2,297 research outputs found
Asymmetric reduction by transition metals complexes and biocatalysts
No full textIn the last years the importance of α- and -amnimoacids is increased since these molecules are interesting synthons for the preparation of unnatural peptides and bioactive compounds, in particular antibiotics or anticancer.
They can be easily obtained in optically pure form by reduction using metal catalyzed asymmetric hydrogenation1(chemocatalysis) or by enzyme mediated reduction2 (biocatalysis). In particular with the biocatalytical approach we used whole cells of different microorganisms endowed with enantioselective dehydrogenases, in chemocatalysis we used essentially Ir(I) and Ru(II) complexes of different atropoisomeric diphosphines.
In both cases our research efforts let us to obtain chiral enriched unnatural aminoacids by reduction of prochiral ketones3 and by reduction of tetra substituted double bonds4, which are generally very low active. Our research will show that the process robustness and stereochemical outcome is strongly dependent on thermodynamic parameters but also on the presence of additives.
We will discuss in detail nature and function of such compounds and we will demonstrate that it is possible to combine metal enantioselective reduction with stereoselective biocatalytic one.
1. E. Cesarotti; I. Rimoldi, P. Spalluto, F. Demartin Tetrahedron Asymmetry. 2007, 18, 1278-1283.
2. R. Gandolfi, E. Cesarotti, F. Molinari; D. Romano; I. Rimoldi Tetrahedron Asymmetry. 2009, 20, 411-414.
3. I. Rimoldi, E. Cesarotti, D. Zerla, F. Molinari, D. Albanese, R. Gandolfi submitted
4. R. Gandolfi, E. Cesarotti, D. Zerla, F. Molinari, I. Rimoldi submitte
Gandolfi, Silvana
No full textA brief description of the main characteristics of the works for children of the Italian author Silvana Gandolfi, the themes she privileges, her way of portraying children, the influence of Oriental culture and philosophy upon her writing
Enzymatic synthesis of (S)-1,2-O-isopropylidene glycerol
No full textThis invention relates to a process for the synthesis of (S)-1,2-O-isopropylidene glycerol by hydrolysis of a racemic mixture of (R,S)-1,2-O-isopropylidene glycerol acetate catalysed by Kluyveromyces marxianus, recovery of unreacted (R)-1,2-O-isopropylidene glycerol acetate, and hydrolysis thereo
Phases of Cost Cutting: Downsizing is Dead; Long Live the Downsizing Phenomenon
No full textThis downsizing research article presents a phase typology of job cutting which includes three distinct phases and three levels of argument. Conceptually, the paper draws heavily upon the seminal work of Littler and Gandolfi (2008) seeking to expand and update their 2008 Academy of Management (AOM) Conference paper. The paper culminates with a contemporary discussion of current downsizing practices showcasing that the strategy of downsizing has remained a popular restructuring method on a global scale.downsizing; cost cutting; phase; strategy.
Solid state fermentation for the production of lipolytic fungal enzymes
No full textThe production of lypolitic moulds in solid state fermentation was studied.
Aspergillus oryzae and Rhizopus oryzae were grown on rice hulls using different
media. Tween 80 and olive oil were employed as main carbon sources; the whole
solid cultures were lyophilised and employed in heptane for catalysing the
formation of various geranyl esters with molar conversions ranging from 40 to
95%, under optimised conditions, starting from 50 mM geraniol and equimolar
amount of the acid
Resolution of (R,S)-2-phenylpropanoic acid by enantioselective esterification with dry microbial cells in organic solvent
No full textThe microbial direct esterification of racemic 2-phenyl-1-propanoic acid with ethanol by lyophilized mycelium of Aspergillus oryzae MIM and Rhizopus oryzae CBS 112.07 in organic solvents has been investigated. Dry cells of Rhizopus oryzae CBS 112.07 gave the (R)-ethyl ester with high enantiomeric excess (>97%) when the biotransformation was carried out in heptane or pentadecane. Dry mycelium of Aspergillus oryzae MIM furnished the ethyl ester of (S)-(+)-2-phenylpropanoic acid with 90% enantiomeric excess when used in toluene in a temperature range of 20-40°C
Ubaldo Gandolfi, Ercole e l'idra di Lerna
No full textSi discute un dipinto dell'artista bolognese Ubaldo Gandolfi, già assegnato al pittore da M. Gregori, esaminandone i caratteri stilistici così da poterlo collocare nel suo percorso di carriera. La maniera che si evince dalla definizione della figura di Ercole conduce ad una esercitazione dal vero, quale era condotta con costanza e dedizione dal Gandolfi presso la Scuola del Nudo che si teneva nelle aule dell'Accademia Clementina dell'Istituto delle Scienze di Bologna, talune ingenuità conducono a datare l'opera al periodo giovanile dell'artista, all'epoca in cui andava formando il suo stile personalissimo che farà di lui uno tra i più apprezzati pittori della grande scuola bolognese settecentesca
Enantioselective oxidation of prochiral 2-methyl-1,3-propandiol by Acetobacter pasteurianus
No full textThe microbial oxidation of prochiral 2-methyl-1,3-propandiol into (R)-3-hydroxy-2-methyl propionic acid with Acetobacter pasteurianus DSM 8937 is reported. The biotransformation was optimised furnishing (R)-3-hydroxy-2-methyl propionic acid with 97% enantiomeric excess and 100% molar conversion of 5 g/L within 2 h. A simple fed-batch procedure allowed for the obtainment of 25 g/L of the enantiomerically enriched acid. (R)-3-Hydroxy-2-methyl propionic acid is an important building block for the synthesis of Captopril, a widely used antihypertensive drug
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