Engineering Hydroxylase Activity, Selectivity, and Stability for a Scalable Concise Synthesis of a Key Intermediate to Belzutifan.

Biocatalytic oxidations are an emerging technology for selective C-H bond activation. While promising for a range of selective oxidations, practical use of enzymes catalyzing aerobic hydroxylation is presently limited by their substrate scope and stability under industrially relevant conditions. Here, we report the engineering and practical application of a non-heme iron and α-ketoglutarate-dependent dioxygenase for the direct stereo- and regio-selective hydroxylation of a non-native fluoroindanone en route to the oncology treatment belzutifan, replacing a five-step chemical synthesis with a direct enantioselective hydroxylation. Mechanistic studies indicated that formation of the desired product was limited by enzyme stability and product overoxidation, with these properties subsequently improved by directed evolution, yielding a biocatalyst capable of >15,000 total turnovers. Highlighting the industrial utility of this biocatalyst, the high-yielding, green, and efficient oxidation was demonstrated at kilogram scale for the synthesis of belzutifan.

Overcoming Product Inhibition in a Nucleophilic Aromatic Substitution Reaction.

The development of a nucleophilic aromatic substitution (SNAr) reaction for the synthesis of belzutifan and related analogues is disclosed. This classical transformation suffered from reaction stalling, despite prolonged reaction times. Through experimental and mechanistic studies, product inhibition was revealed and rationalized. Herein, we describe our efforts to overcome this synthetic challenge and demonstrate the importance of the judicious choice of the solvent to achieve reactivity.