1006-64-0Relevant articles and documents
Chemoselective three-component synthesis of homoallylic azides using an FeCl3 catalyst
Pramanik, Suman,Ghorai, Prasanta
, p. 23157 - 23165 (2013)
A one-pot, three-component synthesis of homoallylic azides from corresponding aldehydes, TMS-allyl, and TMS-N3 has been developed for the first time using an FeCl3 catalyst. The aromatic and hetero-aromatic aldehydes provided the cor
Expanding the chemical diversity in artificial imine reductases based on the biotin-streptavidin technology
Quinto, Tommaso,Schwizer, Fabian,Zimbron, Jeremy M.,Morina, Albert,Koehler, Valentin,Ward, Thomas R.
, p. 1010 - 1014 (2014)
We report on the optimization of an artificial imine reductase based on the biotin-streptavidin technology. With the aim of rapidly generating chemical diversity, a novel strategy for the formation and evaluation of biotinylated complexes is disclosed. Tethering the biotin-anchor to the Cp* moiety leaves three free coordination sites on a d6 metal for the introduction of chemical diversity by coordination of a variety of ligands. To test the concept, 34 bidentate ligands were screened and a selection of the 6 best was tested in the presence of 21 streptavidin (Sav) isoforms for the asymmetric imine reduction by the resulting three legged piano stool complexes. Enantiopure α-amino amides were identified as promising bidentate ligands: up to 63 % ee and 190 turnovers were obtained in the formation of 1-phenyl-1,2,3,4-tetrahydroisoquinoline with [IrCp*biotin(L-ThrNH2)Cl]?SavWT as a catalyst. Biotinspired! A new strategy for the generation of chemical diversity in artificial transfer hydrogenases (ATHases) based on the biotin-streptavidin technology is disclosed. By combining a biotinylated MCp* fragment with 34 commercially available ligands in the presence of wild-type streptavidin, promising candidates for the asymmetric reduction of imines are identified. Selected ligands are screened against 21 streptavidin isoforms and the performance of the resulting constructs is evaluated.
Asymmetric reduction of cyclic imines catalyzed by a whole-cell biocatalyst containing an (S)-imine reductase
Leipold, Friedemann,Hussain, Shahed,Ghislieri, Diego,Turner, Nicholas J.
, p. 3505 - 3508 (2013)
Biocatalytic imine reduction: A whole-cell recombinant E. coli system, producing an (S)-selective imine reductase (IRED) from Streptomyces sp. GF3546, is developed. This biocatalyst is used for the enantioselective reduction of a broad range of substrates such as dihydroisoquinolines and dihydro-β- carbolines as well as iminium ions. Copyright
Development of an R-selective amine oxidase with broad substrate specificity and high enantioselectivity
Heath, Rachel S.,Pontini, Marta,Bechi, Beatrice,Turner, Nicholas J.
, p. 996 - 1002 (2014)
Amine oxidases are useful bio-catalysts for the synthesis of enantiomerically pure 1°, 2° and 3° chiral amines. Enzymes in this class (e.g., MAO-N from Aspergillus niger) reported previously have been shown to be highly S selective. Herein we report the development of an enantiocomplementary R-selective amine oxidase based on 6-hydroxy-D-nicotine oxidase (6-HDNO) with broadened substrate scope and high enantioselectivity. The engineered 6-HDNO enzyme has been applied to the preparative deracemisation of a range of racemic amines to yield S-configured products, for example, (S)-nicotine, in high ee. Nicotine rush: An R-selective amine oxidase based on 6-hydroxy-D-nicotine oxidase (6-HDNO) with broadened substrate scope and high enantioselectivity has been developed. The engineered 6-HDNO enzyme is applied to the preparative deracemization of a range of racemic amines to yield S-configured products, for example, (S)-nicotine, in high ee.
