1,720,960 research outputs found
Enzymatic Resolution of cis-Dimethyl-1-acetylpiperidine-2,3-dicarboxylate for the Preparation of a Moxifloxacin Building Block
Full text linkThis work presents the enantioselective resolution of a water-soluble racemic mixture of cis-dimethyl 1-acetylpiperidine-2,3-dicarboxylate catalyzed by Candida antarctica lipase B. The separation of the carboxylic acid product in its (2R,3S) configuration from non-reacted substrate in the (2S,3R) configuration was easily obtained by organic phase extraction. The latter molecule can be used as an enantiomerically pure precursor in the synthesis of (4aS,7aS)-octahydro-1H-pyrrolo[3,4-b]pyridine, an expensive building block in the production of the antibiotic Moxifloxacin. On the other hand, the hydrolyzed product in the (2R,3S) configuration can be used for the preparation of a neuromediator analogue. The lipase demonstrated enantioselectivity towards the (2R,3S) substrate enantiomer and regioselectivity towards the ester in position 3 of the molecule. Studies of hydrolysis kinetics and the use of the immobilized enzyme were performed to evaluate its industrial application
Cooperativity in benzotriazole-amine complexes: allosteric tuning of molecular recognition interfaces
No full textBenzotriazole forms with amines stable complexes that in some cases separate spontaneously as crystals from solutions of polar organic solvents. The stoichiometries and the binding constants of these complexes have been determined by 1H NMR analysis in deuterochloroform. The quantitative analysis of the equilibria involved in thecomplexation process sheds light on the behaviour of benzotriazoles in solutions and gives an estimate of the influence of allosteric effects when multiple interactions are present
Process for the preparation of testosterone
No full textThe present invention relates to an industrial process for the reduction of 4-androstene-3,17-dione in order to obtain testosterone using a particularly stable and selective enzyme produced in a recombinant manner
BIOCATALYZED SYNTHESIS OF TESTOSTERONE
No full textWe have recently developed and submitted for a patent a new industrial process for the production of testosterone making use of biocatalysis. In particular, a non commercial enzyme was proposed to overcome a critical steps in the organic synthesis of the hormone: the regio- and stereo-specific conversion of 4-androstene-3,17-dione to testosterone. Design of the process was based on a strategy starting with the identification of the enzyme by crossed bioinformatics and literature screening: the chosen candidate was the 17P-hydrosteroid dehydrogenase type 5 from mouse. The coding sequence for the enzyme was cloned in a vector suitable for its expression, in fusion with an His-tag, in E.coli. Small scale preparations of the recombinant enzyme were initially set up and activity tests on the desired substrate were performed, using the co-factor NADPH or NADH. The small scale purifications allowed verification of the product obtained in terms of regio- and stereo-selectivity and yield, evaluation of thermal stability of the enzyme, kinetic analysis of the reaction and choice of an adequate partial organic mixture to work with. A protocol for purification of the enzyme from medium scale cultures was then drawn and performed. The amount of enzyme obtained from these preparations, in combination with the commercially available D-glucose dehydrogenase required for the recycling of the cofactor NADH, allowed the conversion of milligrams of androstendione. Conditions for higher scale synthesis of testosterone are going to be developed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Process for the preparation of (R)-beta-angelica lactone from alpha-angelica lactone employing ene-reductases
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Synthesis of (4aS, 7aS)-octahydro-1H-pyrrolo [3,4-b] pyridine
No full textThe present invention relates to the stereoselective synthesis of (4aS,7aS)-octahydro-1H-pyrrolo[3,4-b]pyridine, as well as the conversion thereof, to give Moxifloxacin. Particularly, the present invention relates to a method for the synthesis of (4aS,7aS)-octahydro-1H-pyrrolo[3,4-b]pyridine of formula (I) comprising: (a) the optical resolution by enzymatic hydrolysis of the intermediate dialkyl-1-alkylcarbonylpiperidine-2,3-dicarboxylate racemate of formula (II) to give, following isolation, the intermediate dialkyl-(2S,3R)-1-alkylcarbonyl-piperidine-2,3-dicarboxylate of formula (III) in which AIk is a straight or branched C1-C5 alkyl group; (b) the conversion of the intermediate (III) to (4aR,7aS)-1-alkylcarbonylhexahydrofuro[3,4-b]pyridine-5,7-dione of formula (IV) in which AIk has the meanings set forth above; (c) the conversion of the intermediate (IV) to (4aS,7as)-octahydro-1H-pyrrolo[3,4-b]pyridine of formula (I) with an optical purity above 99%
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