Intramolecular thermal stepwise [2 + 2] cycloadditions: investigation of a stereoselective synthesis of [n.2.0]-bicyclolactones

YesFused cyclobutanes are found in a range of natural products and formation of these motifs in a straightforward and easy manner represents an interesting synthetic challenge. To this end we investigated an intramolecular variant of the thermal enamine [2 + 2] cyclisation, developing a diastereoselective intramolecular enamine [2 + 2] cyclisation furnishing δ lactone and lactam fused cyclobutenes in good yield and excellent diastereoselectivity.The work was funded by Yorkshire Cancer Researc

Facile Synthesis of 2-Aminocyclobutenylphosphonates

The addition of various amines to diethyl 4-chlorobut-1-yn-1-ylphosphonate produced novel biologically potent substituted diethyl 2-aminocyclobut-1-en-1-ylphosphonates in 70–83% isolated yield. This regioselective reaction was carried out at room temperature in the absence of solvent and catalyst

Control Quality of Welded Joints by Scanning Contact Potentiometry Method

Conducted evaluation of technical state of welded joints, welding the collectors of the primary loop to the body of the sample of steam generator PGV 1000, located in Resource center National Research Nuclear University MEPhI at "AEM-Technologies" Atommash factory in Volgodonsk. The results of point-by-point scan shows that SLS 1000 µv and above, for almost all samples detected multiple superficial imperfections caused by the presence of certain rust spots and traces of a deep spot corrosion, and the presence of small nicks, scratches and other imperfections

The Use Haloperoxidases in Organic Synthesis: Selected Reactions of Oxidation, Epoxydation and Sulfoxidation

Haloperoxidases are ubiquitous metalloenzymes that catalyse a variety of enantioselective oxygen-transfer reactions with hydrogen peroxide or alkylperoxides. Haloperoxidases are enzymes which catalyze the reaction of oxidation, epoxidation and sulfoxidation by hydrogen peroxide. These enzymes usually contain the FeHeme moiety or vanadium as an essential constituent at their active site, however, a few haloperoxidases which lack a metal cofactor are known. This review will examine the reactivity of the different haloperoxidases, particularly the mechanism of oxidation by hydrogen peroxide, and the mechanism of oxidation and sulfoxidation, including the newly reported regioselectivity and enantioselectivity of the haloperoxidases. The structure of chloroperoxidase, the vanadium active site and the role of critical amino acid side chains for catalysis and functional biomimetic systems, with specific relevance to the mechanism of the haloperoxidase enzymes. Advances have recently been made in using them to prepare, under controlled conditions, chiral organic molecules that are valuable for the synthesis of a wide range of useful compounds. The application of biocatalytic methods in asymmetric organic synthesis is of great interest as an alternative to chemical procedures employing chiral auxiliaries. Asymmetric oxidation of prochiral sulfides to yield optically active sulfoxides has been performed by many different techniques yielding varying enantiomeric excess values. Oxygenated metabolites are compounds that are commonly found in nature and they are produced by many different organisms. The oxygen atom is incorporated into organic compounds by enzyme-catalyzed reactions with oxygen ions as the oxygen source. For over 40 years haloperoxidases were thought to be responsible for the incorporation of mainly halogen atoms into organic molecules. However, haloperoxidases lack substrate specificity and regioselectivity, and the connection of haloperoxidases with the in vivo formation of oxygenated as well as halometabolites has been demonstrated. Recently, molecular genetic investigations showed that, at least in bacteria, fungi, and other organisms a different class of halogenases is involved in halo- and oxygenated metabolite formation. These halogenases were found to require FADH2, which can be produced from FAD and NADH by unspecific flavin reductases. The FADH2-dependent halogenases and haloperoxidases show substrate specificity and regioselectivity, and their genes have been detected in many halometabolite-producing organisms, suggesting that this type of halogenating enzymes constitutes the major source for halo- and oxygenated metabolite formation in bacteria and also in other organisms. Distribution of haloperoxidases in nature also is demonstrated in this brief review

