5362-38-9Relevant academic research and scientific papers
Stereoselective Cyclopropanation of Electron-Deficient Olefins with a Cofactor Redesigned Carbene Transferase Featuring Radical Reactivity
Carminati, Daniela M.,Fasan, Rudi
, p. 9683 - 9697 (2019/10/19)
Engineered myoglobins and other hemoproteins have recently emerged as promising catalysts for asymmetric olefin cyclopropanation reactions via carbene-transfer chemistry. Despite this progress, the transformation of electron-poor alkenes has proven to be very challenging using these systems. Here, we describe the design of a myoglobin-based carbene transferase incorporating a non-native iron-porphyrin cofactor and axial ligand, as an efficient catalyst for the asymmetric cyclopropanation of electron-deficient alkenes. Using this metalloenzyme, a broad range of both electron-rich and electron-deficient alkenes are cyclopropanated with high efficiency and high diastereo- A nd enantioselectivity (up to >99% de and ee). Mechanistic studies revealed that the expanded reaction scope of this carbene transferase is dependent upon the acquisition of metallocarbene radical reactivity as a result of the reconfigured coordination environment around the metal center. The radical-based reactivity of this system diverges from the electrophilic reactivity of myoglobin and most of the known organometallic carbene-transfer catalysts. This work showcases the value of cofactor redesign toward tuning and expanding the reactivity of metalloproteins in abiological reactions, and it provides a biocatalytic solution to the asymmetric cyclopropanation of electron-deficient alkenes. The metallocarbene radical reactivity exhibited by this biocatalyst is anticipated to prove useful in the context of a variety of other synthetic transformations.
Origin of High Stereocontrol in Olefin Cyclopropanation Catalyzed by an Engineered Carbene Transferase
Tinoco, Antonio,Wei, Yang,Bacik, John-Paul,Carminati, Daniela M.,Moore, Eric J.,Ando, Nozomi,Zhang, Yong,Fasan, Rudi
, p. 1514 - 1524 (2019/02/03)
Recent advances in metalloprotein engineering have led to the development of a myoglobin-based catalyst, Mb(H64V,V68A), capable of promoting the cyclopropanation of vinylarenes with high efficiency and high diastereo- and enantioselectivity. Whereas many enzymes evolved in nature often exhibit catalytic proficiency and exquisite stereoselectivity, how these features are achieved for a non-natural reaction has remained unclear. In this work, the structural determinants responsible for chiral induction and high stereocontrol in Mb(H64V,V68A)-catalyzed cyclopropanation were investigated via a combination of crystallographic, computational (DFT), and structure-activity analyses. Our results show the importance of steric complementarity and noncovalent interactions involving first-sphere active site residues, heme-carbene, and the olefin substrate in dictating the stereochemical outcome of the cyclopropanation reaction. High stereocontrol is achieved through two major mechanisms: first, by enforcing a specific conformation of the heme-bound carbene within the active site, and second, by controlling the geometry of attack of the olefin on the carbene via steric occlusion, attractive van der Waals forces, and protein-mediated π-π interactions with the olefin substrate. These insights could be leveraged to expand the substrate scope of the myoglobin-based cyclopropanation catalyst toward nonactivated olefins and to increase its cyclopropanation activity in the presence of a bulky α-diazo-ester. This work sheds light on the origin of enzyme-catalyzed enantioselective cyclopropanation, furnishing a mechanistic framework for both understanding the reactivity of current systems and guiding the future development of biological catalysts for this class of synthetically important, abiotic transformations.
Stereoselective Enzymatic Synthesis of Heteroatom-Substituted Cyclopropanes
Brandenberg, Oliver F.,Prier, Christopher K.,Chen, Kai,Knight, Anders M.,Wu, Zachary,Arnold, Frances H.
