132679-16-4Relevant articles and documents
Chemoenzymatic one-pot reaction of noncompatible catalysts: Combining enzymatic ester hydrolysis with Cu(i)/bipyridine catalyzed oxidation in aqueous medium
Sand, Henning,Weberskirch, Ralf
, p. 33614 - 33626 (2017/07/12)
The combination of chemical catalysts and biocatalysts in a one-pot reaction has attracted considerable interest in the past years. However, since each catalyst requires very different reaction conditions, chemoenzymatic one-pot reactions in aqueous media remain challenging and are limited today to metal-catalysts that display high activity in aqueous media. Here, we report the first combination of two incompatible catalytic systems, a lipase based ester hydrolysis with a water-sensitive Cu/bipyridine catalyzed oxidation reaction, in a one-pot reaction in aqueous medium (PBS buffer). Key to the solution was the compartmentalization of the Cu/bipyridine catalyst in a core-shell like nanoparticle. We show the synthesis and characterization of the Cu/bipyridine functionalized nanoparticles and the application in the oxidation of allylic and benzylic alcohols in aqueous media. Furthermore, the work demonstrates the implementation of a one-pot reaction process with optimized reaction conditions involving a lipase (CAL-B) to hydrolyze various acetate ester substrates in the first step, followed by oxidation of the resulting alcohols to the corresponding aldehydes under aerobic conditions in aqueous media.
Water-soluble pendant copolymers bearing proline and permethylated β-cyclodextrin: PH-dependent catalytic nanoreactors
Doyagueez, Elisa G.,Corrales, Guillermo,Fernandez-Mayoralas, Alfonso,Rodriguez-Hernandez, Juan,Gallardo, Alberto
, p. 7676 - 7683,8 (2020/09/15)
To achieve efficient proline-based catalysis in water, proline has been supported in the past to porous and hydrophobic solid resins leading to heterogeneous systems. These solid resins provide a hydrophobic environment to the active centers, mimicking what happens in natural enzymes. However, a more realistic mimetic approach would be to carry out the aldol reaction in a homogeneous way, maintaining the hydrophobic environment, using for example properly designed noncross-linked polymer carriers. In this work, we report the synthesis and aqueous catalytic evaluation of a linear copolymer bearing both pendant proline and permethylated β-cyclodextrin (β-CD) groups. It was designed on the basis that the presence of the hydrophobic cavity of the β-CD could bring aromatic substrates into close proximity to the surrounding catalytic proline residues through host-guest interactions. The compound is water-soluble and catalyzes aldol reactions in this medium without the need for any extra organic solvent. We employed a model reaction between cylohexanone and p-nitrobenzaldehyde, and we observed a decrease of the reaction rate when a competing aromatic compound, known to form a strong inclusion complex with β-CD, was added. The copolymeric catalyst showed a pH-dependent behavior. At pH 7, the copolymer is found in solution as extended single chains with negative charge, catalyzing the reaction in a fast and nonstereoselective mode. At the isoelectric point (pH 3.8) where the positive and negative charges of the zwitterionic proline are canceled by forming charge complexes, the copolymer forms multichain hydrophobic nanoaggregates most probably stabilized by the permethylated β-CD. Although the reaction inside these nanoreactors is slower, it exhibits high stereoselectivity. It is proposed that the observed stereoselectivity is caused by the exclusion of water from the core of these homogeneous entities.
