Searched for: author:"Hanefeld, U."
(1 - 20 of 26)

Pages

document
Mestrom, L. (author), Claessen, J.G.R. (author), Hanefeld, U. (author)
MsAcT catalyzes the esterification of primary alcohols in water. When utilizing acid and alcohol as starting materials low yields dictated by thermodynamics were observed. However, with activated esters such as ethyl acetate and vinyl acetate very high yields of the desired ester can be achieved in combination with the appropriate alcohol....
journal article 2019
document
Tonin, F. (author), Alvarenga Da Silva, N. (author), Ye, Jia Zheng (author), Arends, I.W.C.E. (author), Hanefeld, U. (author)
The C12 specific oxidation of hydroxysteroids is an essential reaction required for the preparation of pharmaceutical ingredients like ursodeoxycholic acid (UDCA) and chenodeoxycholic acid (CDCA), which can be synthesized by Wolff-Kishner reduction of the obtained 12-oxo-hydroxysteroids. 12α-hydroxysteroid dehydrogenases (12α-HSDHs) have...
journal article 2019
document
van der Helm, M.P. (author), Bracco Garcia, M.P. (author), Busch, H. (author), Szymańska, K. (author), Jarzȩbski, A. (author), Hanefeld, U. (author)
Enzymes are supreme catalysts when it comes to high enantiopurities and their immobilization will pave the way for continuous operation. In this context, we show the covalent immobilization of hydroxynitrile lyases HbHNL (from Hevea brasiliensis) and MeHNL (from Manihot esculenta) in a siliceous monolithic microreactor for continuous...
journal article 2019
document
Bracco Garcia, M.P. (author), Torrelo Villa, G. (author), Noordam, Sander (author), de Jong, Glenn (author), Hanefeld, U. (author)
The hydroxynitrile lyase from Prunus amygdalus was immobilized on Celite R-633. The immobilized enzyme could successfully be utilized in buffer saturated MTBE and excellent conversions of benzaldehyde to R-mandelonitrile were observed. No leaching occurred. To achieve high enantioselectivities, the suppression of the undesired background...
journal article 2018
document
Chen, B. (author), Medici, R. (author), van der Helm, M.P. (author), Gjonaj, L. (author), Otten, L.G. (author), Hanefeld, U. (author)
Rhodococcus strains are ubiquitous in nature and known to metabolise a wide variety of compounds. At the same time, asymmetric reduction of C=C bonds is important in the production of high-valued chiral building blocks. In order to evaluate if Rhodococci can be used for this task, we have probed several Rhodococcus rhodochrous and R....
journal article 2018
document
Haridas, M. (author), Eman MahmoudMohamedAbdelraheem, E.M.M. (author), Hanefeld, U. (author)
© 2018, The Author(s). 2-Deoxy-d-ribose-5-phosphate aldolase (DERA) is a class I aldolase that offers access to several building blocks for organic synthesis. It catalyzes the stereoselective C–C bond formation between acetaldehyde and numerous other aldehydes. However, the practical application of DERA as a biocatalyst is limited by its poor...
journal article 2018
document
Medici, R. (author), Stammes, J.K. (author), Otten, L.G. (author), Hanefeld, U. (author), Kwakernaak, Stender (author)
α-Hydroxy ketones and vicinal diols constitute well-known building blocks in organic synthesis. Here we describe one enzyme that enables the enantioselective synthesis of both building blocks starting from diketones. The enzyme 2,3-butanediol dehydrogenase (BudC) from S. marcescens CECT 977 belongs to the NADH-dependent metal-independent short...
journal article 2017
document
ten Dam, J. (author), Ramanathan, A (author), Djanashvili, K. (author), Kapteijn, F. (author), Hanefeld, U. (author)
physisorption, XRD and TEM. Their catalytic performance (activity and...
journal article 2017
document
Marsden, S.R. (author), Gjonaj, L. (author), Eustace, S.J. (author), Hanefeld, U. (author)
Transketolase catalyzes asymmetric C−C bond formation of two highly polar compounds. Over the last 30 years, the reaction has unanimously been described in literature as irreversible because of the concomitant release of CO2 if using lithium hydroxypyruvate (LiHPA) as a substrate. Following the reaction over a longer period of time however, we...
journal article 2017
document
Gjonaj, L. (author), Pinkse, M.W.H. (author), Fernandez Fueyo, E. (author), Hollmann, F. (author), Hanefeld, U. (author)
Nitrile reductases catalyse a two-step reduction of nitriles to amines. This requires the binding of two NADPH molecules during one catalytic cycle. For the nitrile reductase from E. coli (EcoNR) mass spectrometry studies of the catalytic mechanism were performed. EcoNR is dimeric and has no Rossman fold. It was demonstrated that during...
journal article 2016
document
