Wyniki wyszukiwania - Biblioteka Nauki

1

Synthesis of a series of vicinal diamines with potential biological activity

100%

Kurteva V. , Lyapova M.

Open Chemistry

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2004

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tom 2

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nr 4

686-695

EN

A broad range of vicinal diamines based on styrene oxide are synthesisedvia mixtures of regioisomeric amino alcohols. The ring opening of the intermediate aziridinium ions by primary amines proceeds with high regioselectivity, leading to the target diamines as single regioisomers for all reaction series. The compounds are of potential biological interest as ligands for cisplatin analogues. Anticancer activity tests of both groups of compounds are in progress.

2

RuO4-mediated oxidation of N-benzylated tertiary amines. 3. Behavior of 1,4-dibenzylpiperazine and its oxygenated derivatives

100%

Petride H. , Drăghici C. , Florea C. , Petride A.

Open Chemistry

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2006

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tom 4

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nr 4

674-694

EN

1,4-Dibenzylpiperazine (1),-2-piperazinone (7),-2,6-piperazinedione (9), and 1-benzoyl-4-benzylpiperazine (30) were oxidized by RuO4 (generated in situ) by attack at their endocyclic and exocyclic (i.e., benzylic) aminic N-α-C-H bonds to afford various oxygenated derivatives, including acyclic diformamides, benzaldehyde, and benzoic acid. The reaction outcome was complicated by (i) the hydrolysis of diformamides, occurred during the work-up, and (ii) the reaction of benzaldehyde with the hydrolysis-derived amines giving imidazolidines and/or Schiff bases. Benzoic acid resulted from benzaldehyde only. Compounds 7, 30, and 1-benzylpiperazine, but not 9, were transiently formed during the oxidation of 1. In the same reaction conditions, 1,4-dibenzyl-2,3-(or 2,5)-piperazinedione, 1,4-dibenzyl-2,3,6-piperazinetrione, 4-benzyol-1-benzyl-2-piperazinone, and 1,4-dibenzoylpiperazine were inert. The proposed oxidation mechanism involves the formation of endocyclic and exocyclic iminium cations, as well as of cyclic enamines. The latter intermediates probably result by base-induced deprotonation of the iminium cations, provided an N +−β-proton is available. In the case of 1, the cations were trapped with NaCN as the corresponding α-aminonitriles. The statistically corrected regioselectivity (endocyclic/exocyclic) of the RuO4-induced oxidation reaction of 1, 7, and 30 was 1.2–1.3.

3

RuO4-mediated oxidation ofN-benzylated tertiary amines. Are amineN-oxides and iminium cations reaction intermediates?

100%

Petride H. , Drãghici C. , Florea C. , Petride A.

Open Chemistry

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2004

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tom 2

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nr 2

302-322

EN

N-Benzylmorpholine,-piperidine, and-pyrrolidine (1A-C, resp.) are oxidised by RuO4 (generatedin situ) at both endocyclic and exocyclic (benzylic)N-α-methylene positions to afford lactams (and dioxo-derivatives) and benzaldehyde (and benzoyl derivatives), respectively. TheN-oxides of1A-C, formed by a minor side reaction, are not involved as intermediates. Control experiments showed the transient formation of endo- and exocyclic iminium cations trapped with NaCN as the corresponding nitriles. The proposed course of the RuO4-mediated oxidation of1A-C involves the consecutive steps1⇒iminium cations+cyclic enamine⇒oxidation products. The endocyclic/exocyclic regioselectivity of the oxidation reaction lies between 0.8 (for1A) and 2.1 (for1B). The amine cation radical and theN-α-C· carbon-centered radical seem not to be involved.

4

Chiral Counterion Strategy in Cu-Catalyzed Asymmetric Allylic Oxidation of Linear Alkenes

86%

Incerti-Pradillos C. A. , Hudson D. , Malkov A. V.

Asymmetric Catalysis

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2015

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tom 2

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nr 1

EN

Application of a chiral counter-ion strategy in the Kharasch-Sosnovsky reaction is reported. Copper(I) phosphates obtained from axially chiral, BINOL-derived phosphoric acids were investigated as catalysts in the enantioselective allylic oxidation of acyclic alkenes. Good yields and high regioselectivity towards branched allylic ester have been achieved. The chiral phosphates investigated exhibited modest enantioselectivities.

5

Enzymatyczne utlenianie typu Baeyera-Villgera

72%

Kołek T. , Świzdor A. , Panek A.

