Abstract
Deoxypodophyllotoxin contains a core of four fused rings (A to D) with three consecutive chiral centers, the last being created by the attachment of a peripheral trimethoxyphenyl ring (E) to ring C. Previous studies have suggested that the iron(II)- and 2-oxoglutarate–dependent (Fe/2OG) oxygenase, deoxypodophyllotoxin synthase (DPS), catalyzes the oxidative coupling of ring B and ring E to form ring C and complete the tetracyclic core. Despite recent efforts to deploy DPS in the preparation of deoxypodophyllotoxin analogs, the mechanism underlying the regio- and stereoselectivity of this cyclization event has not been elucidated. Herein, we report 1) two structures of DPS in complex with 2OG and (±)-yatein, 2) in vitro analysis of enzymatic reactivity with substrate analogs, and 3) model reactions addressing DPS’s catalytic mechanism. The results disfavor a prior proposal of on-pathway benzylic hydroxylation. Rather, the DPS-catalyzed cyclization likely proceeds by hydrogen atom abstraction from C7', oxidation of the benzylic radical to a carbocation, Friedel–Crafts-like ring closure, and rearomatization of ring B by C6 deprotonation. This mechanism adds to the known pathways for transformation of the carbon-centered radical in Fe/2OG enzymes and suggests what types of substrate modification are likely tolerable in DPS-catalyzed production of deoxypodophyllotoxin analogs.
Original language | English |
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Article number | e2113770119 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 119 |
Issue number | 1 |
DOIs | |
Publication status | Published - 2022 Jan 4 |
Keywords
- CC coupling
- Cyclization
- Natural product
- Oxygenase
- Reaction mechanism
ASJC Scopus subject areas
- General
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Dive into the research topics of 'Mechanistic analysis of carbon–carbon bond formation by deoxypodophyllotoxin synthase'. Together they form a unique fingerprint.Datasets
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Crystal structure of deoxypodophyllotoxin synthase from Sinopodophyllum hexandrum in complex with yatein and succinate
Tang, H. (Contributor), Wu, M.-H. (Contributor), Lin, H.-Y. (Contributor), Han, M.-R. (Contributor), Tu, Y.-H. (Contributor), Yang, Z.-J. (Contributor), Chien, T.-C. (Contributor), Chan, N.-L. (Contributor) & Chang, W.-C. (Contributor), Protein Data Bank (PDB), 2021 Dec 15
DOI: 10.2210/pdb7E38/pdb, https://www.wwpdb.org/pdb?id=pdb_00007e38
Dataset
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Crystal structure of deoxypodophyllotoxin synthase from Sinopodophyllum hexandrum in complex with 2-oxoglutarate
Tang, H. (Contributor), Wu, M.-H. (Contributor), Lin, H.-Y. (Contributor), Han, M.-R. (Contributor), Tu, Y.-H. (Contributor), Yang, Z.-J. (Contributor), Chien, T.-C. (Contributor), Chan, N.-L. (Contributor) & Chang, W.-C. (Contributor), Protein Data Bank (PDB), 2021 Dec 15
DOI: 10.2210/pdb7E37/pdb, https://www.wwpdb.org/pdb?id=pdb_00007e37
Dataset