Asymmetric Reductive Carbocyclization Using Engineered Ene Reductases

Heckenbichler, Kathrin; Schweiger, Anna K.; Brandner, Lea A.; Binter, Alexandra; Toplak, Marina; Macheroux, Peter; Gruber, Karl; Breinbauer, Rolf

doi:10.1002/anie.201802962

Cited by 52 publications

(52 citation statements)

References 71 publications

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“…Members of the enzyme families collectively called ene reductases (ERs) are effective biocatalysts for the stereoselective trans and—in rare cases— cis hydrogenation of activated alkenes, thus complementing chemical cis hydrogenations by using chiral rhodium or ruthenium phosphines (Knowles and Noyori, Nobel Prize in Chemistry 2001) . Recently, the canonical function of ene reductases was further expanded by enzyme engineering to include asymmetric reductive carbocyclization, which yields chiral cyclopropanes …”

Section: Introductionmentioning

confidence: 99%

Novel Old Yellow Enzyme Subclasses

et al. 2019

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Many drug candidate molecules contain at least one chiral centre, and consequently, the development of biocatalytic strategies to complement existing metal‐ and organocatalytic approaches is of high interest. However, time is a critical factor in chemical process development, and thus, the introduction of biocatalytic steps, even if more suitable, is often prevented by the limited availability of off‐the‐shelf enzyme libraries. To expand the biocatalytic toolbox with additional ene reductases, we screened 19 bacterial strains for double bond reduction activity by using the model substrates cyclohexanone and carvone. Overall, we identified 47 genes coding for putative ene reductases. Remarkably, bioinformatic analysis of all genes and the biochemical characterization of four representative novel ene reductases led us to propose the existence of two new Old Yellow Enzyme subclasses, which we named OYE class III and class IV. Our results demonstrate that although, on a DNA level, each new OYE subclass features a distinct combination of sequence motifs previously known from the classical and the thermophilic‐like group, their substrate scope more closely resembles the latter subclass.

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Section: Introductionmentioning

confidence: 99%

Novel Old Yellow Enzyme Subclasses

et al. 2019

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“…Flavin-dependent 'ene'-reductases (EREDs) are substrate promiscuous oxidoreductases widely used in chemical synthesis for the stereoselective reduction of activated alkenes (14). Mechanistically, the reduction occurs via hydride transfer from the flavin hydroquinone (FMN hq ) to the electrophilic β-position of the alkene (15,16). In other protein scaffolds, such as ferredoxin reductase or P450 reductase, flavin effects the reduction via two single electron transfers (17).…”

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confidence: 99%

Asymmetric redox-neutral radical cyclization catalysed by flavin-dependent ‘ene’-reductases

et al. 2019

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Flavin-dependent 'ene'-reductases (EREDs) are exquisite catalysts for effecting stereoselective reductions. While these reactions typically proceed through a hydride transfer mechanism, we recently found that EREDs can also catalyze reductive dehalogenations and cyclizations via single electron transfer mechanisms. Here we demonstrate that these enzymes can catalyze redox-neutral radical cyclizations to produce enantioenriched oxindoles from α-haloamides. This transformation is a CC bond forming reaction currently unknown in nature and one for which there are no catalytic asymmetric examples. Mechanistic studies indicate the reaction proceeds via the flavin semiquinone/quinone redox couple, where ground state flavin semiquinone provides the electron for substrate reduction and flavin quinone oxidizes the vinylogous α-amido radical formed after cyclization. This mechanistic manifold was previously unknown for this enzyme family, highlighting the versatility of EREDs in asymmetric synthesis.

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“…Generally, the ene-reductases, depending on whether the process takes place in eukaryotes or prokaryotes, utilize NADPH or FMNH2 to reduce electron-deficient alkenes, coaxed along by some simultaneous Lewis acidic coordination to a polar function, such as an ester, ketone or aldehyde. Synthetically, it has been demonstrated that the ene-reductases are competent at forming C–C bonds [77]. However, a brief glance at 16 reveals that the reacting termini cannot be activated in a similar manner as above.…”

Section: Resultsmentioning

confidence: 99%

Some Biogenetic Considerations Regarding the Marine Natural Product (−)-Mucosin

et al. 2019

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Recently, the identity of the marine hydrindane natural product (−)-mucosin was revised to the trans-fused structure 6, thereby providing a biogenetic puzzle that remains to be solved. We are now disseminating some of our insights with regard to the possible machinery delivering the established architecture. Aspects with regard to various modes of cyclization in terms of concerted versus stepwise processes are held up against the enzymatic apparatus known to be working on arachidonic acid (8). To provide a contrast to the tentative polyunsaturated fatty acid biogenesis, the structural pattern featured in (−)-mucosin (6) is compared to some marine hydrinane natural products of professed polyketide descent. Our appraisal points to a different origin and strengthens the hypothesis of a polyunsaturated fatty acids (PUFA) as the progenitor of (−)-mucosin (6).

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Asymmetric Reductive Carbocyclization Using Engineered Ene Reductases

Cited by 52 publications

References 71 publications

Novel Old Yellow Enzyme Subclasses

Novel Old Yellow Enzyme Subclasses

Asymmetric redox-neutral radical cyclization catalysed by flavin-dependent ‘ene’-reductases

Some Biogenetic Considerations Regarding the Marine Natural Product (−)-Mucosin

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