Bracco Garcia, M.P. (author), Busch, H. (author), von Langermann, J. (author), Hanefeld, U. (author)
The first enantioselective synthesis was the selective addition of cyanide to benzaldehyde catalysed by a hydroxynitrile lyase (HNL). Since then these enzymes have developed into a reliable tool in organic synthesis. HNLs to prepare either the (R)- or the (S)-enantiomer of the desired cyanohydrin are available and a wide variety of reaction...
journal article 2016
document
Szymańska, K. (author), Odrozek, K. (author), Zniszczoł, A. (author), Torrelo, G. (author), Resch, V. (author), Hanefeld, U. (author), Jarzębskia, A.B. (author)
Acyltransferase from Mycobacterium smegmatis (MsAcT) immobilised in continuous-flow microchannel (30-50 ?m dia.) reactors with hierarchical pore structure (4 cm3/g total pore volume) enabled quantitative, full and rapid transesterification of neopentylglycol with ethyl acetate in a biphasic 50/50 % system in less than one minute. MsAcT was...
journal article 2016
document
Vasudevan Srinivasan, V. (author), Ranoux, A. (author), Maheswari, R. (author), Hanefeld, U. (author), Ramanathan, A. (author), Subramaniam, B. (author)
The acidity of Zr-incorporated large pore cubic mesoporous silicate, KIT-5, with Fm3m symmetry was explored as catalyst in the Hantzsch reaction for preparation of 1,4-dihydropyridine (DHP) derivatives, Meerwein–Ponndorf–Verley (MPV) reduction of 4-tert-butylcyclohexanone, and Prins reaction of citronellal. The catalyst showed ~82–94 %...
journal article 2015
document
Chen, B.S. (author), Resch, V. (author), Otten, L.G. (author), Hanefeld, U. (author)
The enantioselective Michael addition using water as both nucleophile and solvent has to date proved beyond the ability of synthetic chemists. Herein, the direct, enantioselective Michael addition of water in water to prepare important ?-hydroxy carbonyl compounds using whole cells of Rhodococcus strains is described. Good yields and excellent...
journal article 2014
document
Resch, V. (author), Hanefeld, U. (author)
Water is omnipresent and essential. Yet at the same time it is a rather unreactive molecule. The direct addition of water to C[double bond, length as m-dash]C double bonds is therefore a challenge not answered convincingly. In this perspective we critically evaluate the selectivity and the applicability of the different catalytic approaches for...
journal article 2014
document
Resch, V.A. (author), Jin, J. (author), Chen, B.S. (author), Hanefeld, U. (author)
The Michael hydratase – alcohol dehydrogenase (MhyADH) from Alicycliphilus denitrificans was previously identified as a bi-functional enzyme performing a hydration of ?,?-unsaturated ketones and subsequent oxidation of the formed alcohols. The investigations of the bi-functionality were based on a spectrophotometric assay and an activity...
journal article 2014
document
Resch, V. (author), Seidler, C. (author), Chen, B.S. (author), Degeling, I. (author), Hanefeld, U. (author)
The use of water as a nucleophile for Michael additions is still a challenge in organic chemistry. In this report we describe the use of amino acids as catalysts for the Michael addition of water to ?,?-unsaturated ketones. All 20 proteinogenic amino acids were screened and L-lysine was identified as the best candidate. To obtain a better...
journal article 2013
document
Chen, B.S. (author), Otten, L.G. (author), Resch, V. (author), Muyzer, G. (author), Hanefeld, U. (author)
Rhodococcus rhodochrous ATCC 17895 possesses an array of mono- and dioxygenases, as well as hydratases, which makes it an interesting organism for biocatalysis. R. rhodochrous is a Gram-positive aerobic bacterium with a rod-like morphology. Here we describe the features of this organism, together with the complete genome sequence and annotation....
journal article 2013
document
Ranoux, A. (author), Djanashvili, K. (author), Arends, I.W.C.E. (author), Hanefeld, U. (author)
Novel amorphous mesoporous borosilicate, B-TUD-1, was prepared to test its performance for different sustainable reactions. The structure of the material, the effective incorporation of boron into the framework as well as the nature of incorporated boron were verified by N2-sorption, XRD, ICP-OES, TEM, NH3-desorption, MAS NMR and FTIR. The...
journal article 2013
document
Hanefeld, U. (author)
Hydroxynitrile lyases are a versatile group of enzymes that are applied both in the laboratory and on an industrial scale. What makes them particularly interesting is that to date five structurally unrelated categories of hydroxynitrile lyases have been discovered. Given their great importance they have often been immobilised utilising many...
journal article 2013
Searched for: author:"Hanefeld, U."
(1 - 20 of 26)

Pages