Copper Cyanide-Catalyzed Palladium Coupling of N-tert-Butoxycarbonyl-Protected α-Lithio Amines with Aryl Iodides or Vinyl Iodides
Karl Dieter,Li, ShengJian
, p. 7726 - 7735 (1997)
Treatment of (α-aminoalkyl)lithium reagents with aryl iodides in the presence of catalytic amounts of CuCN and PdCl2(PPh3)2 or [(p-MeOC6H4)3P]4Pd affords 2-aryl substituted amines in modest to good yields. The yields can be improved by use of softer ligands such as AsPh3 and SbPh3 or by use of bis(diphenylphosphino)ferrocene (dppf). Coupled products are obtained with electron-rich aryl iodides (XArI, X = Me, OMe), and the reaction fails with electron-poor aryl iodides (XArI, X = NO2, CO2Li). Treatment of the (α-aminoalkyl)lithium reagents with vinyl iodides and Pd(0)/dppf/ CuCN afforded the coupling products in low to modest yields.
Sequence-Based In-silico Discovery, Characterisation, and Biocatalytic Application of a Set of Imine Reductases
Velikogne, Stefan,Resch, Verena,Dertnig, Carina,Schrittwieser, Joerg H.,Kroutil, Wolfgang
, p. 3236 - 3246 (2018)
Imine reductases (IREDs) have recently become a primary focus of research in biocatalysis, complementing other classes of amine-forming enzymes such as transaminases and amine dehydrogenases. Following in the footsteps of other research groups, we have established a set of IRED biocatalysts by sequence-based in silico enzyme discovery. In this study, we present basic characterisation data for these novel IREDs and explore their activity and stereoselectivity using a panel of structurally diverse cyclic imines as substrates. Specific activities of >1 U/mg and excellent stereoselectivities (ee>99 %) were observed in many cases, and the enzymes proved surprisingly tolerant towards elevated substrate loadings. Co-expression of the IREDs with an alcohol dehydrogenase for cofactor regeneration led to whole-cell biocatalysts capable of efficiently reducing imines at 100 mM initial concentration with no need for the addition of extracellular nicotinamide cofactor. Preparative biotransformations on gram scale using these ‘designer cells’ afforded chiral amines in good yield and excellent optical purity.
Design, synthesis and biological evaluation of N-hydroxy-aminobenzyloxyarylamide analogues as novel selective κ opioid receptor antagonists
He, Guangchao,Peng, Kewen,Song, Qiao,Wang, Junwei,Xu, Anhua,Xu, Yungen,Zhu, Qihua
, (2020)
Aminobenzyloxyarylamide derivatives 1a-i and 2a-t were designed and synthesized as novel selective κ opioid receptor (KOR) antagonists. The benzoyl amide moiety of LY2456302 was changed into N-hydroxybenzamide and benzisoxazole-3(2H)-one to investigate whether it could increase the binding affinity or selectivity for KOR. All target compounds were evaluated in radioligand binding assays for opioid receptor binding affinity. These efforts led to the identification of compound 1c (κ Ki = 179.9 nM), which exhibited high affinity for KOR. Moreover, the selectivity of KOR over MOR and DOR increased nearly 2-fold and 7-fold, respectively, compared with (±)LY2456302.
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Seeman
, p. 498 (1977)
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H2 Activation by Non-Transition-Metal Systems: Hydrogenation of Aldimines and Ketimines with LiN(SiMe3)2
Elliott, Daniel C.,Marti, Alex,Mauleón, Pablo,Pfaltz, Andreas
, p. 1918 - 1922 (2019)
In recent years, H2 activation at non-transition-metal centers has met with increasing attention. Here, a system in which H2 is activated and transferred to aldimines and ketimines using substoichiometric amounts of lithium bis(trimethylsilyl)amide is reported. Notably, the reaction tolerates the presence of acidic protons in the α-position. Mechanistic investigations indicated that the reaction proceeds via a lithium hydride intermediate as the actual reductant.
Directed Evolution of an Artificial Imine Reductase
Hestericová, Martina,Heinisch, Tillman,Alonso-Cotchico, Lur,Maréchal, Jean-Didier,Vidossich, Pietro,Ward, Thomas R.
