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Reakcje asymetrycznego otwierania pierścienia azyrydyn

Prusinowska N.

Wiadomości Chemiczne

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2013

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[Z] 67, 5-6

585--618

EN

Aziridines, the nitrogenous analogues of epoxides, are useful building blocks for the synthesis of various functional materials and biologically active compounds. The reactivity of aziridines toward ring opening and expansion is dependent upon their extremely strained ring structures. Among the procedures of ring opening of aziridines, a nucleophilic ring-opening reaction is one of the major routes to highly functionalized compounds (Scheme 2). This short review focused on essentiac asymmetric ring opening reactions of aziridines including enantioselective ring opening of meso-aziridines and kinetic resolution of racemic aziridines with various hetero and carbon nucleophiles towards the synthesis of highly enantiomerically enriched 1,2-difunctionalized fine chemicals.

2

Enancjoselektywna enzymatyczna desymetryzacja katalizowana lipazami. Część 1, Związki prochiralne

Kołodziejska R., Karczmarska-Wódzka A., Tafelska-Kaczmarek A., Studzińska R., Dramiński M.

Wiadomości Chemiczne

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2013

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[Z] 67, 7-8

751--772

EN

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].

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Enancjoselektywna enzymatyczna desymetryzacja katalizowana lipazami. Część II, Optymalizacja warunków reakcji. Związki mezo

Karczmarska-Wódzka A., Kołodziejska R., Tafelska-Kaczmarek A., Przybyła T., Dramiński M.

Wiadomości Chemiczne

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2013

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[Z] 67, 9-10

819--841

EN

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].

4

Wpływ nieliniowego sumowania wpływów na kształt profilu niecki obniżeniowej opisywanej przez deterministyczny model górotworu zbudowany na podstawie teorii automatów komórkowych

Sikora P.

Przegląd Górniczy

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2013

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T. 69, nr 8

195--199

PL

Obserwacje geodezyjne skutków podziemnej eksploatacji złóż pokładowych wskazują, że pomierzone kształty profili pełnych niecek obniżeniowych charakteryzują się licznymi odstępstwami od kształtu profili teoretycznych uzyskiwanych teoriami geometryczno-całkowymi z zastosowaniem zasady liniowej superpozycji wpływów. Są to m.in. zależność nachylenia profilu niecki od kierunku frontu eksploatacyjnego, wpływ grubości i krotności eksploatacji na stosunek maksymalnego nachylenia profilu do maksymalnego obniżenia itp. W pracy przedstawiono sposób opisu tych efektów za pomocą modelu górotworu zbudowanego na podstawie deterministycznego automatu komórkowego. Opisana metoda, polega na uzależnieniu funkcji przejścia od doznanego uprzednio nachylenia w danej komórce automatu. Metoda nawiązuje do prac J. Litwiniszyna dotyczących opisu niecki obniżeniowej przy zastosowaniu ośrodka stochastycznego.

EN

Geodetic observations of underground mining effects show that the measured shapes of profiles of complete subsidence troughs are different from the shapes of theoretical profiles obtained on the basis of geometrical-integral theories, including the principle of linear superposition of mining effects. There are, among others, the following differences: relation between the inclination of the trough’s profile and the direction of exploitation, influence of the thickness and summation of exploitation on the ratio of maximum inclination of the profile to maximum subsidence, etc. This paper presents the method of description of these effects which was developed on the basis of cellular automata model of rock mass. The method consists in the interlocking of the passing function from the already experienced inclination in the particular automata cell. This method refers to the works of J. Litwiniszyn which describe a subsidence trough in the stochastic environment.