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>
Exploratory studies on the sequential exo-mode oxacyclizations of acyclic polyene precursors have provided a substantial substructure of brevenal, including the fused tricyclic polyether with stereochemical patterns consistent with the AB and BC ring fusions. The synthesis of acyclic substrates featured two variations of Cr(II)/Ni(II) couplings for preparing 1,1-disubstituted allylic alcohols. A sequence of iodine-promoted cycloetherification, base-promoted intramolecular conjugate addition, and mercury-promoted cycloetherification produced the tricyclic substructure.
Supporting InformationS-3 II. Synthesis of diynyl triol (S,S)-6Preparation of (±)-8: HgCl 2 (90 mg; 0.33 mmol) and Mg 0 (3.65 g; 150 mmol) were added to a two-neck oven-dried 250 mL round bottom flask equipped with reflux condenser. A solution of propargyl bromide (0.4 mL) in Et 2 O (16 mL) was added. The resulting suspension was heated gently with a heating gun to initiate the reaction, resulting in bubbling which persisted after heating ceased. The flask was then cooled to 0 °C, before dropwise addition of the remaining propargyl bromide (5.2 mL; 50 mmol total) in Et 2 O (30 mL) over 20 min. The reaction continued to bubble upon and after addition of propargyl bromide. After stirring at 0 °C for 15 min, the grey Grignard solution was transferred via cannula to a flask containing propargyl aldehyde 7 2 (2.38 g; 12.6 mmol) in THF (62 mL) at -78 °C. The reaction was stirred at -78 °C for 3 h, after which time it was quenched by addition of sat'd aq. NH 4 Cl (20 mL) and allowed to warm to room temperature. The organic layer was separated and the aqueous layer was extracted with Et 2 O (3 x 20 mL). The combined organic extracts were washed with brine, dried over Na 2 SO 4 , filtered, and concentrated under reduced pressure to afford the crude product as a yellow oil, which was purified by silica gel flash column chromatography (20% EtOAc in hexanes) to afford racemic diynyl alcohol 8 as a clear, colorless oil (2.44 g; 10.7 mmol; 85% yield). O OBn H 7 R + OR OBn H H S Supporting Information S-4 1 H NMR for diynyl alcohol (±)-8: (600 MHz, CDCl 3 ) δ 7.39 -7.29 (m, 5H), 4.56 (s, 2H), 4.52 (dtd, J = 8.0, 5.9, 1.9 Hz, 1H), 3.60 (t, J = 7.0 Hz, 2H), 2.61 (m, 2H), 2.56 (td, J = 7.0, 1.9 Hz, 2H), 2.20 (d, J = 6.3 Hz, 1H), 2.11 (t, J = 2.6 Hz, 1H).Resolution of (±)-8 to prepare diynyl ester (R)-8 and diynyl alcohol (S)-9: Powdered 3Å molecular sieves (1.5 g) and Pseudomonas AK (1.12 g) were added to a solution of racemic diynyl alcohol 8 (2.24 g; 9.80 mmol) in hexanes (100 mL). Vinyl acetate (4.0 mL) was then added. The suspension was stirred and monitored for conversion by 1 H NMR spectroscopy.After 4 h, the reaction had reached 50% conversion by 1 H NMR. The reaction mixture was filtered through Celite, rinsed with CH 2 Cl 2 , and concentrated under reduced pressure to afford a pale-yellow oil. The crude reaction mixture was purified by silica gel flash column chromatography (18% EtOAc in hexanes) to afford diynyl ester (R)-9 (1.10 g; 4.07 mmol; 42% yield) and diynyl alcohol (S)-8 (854 mg; 3.74 mmol; 38% recovery; 80% combined yield of 8 and 9). MTPA-esters confirmed the stereochemical assignment and purity of (S)-8 (er > 95:5; the other stereoisomer was not visible). Data for diynyl ester (R)-9: [α] D 25 +48.8 (c=1.0, CHCl 3 ) 1 H NMR (600 MHz, CDCl 3 ) δ 7.39 -7.30 (m, 5H), 5.50 (app. tt, J = 6.3, 2.0 Hz, 1H), 4.56 (s, 2H), 3.60 (t, J = 7.1 Hz, 2H), 2.67 (dd, J = 6.2, 2.6 Hz, 2H), 2.56 (td, J = 7.1, 2.0 Hz, 2H), 2.11 (s, 3H), 2.05 (t, J = 2.7 Hz, 1H).OH OBn
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