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2009

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tom [Z] 63, 9-10

819-845

EN

Baeyer-Villiger (BV) reaction is oxidation of ketones, leading to cleavage of one of the C-CO-C bonds with simultaneous insertion of an oxygen atom into the cleaved bond. Resulting products obtained from cyclic ketones are lactones, while esters are obtained from acyclic ketones. Numerous strains of microorganisms produce enzymes catalyzing BV oxidation. These enzymes participate in the processes of degradation of natural and synthetic ketones, which can be used by the microorganisms as carbon source (Scheme 3 and 4). The enzymes are monooxygenases (Baeyer-Villigerases, BVMOs), usually containing flavinoadenine nucleotide and cooperating with NAD(P)H reductases. Research on the role of BV oxidation in degradation processes has evolved into intensive studies on the mechanism of this reaction and its use in synthesis, especially after isolation (in 1976) of cyclohexane monooxygenase from Acinetobacter sp. NCIB9871(CHMOAcineto 1) [9]. Subsequently, further strains were identified which produced BVMOs catalyzing oxidation of ketones of diverse structures. In addition to the best-characterized cyclohexane monooxygenase, there are: cyclopentanone, phenylacetone, cyclododecanone, aliphatic ketone and 2-oxo-3-en-4,5,5-trimethyl-cyclopentenylacetic acid monooxygenases. The adjective characterizing a given BVMO is derived from the ketone constituting carbon source, or from the ketone which is oxidized with the highest yield. In addition to these ketones, the enzymes accept their various structural analogues, therefore it is possible to select a biocatalyst which carries out oxidation of a given substrate. Among BVMOs, particularly selective are the enzymes carrying out BV oxidation of steroidal ketones: these enzymes operate only on steroid substrates, mostly containing 3-oxo--4-en moiety, but also they exhibit regioselectivity as well - the oxidation of ketones takes place only at C-17. During the regioselective enzymatic oxidation, "atypical" lactones [2, 4], which are not produced in chemical BV oxidation processes, are sometimes formed. Products of stereoselective enzymatic reactions are optically pure lactones and esters, which are starting points for further asymmetric synthesis of biologically active compounds, including medicines. The application of genetic engineering allows obtaining recombinant microbial strains, which are non-pathogenic and produce larger amounts of the enzyme than the wild-type strains. The recombinants are also able to produce mutated BVMOs exhibiting higher selectivity and/or lifetime, as well as activity towards different spectrum of substrates than the parent enzymes [2]. However, reaction yields of transformations carried out by the recombinants are still not significantly better than the results obtained with the wild-type strains. The recombinants usually require an expensive reagent, isopropyl-? --D-tiogalactopyranoside (ITPG), to induce their BVMOs [23]. Enzymatic BV oxidation, due to the selectivity of the enzymatic action, is competitive to the chemical oxidation. The enzyme selectivity allows for using pure products, including enantiopure compounds, with high yield. The process is environmentally friendly, because the oxidizer in the enzymatic BV reaction is molecular oxygen, and the amount of byproducts is limited. Synthetic application of BVMOs is limited by three principal factors: isolation of the enzyme in amounts suitable for large-scale applications, decrease in the enzymatic activity in the presence of the substrate and/or the product, and the isolation of the product. Separation of the unreacted enantiomer of the substrate in the process of kinetic separation of the racemic mixture, or separation of regioisomeric lactones are costly and time-consuming operations. Another possible problem is the fact that some strains producing useful BVMOs are pathogenic. Therefore, multidirectional research efforts are devoted to overcome the aforementioned barriers with the goal of establishing economically viable methods of biotransformations [4].

6

Peri- i regioselektywność cykloprzyłączenia nitroetenu do Z-C-antranilo-N-arylonitronów w świetle teorii FMO

72%

Pawlik H. , Jasiński R. , Barański A.

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2008

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tom R. 105, z. 1-Ch

93-99

PL

Na podstawie danych obliczeń AM1 przedyskutowano charakter pierwotnych efektów orbitalnych cykloprzyłączenia Z-C-antranilo-N-arylonitronów do nitroetenu. Ustalono, że efekty te powinny sprzyjać konwersji reagentów wg mechanizmu [2+4] cykloaddycji.

EN

Using data of AM1 calculations we carried out discussion about character of FMO interaction in cycloadditions of Z-C-anthranil-N-arylonitrones to nitroethene. In all cases that effects should favored conversion of reagents in [2+4] mechanism of cycloaddition.

7

Regionoselektywność [2+3] cykloaddycji nitroetenu z Z-C,N-diarylonitronami w świetle teorii FMO

72%

Jasiński R. , Mikulska M. , Pawlik H. , Barański A.

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2008

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tom R. 105, z. 2-M

121-127

PL

Na podstawie danych obliczeń kwantowochemicznych przeprowadzono analizę pierwotnych efektów orbitalnych oraz coulombowskich w reakcjach [2+3] cykloaddycji diarylonitronów z nitroetenem. Ustalono, że efekty te generalnie sprzyjają powstawaniu odpowiednich 4-nitroizoksazolidyn.

EN

Using quantum-chemical calculations we have carried out an analysis of frontier molecular orbital interactions in the [2+3] cycloaddition reactions of nitroethene with diarylnitrones. In all cases the primary orbital effects and coulombic interactions favored the corresponding 4-nitroisoxazolidines.