Enantioselective bioreduction of benzo-fused cyclic ketones with engineered Candida glabrata ketoreductase 1 – a promising synthetic route to ladostigil (TV3326)

Abstract

Biocatalysis has been recently emerging as a promising alternative to traditional chemical synthesis because of its "green" characteristics and comparable selectivities, which accord with the concept of sustainable development and demand for asymmetric synthesis. In this study, whole-cell biocatalysts containing glucose dehydrogenase (GDH) and Candida glabrata ketoreductase 1 (CgKR1) variants were constructed. These biocatalysts were applied to the reduction of benzo-fused cyclic ketones and showed good to high activities and enantioselectivities. Particularly, CgKR1 variants displayed high activities (90.6%-98.4% conversions) and enantioselectivities (>99.9% ee) towards 5a, a key intermediate of ladostigil (TV3326). Based on these results, a chemoenzymatic synthesis of (S)-5b was developed by using biocatalytic asymmetric reduction as a key step, giving the product with a total yield of 34.0% and 99.9% ee.

Engineering ketoreductases for the enantioselective synthesis of chiral alcohols

“…Similarly, Ou-Yang and coworkers 32 reported that mutations at residues Phe92, Tyr208, Met144, Phe145 of CgKR1, which are important for the binding pocket, afforded engineered CgKR1s with high activity and stereoselectivity towards benzo-fused cyclic ketones. Particularly, the whole-cell biocatalysts prepared by the co-expression of CgKR1 variants and GDH displayed excellent stereoselectivity (>99.9% ee) in the reduction of N -ethyl- N -methyl-2-(3-oxo-2,3-dihydro-1 H -inden-5-yl) acetamide, the key intermediate of the anti-Alzheimer drug ladostigil (TV3326).…”