Experimental and Computational Analysis of the Inability of an Iron(II)- and 2-Oxoglutarate-Dependent Aliphatic Halogenase to Mediate Fluorination

作者：Vishal Yadav, Chao Wang, Christopher J. Pollock, Jiang Ren, Evan Burke, Chi‐Yun Lin, Jeffrey W. Slater, Irene Schaperdoth, Elvira R. Sayfutyarova, Alexey Silakov, Carsten Krebs, J. Martin Bollinger · 发表于：ChemRxiv · 年份：2025 · DOI：10.26434/chemrxiv-2025-n90dx · 被引用次数：1 · 研究领域：Metal-Catalyzed Oxygenation Mechanisms、Metalloenzymes and iron-sulfur proteins、Porphyrin Metabolism and Disorders

Incorporation of fluorine into pharmaceuticals, agrochemicals, and molecular-imaging agents is of growing importance. Multiple synthetic fluorination methods have recently emerged, and metalloenzymes that are potentially capable of even C(sp3)–H fluorination have been reported. Nevertheless, direct, regioselective fluorination of aliphatic carbon centers remains an unsolved problem. Here, we show for the iron(II) and 2-oxoglutarate-dependent (Fe/2OG) L-Lysine 4-chlorinase, BesD, which can be envisaged to support C(sp3)–H fluorination by the direct cognate of its native chlorination mechanism, that the enzyme can (1) coordinate F– at its Fe(II) cofactor, (2) activate O2 to form a cis-FeIV(O)(F) (fluoroferryl) intermediate, and (3) use the intermediate to abstract hydrogen from its substrate. In what would be the key final step, fluorine (F•) transfer to the substrate radical is unable to compete with the hydroxyl-radical (HO•) "rebound" step characteristic of related hydroxylases. Electron paramagnetic resonance (EPR) and X-ray absorption spectroscopic data establish that fluorine remains bonded to the cofactor through steps 1-3 and therefore available for transfer to the substrate radical. QM/MM calculations suggest that the F•-coupling step is associated with an activation barrier considerably higher than that of HO• rebound, consistent with the observed outcome. The findings experimentally verify prior proposals that the impediment to C(sp3)–H fluorination by the canonical ...