A Concise Route to MK-4482 (EIDD-2801) from Cytidine: Part 2

Abstract

A new route to MK-4482 was developed. The route replaces uridine with the more available and less expensive cytidine. Low-cost, simple reagents are used for the chemical transformations, and the yield is improved from 17% to 44%. A step is removed from the longest linear sequence, and these advancements are expected to expand access to MK-4482 should it become a viable drug substance.

Key words

antiviral - nucleoside - COVID-19

Publication History

Received: 10 September 2020

Accepted after revision: 30 September 2020

Accepted Manuscript online:
30 September 2020

Article published online:
30 October 2020

• References and Notes

• 1a Sheahan TP, Sims AC, Zhou S, Graham RL, Pruijssers AJ, Agostini ML, Leist SR, Schäfer A, Dinnon KH. III, Stevens LJ, Chappel JD, Lu X, Hughes TM, George AS, Hill CS, Montgomery SA, Brown AJ, Bluemling GR, Natchus MG, Saindane M, Kolykhalov AA, Painter G, Harcourt J, Tamin A, Thornburg NJ, Swanstrom R, Denison MR, Baric RS. Sci. Transl. Med. 2020; 12: 541
• 1b Halford B. Chem. Eng. News 2020; 98: 22
• 1c Cross R. Chem. Eng. News 2020; 98: 12
• 2a Painter GR, Bluemling GR, Natchus MG, Guthrie D. WO2019113462, 2018
• 2b Painter GR, Perryman D, Bluemling GR. WO2019173602, 2019
• 3 Price obtained through analysis of Indian import/export records.
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• 5 Painter GR, Guthrie DB, Bluemling GR, Natchus MG. WO2016106050A1, 2016
• 6 Camacho-García J, Montoro-García C, López-Pérez AM, Bilbao N, Romero-Pérez S, González-Rodríguez D. Org. Biomol. Chem. 2015; 13: 4506
• 7 Cytidine Acetonide Ester 4 To acetonide salt 3 (5.003 g, 98.7% purity, 13.1 mmol) in a single-neck dry100 mL round-bottom flask was added anhydrous acetonitrile (50 mL). DMAP (327 mg, 2.68 mmol, 0.204 equiv.) was added to the above flask. DBU (4.06 mL, 2.1 equiv.) was added upon which the suspension became a clear solution after stirring at room temperature for 5 min. Isobutyric anhydride (2.36 mL, 1.1 equiv.) was then added dropwise, and the resultant reaction was left stirring at room temperature overnight. The reaction was then directly concentrated under reduced pressure to afford a waxy solid (12.35 g, 95% assay yield, 35% purity). The resultant material was re-dissolved in dichloromethane, and silica gel was added to prepare the dry loaded sample for column chromatography. Purification using 5% MeOH in CHCl₃ then afforded the ester (3.72 g, 78%). ¹H NMR (600 MHz, CD₃OD): δ = 7.90 (s, 1 H), 7.63 (d, J = 7.4 Hz, 1 H), 5.86 (d, J = 7.4 Hz, 1 H), 5.71 (d, J = 6.9 Hz, 1 H), 5.03 (dd, J = 4.7, 1.6 Hz, 1 H), 4.84 (dd, J = 6.3, 3.4 Hz, 1 H), 4.31 (m, 1 H), 2.55 (sept, J = 7.0 Hz, 1 H), 1.53 (s, 3 H), 1.34 (s, 3 H), 1.13 (ddd, J = 3.2, 1.8, 1.3 Hz, 6 H). ¹³C NMR (151 MHz, CD₃OD): δ = 178.49, 168.31, 158.14, 145.15, 115.34, 97.21, 96.25, 87.04, 86.71, 83.36, 65.86, 35.35, 27.74, 25.75, 19.75, 19.60, 19.52 ppm. HRMS: m/z calcd: 354.1665 [M⁺]; found: 354.1677.
• 8 N-Hydroxycytidine Acetonide Ester 5 To acetonide ester 4 (2 g, 83% purity) in a 100 mL single-neck round-bottom flask was added hydroxylamine sulfate (2.47 g, 3.2 equiv.) followed by 70% i-PrOH (by Karl Fisher titration, 24% water content, 40 mL). The resultant solution was heated to 78 °C (internal temperature 72–73 °C) for 17 h upon which time HPLC showed the formation of product. Solvent was removed on a rotary evaporator, and acetonitrile (20 mL) was then added. The resulting slurry was sonicated for 5 min. The insoluble residue was then filtered, and the filtrate was concentrated under reduced pressure to afford crude material. Toluene (20 mL) was added, and concentration done under reduced pressure to remove water azeotropically to give a white solid (1.81 g, 94% purity, 96% isolated yield corrected for purity). ¹H NMR (600 MHz, CD₃OD): δ = 6.85 (d, J = 8.2 Hz, 1 H), 5.69 (d, J = 2.2 Hz, 1 H), 5.57 (d, J = 8.2 Hz, 1 H), 4.97–4.99 (dd, J = 6.4, 2.2 Hz, 1 H), 4.79–4.81 (dd, J = 6.3, 4.8 Hz, 1 H), 4.26 (d, J = 5.3 Hz, 2 H), 4.21 (q, J = 4.9 Hz, 1 H), 2.60 (sept, J = 7.0 Hz, 1 H), 1.53 (s, 3 H), 1.34 (s, 3 H), 1.15–1.17 (dd, J = 7.0, 1.8 Hz, 6 H). ¹³C NMR (151 MHz, CD₃OD): δ = 178.61, 151.42, 146.49, 134.21, 115.73, 99.73, 94.53, 85.62, 85.58, 82.87, 65.54, 35.36, 30.97, 27.79, 25.82, 19.61, 19.58 ppm. HRMS: m/z calcd: 370.1614; found: 370.1624.
• 9 EIDD-2801 To a 20 mL vial was added N-hydroxycytidine acetonide ester 5 (0.25 g, 96% purity) followed by formic acid (4 mL). The resultant solution was stirred at room temperature for 4 h 20 min. Solvent was removed under reduced pressure, and fresh EtOH (5 mL) was added. The resultant solution was again concentrated under vacuum to afford an oil. Methyl tert-butyl ether and i-PrOH (5 mL each) were successively added as described earlier for preparation of compound 4 and concentrated to give 0.205 g of crude material (77% assay yield, 79% purity). This material was purified by silica gel column chromatography in 8% MeOH/CHCl₃ to afford 130 mg of EIDD-2801 as a solid (60% isolated yield corrected for purity, 98% purity). ¹H NMR (600 MHz, CD₃OD): δ = 6.91 (d, J = 8.2 Hz, 1 H), 5.82 (d, J = 4.8 Hz, 1 H), 5.61 (d, J = 8.2 Hz, 1 H), 4.29 (d, J = 3.6 Hz, 2 H), 4.14 (t, J = 4.9 Hz, 1 H), 4.08 (p, J = 4.9 Hz, 2 H), 2.62 (sept, J = 7.0 Hz, 1 H), 1.19 (d, J = 7.0 Hz, 6 H). ¹³C NMR (151 MHz, CD₃OD): δ = 178.6, 151.81, 146.44, 132.04, 99.84, 90.74, 82.88, 74.67, 71.80, 65.23, 35.45, 27.49, 19.65, 19.61 ppm.