Cyclobutane-Containing Alkaloids: Origin, Synthesis, and Biological Activities

Present review describes research on novel natural cyclobutane-containing alkaloids isolated from terrestrial and marine species. More than 60 biological active compounds have been confirmed to have antimicrobial, antibacterial, antitumor, and other activities. The structures, synthesis, origins, and biological activities of a selection of cyclobutane-containing alkaloids are reviewed. With the computer program PASS some additional biological activities are also predicted, which point toward new possible applications of these compounds. This review emphasizes the role of cyclobutane-containing alkaloids as an important source of leads for drug discovery

The freshwater Sponge Ephydatia Fluviatilis harbours diverse pseudomonas species (Gammaproteobacteria, Pseudomonadales) with broad-spectrum antimicrobial activity

Bacteria are believed to play an important role in the fitness and biochemistry of sponges (Porifera). Pseudomonas species (Gammaproteobacteria, Pseudomonadales) are capable of colonizing a broad range of eukaryotic hosts, but knowledge of their diversity and function in freshwater invertebrates is rudimentary. We assessed the diversity, structure and antimicrobial activities of Pseudomonas spp. in the freshwater sponge Ephydatia fluviatilis. Polymerase Chain Reaction - Denaturing Gradient Gel Electrophoresis (PCR-DGGE) fingerprints of the global regulator gene gacA revealed distinct structures between sponge-associated and free-living Pseudomonas communities, unveiling previously unsuspected diversity of these assemblages in freshwater. Community structures varied across E. fluviatilis specimens, yet specific gacA phylotypes could be detected by PCR-DGGE in almost all sponge individuals sampled over two consecutive years. By means of whole-genome fingerprinting, 39 distinct genotypes were found within 90 fluorescent Pseudomonas isolates retrieved from E. fluviatilis. High frequency of in vitro antibacterial (49%), antiprotozoan (35%) and anti-oomycetal (32%) activities was found among these isolates, contrasting less-pronounced basidiomycetal (17%) and ascomycetal (8%) antagonism. Culture extracts of highly predation-resistant isolates rapidly caused complete immobility or lysis of cells of the protozoan Colpoda steinii. Isolates tentatively identified as P. jessenii, P. protegens and P. oryzihabitans showed conspicuous inhibitory traits and correspondence with dominant sponge-associated phylotypes registered by cultivation-independent analysis. Our findings suggest that E. fluviatilis hosts both transient and persistent Pseudomonas symbionts displaying antimicrobial activities of potential ecological and biotechnological value.European Regional Development Fund (ERDF) through the COMPETE (Operational Competitiveness Programme); national funds through FCT (Foundation for Science and Technology) [PEst-C/MAR/LA0015/2011]; FCT-funded project [PTDC/BIA-MIC/3865/2012]; Federation of European Microbiological Societies (FEMS)info:eu-repo/semantics/publishedVersio

Boranes in Organic Chemistry 2. ОІ-Aminoalkyl- and ОІ-Sulfanylalkylboranes in Organic Synthesis

