
    Kołodziejska, R.
    Wróblewski, M.
    Karczmarska-Wódzka, A.
    Studzińska, R.
    Dramiński, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/171560.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    międzycząsteczkowa reakcja aldolowa donor
    akceptor
    prolina
    anti-aldole
    intermolecular aldol reaction
    donor
    acceptor
    proline
    anti-aldol
    Opis:
    Proline in organic synthesis is used as a small molecular organocatalyst. In a catalytic act proline, similarly to an enzyme, activates reagents, stabilizes transition state and influences an orientation of substrates [1–12]. Proline works as aldolase I (so called microaldolase I). In comparison with other amino acids it shows exceptional nucleophilicity which makes imines and enamines formation easier. In the intermolecular aldol reaction proline was used for the first time by List and co-workers (Scheme 1) [3, 9, 20]. Since then an immense progress has been observed in this field. Several aldolization reactions were performed in the presence of proline. Reactions of this type proceed between the donor (nucleophile) and the acceptor (electrophile). In aldol reaction the donors can be both ketones and aldehydes which next are condensed with ketones and aldehydes acting as electrophiles (Scheme 2–18; Tab. 1–7) [21–72]. The presence of proline ensures not only high yield of homo- and heteroaldolization but mainly enables conducting enantio- and diastereoselective synthesis. Intermolecular proline-catalyzed aldol condensation proceeds according to enamine mechanism. Anti-aldols, which make a valuable source of intermediates in the synthesis of important biologically active compounds, are mainly obtained in this reaction [35–44, 54, 58, 62, 63, 68, 69, 71].
    Źródło:
    Wiadomości Chemiczne; 2013, 67, 11-12; 1027-1050
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prolina – pospolity aminokwas wyjątkowy katalizator. Część I, Biosynteza proliny. Wewnątrzcząsteczkowa kondensacja aldolowa
    Proline as a common amino acid and an exceptional catalyst. Part I, Proline biosynthesis. Intramolecular aldol reaction
    Autorzy:
    Wróblewski, M.
    Kołodziejska, R.
    Studzińska, R.
    Karczmarska-Wódzka, A.
    Dramiński, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172473.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    biosynteza proliny
    mechanizm kondensacji aldolowej
    wewnątrzcząsteczkowa reakcja aldolowa
    proline biosynthesis
    mechanism of aldol reaction
    intramolecular aldol reaction
    Opis:
    In asymmetric synthesis of organic compounds more effective solutions are being looked for which will result in higher yield(s) of product(s) and their high enantioselectivity [1]. One of such solutions is an use of a multilevel and cheap catalyst. Proline used as a catalyst is a substance of natural origin which was synthetically obtained by Willstätter who was carrying out research on hygric acid (Scheme 1) [10]. The cells of many organisms have a suitable enzymatic system essential for proline biosynthesis [15]. So far, three proline biosynthesis pathways have been described: from glutamate (Scheme 3 and 4), ornithine (Scheme 5 and 6), and arginine (Scheme 7) [16–28]. Proline which is obtained as a result of biosynthesis or supplementation is a substrate for many proteins. Characteristic and significant content (about 23%) of this amino acid was observed in collage. In cells proline can play an important role of osmoregulator [31–35] – a protective substance regulating the activity of such enzymes as catalase and peroxidase [36]. Proline as a secondary amine shows exceptional nucleophilicity facilitating imine and enamine formation. Used as a catalyst in aldol reaction makes with substrates like imine or enamine transition state imitating the activity of naturally occurring enzymes for this type of reaction, that is aldolases. In their research Hajos and Parrish, and Eder, Sauer and Wiechert used proline in intramolecular aldol reaction obtaining proper enones (Scheme 9) [60–62]. The process of intramolecular aldol reaction was used for a separation of racemic mixture of diketones (Scheme 10) [63, 64], cyclization of ortho-substituted aromatic aldehydes and ketones (Scheme 11) [65], synthesis of cyclic diketones (Scheme 13) [68] and domino reaction to obtain substituted cyclohexanones from beta-diketones and unsaturated ketones (Scheme 14) [69].
