Molnupiravir (MK-4482) is an investigational antiviral agent that is under development for the treatment of COVID-19. Given the potential high demand and urgency for this compound, it was critical to develop a short and sustainable synthesis from simple raw materials that would minimize the time needed to manufacture and supply molnupiravir. The route reported here is enabled through the invention of a novel biocatalytic cascade featuring an engineered ribosyl-1-kinase and uridine phosphorylase. These engineered enzymes were deployed with a pyruvate-oxidase-enabled phosphate recycling strategy. Compared to the initial route, this synthesis of molnupiravir is 70% shorter and approximately 7-fold higher yielding. Looking forward, the biocatalytic approach to molnupiravir outlined here is anticipated to have broad applications for streamlining the synthesis of nucleosides in general.

<p>Molnupiravir (MK-4482) is an investigational direct-acting antiviral agent that is under development for the treatment of COVID-19. Given the potential high demand for this compound, it was critical to develop a sustainable and efficient synthesis from commodity raw materials. The three-step route that we report here embodies the shortest possible synthesis to molnupiravir, and was enabled through the invention of a novel biocatalytic cascade and final condensation step. Each step occurs in over 95% yield and only utilizes widely available commodity reagents and simple operations. Compared to the initial route, the new route is 70% shorter, and approximately seven-fold higher in overall yield. <br></p>

As practitioners of organic chemistry strive to deliver efficient syntheses of the most complex natural products and drug candidates, further innovations in synthetic strategies are required to facilitate their efficient construction. These aspirational breakthroughs often go hand-in-hand with considerable reductions in cost and environmental impact. Enzyme-catalyzed reactions have become an impressive and necessary tool that offers benefits such as increased selectivity and waste limitation. These benefits are amplified when enzymatic processes are conducted in a cascade in combination with novel bond-forming strategies. In this article, we report a highly diastereoselective synthesis of MK-1454, a potent agonist of the stimulator of interferon gene (STING) signaling pathway. The synthesis begins with the asymmetric construction of two fluoride-bearing deoxynucleotides. The routes were designed for maximum convergency and selectivity, relying on the same benign electrophilic fluorinating reagent. From these complex subunits, four enzymes are used to construct the two bridging thiophosphates in a highly selective, high yielding cascade process. Critical to the success of this reaction was a thorough understanding of the role transition metals play in bond formation.

Ulevostinag (MK-1454) is a potent cyclic dinucleotide stimulator of interferon genes (STING) that was selected as a clinical candidate for evaluation in multiple solid tumor types. Nucleoside analogue 3′-deoxy-3′-α-fluroguanosine (3′FG) is one of two key monomeric subunits comprising Ulevostinag, and its efficient preparation was set as a key deliverable in the development of this novel therapeutic. We recently reported a novel synthetic approach to 3′FG, involving the aminocatalytic electrophilic fluorination and subsequent substrate-directed reduction of an isolable 2′-keto-nucleoside (i-Bu-3). Herein, we describe the process development of these key stereodefining steps, enabling the kilogram-scale preparation of i-Bu-3′FG (1). Key features of this process include (1) identification of commercially available L-leucine amide as an excellent fluorination catalyst, (2) development of a highly stereoselective (>95:5) intramolecular hydride delivery from the hindered nucleoside β-face, and (3) use of dispersive Raman spectroscopy to guide form control during the crystallization of 1.

Herein, we present a strategy for the preparation of 3′-fluorinated nucleoside analogues via the aminocatalytic, electrophilic fluorination of readily accessible and bench-stable 2′-ketonucleosides. Initially developed to facilitate the manufacture of 3′-fluoroguanosine (3′-FG)a substructure of anticancer therapeutic MK-1454this strategy has been extended to the synthesis of a variety of 3′-fluoronucleosides. Finally, we demonstrate the utility of the 2′-ketonucleoside synthon as a platform for further diversification and suggest that this methodology should be broadly applicable to the discovery of novel nucleoside analogues.