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| 2. |
- Engström, Karin, et al.
(författare)
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Dynamic Kinetic Resolution of β-Amino Esters by a Heterogeneous System of a Palladium Nanocatalyst and Candida antarctica Lipase A
- 2011
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :10, s. 1827-1830
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Tidskriftsartikel (refereegranskat)abstract
- A dynamic kinetic resolution (DKR) of β-amino esters have been developed by the use of a heterogeneous racemization catalyst and an immobilized enzyme that accepts aromatic, heteroaromatic and aliphatic substrates. The reaction conditions were optimized to yield an efficient catalytic system without by-product formation. The products are obtained in 96–99 % ee and high yields
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| 3. |
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| 4. |
- Shakeri, Mozaffar, et al.
(författare)
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Highly enantioselective resolution of β-amino esters by Candida antarctica lipase A immobilized in mesocellular foam : application to dynamic kinetic resolution
- 2010
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Ingår i: ChemCatChem. - : Wiley. - 1867-3899 .- 1867-3880. ; 2:5, s. 534-538
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Tidskriftsartikel (refereegranskat)abstract
- Candida antarctica lipase A (CALA) immobilized in functionalized mesocellular foam in the presence of sucrose, followed by lyophilization, led to a dramatic increase in the enantioselectivity as well as an improved thermostability of the enzyme. The immobilized lipase was used for kinetic resolution (KR) and dynamic kinetic resolution (DKR) of the β-amino ester, ethyl 3-amino-3-phenylpropanoate. The temperature of optimum activity of CALA shifted from 20–30 °C to 80–90 °C on immobilization in the MCF. An “enantiomeric ratio” E (E=νA/νB; νA and νB are the rate constants for entantiomers A and B) of 69 and a conversion of 43 % in 1 h were obtained at 80 °C, whereas non-immobilized CALA lost its activity at T≥50 °C. The obtained immobilized CALA showed an E value of greater than 500 at 22 °C. Combination of the immobilized CALA with a ruthenium complex, acting as a racemization catalyst, allowed for a successful DKR of ethyl 3-amino-3-phenylpropanoate resulting in 85 % conversion and 89 % ee.
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| 5. |
- Shakeri, Mozaffar, et al.
(författare)
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Significant changes in the transesterification activity of free and mesoporous-immobilized Rhizopus oryzae lipase in ionic liquids
- 2010
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 145:3, s. 281-283
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Tidskriftsartikel (refereegranskat)abstract
- We examined the activity of free Rhizopus oryzae lipase (ROL) and ROL immobilized on mesoporous materials in transesterification reactions in various dialkylimidazolium-cation based ionic liquids. For free ROL, the highest activity (0.39 U/mg protein) was obtained in [OMIm][PF6] followed by that (0.28 U/mg protein) in [BMIm][PF6]. Specific activities of ROL immobilized on mesocellular foam (MCF) were only 0.47 and 0.43 U/mg protein in [OMIm][PF6] and [BMIm][PF6], respectively. However, the specific activities of ROL immobilized on octaclecyl functionalized MCF (C-18-MCF) increased significantly to 15.64 and 14.84U/mg protein in [OMIm][PF6] and [BMIm][PF6], respectively. Consequently, ROL immobilized on C18-MCF is a promising biocatalyst for biotransformation reactions in ionic liquids.
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| 6. |
- Shakeri, Mozaffar, et al.
(författare)
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Small Pd Nanoparticles Supported in Large Pores of Mesocellular Foam : An Excellent Catalyst for Racemization of Amines
- 2011
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 17:47, s. 13269-13273
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Tidskriftsartikel (refereegranskat)abstract
- Highly dispersed palladium nanoparticles (1–2 nm) supported in large-pore mesocellular foam (MCF; 29 nm) were synthesized. The Pd-nanocatalyst/MCF system was characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The performance of the Pd nanocatalyst obtained was examined for amine racemization. The Pd nanocatalyst showed higher activity and selectivity toward racemization of (S)-1-phenylethyl amine than any other amine racemization catalyst reported so far and it could be reused several times. Our data from TEM and XRD suggest a restructuring of the Pd nanocatalyst from amorphous to crystalline and an increase in Pd nanocatalyst size during the racemization reaction. This led to an unexpected increase of activity after the first use. The Pd nanocatalyst obtained can be integrated with other resolving processes of racemic organic compounds to increase the yield of chiral organic products.
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| 7. |
- Shal, ZeynabAlsadat Khatami, et al.
(författare)
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In-Situ Growth of Embryonic TS-1 on Amorphous Silica via Steam-Assisted Crystallization : Correlation of Structural Properties and Catalytic Performance of Embryonic, Crystalline, and Amorphous Titanosilicate Catalysts
- 2023
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Ingår i: Crystal Growth & Design. - 1528-7483 .- 1528-7505. ; 23:7, s. 4883-4895
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Tidskriftsartikel (refereegranskat)abstract
- In-situ growth of supported embryonic TS-1 zeolite (<10nm)on a silica support was achieved by steam-assisted crystallization(SAC). The use of low amounts of TPABr and steam at a moderate temperatureof 130 degrees C was the key factor to control partial transformationof silica into supported embryonic TS-1. Compared with the referencecrystalline TS-1, supported embryonic TS-1 exhibits a higher activityin dibenzothiophene (DBT) oxidation (TOF: 8-275 h(-1) vs 2.7-160 h(-1) at 30-98 degrees C),a higher resistance to poisoning by nitrogen-containing compounds,and a higher selectivity (>97%) in the productive utilization oftheoxidant in DBT oxidation. The activity of the amorphous titanosilicate(TOF: 21.2-210 h(-1) at 30-80 degrees C),the solid precursor of the SAC process, was higher than that of theembryonic and the crystalline TS-1. The analysis of the structuralproperties-catalytic performance of these catalysts showedan improved accessibility to defective Ti active sites Ti(OH)(OSi)(3) with higher catalytic activity. The results of thisstudy should be encouraging to unearth many other active amorphouscatalysts with the potential of industrial application.
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| 8. |
- von Langermann, Jan, et al.
(författare)
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Design of an Integrated Process of Chromatography, Crystallization and Racemization for the Resolution of 2 ',6 '-Pipecoloxylidide (PPX)
- 2012
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Ingår i: Organic Process Research & Development. - : American Chemical Society (ACS). - 1083-6160 .- 1520-586X. ; 16:2, s. 343-352
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Tidskriftsartikel (refereegranskat)abstract
- An integrated process for the chiral separation of the industrially relevant substance 2',6'-pipecoloxylidide (PPX), an intermediate in the manufacture of a number of anesthetics, was developed. By combining three different techniques, chromatography, crystallization, and racemization, high productivity was achieved. All unit operations were executed using a common solvent system, full recycling, and a minimum of solvent exchanges or removals. The target molecule was obtained with an enantiopurity of >99.5 wt %.
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