    Źródło:
    Wiadomości Chemiczne; 2013, 67, 9-10; 801-818
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Rozdzielenie mieszanin racemicznych za pomocą krystalizacji. Część 1, Optymalizacja warunków rozdziału
    Separation of the racemic mixtures by crystallization. Part 1, Optymlization of resolution conditions
    Autorzy:
    Kołodziejska, R.
    Kopkowska, E.
    Studzińska, R.
    Karczmarska-Wódzka, A.
    Augustyńska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/172764.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    krystalizacja
    mieszanina racemiczna
    rozdzielenie mieszaniny racemicznej
    diastereoizomeryczne sole
    diastereoizomeryczne kompleksy
    crystallization
    racemic mixture
    resolution of racemic mixture
    diastereoisomeric salts
    diastereoisomeric complexes
    Opis:
    Methods for obtaining optically active compounds in enantiopure form are commonly classified into three categories: utilization of chiral pool starting materials (stereoselective multistep synthesis), creation of chirality from achiral precursors (asymmetric synthesis) and separation of racemates into their enantiomer constituents (crystallization, chromatography on chiral phases, kinetic resolution). The most important method for the separation of enantiomers is the crystallization. The crystallization can be carried out in the variants: direct crystallization of enantiomer mixtures (homo- and heterochiral aggregates – Scheme 2, 3) and separation of diastereoisomer mixtures (classical resolution) (Scheme 1) [1–5]. The most widely used method for the separation of enantiomers rests on the crystallization of diastereoisomers formed from a racemate and an enantiopure reagent – resolving agent (resolution via salt-formation and complex-formation). The pair of diastereoisomers exhibit different physicochemical properties (e.g., solubility, melting point, boiling point, adsorbtion, phase distribution). For this reason, the crystalline material can be separated from the residue by filtration (Scheme 22) [4, 27], distillation (Scheme 23, 24) [28, 29], sublimation (Scheme 25) [4, 30], or extraction (Scheme 26) [2, 31]. The composition of crystalline diastereoisomers is influenced by resolving agent (structure (Scheme 4) [4] and amount of resolving agent (Scheme 5) [4]), structure of racemates (Scheme 10) [2, 15], the character and amount of supplementary additives (Scheme 6–9) [4, 12–15], nature of the solvent (crystallization with solvent) – Scheme 11–18 [2, 4, 16–23] and time of crystaillzation (Scheme 19–21) [4, 14, 25, 26].
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 1-2; 65-88
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Enancjoselektywna enzymatyczna desymetryzacja katalizowana lipazami. Część 1, Związki prochiralne
    Enantioselectve enzymatic desymmetrization catalyzed in the presence of lipase. Part 1, Prochiral compounds
    Autorzy:
    Kołodziejska, R.
    Karczmarska-Wódzka, A.
    Tafelska-Kaczmarek, A.
    Studzińska, R.
    Dramiński, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/171684.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    związki prochiralne
    desymetryzacja
    transestryfikacja
    hydroliza
    lipazy
    prochiral compounds
    desymmetrization
    transesterification
    hydrolysis
    lipase
    Opis:
    In the enzymatic asymmetric synthesis, the enzyme allows the desymmetrization of achiral compounds resulting in chiral compounds of high optical purity. Therefore, this type of biotransformation is known as enantioselective enzymatic desymmetrization (EED) [1–11]. This method is related to the generation of an asymmetry (loss of symmetry elements) in prochiral molecules (most often an sp3 or sp2 hybridized carbon atom), in meso synthones, and centrosymmetric compounds. An achiral center of the tetrahedral system is defined as a prochiral one if it becomes chiral as a result of one of the two substituents replacement which, when separated from the particles, are indistinguishable (Scheme 1, 2) [1–4, 9, 12]. Asymmetric synthesis is enantioselective when one of the enantiotopic groups or faces of an optically inactive compound is biotransformed faster than the other (Scheme 3–5) [1, 10, 11, 13–15]. Lipases are enzymes of highest importance in stereoselective organic synthesis, mainly due to their exceptionally broad substrate tolerance, stability, activity in unphysiological systems, and relatively low price [9, 14]. The mechanism of enzymatic hydrolysis catalysed by hydrolases is similar to that observed in the chemical hydrolysis with the use of base. The selectivity of enzymatic catalysis depends on the substrate orientation in the enzyme active site (Scheme 6, 7) [25–29]. Lipases were successfully used for the desymmetrization of different prochiral diesters, alcohols and amines. Most lipases preferentially convert the same prochiral groups in the above mentioned types of reaction. This allows the preparation of the both enantiomers of the product in high chemical and optical yield (Scheme 9–13) [9, 13, 32–56].
