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Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Engineering a Thiamine-Dependent Benzoylformate Decarboxylase for Stereodivergent Radical C(sp3)-C(sp3) Bond
Zhouping Wu1, Yuyan Bao1, Jianlin Chun1
1State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), Frontier Interdisciplinary Science Research Center, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
Abstract:
The stereodivergent construction of C(sp3)-C(sp3) bonds between two prochiral radicals remains a formidable challenge. Here, we report the engineering of a thiamine-diphosphate-dependent radical enzyme to catalyze redox-neutral and stereodivergent cross-coupling of two electrophilic C(sp3) precursors. This new-to-nature enzyme reactivity was achieved via light-accelerated single-electron transfer from an unprecedented enzymatic vinyl Breslow intermediate, generating two distinct prochiral radicals whose stereoselective recombination forges the new C(sp3)-C(sp3) bond. Through systematic protein engineering, we developed four enzyme variants that collectively deliver all four stereoisomers with high efficiency (up to 82% yield, 99% enantiomeric excess (ee) and >20:1 diastereomeric ratio (d.r.)). This work establishes a platform for enzymatic, reductant-free radical cross-coupling with simultaneous control over two C(sp3) stereocenters.
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