Enantioselective Desymmetrization of Methylenedianilines via Enzyme-Catalyzed Remote Halogenation

Abstract

Extensive effort has been devoted to engineering flavin-dependent halogenases (FDHs) with improved stability, expanded substrate scope, and altered regioselectivity. Here we show that variants of rebeccamycin halogenase (RebH) catalyze enantioselective desymmetrization of methylenedianilines via halogenation of these substrates distal to their pro-stereogenic center. Structure-guided engineering was used to increase the conversion and selectivity of these reactions, and the synthetic utility of the halogenated products was shown via conversion of to a chiral α-substituted indole. These results constitute the first reported examples of asymmetric catalysis by FDHs.

Targeted Enzyme Engineering Unveiled Unexpected Patterns of Halogenase Stabilization

“…[45,54] Recently, desymmetrization of prochiral methylene dianilines by a RebH mutant was demonstrated by Lewis et al, providing an example of engineering the enantioselectivity of a flavin-dependent halogenase. [56] In our study, alteration of one residue within the active site allows for a tremendous influence on l-/d-selectivity and we were able to alter specificity of the substrate enantiomer. This points to an unexpected crucial role of Ser in substrate recognition presumably attractive for engineering of halogenase specificity.…”

An Fe2+‐ and α‐Ketoglutarate‐Dependent Halogenase Acts on Nucleotide Substrates

“…A phylogenetic tree of all characterized α‐KG‐dependent oxygenases and halogenases was generated and we could speculate that, using the AdeV sequence as a probe, we could find more halogenated nucleotide natural products through genome mining. The nucleoside halogenase may also aid us in creating new nucleoside analogues through biological, chemical, or biochemical routes for clinical use.…”

Recent Advances in Flavin-Dependent Halogenase Biocatalysis: Sourcing, Engineering, and Application

“…Building on previous learnings, Payne et al recently reported the first enantioselective desymmetrization of methylenedianinelines catalyzed by engineered RebH variants. Docking simulations and structure guided mutagenesis afforded mutants with improved activity and altered selectivity [63]. Tailoring the substrate scope of enzymes towards desired molecules has also been approached through protein engineering.…”