57000-49-4Relevant articles and documents
Fe-catalyzed Fukuyama-type indole synthesis triggered by hydrogen atom transfer
Huang, Hanmin,Yu, Min,Zhang, Tianze
, p. 10501 - 10505 (2021/08/20)
Fe, Co, and Mn hydride-initiated radical olefin additions have enjoyed great success in modern synthesis, yet the extension of other hydrogen radicalophiles instead of olefins remains largely elusive. Herein, we report an efficient Fe-catalyzed intramolec
Directed Evolution of a Cytochrome P450 Carbene Transferase for Selective Functionalization of Cyclic Compounds
Brandenberg, Oliver F.,Chen, Kai,Arnold, Frances H.
supporting information, p. 8989 - 8995 (2019/06/13)
Transfers of carbene moieties to heterocycles or cyclic alkenes to obtain C(sp2)-H alkylation or cyclopropane products are valuable transformations for synthesis of pharmacophores and chemical building blocks. Through their readily tunable active-site geometries, hemoprotein "carbene transferases" could provide an alternative to traditional transition metal catalysts by enabling heterocycle functionalizations with high chemo-, regio-, and stereocontrol. However, carbene transferases accepting heterocyclic substrates are scarce; the few enzymes capable of heterocycle or cyclic internal alkene functionalization described to date are characterized by low turnovers or depend on artificially introduced, costly iridium-porphyrin cofactors. We addressed this challenge by evolving a cytochrome P450 for highly efficient carbene transfer to indoles, pyrroles, and cyclic alkenes. We first developed a spectrophotometric high-throughput screening assay based on 1-methylindole C3-alkylation that enabled rapid analysis of thousands of P450 variants and comprehensive directed evolution via random and targeted mutagenesis. This effort yielded a P450 variant with 11 amino acid substitutions and a large deletion of the non-catalytic P450 reductase domain, which chemoselectively C3-alkylates indoles with up to 470 turnovers per minute and 18000 total turnovers. We subsequently used this optimized alkylation variant for parallel evolution toward more challenging heterocycle carbene functionalizations, including C2/C3 regioselective pyrrole alkylation, enantioselective indole alkylation with ethyl 2-diazopropanoate, and cyclic internal alkene cyclopropanation. The resulting set of efficient biocatalysts showcases the tunability of hemoproteins for highly selective functionalization of cyclic targets and the power of directed evolution to enhance the scope of new-to-nature enzyme catalysts.
A Cooperative Hydrogen Bond Donor–Br?nsted Acid System for the Enantioselective Synthesis of Tetrahydropyrans
Maskeri, Mark A.,O'Connor, Matthew J.,Jaworski, Ashley A.,Davies, Anna V.,Scheidt, Karl A.
supporting information, p. 17225 - 17229 (2018/12/05)
Carbocations stabilized by adjacent oxygen atoms are useful reactive intermediates involved in fundamental chemical transformations. These oxocarbenium ions typically lack sufficient electron density to engage established chiral Br?nsted or Lewis acid catalysts, presenting a major challenge to their widespread application in asymmetric catalysis. Leading methods for selectivity operate primarily through electrostatic pairing between the oxocarbenium ion and a chiral counterion. A general approach to new enantioselective transformations of oxocarbenium ions requires novel strategies that address the weak binding capabilities of these intermediates. We demonstrate herein a novel cooperative catalysis system for selective reactions with oxocarbenium ions. This new strategy has been applied to a highly selective and rapid oxa-Pictet–Spengler reaction and highlights a powerful combination of an achiral hydrogen bond donor with a chiral Br?nsted acid.
