Abstract
Chiral sulfoxides are important biologically active compounds, several of which constitute the active component of marketed pharmaceuticals. They are also privileged chiral ligands, catalysts and auxiliaries in asymmetric synthesis.
Ever since the pivotal work of Kagan, a large number of chemiocatalytic methods have been developed for asymmetric synthesis of chiral sulfoxides. Despite the wealth of these methods, truly general protocols that provide sulfoxides with high enantiomeric purity (>=99% ee) remain scarce.
Recently, we have developed of a highly efficient deracemization method for the preparation of chiral sulfoxides. This chemoenzymatic process utilizes the enantioselective enzyme methionine sulfoxide reductase A (MsrA).
In spite of the excellent enantioselectivity of the enzyme, there is a limitation in terms of substrate scope. Therefore, we aimed to develop a new high-throughput assay for laboratory evolution of MsrA.
A novel fluorescent probe has been synthesized and utilized for the assay development. The newly established assay enables to screen large libraries of mutants of the enzyme (~10(7) variants).
This high-throughput format allowed us to find an active mutant with significantly broader substrate scope while maintaining its enantioselectivity.