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Relevant academic research and scientific papers

Controllable stereoinversion in DNA-catalyzed olefin cyclopropanationviacofactor modification

The assembly of DNA with metal-complex cofactors can form promising biocatalysts for asymmetric reactions, although catalytic performance is typically limited by low enantioselectivities and stereo-control remains a challenge. Here, we engineer G-quadruplex-based DNA biocatalysts for an asymmetric cyclopropanation reaction, achieving enantiomeric excess (eetrans) values of up to +91% with controllable stereoinversion, where the enantioselectivity switches to ?72% eetransthrough modification of the Fe-porphyrin cofactor. Complementary circular dichroism, nuclear magnetic resonance, and fluorescence titration experiments show that the porphyrin ligand of the cofactor participates in the regulation of the catalytic enantioselectivityviaa synergetic effect with DNA residues at the active site. These findings underline the important role of cofactor modification in DNA catalysis and thus pave the way for the rational engineering of DNA-based biocatalysts.

A de novo peroxidase is also a promiscuous yet stereoselective carbene transferase

By constructing an in vivo-assembled, catalytically proficient peroxidase, C45, we have recently demonstrated the catalytic potential of simple, de novo-designed heme proteins. Here, we show that C45's enzymatic activity extends to the efficient and stereoselective intermolecular transfer of carbenes to olefins, heterocycles, aldehydes, and amines. Not only is this a report of carbene transferase activity in a completely de novo protein, but also of enzyme-catalyzed ring expansion of aromatic heterocycles via carbene transfer by any enzyme.

Semi-Rationally Designed Short Peptides Self-Assemble and Bind Hemin to Promote Cyclopropanation

The self-assembly of short peptides gives rise to versatile nanoassemblies capable of promoting efficient catalysis. We have semi-rationally designed a series of seven-residue peptides that form hemin-binding catalytic amyloids to facilitate enantioselect

Chiral 2,2'-dipyridine ligand, preparation method thereof, and application of ligand in preparation of chiral cyclopropane derivatives

The invention provides a chiral 2,2'-dipyridine ligand, a preparation method thereof, and an application of the ligand in the preparation of chiral cyclopropane derivatives. The chiral 2,2'-dipyridineligand is represented by formula (1) or formula (1'), can be used for efficiently preparing the chiral cyclopropane derivatives, and has the advantages of high yield, good stereoselectivity, easinessin separation and purification, and high practical values.

Z-bpy, a New C2-Symmetric Bipyridine Ligand and Its Application in Enantioselective Copper(I)-Catalyzed Cyclopropanation of Olefins

A rigid C2-symmetric chiral bipyridine ligand Z-bpy with a triptycene-like backbone was designed and synthesized from simple chemicals in a scalable route. Using this new ligand, copper(I) catalyzed cyclopropanation of styrenes with commercial ethyl diazoacetate produced various corresponding cyclopropanes in high yields, diastereoselectivity and enantioselectivity up to 97% ee.

Gram-Scale Synthesis of Chiral Cyclopropane-Containing Drugs and Drug Precursors with Engineered Myoglobin Catalysts Featuring Complementary Stereoselectivity

Engineered hemoproteins have recently emerged as promising systems for promoting asymmetric cyclopropanations, but variants featuring predictable, complementary stereoselectivity in these reactions have remained elusive. In this study, a rationally driven strategy was implemented and applied to engineer myoglobin variants capable of providing access to 1-carboxy-2-aryl-cyclopropanes with high trans-(1R,2R) selectivity and catalytic activity. The stereoselectivity of these cyclopropanation biocatalysts complements that of trans-(1S,2S)-selective variants developed here and previously. In combination with whole-cell biotransformations, these stereocomplementary biocatalysts enabled the multigram synthesis of the chiral cyclopropane core of four drugs (Tranylcypromine, Tasimelteon, Ticagrelor, and a TRPV1 inhibitor) in high yield and with excellent diastereo- and enantioselectivity (98–99.9% de; 96–99.9% ee). These biocatalytic strategies outperform currently available methods to produce these drugs.

Aqueous asymmetric cyclopropanation reactions in polymersome membranes

Copper-bis(oxazoline) complexes have been immobilised in the hydrophobic domain of a polymersome membrane to perform asymmetric cyclopropanation reactions in aqueous media with enhanced conversions and enantioselectivities. This journal is the Partner Organisations 2014.

Continuous flow asymmetric cyclopropanation reactions using Cu(i) complexes of Pc-L* ligands supported on silica as catalysts with carbon dioxide as a carrier

Continuous flow heterogeneous asymmetric cyclopropanations catalysed by supported hydrogen-bonded (SHB) chiral copper(i) complexes of pyridine containing tetraazamacrocyclic ligands Pc-L* using CO2 as a transport vector are described. The catalytic system showed high stability and good recyclability without loss of activity for at least 24 h in CO2 and catalyst turnover numbers up to 440 were obtained with excellent conversion (up to 99%) and high selectivity (up to 88%). No leaching of copper was observed. Cyclopropane products from both aromatic and aliphatic olefins were obtained in good yields with enantiomeric excesses up to 72%. This journal is the Partner Organisations 2014.

Asymmetric cyclopropanation of olefins catalysed by Cu(i) complexes of chiral pyridine-containing macrocyclic ligands (Pc-L*)

The synthesis and characterisation of copper(i) complexes of chiral pyridine-containing macrocyclic ligands (Pc-L*) and their use as catalysts in asymmetric cyclopropanation reactions are reported. All ligands and metal complexes were fully characterised, including crystal structures of some species determined by X-ray diffraction on single crystals. This allowed characterising the very different conformations of the macrocycles which could be induced by different substituents or by metal complexation. The strategy adopted for the ligand synthesis is very flexible allowing several structural modifications. A small library of macrocyclic ligands possessing the same donor properties but with either C1 or C2 symmetry was synthesized. Cyclopropane products with both aromatic and aliphatic olefins were obtained in good yields and enantiomeric excesses up to 99%.

Silica "sHB" chiral Pc-L* copper complexes for halogen-free solvent cyclopropanation reactions

The grafting of the preformed Pc-L* (pyridine containing macrocyclic ligands) copper(i) complexes on different ordered and non-ordered silicas, and their use, under heterogeneous batch conditions, as catalysts for the olefin cyclopropanation are reported.