    Źródło:
    Wiadomości Chemiczne; 2013, 67, 7-8; 751-772
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Enancjoselektywna enzymatyczna desymetryzacja katalizowana lipazami. Część II, Optymalizacja warunków reakcji. Związki mezo
    Enantioselectve enzymatic desymmetrization catalyzed in the presence of lipase. Part II, Optymalization of reaction conditions. Meso compounds
    Autorzy:
    Karczmarska-Wódzka, A.
    Kołodziejska, R.
    Tafelska-Kaczmarek, A.
    Przybyła, T.
    Dramiński, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172192.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    związki mezo
    desymetryzacja
    transestryfikacja
    hydroliza
    lipaza
    meso compounds
    desymmetrization
    transesterification
    hydrolysis
    lipase
    Opis:
    In the enzymatic asymmetric synthesis, the enzyme allows the desymmetrization of achiral compounds resulting in chiral compounds of high optical purity. Meso compounds (bearing a plane of symmetry) are very important group of compounds used in EEDs (Scheme 1) [1–4]. Similarly to prochiral compounds, selective acylation or hydrolysis of meso substrates leads to optically active products. Most lipases preferentially convert the same enantiomers in the above mentioned types of reaction. This allows the preparation of the both enantiomers of the product in high chemical and optical yield (Scheme 3–20) [35–58]. An effective enzymatic catalysis should be performed under conditions optimal for a biocatalyst performance. Hence, it is essential to select an appropriate reaction medium, the pH, and temperature [6–34]. Optimization of the reaction conditions in terms of an appropriate solvent selection is effective and most frequently the simplest way to modify the enzyme selectivity. One of the most important criteria for the solvent selection is its nature [25]. The enzyme selectivity is conditioned by its conformational rigidity, which increases in more hydrophobic medium (typical hydrophobic solvents, scCO2). A hydrophobic solvent decreases biocatalyst lability, which does not allow the connection between the structurally mismatched substrate and the active side of an enzyme [10, 26–31]. Ionic liquids are a separate group of solvents which, despite their high hydrophobicity (logP << 0) and polarity, can constitute an ideal medium for the biotransformation reactions [18–23].
    Źródło:
    Wiadomości Chemiczne; 2013, 67, 9-10; 819-841
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Enancjoselektywna enzymatyczna desymetryzacja katalizowana oksydoreduktazami. Dehydrogenazy w reakcji redukcji. Część I
    Enantioselective enzymatic desymmetrization catalyzed by oxidoreductases. Dehydrogenases in reduction reactions. Part I
    Autorzy:
    Kołodziejska, R.
    Karczmarska-Wódzka, A.
    Tafelska-Kaczmarek, A.
    Studzińska, R.
    Wróblewski, M.