, p. 1863 - 1868 (2018)
Artificial metalloenzymes, resulting from incorporation of a metal cofactor within a host protein, have received increasing attention in the last decade. The directed evolution is presented of an artificial transfer hydrogenase (ATHase) based on the biotin-streptavidin technology using a straightforward procedure allowing screening in cell-free extracts. Two streptavidin isoforms were yielded with improved catalytic activity and selectivity for the reduction of cyclic imines. The evolved ATHases were stable under biphasic catalytic conditions. The X-ray structure analysis reveals that introducing bulky residues within the active site results in flexibility changes of the cofactor, thus increasing exposure of the metal to the protein surface and leading to a reversal of enantioselectivity. This hypothesis was confirmed by a multiscale approach based mostly on molecular dynamics and protein–ligand dockings.
Genetic Engineering of an Artificial Metalloenzyme for Transfer Hydrogenation of a Self-Immolative Substrate in Escherichia coli's Periplasm
Zhao, Jingming,Rebelein, Johannes G.,Mallin, Hendrik,Trindler, Christian,Pellizzoni, Michela M.,Ward, Thomas R.
, p. 13171 - 13175 (2018)
Artificial metalloenzymes (ArMs), which combine an abiotic metal cofactor with a protein scaffold, catalyze various synthetically useful transformations. To complement the natural enzymes' repertoire, effective optimization protocols to improve ArM's performance are required. Here we report on our efforts to optimize the activity of an artificial transfer hydrogenase (ATHase) using Escherichia coli whole cells. For this purpose, we rely on a self-immolative quinolinium substrate which, upon reduction, releases fluorescent umbelliferone, thus allowing efficient screening. Introduction of a loop in the immediate proximity of the Ir-cofactor afforded an ArM with up to 5-fold increase in transfer hydrogenation activity compared to the wild-type ATHase using purified mutants.
Regioselective 2-Alkylation and 2-Arylation of Piperidine and Pyrrolidine via Organolithiation of Cyclic Imines
Scully, Frank E.
, p. 1515 - 1517 (1980)
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Reduction of imines via titanium-catalyzed hydromagnesation
Amin, Sk. Rasidul,Crowe, William E.
, p. 7487 - 7490 (1997)
We have recently discovered that imines can be reduced to amines via a titanium catalyzed hydromagnesation reaction. These reactions employ n-BuMgCl (1.2 eq) as the stoichiometric reducing agent and Cp2TiCl2 (3-5 mol%) as a catalyst. Reactions are run under nitrogen at ambient temperature and pressure. For most aldimine and cyclic ketimine substrates amine products are obtained in yields ranging from 69-94%. The reaction is not tolerant of bulky nitrogen substituents or primary enolizable protons on the imine substrate.
Enantioselective Intermolecular C-H Amination Directed by a Chiral Cation
Fanourakis, Alexander,Paterson, Kieran J.,Phipps, Robert J.,Williams, Benjamin D.
, p. 10070 - 10076 (2021/07/21)
The enantioselective amination of C(sp3)-H bonds is a powerful synthetic transformation yet highly challenging to achieve in an intermolecular sense. We have developed a family of anionic variants of the best-in-class catalyst for Rh-catalyzed C-H amination, Rh2(esp)2, with which we have associated chiral cations derived from quaternized cinchona alkaloids. These ion-paired catalysts enable high levels of enantioselectivity to be achieved in the benzylic C-H amination of substrates bearing pendant hydroxyl groups. Additionally, the quinoline of the chiral cation appears to engage in axial ligation to the rhodium complex, providing improved yields of product versus Rh2(esp)2 and highlighting the dual role that the cation is playing. These results underline the potential of using chiral cations to control enantioselectivity in challenging transition-metal-catalyzed transformations.
An Iron-Mesoionic Carbene Complex for Catalytic Intramolecular C-H Amination Utilizing Organic Azides
Albrecht, Martin,Keilwerth, Martin,Meyer, Karsten,Pividori, Daniel M.,Stroek, Wowa
, p. 20157 - 20165 (2021/12/09)
The synthesis of N-heterocycles is of paramount importance for the pharmaceutical industry. They are often synthesized through atom economic and environmentally unfriendly methods, generating significant waste. A less explored, but greener, alternative is
