posted on 2024-02-08, 13:16authored byMark R. Petchey, Yuxuan Ye, Victor Spelling, James D. Finnigan, Samantha Gittings, Magnus J. Johansson, Martin A. Hayes, Todd K. Hyster
Radical hydrofunctionalizations
of electronically unbiased dienes
are challenging to render regioselective, because the products are
nearly identical in energy. Here, we report two engineered FMN-dependent
“ene”-reductases (EREDs) that catalyze regiodivergent
hydroalkylations of cyclic and linear dienes. While previous studies
focused exclusively on the stereoselectivity of alkene hydroalkylation,
this work highlights that EREDs can control the regioselectivity of
hydrogen atom transfer, providing a method for selectively preparing
constitutional isomers that would be challenging to prepare using
traditional synthetic methods. Engineering the ERED from Gluconabacter sp. (GluER) furnished a variant that favors the γ,δ-unsaturated
ketone, while an engineered variant from a commercial ERED panel favors
the δ,ε-unsaturated ketone. The effect of beneficial mutations
has been investigated using substrate docking studies and the mechanism
probed by isotope labeling experiments. A variety of α-bromo
ketones can be coupled with cyclic and linear dienes. These interesting
building blocks can also be further modified to generate difficult-to-access
heterocyclic compounds.