    Augustyńska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/171686.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    redukcja asymetryczna
    dehydrogenaza alkoholowa
    kofaktor
    asymmetric reduction
    alcohol dehydrogenase
    cofactor
    Opis:
    Enzymes act as biocatalysts whether are also mediating in all anabolic and catabolic pathways, playing an extremely important role in the cells of all life forms. Catalytic potential of oxidoreductases is most commonly used in reduction reactions. Dehydrogenases and reductases catalyze the reversible desymmetrization reactions of meso and prochiral carbonyl compounds and alkenes. The oxidoreductase- catalyzed reactions require cofactors to initiate catalysis. In most cases, it is nicotinamide adenine dinucleotide (NADH) or its phosphorylated derivative (NADPH), which acts as a hydride donor. The necessity of employing expensive cofactors was, for the long time, one of the main limitations to the use of dehydrogenases. This problem was solved by developing a regeneration system of a cofactor in the reaction environment. Various systems are used for the cofactor recycling. In the case of a carbonyl compound reduction, an irreversible oxidation of formic acid to carbon dioxide is most frequently used. In this paper, selected examples of whole-cell and isolated enzymes applications in the carbonyl compound reduction are discussed. The application of baker’s yeast, microorganisms and dehydrogenases in enantioselective enzymatic desymmetrization (EED) of prochiral ketones leads to a broad spectrum of chiral alcohols used as intermediates in the syntheses of many pharmaceuticals and compounds presenting a potential biological activity.
    Źródło:
    Wiadomości Chemiczne; 2014, 68, 9-10; 763-782
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Enancjoselektywna enzymatyczna desymetryzacja katalizowana oksydoreduktazami. Reakcje redukcji. Część 2
    Enantioselective enzymatic desymmetrization catalyzed by oxidoreductases. Reduction reactions. Part 2
    Autorzy:
    Kołodziejska, R.
    Karczmarska-Wódzka, A.
    Tafelska-Kaczmarek, A.
    Studzińska, R.
    Wróblewski, M.
    Augustyńska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/171910.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Opis:
    Biotransformation reactions of many organic compounds under the influence of enzymes take place with the high selectivity, rarely achieved by other methods. Ketoesters represent an extensive group of selectively bioreduced compounds. Chiral hydroxyesters and, subsequently, hydroxyacids are valuable intermediates in the syntheses of various biologically active compounds. Acyclic α- and β-ketoesters are transformed to the corresponding (R)- and (S)-hydroxyesters by using a specific dehydrogenases. The whole-cells enzymes, e.g. baker’s yeast, may exhibit a different catalytic activity depending on the substrate structure. Baker’s yeast enzymes selectively reduce the cyclic β-ketoesters providing mainly anti diastereomers due to the lack of rotation around the single α,β carbon-carbon bond. The enzymatic reduction of the esters, cyclopentanone, and cyclohexanone derivatives gave the optically active anti-alcohol enantiomers. The reductive EED of prochiral α-ketoesters, as well as β-ketoesters is an interesting transformation in organic chemistry due to the importance of the resulting chiral α-hydroxy acids and their derivatives used as building blocks. Baker’s yeast-catalyzed reduction of alkyl esters derived from pyruvate and benzoylformate allows the preparation of the (R)-alcohols. Polyketones can also be subjected to the reductive EED to give different compounds bearing the quaternary stereogenic centers which are broadly applied in asymmetric synthesis. In asymmetric synthesis, similarly to carbon-oxygen double bonds, carbon-carbon double bonds of prochiral alkanes can be reduced to obtain the optically active saturated compounds. The reduction of alkenes is catalyzed by both, the whole cells (microorganisms, plant cells) as well as isolated enzymes belonging to the oxydoreductases, so-called ene-reductases. The whole-cell catalysts are suitable, most frequently, for the preparative scale syntheses, but they are less chemoselective in comparison to the isolated reductases. In the case of polyfunctionalized alkenes, microorganisms can cause the additional side reaction reducing the desired product yield.
    Źródło:
    Wiadomości Chemiczne; 2014, 68, 11-12; 1009-1030
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Enancjoselektywna enzymatyczna desymetryzacja katalizowana oksydoreduktazami. Reakcje utleniania. Część 2
    Enantioselective enzymatic desymmetrization catalyzed by oxidoreductases. Oxidation reactions. Part 2
    Autorzy:
    Karczmarska-Wódzka, A.