Problems on using of ОІ-aminoalkyl- and ОІ-sulfanylalkylboranes in organic synthesis are considered in this review. The synthesis of boron containing a-aminoacids by Curtius rearrangement draws attention. The use of ОІ-aminoalkylboranes available by enamine hydroboration are described. Examples of enamine desamination with the formation of alkenes, aminoalcohols and their transformations into allylic alcohol are presented. These conversions have been carried out on steroids and nitrogen containing heterocyclic compounds. The dihydroboration of N-vinyl-carbamate and N-vinyl-urea have been described. Examples using nitrogen and oxygen containing boron derivatives for introduction of boron functions were presented. The route to borylhydrazones by hydroboration of enehydrazones was envisaged. The possibility of trialkylamine hydroboration was shown on indole alkaloids and 11-azatricyclo-[6.2.11,802,7]2,4,6,9-undecatetraene examples. The synthesis of ОІ-sulfanyl-alkylboranes by various routes was described. The synthesis of boronic thioaminoacids was carried out by free radical thiilation of dialkyl-vinylboronates. Ethoxyacetylene has been shown smoothly added 1-ethylthioboracyclopentane. Derivatives of 1,4-thiaborinane were readily obtained by divinylboronate hydroboration. Dialkylvinylboronates react with mercaptoethanol with the formation of 1,5,2-oxathioborepane derivatives. Stereochemistry of thiavinyl esters hydroboration leading to stereoisomeric ОІ-sulfanylalkylboranes are discussed. Examples of radical thiilation of various structural types vinylboronates were presented. In particular, 1,3,2-dioxaborinanes and 1,3,2-dioxaborolanes, containing by boron atom vinyl-, propenyl-, isopropenylor isopropylidene substituents have been used. Thiilation has been achieved by use of alkylmercaptanes, as well as mercaptamine derivatives. Alkylmercaptanes were able to replace the bromine substituent in tris-(2-bromoctyl)-borane.  Dialkylvinylborates have been added hydrosulfite with the formation of 2-boronoethane sulfuric acids. A lot of examples of radical thiilation of vinylboronic acid dialkyl esters with mercaptoacids are presented. Under the azaisobutyric acid dinitryle conditions thioglycolic, ОІ-mercaptopropionic, 2-mercaptoamberic acids and their esters as well as cysteine were added. Vinyl-, propenyl- and isopropenyldioxaborolanes were also participated in the thiilation with the formation of acetic, propionic or amberic acid thioethanoboronates. The high reactivity of B,B,B-trivinyl-N,N,N-triphenylborazine in the reaction with thiophenol, leading to B-tris-(phenylmercaptoethyl)-N-phenylborazine was shown. The problems of asymmetric hydroboration leading to chiral ОІ-sulfanylalkylboranes were discussed briefly. In particular, an example, including dihydro-thiophene hydroboration, leading to (+)-R-thiofan-3-yl-diisopinocamphenylborane, and the interaction with acetaldehyde with the formation of (+)-R-3-thiophanyl-diethoxyborane was implemented. The reaction with 3,4-dihydrothiapyrane proceeds analogously. A synthetic route to sulfono-norbornen-boronic acid esters by Diels-Alder reaction of cyclopentadiene with arylsulfanyl-vinylboronic acid esters has been discussed

Boranes in Organic Chemistry 3. О±-, ОІ- and Оі-Haloalkylboranes: The Perspective Vehicles for Organic Synthesis

The methods of synthesis of α− and β−haloalkylboranes, including chloration of alkylboronic acid esters, additive bromation and chloration of esters of vinyl- and alkenylboronic acids, addition of bromine to trivinylborazines have been considered. The reactions of radical addition of polyhaloidmethanes to vinylboranes, α− and β−unsaturated boronic esters, B-vinyl-B-arylboronic esters, B-trivinyl-B-triarylborazines were discussed. The hydroboration of acetylenic halogenides of dicycloalkylboranes, which led to halocontaining derivatives of dialkylvinylborane was separately considered. The examples of hydroboration of halogenides of allyl and vinyl types are presented.The reaction of dienic synthesis, which takes place between vinylchloroboranes or vinylboronic esters and tetra- or hexachlorocyclopentadienes has been discussed. The reaction of alkenes and allenes with boron tribromide was described. The Markovnikov and non- Markovnikov hydrobromation of boron vinylderivatives has been envisaged. The approaches to the synthesis of perfluoroalkylboranes on the base of hydroboration of perfluoroalkenes have been discussed. The methods of the synthesis of boronates, containing halogetaryl substituents, have been performed. The reactions of hydroboration of halogenides of allylic and propargylic types by 9-borabicyclononane have been shown. The regio- and stereoselectivity of the reaction has been discussed. The examples of the synthesis of boranes of the norbornene type were presented. The reaction of boroallylilation of allyl- and propargylhalogenides leading to the derivatives of 3-bora-bicyclo[3,3,1]-nonane has been discussed. Some directions of using of haloidalkylboranes in the synthesis have been discussed. The examples of nucleophilic substitution leading to oxyalkyl- and azidoalkylboranes have been presented. The route of obtaining of alcohols from α−haloidalkylboranes has been shown. The general scheme of synthesis of α−aminoboronic acids was perfomed. The general approach to the synthesis of allenes on the base of hydroboration products of propargyl halogenides has been discussed. The schemes of synthesis of 1,4-disubstituted-1,2,3-butatrienes are presented. The wide using reaction of introducing of vinylic group into substituent, bonding with boron atom in molecules of dialkylvinylboranes, was discussed. The reactions of new C-C bonds formation, based on the action of iodine on the  alkylvinylboronates leading to 1,3-dienes and alkylidencyclanes have been shown. Τhe route of the synthesis of cyclopropanes from β−haloidalkylboranes has been discussed