Evolution of a Green and Sustainable Manufacturing Process for Belzutifan: Part 5─Chemoenzymatic Diastereoselective Fluorination/DKR

Abstract

A ketone fluorination/reduction dynamic kinetic resolution (DKR) was developed for a third-generation synthesis of belzutifan. This new process replaced a precious metal catalyst with a ketoreductase (KRED) in the DKR. Achieving this one-pot reaction required several rounds of enzyme evolution that improved enzyme stability in the presence of acetonitrile and methanol. To maintain development progress and satisfy program timelines, process development around the reaction, workup, and isolation operations was performed in parallel with the enzyme evolution and required ongoing modification, as new variants were made available. Additionally, opportunities for improvements to product quality and process robustness were identified by resolving issues observed in piloting experiments.

Evolution of a Green and Sustainable Manufacturing Process for Belzutifan: Part 1─Process History and Development Strategy

“…Over the course of 14 rounds of evolution, the enzyme was evolved to tolerate all of the reaction components, including up to 50% ACN/MeOH as well as IPA necessary for NADP + turnover. Not only is the final variant KRED-15 robust to the fluorination conditions, but it also provides high yield, high turnover, and exquisite diastereoselectivity (>200:1), surpassing the Ru-catalyzed process …”

Evolution of a Green and Sustainable Manufacturing Process for Belzutifan: Part 6─Development of a Nucleophilic Aromatic Substitution in Water

“…Toward this end, a new endgame strategy was developed involving a novel biocatalytic oxidation and an α-fluorination/dynamic kinetic reduction (DKR) sequence using a ketoreductase (Figure ). Furthermore, our previously developed deoxyfluorination conditions were successfully adapted and implemented in the synthesis of the penultimate aryl fluoride 1 . Thus, the final area of focus was the introduction of the biaryl ether via S N Ar of the aryl fluoride with phenol 2 .…”

Enantio- and Diastereoselective Total Synthesis of Belzutifan Enabled by Rh-Catalyzed Hydrogenation

“…To this end, our group developed a biocatalytic route that involved direct enzymatic oxidation of indanone 11 (made in three steps from 5-bromo-2-fluorobenzaldehyde) to hydroxyketone 12 in >99% ee followed by a one-pot fluorination–ketoreductase (KRED) cascade to give stereotriad 13 in >200:1 dr, significantly shortening the overall synthesis to belzutifan (Figure B) . At the same time, we also envisioned a complementary chemocatalytic approach for installing the stereotriad that could take advantage of an asymmetric hydrogenation disconnection to install the vicinal syn -difluoro motif, ultimately requiring the asymmetric hydrogenation of vicinal difluoroalkene 7 to form difluoroalkane 8 (Figure C).…”