@article{d760a7608da248ec80bb38dcf1dd51a7,
title = "Regioselective Radical Alkylation of Arenes Using Evolved Photoenzymes",
abstract = "Substituted arenes are ubiquitous in molecules with medicinal functions, making their synthesis a critical consideration when designing synthetic routes. Regioselective C-H functionalization reactions are attractive for preparing alkylated arenes; however, the selectivity of existing methods is modest and primarily governed by the substrate's electronic properties. Here, we demonstrate a biocatalyst-controlled method for the regioselective alkylation of electron-rich and electron-deficient heteroarenes. Starting from an unselective {"}ene{"}-reductase (ERED) (GluER-T36A), we evolved a variant that selectively alkylates the C4 position of indole, an elusive position using prior technologies. Mechanistic studies across the evolutionary series indicate that changes to the protein active site alter the electronic character of the charge transfer (CT) complex responsible for radical formation. This resulted in a variant with a significant degree of ground-state CT in the CT complex. Mechanistic studies on a C2-selective ERED suggest that the evolution of GluER-T36A helps disfavor a competing mechanistic pathway. Additional protein engineering campaigns were carried out for a C8-selective quinoline alkylation. This study highlights the opportunity to use enzymes for regioselective radical reactions, where small molecule catalysts struggle to alter selectivity.",
author = "Page, {Claire G.} and Jingzhe Cao and Oblinsky, {Daniel G.} and Macmillan, {Samantha N.} and Shiva Dahagam and Lloyd, {Ruth M.} and Charnock, {Simon J.} and Scholes, {Gregory D.} and Hyster, {Todd K.}",
note = "Funding Information: The research reported here was supported by the National Institutes of Health National Institute of General Medical Sciences (R01GM127703). Mechanistic experiments, including transient absorption and UV–vis spectroscopy, were supported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy (DOE) through grant DE-SC0019370. This work made use of the Cornell University NMR Facility, which is supported, in part, by the NSF through MRI Award CHE-1531632. This work also made use of ACERT at Cornell, which is supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number 1R24GM146107. The authors thank Dr. Alex Lai and Professor Jack Freed for their help with the EPR spectroscopy. This work is based on research conducted at the Center for High-Energy X-ray Sciences (CHEXS), which is supported by the National Science Foundation (BIO, ENG, and MPS Directorates) under award DMR-1829070, and the Macromolecular Diffraction at CHESS (MacCHESS) facility, which is supported by award 1-P30-GM124166-01A1 from the National Institute of General Medical Sciences, National Institutes of Health, and by New York State{\textquoteright}s Empire State Development Corporation (NYSTAR). The authors would like to acknowledge the Ando Lab of Cornell for their assistance and expertise in preparing the crystal samples of PagER. The authors thank Michael G. Patterson for his help in solving the crystal structure of PagER. D.G.O. acknowledges support from the Postgraduate Scholarships Doctoral Program of the Natural Sciences and Engineering Research Council of Canada. C.G.P. acknowledges the NSF-GRFP for support. Publisher Copyright: {\textcopyright} 2023 American Chemical Society. All rights reserved.",
year = "2023",
month = may,
day = "31",
doi = "https://doi.org/10.1021/jacs.3c03607",
language = "English (US)",
volume = "145",
pages = "11866--11874",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "21",
}