, p. 2629 - 2634 (2018/04/14)
The repurposing of hemoproteins for non-natural carbene transfer activities has generated enzymes for functions previously accessible only to chemical catalysts. With activities constrained to specific substrate classes, however, the synthetic utility of these new biocatalysts has been limited. To expand the capabilities of non-natural carbene transfer biocatalysis, we engineered variants of Cytochrome P450BM3 that catalyze the cyclopropanation of heteroatom-bearing alkenes, providing valuable nitrogen-, oxygen-, and sulfur-substituted cyclopropanes. Four or five active-site mutations converted a single parent enzyme into selective catalysts for the synthesis of both cis and trans heteroatom-substituted cyclopropanes, with high diastereoselectivities and enantioselectivities and up to 40 000 total turnovers. This work highlights the ease of tuning hemoproteins by directed evolution for efficient cyclopropanation of new substrate classes and expands the catalytic functions of iron heme proteins.
Mechanistic Studies on Dopamine β-Monooxygenase Catalysis: N-Dealkylation and Mechanism-Based Inhibition by Benzylic-Nitrogen-Containing Compounds. Evidence for a Single-Electron-Transfer Mechanism
Wimalasena, Kandatege,May, Sheldon W.
, p. 4036 - 4046 (2007/10/02)
Dopamine β-monooxygenase (DBM) readily catalyzes oxidative N-dealkylation of N-phenylethylenediamine (PEDA) and N-methyl-N-phenylethylenediamine (N-MePEDA) with the reaction characteriscics expected for a monooxygenase-catalyzed process.The products of this reaction have been quantitatively identified as aniline (or N-methylaniline for N-MePEDA) and 2-aminoacetaldehyde, the latter compound being successfully trapped by using NaBH4 reduction followed by N-succinimidyl p-nitriphenylacetate (SNPA) derivatization, and identified by HPLC and mass spectroscopy.In contrast, either analogues of PEDA, i.e. phenyl 2-aminoethyl ether (PAEE) and its p-hydroxy derivative (p-OHPAEE), as well as 2-phenoxycycloprpylamine are not substrates but are competitive inhibitors.Furthermore, 2-methyl-2-anilino-1-aminoethane (β-MePEDA) did not exhibit measurable substrate activity with DBM, in contrast to the excellent substrate activity of the sulfur analogue of β-MePEDA, 2-methyl-2-(phenylthio)-1-aminoethane (β-MePAES).DBM is inactivated during the N-dealkylation reaction in a time- and concentration-dependent manner, a phenomenon that has not, to our knowledge, been observed for any other oxygenase-catalyzed N-dealkylation reaction.Both PEDA and N-MePEDA, as well as β-MePEDA, inactivate DBM under turnover conditions.The inactivation exhibited pseudo-first-order saturable kinetics and expected protection by the DBM substrate, tyramine.No reappearance of enzyme activity was observed after extensive dialysis.Radioactive labeling experiments with ring-tritiated PEDA showed incorporation of nondialyzable radioactivity into DBM in the expected amount, consistent with covalent attachment of a reactive species derivd from PEDA to the DBM active site during enzyme inactivation.Although aniline, N-ethylaniline, N-(2-fluoroethyl)aniline, m- and p-anisidine, p-toluidine, and 5-hydroxyindole were found not to exhibit detectable DBM substrate activity, all of these inactivated the enzyme under turnover conditions.The isotope effect on partition ratio measured for dideuteriated PEDA was found to be a reflection of an isotope effect on Vmax and not on kinact.Our results provide a strong support for the conclusion that the initial nitrogen cation radical species is responsible for enzyme inactivation.Results with ring-deuteriated and ring-tritiated PEDA revealed that the amount of radioactivity incorporated into covalently inactivated DBM by ring-tritiated PEDA is in agreement with that expected for covalent attachment of the para carbon to the protein.An 18O labeling study was carried out to test for oxygen rebound into the aminoacetaldehyde product, and results demonstrated that the aldehyde oxygen of enzymatically produced 2-aminoacetaldehyde exchanges very rapidly with solvent water, in agreement with literature reports.On the basis ...