    Kołodziejska, R.
    Tafelska-Kaczmarek, A.
    Studzińska, R.
    Wróblewski, M.
    Augustyńska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/172457.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    dioksygenaza
    oksydaza
    peroksydaza
    reakcja utleniania
    dioxygenase
    oxidase
    peroxidase
    oxidation reaction
    Opis:
    In continuation of our work, we herein describe next enzyme classes applied for oxidation reaction. Dioxygenases, oxidases, and peroxidases are successfully used in the synthesis of desymmetrization products with high yields and enantiomeric excesses. Aromatic dioxygenases, such as toluene dioxygenase (TDO), naphthalene dioxygenase (NDO), and biphenyl dioxygenase (BPDO) found in the prokaryotic microorganisms are enzymes belonging to the dioxygenase class and are the most commonly used in organic synthesis. The α-oxidation of various fatty acids in the presence of an α-oxidase from germinating peas is one of the few examples of oxidases application in asymmetric organic synthesis. The intermediary α-hydroxyperoxyacids can undergo two competing reactions: decarboxylation of the corresponding aldehydes or reduction to the (R)-2-hydroxy acids. In order to eliminate the competitive decarboxylation reaction tin(II) chloride is used as an in situ reducing agent. Peroxidases are the redox enzymes found in various sources such as animals, plants, and microorganisms. Due to the fact that, in contrast to monooxygenases, no additional cofactors are required, peroxidases are highly attractive for the preparative biotransformation. Oxidation reactions catalyzed by (halo)peroxydases are also often used in organic synthesis. N-Oxidation of amines, for instance, leads to the formation of the corresponding aliphatic N-oxides, aromatic nitro-, or nitrosocompounds. From a preparative synthesis standpoint, however, sulfoxidation of thioether is important since it was proven to proceed in a highly stereo- and enantioselective manner. Furthermore, depending on the source of haloperoxidase, chiral sulfoxides of opposite configurations can be obtained.
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 1-2; 53-64
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Enancjoselektywna enzymatyczna desymetryzacja katalizowana oksydoreduktazami. Reakcje utleniania. Część 1
    Enantioselective enzymatic desymmetrization catalyzed by oxidoreductases. Oxidation reactions. Part 1
    Autorzy:
    Karczmarska-Wódzka, A.
    Kołodziejska, R.
    Tafelska-Kaczmarek, A.
    Studzińska, R.
    Wróblewski, M.
    Augustyńska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/172799.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    dehydrogenaza
    monooksygenaza
    reakcja utleniania
    dehydrogenase
    monooxygenase
    oxidation reaction
    Opis:
    The main advantage of biotransformation involving enzymes, compared to chemical processes, is a highly selective formation of products with precise configuration. Herein we describe enzymes participating in the oxidation processes, especially dehydrogenases and monooxygenases. Dehydrogenases are not only able to catalyze the enantioselective reduction of prochiral ketones, but they can also desymmetrize meso and prochiral diols through the enantioselective oxidation. As a result of this processes, optically active hydroxyketones, hydroxycarboxylic acids, and their derivatives are obtained. Cytochrome P450 monooxygenases (CYPs) constitute a family of heme-containing enzymes which exhibits a variety of catalytic activities. They catalyze different reactions, such as hydroxylation, epoxidation, oxidative deamination, or N- and (S)-oxidation. In the oxidation reaction with monooxygenases, the whole cells are commonly used as catalysts. The use of monooxygenases in the oxidation reaction of prochiral alkanes provides the optically active alcohols. It is very significant that these transformations are still difficult to carry out by chemical methods. Baeyer-Villiger monooxygenases (BVMO EC 1.14.13.X) effectively catalyze the nucleophilic and electrophilic oxidation reactions of various functional groups. BVMO are highly regio- and stereoselective enzymes, and their catalytic potential is used in the synthesis of optically pure lactones and esters. Keywords:
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 1-2; 35-51
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-15 z 15

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